Features

Provides accurate measure-
ment of available charge in
NiCd, NiMH, and Li-Ion re-
chargeable batteries

Supports SBData charge con-
trol commands for Li-Ion,
NiMH, and NiCd chemistries

Designed for battery pack inte-
gration

120

µA typical operating

current

Small size enables
implementations in as little as

square inch of PCB

Two-wire SMBus-like interface

Measurements compensated for
current and temperature

Programmable self-discharge
and charge compensation

16-pin narrow SOIC

General Description

The bq2092 Gas Gauge IC With
SMBus-Like Interface is intended
for battery-pack or in-system instal-
lation to maintain an accurate
record of available battery charge.
The bq2092 directly supports capac-
ity monitoring for NiCd, NiMH, and
Li-Ion battery chemistries.

The bq2092 uses the SMBus proto-
col that supports many of the Smart
Battery Data (SBData) commands.
The bq2092 also supports SBData
charge control.

Battery state-of-

charge, capacity remaining, remain-
ing time and chemistry are available
over the serial link. Battery-charge
state can be directly indicated using
a four-segment LED display to
graphically depict battery full-to-
empty in 25% increments.

The bq2092 estimates battery self-
discharge based on an internal
timer and temperature sensor and
user-programmable rate informa-
tion stored in external EEPROM.
The bq2092 also automatically
recalibrates or "learns" battery
capacity in the full course of a
discharge cycle from full to empty.

The bq2092 may operate directly
from three nickel chemistry cells.
With the REF output and an exter-
nal transistor, a simple, inexpensive
regulator can be built to provide V

for other battery cell configurations.

An external EEPROM is used to
program initial values into the
bq2092 and is necessary for proper
operation.

bq2092

Gas Gauge IC with SMBus-Like Interface

3.05.5V

SCL

Serial memory
clock

SDA

Serial memory
data

SEG

LED segment 1

SEG

LED segment 2

SEG

LED segment 3

SEG

LED segment 4

System ground

PN209101.eps

16-Pin Narrow SOIC

VOUT

REF

SCC

SCD

DISP

VCC

SCL

SDA

SEG1

SEG2

SEG3

SEG4

VSS

Sense resistor input

DISP

Display control input

Battery sense input

SCD

Serial communication
data input/output

SCC

Serial communication
clock

REF

Voltage reference
output

OUT

EEPROM supply
output

6/99 C

Pin Connections

Pin Names

Pin Descriptions

Supply voltage input

SCL

Serial memory clock

This output is used to clock the data
transfer between the bq2092 and the ex-
ternal nonvolatile configuration memory.

SDA

Serial memory data and address

This bi-directional pin is used to trans-
fer address and data to and from the
bq2092 and the external configuration
memory.

SEG

LED display segment outputs

Each output may activate an external LED
to sink the current sourced from V

Ground

Sense resistor input

The voltage drop (V

) across pins SR and

is monitored and integrated over time

to interpret charge and discharge activity.
The SR input is connected to the sense re-
sistor and the negative terminal of the
battery. V

< V

indicates discharge, and

> V

indicates charge. The effective

voltage drop, V

SRO

, as seen by the bq2092

is V

+ V

(see Table 3).

DISP

Display control input

DISP high disables the LED display. DISP
floating allows the LED display to be active
during charge if the rate is greater than
100mA. DISP low activates the display for 4
seconds.

Secondary battery input

This input monitors the cell pack voltage as
a single-cell potential through a high-
impedance resistor divider network.

The

cell pack voltage is reported in the SBD
register function Voltage (0x09) and is com-
pared to end-of-discharge voltage and
charging voltage parameters.

No connect

SCD

Serial communication data

This open-drain bidirectional pin is used to
transfer address and data to and from the
bq2092.

SCC

Serial communication clock

This open-drain bidirectional pin is used to
clock the data transfer to and from the
bq2092.

REF

Reference output for regulator

REF provides a reference output for an op-
tional micro-regulator.

OUT

Supply output

This output supplies power to the exter-
nal EEPROM configuration memory.

bq2092

Functional Description

General Operation

The bq2092 determines battery capacity by monitoring
the amount of charge input to or removed from a
rechargeable battery. The bq2092 measures discharge
and charge currents, estimates self-discharge, and
monitors the battery for low-battery voltage thresh-
olds. The charge measurement is made by monitoring
the voltage across a small-value series sense resistor
between the battery's negative terminal and ground.
The available battery charge is determined by moni-
toring this voltage over time and correcting the meas-
urement for the environmental and operating condi-
tions.

Figure 1 shows a typical battery pack application of the
bq2092 using the LED capacity display, the serial port,
and an external EEPROM for battery pack program-
ming information. The bq2092 must be configured and
calibrated for the battery-specific information to ensure
proper operation. Table 1 outlines the externally
programmable functions available in the bq2092. Refer
to the Programming the bq2092 section for further
details.

An internal temperature sensor eliminates the need
for an external thermistor--reducing cost and compo-
nents.

An internal, temperature-compensated time-

base eliminates the need for an external resonator,
further reducing cost and components.

The entire

circuit in Figure 1 can occupy less than

square inch

of board space.

bq2092

VCC

SCL
SDA
SEG1
SEG2
SEG3
SEG4

VOUT

REF

SCC
SCD

DISP

BZX84C5V6

2192L.eps

Figure 1. Battery Pack Application Diagram--LED Display

Parameter Name

Address

Length

Units

Design capacity

0x00/0x01

16 bits: low byte, high byte

mAh

Initial battery voltage

0x02/0x03

16 bits: low byte, high byte

Fast charging current

0x04/0x05

16 bits: low byte, high byte

Charging voltage

0x06/0x07

16 bit: low byte, high byte

Remaining capacity alarm

0x08/0x09

16 bits: low byte, high byte

mAh

FLAGS1

0x0a

8 bits

N/A

FLAGS2

0x0b

8 bits

N/A

Current measurement gain

0x0c/0x0d

16 bits: low byte, high byte

N/A

EDV

0x0e/0x0f

16 bits: low byte, high byte

EDV

0x10/0x11

16 bits: low byte, high byte

Temperature offset

0x12

8 bits

0.1°K

Maximum charge temperature/

T/t

0x13

8 bits

N/A

Self-discharge rate

0x14

8 bits

N/A

Digital filter

0x15

8 bits

N/A

Current integration gain

0x16/0x17

16 bits: low byte, high byte

N/A

Full charge percentage

0x18

8 bits

N/A

Charge compensation

0x19

8 bits

N/A

Battery voltage offset

0x1a

8 bits

Battery voltage gain

0x1b/0x1c

16 bits: high byte, low byte

N/A

Serial number

0x1d/0x1e

16 bits: low byte, high byte

N/A

Hold-off timer

0x1f

8 bits

N/A

Cycle count

0x20/0x21

16 bits: low byte, high byte

N/A

Maintenance charge current

0x22/0x23

16 bits: low byte, high byte

Reserved

0x24/0x31

Design voltage

0x32/0x33

16 bits: low byte, high byte

Specification information

0x34/0x35

16 bits: low byte, high byte

N/A

Manufacturer date

0x36/0x37

16 bits: low byte, high byte

N/A

Reserved

0x38/0x3f

Manufacturer name

0x40/0x4f

8 + 120 bits

N/A

Device name

0x50/0x5f

8 + 120 bits

N/A

Chemistry

0x60/0x6f

8 + 120 bits

N/A

Manufacturer data

0x70/0x7f

8 +120 bits

N/A

Table 1. Configuration Memory Programming Values

Note:

N/A = Not applicable; data packed or coded. See "Programming the bq2092" for details.

bq2092

Voltage Thresholds

In conjunction with monitoring V

for charge/discharge

currents, the bq2092 monitors the battery potential
through the SB pin.

The voltage potential is deter-

mined through a resistor-divider network per the
following equation:

MBV

2.25

where MBV is the maximum battery voltage, R

connected to the positive battery terminal, and R

connected to the negative battery terminal. R

should

be rounded to the next highest integer. The voltage at
the SB pin (V

) should never exceed 2.4V.

The battery voltage is monitored for the end-of-
discharge voltage (EDV), for maximum pack voltage and
for alarm warning conditions. EDV threshold levels are
used to determine when the battery has reached an
"empty" state, and the charging voltage plus 5% thresh-
old is used for fault detection during charging. The
battery voltage gain, two EDV thresholds, and charge
voltage limit are programmed via EEPROM.

See the

Programming the bq2092 section for further details.

If V

is below either of the two EDV thresholds, the associ-

ated flag is latched and remains latched, independent of
V

, until the next valid charge.

EDV monitoring may be disabled under certain condi-
tions. If the discharge current is greater than approxi-
mately 6A, EDV monitoring is disabled and resumes
after the current falls below 6A.

Reset

The bq2092 is reset when first connected to the battery
pack. The bq2092 can also be reset with a command
over the serial port, as described in the Software Reset
section.

Temperature

The bq2092 monitors temperature using an internal
sensor. The temperature is used to adapt charge/dis-
charge and self-discharge compensations as well as
maximum temperature and

T/t during bq2092 con-

trolled charge. Temperature may also be accessed over
the serial port. See the Programming the bq2092 section
for further details.

Layout Considerations

The bq2092 measures the voltage differential between
the SR and V

pins. V

(the offset voltage at the SR

pin) is greatly affected by PC board layout. For optimal
results, the PC board layout should follow the strict rule

of a single-point ground return. Sharing high-current
ground with small signal ground causes undesirable
noise on the small signal nodes. Additionally, in refer-
ence to Figure 1:

The capacitors (C1, C2, and C4) should be placed as
close as possible to the SB and V

pins, and their paths

to V

should be as short as possible. A high-quality

ceramic capacitor of 0.1

µf is recommended for V

The sense resistor capacitor (C3) should be placed as
close as possible to the SR pin.

The sense resistor (R1) should be as close as possible
to the bq2092.

The IC should be close to the cells for the best
temperature measurement.

An optional zener may be necessary to ensure V

not above the maximum rating during operation.

Gas Gauge Operation

The operational overview diagram in Figure 2 illus-
trates the operation of the bq2092. The bq2092 accumu-
lates a measure of charge and discharge currents, as
well as an estimation of self-discharge. Charge currents
are compensated for temperature and state-of-charge.
Self-discharge is only temperature-compensated.

The main counter, RemainingCapacity (RM), represents
the available battery capacity at any given time. Battery
charging increments the RM register, whereas battery
discharging and self-discharge decrement the RM register
and increment the Discharge Count Register (DCR).

The Discharge Count Register (DCR) is used to update
the FullChargeCapacity (FCC) register only if a
complete battery discharge from full to empty occurs
without any partial battery charges.

Therefore, the

bq2092 adapts its capacity determination based on the
actual conditions of discharge.

The battery's initial capacity is equal to the DesignCapacity
(DC).

Until FCC is updated, RM counts up to, but not

beyond, this threshold during subsequent charges.

FullChargeCapacity or learned-battery
capacity:

FCC is the last measured discharge capacity of the
battery. On initialization (application of V

or reset),

FCC = DC. During subsequent discharges, the FCC
is updated with the latest measured capacity in the
Discharge Count Register, representing a discharge
from full to below EDV1. A qualified discharge is
necessary for a capacity transfer from the DCR to the
FCC register. The FCC also serves as the 100% ref-
erence threshold used by the relative state-of-charge
calculation and display.

bq2092

DesignCapacity (DC):

The DC is the user-specified battery capacity and is
programmed by using an external EEPROM. The
DC also provides the 100% reference for the abso-
lute display mode.

Remaining Capacity (RM):

RM counts up during charge to a maximum value of
FCC and down during discharge and self-discharge to
0. RM is reset to 0000Ah when EDV1 = 1 and a valid
charge is detected. To prevent overstatement of
charge during periods of overcharge, RM stops in-
crementing when RM = FCC. RM may optionally
be written to a user-defined value when fully
charged when the battery pack is under bq2092
charge control. See the Charge Control section for
further details.

Discharge Count Register (DCR):

The DCR counts up during discharge independent
of RM and can continue increasing after RM has
decremented to 0. Before RM = 0 (empty battery),
both discharge and self-discharge increment the
DCR.

After RM = 0, only discharge increments

the DCR. The DCR resets to 0 when RM = FCC.
The DCR does not roll over but stops counting
when it reaches FFFFh.

The DCR value becomes the new FCC value on the
first charge after a valid discharge to V

EDV1

if:

No valid charge initiations (charges greater than
10mAh, where V

SRO

> |V

SRD

|) occurred during

the period between RM = FCC and EDV1 de-
tected.

The self-discharge count is not more than
256mAh.

The temperature is

273°K (0°C) when the

EDV1 level is reached during discharge.

The valid discharge flag (VDQ) indicates whether
the present discharge is valid for FCC update. FCC
cannot be reduced by more than 256mAh during
any single cycle.

Charge Counting

Charge activity is detected based on a positive voltage
on the V

input.

If charge activity is detected, the

bq2092 increments RM at a rate proportional to V

SRO

and, if enabled, activates an LED display.

Charge

actions increment the RM after compensation for charge
rate and temperature.

The bq2092 determines charge activity sustained at a
continuous rate equivalent to V

SRO

> |V

SRD

|. A valid

charge equates to sustained charge activity
greater than 10 mAh. Once a valid charge is detected,
charge counting continues until V

SRO

falls below

S R D

is a programmable threshold as

described in the Digital Magnitude Filter section.

Discharge Counting

All discharge counts where V

SRO

< |V

SRD

| cause the

RM register to decrement and the DCR to increment.
V

SRD

is a programmable threshold as described in the

Digital Magnitude Filter section.

Self-Discharge Estimation

The bq2092 continuously decrements RM and incre-
ments DCR for self-discharge based on time and
temperature. The self-discharge rate is dependent on
the battery chemistry. The bq2092 self-discharge esti-
mation rate is externally programmed in EEPROM

bq2092

Rate and

Temperature

Compensation

Temperature

Compensation

Charge
Current

Discharge

Current

Self-Discharge

Timer

Remaining

Capacity

(RM)

Full

Charge

Capacity

(FCC)

Discharge

Count

(DCR)

Qualified

Transfer

Temperature, Other Data

Inputs

Main Counters

and Capacity

Reference (FCC)

Outputs

Two-Wire

Serial Interface

Chip-Controlled

Available Charge

LED Display

Rate and

Temperature

Compensation

Figure 2. Operational Overview

and can be programmed from 0 to 25% per day at
20-30°C. This rate doubles every 10°C increase until T
> 70

°C or is halved every 10° decrease until T < 10°C.

The self-discharge estimate reduces RM by 0.39% of its
current value at time intervals spaced so that the aver-
age reduction equals the programmed value adjusted for
temperature. The EEPROM program constant is the 2's
complement of 52 73

X , where X

day

= %

self-discharge

rate desired at 25

°C.

Charge Control

The bq2092 supports SBD charge control by broadcast-
ing ChargingCurrent() and ChargingVoltage() to the
Smart Charger address. Smart Charger broadcasts can
be disabled by writing bit 14 of Battery Mode() to 1. The
bq2092-based charge control can be enabled by setting
bit 4 in FLAGS2 (MSB of 0x2f) to 1. See Programming
the bq2092 for further details. If the Fully_Charged bit
is not set in BatteryStatus, the bq2092 broadcasts the
fast charge current and voltage to the Smart Charger.
The bq2092 broadcasts the maintenance current values
(trickle rate) if the Fully_Charged bit is set or Voltage is
below EDVF.

The bq2092 internal charge control is compatible with
nickel-based and Li-Ion chemistries.

For Li-Ion, the bq2092 broadcasts the required Charg-
ingCurrent and ChargingVoltage according to the values
programmed in the external EEPROM. During a valid
charge (VQ = 1), the bq2092 signals a valid charge
termination when the Terminate_Charge_Alarm and
Fully_Charged bits are set in BatteryStatus. These bits
are set when the battery is charged more than 256mAh
above FCC.

For nickel-based chemistries, the bq2092 broadcasts the
required charge current and voltage according to the
programmed values in the external EEPROM.

Maxi-

mum temperature and

T/t are used as valid charge

termination methods. Note: Nickel-based chemistries
require a charge voltage higher than the maximum cell
voltage during charge to ensure constant-current charg-
ing. During a valid charge (VQ = 1), if the bq2092 deter-
mines a maximum temperature condition, a

T/t rate

greater than the programmed value, or a charge state
greater than 256mAh above FCC, then the Termi-
n a t e _ C h a r g e _ A l a r m , O v e r _ C h a r g e _ A l a r m , a n d
Fully_Charged bits are set in BatteryStatus.

Once the bq2092 detects a valid charge termination, the
Fully_Charged bit, Terminate_Charge_Alarm, and
Over_Charge_Alarm bits are set and the ChargingCurrent
is set to zero. Once the terminating condition ceases, the
Terminate_Charge_Alarm and OverCharge Alarm bits are
cleared and the ChargingCurrent is set to the maintenance
rate. The bq2092 requests the maintenance current and
charging voltage until RM falls below the full charge

percentage. Once this occurs, the Fully_Charged bit is
cleared, and the bq2092 requests the fast charging current
and charging voltage.

During fast charge, the bq2092 suspends charge by
requesting zero current and setting the Termi-
nate_Charge_Alarm bit in BatteryStatus.

Charge is

suspended if the actual charge current is 25% greater
t h a n t h e p r o g r a m m e d ch a r g e d c u r r e n t .

I f t h e

programmed charge current is less than 1024mA, over-
current suspend occurs if the actual charge current is
256mA greater than the programmed value. Charge is
also suspended if the actual battery voltage is 5%
greater than the programmed charge voltage.

If the

battery temperature is greater than the programmed
maximum temperature before charge, then the bq2092
suspends charge requests until the temperature falls
below 50°C.

If the battery temperature is less than 0°C, the charging
current sets to maintenance (trickle) charge current.
The fast charging current is requested when the
temperature is above 5

°C.

T/t

The

T/t used by the bq2092 is programmable in both

the temperature step (1.6

°C4.6°C) and time step (20

seconds320seconds). Typical settings for 1

°C/min

include 2

°C over 120 seconds and 3°C over 180 seconds.

Longer times are required for increased slope resolution.

is set by the formula:

(

)

[

]

lower nibble of 0 13 in E PROM

lower nibble

2' s

(

)

[

]

of 0 1f in E PROM

minute

3 33

In addition to the

T/t timer, there is a hold-off timer,

which starts when the battery is being charged at more
than 256mA and the temperature is above 25

°C. (This is

valid only for NiMH chemistry, bit 5 in FLAGS2 set to
0.) Until this timer expires,

T/t is suspended. If the

temperature falls below 25

°C, or if charging current

fallls below 255mA, the timer is reset and restarts only
if the above conditions are once again met.

Safety Termination

If charging continues for more than

256mAh beyond

R M = F C C, t h e Te r m i n a t e _ C h a r g e _ A l a r m a n d
Fully_Charged bits are set, and the charging current is
modified to request maintenance current. If the battery
is discharged from full by less than 256mAh, then the
safety overcharge termination, for NiMH only, is allowed
to extend to 512 mAh.

Updating RM after a valid charge termination, RM may
optionally be set to a value from 0 to 100% of the Full-
ChargeCapacity. If RM is below the value programmed

bq2092

in full charge percentage, RM is set to full charge
percentage of FCC on valid charge termination. If RM is
above the full charge percentage, RM is not modified.

Count Compensations

Charge activity is compensated for temperature and
state-of-charge before updating the RM and/or DCR. RM
is compensated for temperature before updating the RM
register.

Self-discharge estimation is compensated for

temperature before updating RM or DCR.

Charge Compensation

Charge efficiency is compensated for state-of-charge,
temperature, and battery chemistry. For Li-Ion chemis-
try cells, the charge efficiency is unity for all cases. The
charge efficiency for nickel chemistry cells, however, is
adjusted using the following equation:

EFC

(

)

where RelativeStateofCharge

FullChargePercentage

and Q

EFC

is the programmed fast charge efficiency vary-

ing from .75 to .99.

ETC

(

)

where RelativeStateofCharge

FullChargePercentage

and Q

ETC

is the programmed maintenance (trickle)

charge efficiency varying from 0.50 to 0.97.

is used to adjust the charge efficiency as the battery

temperature increases according to the following:

if T

°C

0 02

0 05

Remaining Capacity Compensation

The bq2092 adjusts the RM as a function of tempera-
ture. This adjustment accounts for the reduced capacity
of the battery at colder temperatures. The following
equation is used to adjust RM:

If T

RemainingCapacity

Nominal Available Capacity (NAC)

If T < 5°C

RM()

NAC()

TCC

5 C))

- °

(

Where T = temperature

°C

TCC = 0.004

RM adjusts upward to Nominal Available Capacity as
the temperature increases.

Digital Magnitude Filter

The bq2092 has a programmable digital filter to elimi-
nate charge and discharge counting below a set
threshold. Table 2 shows typical digital filter settings.
The proper digital filter setting can be calculated
using the following equation.

SRD

(mV)| = 45 / DMF

Error Summary

Capacity Inaccurate

The FCC is susceptible to error on initialization or if no
updates occur. On initialization, the FCC value includes
the error between the design capacity and the actual
capacity. This error is present until a valid discharge
occurs and FCC is updated (see the DCR description on
page 6). The other cause of FCC error is battery wear-
out. As the battery ages, the measured capacity must be
adjusted to account for changes in actual battery capac-
ity.

Periodic discharges from full to empty will mini-

mize errors in FCC.

Current-Sensing Error

Table 3 illustrates the current-sensing error as a func-
tion of V

A digital filter eliminates charge and

discharge counts to the RM register when V

SRO

between V

SRQ

and V

SRD

Display

The bq2092 can directly display capacity information
using low-power LEDs. The bq2092 displays the battery
charge state in either absolute or relative mode. In rela-
tive mode, the battery charge is represented as a
percentage of the FCC. Each LED segment represents
25% of the FCC.

bq2092

DMF

Hex.

SRD

(mV)|

±0.60

100

±0.45

150 (default)

±0.30

175

±0.26

200

±0.23

Table 2. Typical Digital Filter Settings

In absolute mode, each segment represents a fixed
amount of charge, 25% of the design capacity. As the
battery wears out over time, it is possible for the FCC to
be below the design capacity.

In this case, all of the

LEDs may not turn on in absolute mode, representing
the reduction in the actual battery capacity.

The displayed capacity is compensated for the present
battery temperature. The displayed capacity varies as
temperature varies, indicating the available charge at
the present conditions.

When DISP is tied to V

, the SEG

outputs are inac-

tive. When DISP is left floating, the display becomes
active whenever the bq2092 detects a charge rate of
100mA or more. When pulled low, the segment outputs
become active immediately for a period of approximately
4 seconds. The DISP pin must be returned to float or
V

to reactivate the display.

The segment outputs are modulated as two banks of two,
with segments 1 and 3 alternating with segments 2 and 4.
The segment outputs are modulated at approximately
100Hz with each segment bank active for 30% of the period.

SEG

blinks at a 4Hz rate whenever V

has been

detected to be below V

EDV1

(EDV

= 1), indicating a low-

battery condition. V

below V

EDVF

(EDV

= 1) disables

the display output.

Microregulator

The bq2092 can operate directly from three nickel chem-
istry cells. To facilitate the power supply requirements
of the bq2092, an REF output is provided to regulate an
external low-threshold n-FET. A micropower source for
the bq2092 can be inexpensively built using the FET
and an external resistor; see Figure 1.

Note that an

optional zener diode may be necessary to limit V

during charge.

Communicating With the bq2092

The bq2092 includes a simple two-pin (SCC and SCD)
bidirectional serial data interface. A host processor uses

the interface to access various bq2092 registers; see
Table 4. This allows battery characteristics to be easily
monitored. The open-drain SCD and SCC pins on the
bq2092 are pulled up by the host system, or may be
connected to V

, if the serial interface is not used.

The interface uses a command-based protocol, where the
host processor sends the battery address and an eight-
bit command byte to the bq2092. The command directs
the bq2092 to either store the next data received to a
register specified by the command byte or output the
data specified by the command byte.

bq2092 Data Protocols

The host system, acting in the role of a Bus master, uses
the read word and write word protocols to communicate
integer data with the bq2092. (See Figure 3.)

Host-to-bq2092 Message Protocol

The Bus Host communicates with the bq2092 using one
of three protocols:

Read word

Write word

Read block

The particular protocol used is a function of the
command. The protocols used are shown in Figure 3.

Host-to-bq2092 Messages (see Table 4)

ManufacturerAccess() (0x00)

This optional function is not operational for the bq2092.

RemainingCapacityAlarm() (0x01)

This function sets or returns the low-capacity alarm
value.

When RM falls below the RemainingCapac-

ityAlarm value, the Remaining_Capacity_Alarm bit
is set in BatteryStatus (0x16). The system may alter
this alarm value during operation.

Symbol

Parameter

Typical

Maximum

Units

Notes

Offset referred to V

± 50

± 150

µV

DISP = V

INL

Integrated non-linearity
error

± 2

± 4

Add 0.1% per °C above or below 25°C
and 1% per volt above or below 4.25V.

INR

Integrated non-
repeatability error

± 1

± 2

Measurement repeatability given
similar operating conditions.

Table 3. bq2092 Current-Sensing Errors

bq2092

Function

Code

Access

Units

Defaults

ManufacturerAccess

0x00

read/write

RemaningCapacityAlarm

0x01

read/write

unsigned int.

RemainingTimeAlarm

0x02

read/write

unsigned int.

BatteryMode

0x03

read/write

bit flag

Temperature

0x08

read

0.1°K

Voltage

0x09

read

Current

0x0a

read

0000h

AverageCurrent

0x0b

read

0000h

MaxError

0x0c

read

percent

100

RelativeStateOfCharge

0x0d

read

percent

0000h

AbsoluteStateOfCharge

0x0e

read

percent

0000h

RemainingCapacity

0x0f

read

mAh

0000h

FullChargeCapacity

0x10

read

mAh

RunTimeToEmpty

0x11

read

minutes

AverageTimeToEmpty

0x12

read

minutes

Reserved

0x13

ChargingCurrent

0x14

read

ChargingVoltage

0x15

read

BatteryStatus

0x16

read

number

0000h

CycleCount

0x17

read

count

DesignCapacity

0x18

read

mAh

DesignVoltage

0x19

read

SpecificationInfo

0x1a

read

number

ManufactureDate

0x1b

read

unsigned int

SerialNumber

0x1c

read

number

Reserved

0x1d - 0x1f

ManufacturerName

0x20

read

string

DeviceName

0x21

read

string

DeviceChemistry

0x22

read

string

ManufacturerData

0x23

read

string

FLAGS1 and FLAGS2

0x2f

read

bit flag

Endof DischargeVoltage1

0x3e

read

EndofDischargeVoltageFinal

0x3f

read

Note:

Defaults after reset or power-up.

Table 4. bq2092 Register Functions

bq2092

Input/Output: unsigned integer. This sets/re-

turns the value where the Remaining Ca-
pacity Alarm bit is set in BatteryStatus.

RemainingTimeAlarm() (0x02)

This function sets or returns the low remaining time
alarm value. When the AverageTimeToEmpty (0x12)
falls below this value, the Remaining_Time_Alarm bit in
BatteryStatus is set. The default value for this register
is set in EEPROM. The system may alter this alarm
value during operation.

Input/Output: unsigned integer. This sets/returns
the value where the Remaining_Time_Alarm bit is
set in BatteryStatus.

BatteryMode() (0x03)

This read/write word selects the various battery opera-
tional modes. The bq2092 supports the battery capacity
information specified in mAh. This function also deter-
mines whether the bq2092 charging values are broad-
casted to the Smart Battery Charger address.

Writing bit 14 to 1 disables voltage and current Smart
Battery Charger messages. Bit 14 is reset to 0 once the
pack is removed from the system (SCC and SCD = 0 for
greater than 2 seconds.)

Writing bit 13 to 1 disables all Smart Battery Charger
messages including alarm messages. This bit remains set
until overwritten. Programming bit 3 of FLAGS2 in
EEPROM (EE 0x0b) initializes bit 13 of BatteryMode to 1.

Temperature() (0x08)

This read-only word returns the cell-pack's internal
temperature (0.1°K).

Output: unsigned integer. Returns cell tempera-
ture in tenths of degrees Kelvin increments

Units: 0.1°K

Range: 0 to +500.0°K

Granularity: 0.5°K or better

Accuracy:

±3°K after calibration

Voltage() (0x09)

This read-only word returns the cell-pack voltage (mV).

Output: unsigned integer. Returns battery terminal
voltage in mV

Units: mV

Range: 0 to 65,535 mV

Granularity: 0.2% of DesignVoltage

Accuracy:

±1% of DesignVoltage after calibration

Current() (0x0a)

This read-only word returns the current through the
battery's terminals (mA).

Output:

signed integer. Returns the charge/dis-

charge rate in mA, where positive is for charge
and negative is for discharge

Units: mA

Range: 0 to 32,767 mA for charge or 0 to

32,768 mA for discharge

Granularity: 0.2% of the DesignCapacity or better

Accuracy:

±1% of the DesignCapacity after calibration

AverageCurrent() (0x0b)

This read-only word returns a rolling average of the
current through the battery's terminals. For the bq2092
Current = AverageCurrent. The AverageCurrent func-
tion returns meaningful values after the battery's first
minute of operation.

Output:

signed integer. Returns the charge/dis-

charge rate in mA, where positive is for charge
and negative is for discharge

Units: mA

Range: 0 to 32,767 mA for charge or 0 to
32,768 mA for discharge

Granularity: 0.2% of the DesignCapacity or better

Accuracy:

±1% of the DesignCapacity after cali-

bration

MaxError() (0x0c)

This read-only word returns the expected margin of
error (%).

Output: unsigned integer. Returns percent uncer-
tainty

Units: %

Range: 0 to 100%

RelativeStateOfCharge() (0x0d)

This read-only word returns the predicted remaining
battery capacity expressed as a percentage of FullChar-
geCapacity (%).

RelativeStateOfCharge is only

valid for battery capacities less than 10,400mAh.

Output: unsigned integer. Returns the percent of re-
maining capacity

bq2092

Units: %

Range: 0 to 100%

Granularity: 1%

AbsoluteStateOfCharge() (0x0e)

This read-only word returns the predicted remaining
battery capacity expressed as a percentage of DesignCa-
pacity (%). Note that AbsoluteStateOfCharge can return
values greater than 100%. Absolute StateOfCharge
is only valid for battery capacities less than
10,400mAh.

Output: unsigned integer. Returns the percent of
remaining capacity.

Units: %

Range: 0 to 65,535 %

Granularity: 1% or better

Accuracy:

±MaxError

RemainingCapacity() (0x0f)

This read-only word returns the predicted remaining
battery capacity.

The RemainingCapacity value is

expressed in mAh.

Output: unsigned integer. Returns the estimated re-
maining capacity in mAh.

Units: mAh

Range: 0 to 65,535 mAh

Granularity: 0.2% of DesignCapacity or better

FullChargeCapacity() (0x10)

This read-only word returns the predicted pack capacity
when it is fully charged. FullChargeCapacity defaults to
the value programmed in the external EEPROM until a
new pack capacity is learned.

Output: unsigned integer. Returns the estimated full
charge capacity in mAh.

Units: mAh

Range: 0 to 65,535 mAh

Granularity: 0.2% of DesignCapacity or better

RunTimeToEmpty() (0x11)

This read-only word returns the predicted remaining
battery life at the present rate of discharge (minutes).
The RunTimeToEmpty() value is calculated based on
Current().

Output: unsigned integer. Returns the minutes of
operation left.

Units: minutes

Range: 0 to 65,534 minutes

Granularity: 2 minutes or better

Invalid data indication: 65,535 indicates battery is
not being discharged

AverageTimeToEmpty() (0x12)

This read-only word returns the predicted remaining
battery life at the present average discharge rate
(minutes).

The AverageTimeToEmpty is calculated

based on AverageCurrent.

Output: unsigned integer. Returns the minutes of
operation left.

Units: minutes

Range: 0 to 65,534 minutes

Granularity: 2 minutes or better

Invalid data indication: 65,535 indicates battery
is not being charged

ChargingCurrent() (0x14)

If enabled, the bq2092 sends the desired charging rate
in mA to the Smart Battery Charger.

Output:

unsigned integer.

Transmits/returns the

maximum charger output current in mA.

Units: mA

Range: 0 to 65,534 mA

Granularity: 0.2% of the design capacity or better

Invalid data indication: 65,535 indicates that the
Smart Charger should operate as a voltage source
outside its maximum regulated current range.

ChargingVoltage() (0x15)

If enabled, the bq2092 sends the desired voltage in mV
to the Smart Battery Charger.

Output: unsigned integer. Transmits/returns the
charger voltage output in mV.

Units: mV

Range: 0 to 65,534mV

Granularity: 0.2% of the DesignVoltage or better

Invalid data indication: 65,535 indicates that the
Smart Battery Charger should operate as a cur-

bq2092

rent source outside its maximum regulated voltage
range.

BatteryStatus() (0x16)

This read-only word returns the BatteryStatus word.

Output: unsigned integer. Returns the status reg-
ister with alarm conditions bitmapped as shown in
Table 5.

Some of the BatteryStatus flags (Remaining_Capac-
ity_Alarm and Remaining_Time_Alarm) are calculated
based on current. See Table 8 for definitions.

CycleCount() (0x17)

This

read-only

word

returns

the

number

charge/discharge cycles the battery has experienced.

charge/discharge cycle starts from a base value equivalent
to the battery's state-of-charge, on completion of a charge
cycle. The bq2092 increments the cycle counter during the
current charge cycle, if the battery has been discharged
15% below the state-of-charge at the end of the last charge
cycle. This prevents false reporting of small
charge/discharge cycles.

Output:

unsigned integer. Returns the count of

charge/discharge cycles the battery has
experienced.

Units: cycles

Range: 0 to 65,535 cycles; 65,535 indicates battery
has experienced 65,535 or more cycles

Granularity: 1 cycle

DesignCapacity() (0x18)

This read-only word returns the theoretical capacity of a
new pack. The DesignCapacity() value is expressed in
mAh at the nominal discharge rate.

Output: unsigned integer. Returns the battery ca-
pacity in mAh.

Units: mAh

Range: 0 to 65,535 mAh

DesignVoltage() (0x19)

This read-only word returns the theoretical voltage of
a new pack in mV.

Output: unsigned integer. Returns the battery's
normal terminal voltage in mV.

Units: mV

Range: 0 to 65,535 mV

SpecificationInfo() (0x1a)

This read-only word returns the specification revision
the bq2092 supports. It is typically set to all zeros to
represent non-Rev 1.0 compliance to the SMBus speci-
fication output: unsigned integer.

ManufactureDate() (0x1b)

This read-only word returns the date the cell was manu-
factured in a packed integer word. The date is packed
as follows: (year - 1980)

512 + month 32 + day.

Field

Bits

Used

Format

Allowable Value

Day

5-bit binary

value

131 (corresponds to
date)

Month

4-bit binary

value

112 (corresponds to
month number)

Year

915

7-bit binary

value

0127 (corresponds
to year biased by
1980)

SerialNumber() (0x1c)

This read-only word returns a serial number.

This

number, when combined with the ManufacturerName,
the DeviceName, and the ManufactureDate, uniquely
identifies the battery.

Output: unsigned integer

bq2092

Alarm Bits

0x8000

Overcharge_Alarm

0x4000

Terminate_Charge_Alarm

0x2000

Reserved

0x1000

Over_Temp_Alarm

0x0800

Terminate_Discharge_Alarm

0x0400

Reserved

0x0200

Remaining_Capacity_Alarm

0x0100

Remaining_Time_Alarm

Status Bits

0x0080

Initialized

0x0040

Discharging

0x0020

Fully_Charged

0x0010

Fully_Discharged

Error Code

0x0000-

0x000f

Reserved for error codes

Table 5. Status Register

ManufacturerName() (0x20)

This read-only string returns a character string where the
first byte is the number of characters available. The maxi-
mum number of characters is 15. The character string
contains the battery manufacturer's name. For example,
"Unitrode" identifies the battery pack manufacturer as
Unitrode.

Output: string or ASCII character string

DeviceName() (0x21)

This read-only string returns a character string where the
first byte is the number of characters available. The maxi-
mum number of characters is 15. The 15-byte character
string contains the battery's name.

For example, a

DeviceName of "bq2092" indicates that the battery is a
model bq2092.

Output: string or ASCII character string

DeviceChemistry() (0x22)

This read-only string returns a character string where
the first byte is the number of characters available. The
maximum number of characters is 15. The 15-byte char-
acter string contains the battery's chemistry. For exam-
ple, if the DeviceChemistry function returns "NiMH,"
the battery pack contains nickel-metal hydride cells.

Output: string or ASCII character string

ManufacturerData() (0x23)

This read-only string allows access to an up to 15-byte
manufacturer data string.

Output: block data--data whose meaning is as-
signed by the Smart Battery's manufacturer.

EndofDischargeVoltage1() (0x3e)

This read-only word returns the first end-of-discharge
voltage programmed for the pack.

Output: two's complemented unsigned integer. Re-
turns battery end-of-discharge voltage pro-
grammed in EEPROM in mV.

EndofDischargeVoltageF() (0x3f)

This read-only word returns the final end-of-discharge
voltage programmed for the pack.

Output:

two's complemented unsigned integer.

Returns battery final end-of-discharge voltage pro-
grammed in EEPROM in mV.

FLAGS1&2() (0x2f)

This read-only register returns an unsigned integer
representing the internal status registers of the bq2092.
The MSB represents FLAGS2, and the LSB represents
FLAGS1.

See Table 6 for the bit description for

FLAGS1 and FLAGS2.

FLAGS2

The Display Mode flag (DMODE), bit 7, determines
whether the bq2092 displays Relative or Absolute capac-
ity.

The DMODE values are:

FLAGS2 Bits

DMODE

Where DMODE is:

Selects Absolute display

Selects Relative display

Bit 6 is reserved.

The Chemistry flag (CHM), bit 5, selects Li-Ion or nickel
compensation factors.

The CHM values are:

FLAGS2 Bits

CHM

bq2092

(MSB) 7

0 (LSB)

FLAGS2 DMODE

CHM

LTF

FLAGS1

WRINH

VDQ

SEDV

EDV1

EDVF

Note: - = Reserved

Table 6. Bit Descriptions for FLAGS1 and FLAGS2

Where CHM is:

Selects Nickel

Selects Li-Ion

Bit 4, the Charge Control flag (CC), determines whether
a bq2092-based charge termination will set RM to a
user-defined programmable full charge capacity.

The CC values are:

Where CC is:

RM is not modified on valid bq2092
charge termination

RM is set to a programmable percentage of
the FCC when a valid bq2092 charge termi-
nation occurs

Bit 3 is reserved.

Bit 2, the Overvoltage flag (OV), is set when the bq2092
detects a pack voltage 5% greater than the programmed
charging voltage. This bit is cleared when the pack volt-
age falls 5% below the programmed charging voltage.

The OV values are:

Where OV is:

BatteryVoltage() < 1.05

ChargingVoltage

BatteryVoltage()

1.05 ChargingVoltage

Bit 1, the Low Temperature Fault flag (LTF), is set when
temperature < 0°C and cleared when temperature > 5°C.

The LTF values are:

Where LTF is:

Temperature > 5°C

Temperature < 0°C

Bit 0, the Overcurrent flag (OC), is set when the average
current is 25% greater than the programmed charging
current. If the charging current is programmed less than
1024mA, overcurrent is set if the average current is
256mA greater than the programmed charging current.

This flag is cleared when the average current falls below
256mA.

The OC values are:

Where OC is:

Average current is less than 1.25

charg-

ing current or less than 256mA if charging
current is programmed less than 1024mA

Average current exceeds 1.25

charging

current or 256mA if the charging current is
programmed less than 1024mA. This bit is
cleared if average current < 256mA

FLAGS1

Bits 7 and 6 are reserved. The Valid Charge flag (VQ),
bit 5, is set when V

SRO

SRD

| and 10mAh of charge

has accumulated. This bit is cleared during a discharge
and when V

SRO

SRD

The VQ values are:

Where VQ is:

SRO

|VSRD

SRO

SRD

| and 10mAh of charge has

accumulated

The Write Inhibit flag (WRINH), bit 4, allows or inhibits
writes to all registers.

The WRINH values are:

Where WRINH is:

Allows writes to all registers

Inhibits all writes and secures the bq2092
from invalid/undesired writes.

bq2092

FLAGS2 Bits

FLAGS1 Bits

WRINH

FLAGS2 Bits

WRINH should be set at the time of pack assembly and
tested to prevent special read-write registers from acci-
dental over-writing.

The Valid Discharge flag (VDQ), bit 3, is set when a
valid discharge is occurring (discharge cycle valid for
learning new full charge capacity) and cleared if a
partial charge is detected, EDV1 is asserted when T <
0°C, or self-discharge accounts for more than 256mAh of
the discharge.

The VDQ values are:

Where VDQ is:

Self-discharge is greater than 256mAh,
EDV1 = 1 when T < 0°C or VQ = 1

On first discharge after RM=FCC

The Stop EDV flag (SEDV), bit 2, is set when the
discharge current > 6.15A and cleared when the
discharge current falls below 6.15A.

The SEDV values are:

Where SEDV is:

Current < 6.15A

Current > 6.15A

The First End-of-Discharge Voltage flag (EDV1), bit 1, is
set when Voltage < EDV1 = 1 if SEDV = 0 and cleared
when VQ = 1 and Voltage > EDV1.

The EDV1 values are:

Where EDV1 is:

VQ = 1 and Voltage > EDV1

Voltage < EDV1 and SEDV = 0

The Final End-of-Discharge Voltage flag (EDVF), bit 0, is
set when Voltage < EDVF = 1 if SEDV = 0 and cleared
when VQ = 1 and Voltage() > EDVF.

The EDVF values are:

Where EDVF is:

VQ = 1 and Voltage > EDVF

Voltage < EDVF and SEDV = 0

Software Reset

The bq2092 can be reset over the serial port by confirm-
ing that the WRINH bit is set to zero in FLAGS1, writ-
ing MaxError (0x0c) to any value other than 2, and writ-
ing the reset register (0x44) to 8009, causing the bq2092
to reinitialize and read the default values from the
external EEPROM.

Error Codes and Status Bits

Error codes and status bits are listed in Table 7 and
Table 8, respectively.

Programming the bq2092

The bq2092 requires the proper programming of an
external EEPROM for proper device operation.

Each

module can be calibrated for the greatest accuracy, or
general "default" values can be used. A programming
kit (interface board, software, and cable) for an IBM-
compatible PC is available from Unitrode.

Please

contact Unitrode for further details

The bq2092 uses a 24LC01 or equivalent serial
EEPROM for storing the various initial values, calibra-
tion data, and string information. Table 1 outlines the
parameters and addresses for this information. Tables 9
and 10 detail the various register contents and show an
example program value for an 1800mAh NiMH battery
pack, using a 50m

sense resistor.

bq2092

FLAGS1 Bits

SEDV

FLAGS1 Bits

EDV1

FLAGS1 Bits

VDQ

FLAGS1 Bits

EDVF

Alarm Bits

Bit Name

Set When:

Reset When:

OVER_CHARGE_ALARM

bq2092 detects over-temperature or

t. (Note: valid charge termina-
tion).

A discharge occurs or when

T/t, or

over-temperature, ceases during
charge.

TERMINATE_CHARGE_ALARM

bq2092 detects over-current, over-
voltage, over-temperature, or

T/t

conditions exist during charge.
Charging current is set to zero, indi-
cating a charge suspend.

A discharge occurs or when all condi-
tions causing the event cease.

T/t_ALARM

bq2092 detects the rate-of-
temperature increase is above the pro-
grammed value (valid termination)

The temperature rise falls below the
programmed rate.

OVER_TEMP_ALARM

bq2092 detects that its internal tem-
perature is greater than the pro-
grammed value (valid termination).

Internal temperature falls below
50°C.

TERMINATE_DISCHARGE_ALARM

bq2092 determines that it has sup-
plied all the charge that it can with-
out being damaged (EDVF).

BAT

> V

EDVF

signifying that the

battery has reached a state of charge
sufficient for it to once again safely
supply power.

REMAINING_CAPACITY_ALARM

bq2092 detects that the Remaining-
Capacity() is less than that set by
the RemainingCapacity() function.

Either the value set by the Remain-
ingCapacityAlarm() function is lower
than the Remaining Capacity() or
the RemainingCapacity() is in-
creased by charging.

REMAINING_TIME_ALARM

bq2092 detects that the estimated
remaining time at the present dis-
charge rate is less than that set by
the RemainingTimeAlarm() function.

Either the value set by the Remain-
ingTimeAlarm() function is lower
than the AverageTimeToEmpty() or
a valid charge is detected.

Status Bits

Bit Name

Set When:

Reset When:

INITIALIZED

bq2092 is set when the bq2092 has
reached a full or empty state.

Battery detects that power-on or
user-initiated reset has occurred.

DISCHARGING

bq2092 determines that it is not be-
ing charged.

Battery detects that it is being
charged.

FULLY_CHARGED

bq2092 determines a valid charge
termination. RM will then be set to
full charge percentage if necessary.

RM discharges below the full charge
percentage

FULLY_DISCHARGED

bq2092 determines that it has
supplied all the charge that it can
without being damaged (that is, con-
tinued use will result in permanent
capacity loss to the battery)

RelativeStateOfCharge is greater
than or equal to 20%

Table 8. Status Bits

bq2092

Description

EEPROM

Address

EEPROM

Hex Contents

Example

Values

Notes

Low

Byte

High
Byte

Low

Byte

High
Byte

D e s i g n
C a p a c i t y

0x00

0x01

1800mAh

This sets the initial full charge battery capacity
stored in FCC. FCC is updated with the actual full
to empty discharge capacity after a valid discharge
from RM = FCC to Voltage() = EDV1.

Initial
Battery
Voltage

0x02

0x03

10800mV

This register is used to set the battery voltage on reset.

Fast charging
current

0x04

0x05

1800mA

This register is used to set the fast charge current for
the Smart Charger.

Fast charging
voltage

0x06

0x07

15300mV

This register is used to set the fast charge voltage for
the Smart Charger.

Remaining
Capacity
Alarm

0x08

0x09

180mAh

This value represents the low capacity alarm value.

FLAGS1

0x0a

FLAGS1 should be set to 10h before pack shipment to
inhibit undesirable writes to the bq2092. (WRINH = 1.)

FLAGS2

0x0b

Li-Ion = b0h

NiMH = 90h

See FLAGS2 register for the bit description and the
proper value for programming FLAGS2. Selects rela-
tive display mode, selects NiMH compensation factors,
and enables bq2092 Smart Charger control.

Current
Measurement
Gain

0x0c

0x0d

37.5/.05

The current gain measurement and current integration
gain are related and defined for the bq2092 current
measurement. 0x0c = 37.5/sense resistor value in
ohms.

EDV1

0x0e

0x0f

9450mV

(1.05V/cell)

The value programmed is the two's complement of the
threshold voltage in mV.

EDVF

0x10

0x11

9000mV

(1.0V/cell)

The value programmed is the two's complement of the
threshold voltage in mV.

Note:

Can be adjusted to calibrate the battery pack.

Table 9. Example Register Contents

bq2092

Description

EEPROM

Address

EEPROM

Hex

Contents

Example

Values

Notes

Low

Byte

High
Byte

Low

Byte

High
Byte

Temperature
Offset

0x12

5.0°C

The default value is 0x80 (12.8° + nominal value).
Actual temp (20°C) = Nominal temp. (15°C) - temp.
offset (5°C) where temperature determined by the
bq2092 can be adjusted from 0° to 25.5° (Tempera-
ture offset (0-255)

0 .1) + nominal value temp.

Maximum
Charge
Temperature,

Temp.

0x13

MaxT = 61.2°C

(74 - (8 * 1.6))

T = 3°C

((7*2) + 16)/10

Maximum charge temperature is 74 - (mt x 1.6)°C
(mt = upper nibble). The

T step is (dT*2+16)/10°C

(dT = lower nibble).

Self-
Discharge Rate

0x14

1.5%

This packed field is the two's complement of
52.73/x, where x = %/day is the self-discharge rate
desired at room temperature.

Digital
Filter

0x15

0.3mV

This field is used to set the digital magnitude filter
as described in Table 2.

Current
Integration
Gain

0x16

0x17

3.2/0.05

This field represents the following: 3.2/sense resis-
tor in ohms. It is used by the bq2092 to scale the
measured voltage values on the SR pin in mA and
mAh. This register also compensates for variations
in the reported sense resistor value.

Full Charge
Percentage

0x18

96% = 60h

2's (60h) = a0h

This packed field is the two's complement of the
desired value in RM when the bq2092 determines
a full charge termination. If RM is below this
value, RM is set to this value. If RM is above this
value, then RM is not adjusted.

Charge
Compensation

0x19

85% = mainte-

nance comp.

95% = fast

charge comp.

This packed value is used to set the fast charge and
maintenance charge efficiency for nickel-based batter-
ies. The upper nibble adjusts the maintenance charge
compensation; the lower nibble adjusts the fast
charge compensation.
Maintenance, upper nibble = (eff%

256 - 128)/8

Fast charge, lower nibble = (eff%

256 - 192)/4

Battery
Voltage
Offset

OFF

)

0x1a

10mV

This value is used to adjust the battery voltage offset
according to the following:
Voltage () = (V

(mV) + V

OFF

)

Voltage Gain

Voltage
Gain

0x1b

0x1c

9.09

Voltage gain is packed as two units. For example,
(R

+ R

)/R

= 9.09 would be stored as: whole num-

ber stored in 0x1b (=09h) and the decimal compo-
nent stored in 0x1c as 256 x 0.09 = 23.

Serial
Number

0x1d

0x1e

10002

This contains the optional pack serial number.

Table 9. Example Register Contents (Continued)

bq2092

bq2092

Description

EEPROM

Address

EEPROM

Hex Contents

Example

Values

Notes

Low

Byte

High
Byte

Low

Byte

High
Byte

Hold-off
Timer/
Time

0x1f

320 s hold-off

180 s

time

Hold-off time is 20 s

the two's complement of the

upper nibble value.

T is 20 s the two's comple-

ment of the lower nibble value.

Charge
Cycle
Count

0x20

0x21

This field contains the charge cycle count and should
be set to zero for a new battery.

Maintenance
Charge
Current

0x22

0x23

100mA

This field contains the desired maintenance current
after fast charge termination by the bq2092.

Reserved

0x24

0x31

Design
Voltage

0x32

0x33

10800mV

This is nominal battery pack voltage.

Specification
Information

0x34

0x35

This is the default value for this register.

Manufacturer
Date

0x36

0x37

May 1, 1996 =

8353

Packed per the ManufactureDate description, which
represents May 1, 1996 in this example.

Table 9. Example Register Contents (Continued)

String

Description

Address

Xb-Xf

Reserved

0x38-

0x3f

00-00

Manufacturer's
Name

0x40-
0x4f

00-00

Device Name

0x50-

0x5f

00-00

Chemistry

0x60-
0x6f

00-00

Manufacturer's
Data

0x70-
0x7f

00-00

Table 10. Example Register Contents (String Data)

Absolute Maximum Ratings

Symbol

Parameter

Minimum

Maximum

Unit

Notes

Relative to V

-0.3

+7.0

All other pins

Relative to V

-0.3

+7.0

REF

Relative to V

-0.3

+8.5

Current limited by R1 (see Figure 1)

Relative to V

-0.3

+7.0

Minimum 100

series resistor should

be used to protect SR in case of a
shorted battery (see the bq2092 appli-
cation note for details).

OPR

Operating tempera-
ture

+70

°C

Commercial

Note:

Permanent device damage may occur if Absolute Maximum Ratings are exceeded. Functional opera-
tion should be limited to the Recommended DC Operating Conditions detailed in this data sheet. Expo-
sure to conditions beyond the operational limits for extended periods of time may affect device reliability.

DC Voltage Thresholds

(TA = TOPR; V = 3.0 to 5.5V)

Symbol

Parameter

Minimum

Typical

Maximum

Unit

Notes

VSB

Battery voltage error relative to SB

-50mV

50mV

See note

Note:

The accuracy of the voltage measurement may be improved by adjusting the battery voltage offset and
gain, stored in external EEPROM. For proper operation, V

should be 1.5V greater than V

bq2092

Recommended DC Operating Conditions

(TA = TOPR)

Symbol

Parameter

Minimum

Typical

Maximum

Unit

Notes

Supply voltage

3.0

4.25

5.5

excursion from < 2.0V to

3.0V initializes the unit.

REF

Reference at 25°C

5.7

6.0

6.3

REF

= 5

µA

Reference at -40°C to +85°C

4.5

7.5

REF

= 5

µA

REF

Reference input impedance

2.0

5.0

REF

= 3V

135

µA

= 3.0V

Normal operation

120

180

µA

= 4.25V

170

250

µA

= 5.5V

Battery input

SBmax

SB input impedance

0 < V

< V

DISP

DISP input leakage

µA

DISP

= V

LVOUT

OUT

output leakage

-0.2

0.2

µA

EEPROM off

Sense resistor input

-0.3

2.0

< V

= discharge;

> V

= charge

SR input impedance

-200mV < V

< V

Logic input high

0.5

SCL, SDA

1.4

5.5

SCC, SCD

Logic input low

0.3

SCL, SDA

-0.5

0.6

SCC, SCD

Data, clock output low

0.4

=350

µA, SDA, SCD

Sink current

100

350

µA

0.4V, SDA, SCD

OLSL

SEG

output low, low V

0.1

= 3V, I

OLS

1.75mA

SEG

OLSH

SEG

output low, high V

0.4

= 5.5V, I

OLS

11.0mA

SEG

OHVL

OUT

output, low V

- 0.3

= 3V, I

VOUT

= -5.25mA

OHVH

OUT

output, high V

- 0.6

= 5.5V, I

VOUT

= -33.0mA

VOUT

OUT

source current

-33

At V

OHVH

= V

- 0.6V

OLS

SEG

sink current

11.0

At V

OLSH

= 0.4V

Note:

All voltages relative to V

bq2092

Symbol

Parameter

Min

Max

Units

Notes

SMB

SMBus operating frequency

100

KHz

BUF

Bus free time between stop and
start condition

4.7

µs

HD:STA

Hold time after (repeated) start
condition

4.0

µs

SU:STA

Repeated start condition setup
time

250

SCD

4.7

µs

External Memory

SU:STO

Stop condition setup time

4.0

µs

HD:DAT

Data hold time

µs

SU:DAT

Data setup time

250

EXT1

Data buffering time addresses

0x19, 0x1a, 0x1b

EXT2

String buffering time addresses
0x20-0x23 per character

40ms for first character

Data output delay time

300

3500

External memory only. See Note.

LOW

Clock low period

4.7

µs

HIGH

Clock high period

4.0

µs

Clock/Data fall time

300

Clock/data rise time

1000

Note:

The external memory must provide this internal minimum delay time to bridge the undefined region
(minimum 300 ns) of the falling edge of SCL to avoid unintended generation of START or STOP conditions.

AC Specifications

TD209201.eps

SU:STA

SCC

SCD

SU:STO

BUF

HD:STA

LOW

SU:DAT

HIGH

HD:DAT

(receiver)
(transmitter)

Bus Timing Data

bq2092

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1999, Texas Instruments Incorporated

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