LTC1960
1
1960f
DESCRIPTIO
U
FEATURES
APPLICATIO S
U
TYPICAL APPLICATIO
U
The LTC
1960 is a highly-integrated battery charger and
selector intended for portable products using dual smart
batteries. A serial SPI interface allows an external
microcontroller to control and monitor status of both
batteries.
A proprietary PowerPath architecture supports simulta-
neous charging or discharging of both batteries. Typical
battery run times are extended by 10%, while charging
times are reduced by up to 50%. The LTC1960 automati-
cally switches between power sources in less than 10
s to
prevent power interruption upon battery or wall adapter
removal.
The synchronous buck battery charger delivers 95%
efficiency with only 0.5V dropout voltage, and prevents
audible noise in all operating modes. Patented* input
current limiting with 5% accuracy charges batteries in the
shortest possible time without overloading the wall adapter.
The LTC1960's 36-pin narrow SSOP package allows
implementation of a complete SBS-compliant dual battery
system while consuming minimum PCB area.
, LTC and LT are registered trademarks of Linear Technology Corporation.
s
Complete Dual-Battery Charger/Selector System
s
Serial SPI Interface Allows External
C Control and
Monitoring
s
Simultaneous Dual-Battery Discharge Extends Run
Time by Typically 10%
s
Simultaneous Dual-Battery Charging Reduces
Charging Time by up to 50%
s
Automatic PowerPath
TM
Switching in <10
s
Prevents Power Interruption
s
Available in a 36-Pin Narrow SSOP Package
s
Circuit Breaker Protects Against Overcurrent Faults
s
5% Accurate Adapter Current Limit Maximizes
Charging Rate*
s
95% Efficient Synchronous Buck Charger
s
Charger has Low 0.5V Dropout Voltage
s
No Audible Noise Generation, even with Ceramic
Capacitors
s
11-Bit VDAC Delivers 0.8% Voltage Accuracy
s
10-Bit IDAC Delivers 5% Current Accuracy
s
V
IN
up to 32V; V
BATT
up to 28V
Dual Battery Charger/
Selector with SPI Interface
LTC1960 Dual Battery/Selector System Architecture
PowerPath is a trademark of Linear Technology Corporation.
*U.S. Patent No. 5,723,970
s
Portable Computers
s
Portable Instruments
LTC1960
MICROCONTROLLER
DC
IN
4
SYSTEM POWER
SMBus
1960 TA01
BAT2
BAT1
SPI
Dual vs Sequential Charging
TIME (MINUTES)
BATTERY CURRENT (mA)
3500
3000
2500
2000
1500
1000
500
0
3500
3000
2500
2000
1500
1000
500
0
1960 G10
0
50
100
150
200
250
300
BAT1
CURRENT
BAT2
CURRENT
SEQUENTIAL
DUAL
BAT1
CURRENT
100
MINUTES
BATTERY TYPE: 10.8V Li-Ion (MOLTECH NI2020)
REQUESTED CURRENT = 3A
REQUESTED VOLTAGE = 12.3V
MAX CHARGER CURRENT = 4.1A
BAT2
CURRENT
LTC1960
2
1960f
Voltage from DCIN, SCP, SCN, CLP, V
PLUS
,
SW to GND ................................................32V to 0.3V
Voltage from SCH1, SCH2 to GND .............28V to 0.3V
Voltage from BOOST to GND .....................41V to 0.3V
PGND with Respect to GND ..................................
0.3V
CSP, CSN, BAT1, BAT2 to GND ....................28V to 5V
LOPWR, DCDIV to GND .............................10V to 0.3V
SSB, SCK, MOSI, MISO to GND ................... 7V to 0.3V
COMP1 to GND ............................................ 5V to 0.3V
Operating Ambient Temperature
Range (Note 7) ........................................ 0
C to 70
C
Operating Junction Temperature .......... 40
C to 125
C
Storage Temperature ............................ 65
C to 150
C
Lead Temperature (Soldering, 10 sec).................. 300
C
ORDER PART
NUMBER
T
JMAX
= 125
C,
JA
= 85
C/W
Consult LTC marketing for parts specified with wider operating temperature ranges.
LTC1960CG
ABSOLUTE AXI U
RATI GS
W
W
W
U
PACKAGE/ORDER I FOR ATIO
U
U
W
(Note 1)
ELECTRICAL CHARACTERISTICS
The
q
denotes specifications which apply over the full operating
temperature range (Note 7), otherwise specifications are at T
A
= 25
C. V
DCIN
= 20V, V
BAT1
= 12V, V
BAT2
= 12V unless otherwise noted.
SYMBOL
PARAMETER
CONDITIONS
MIN
TYP
MAX
UNITS
Supply and Reference
DCIN Operating Range
DCIN Selected
6
28
V
I
CH
DCIN Operating Current
Not Charging (DCIN Selected)
1
1.5
mA
Charging (DCIN Selected)
1.3
2
mA
Battery Operating Voltage Range
Battery Selected, PowerPath Function (Note 2)
6
28
V
Battery Drain Current
Battery Selected, Not Charging, V
DCIN
= 0V
175
A
V
PLUS
Diodes Forward Voltage:
V
FDC
DCIN to V
PLUS
I
VCC
= 10mA
0.8
V
V
FB1
BAT1 to V
PLUS
I
VCC
= 0mA
0.7
V
V
FB2
BAT2 to V
PLUS
I
VCC
= 0mA
0.7
V
V
FSCN
SCN to V
PLUS
I
VCC
= 0mA
0.7
V
UVLO
Undervoltage Lockout Threshold
V
PLUS
Ramping Down, Measured at V
PLUS
to GND
q
3
3.5
3.9
V
UVHYS
UV Lockout Hysteresis
V
PLUS
Rising, Measured at V
PLUS
to GND
60
mV
V
VCC
V
CC
Regulator Output Voltage
5
5.2
5.4
V
V
LDR
V
CC
Load Regulation
I
VCC
= 0mA to 10mA
0.2
1
%
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
TOP VIEW
G PACKAGE
36-LEAD PLASTIC SSOP
36
35
34
33
32
31
30
29
28
27
26
25
24
23
22
21
20
19
SCH2
GCH2
GCH1
SCH1
TGATE
BOOST
SW
DCIN
V
CC
BGATE
PGND
COMP1
CLP
CSP
CSN
MOSI
MISO
SCK
V
PLUS
BAT2
BAT1
SCN
SCP
GDCO
GDCI
GB1O
GB1I
GB2O
GB2I
LOPWR
V
SET
I
TH
I
SET
GND
DCDIV
SSB
LTC1960
3
1960f
ELECTRICAL CHARACTERISTICS
The
q
denotes specifications which apply over the full operating
temperature range (Note 7), otherwise specifications are at T
A
= 25
C. V
DCIN
= 20V, V
BAT1
= 12V, V
BAT2
= 12V unless otherwise noted.
SYMBOL
PARAMETER
CONDITIONS
MIN
TYP
MAX
UNITS
Switching Regulator
V
TOL
Overall Voltage Accuracy
5V
V
OUT
< 25V, (Note 3)
0.8
0.8
%
q
1
1
%
I
TOL
Overall Current Accuracy
IDAC Value = 3FF
HEX
5
5
%
V
CSP
, V
CSN
= 12V
q
6
6
%
f
0SC
Regulator Switching Frequency
255
300
345
kHz
f
DO
Regulator Switching Frequency in Low
Duty Cycle
99%
20
25
kHz
Dropout Mode
DC
MAX
Regulator Maximum Duty Cycle
99
99.5
%
I
MAX
Maximum Current Sense Threshold
V
ITH
= 2.2V
140
155
190
mV
I
SNS
CA1 Input Bias Current
V
CSP
= V
CSN
> 5V
150
A
CMSL
CA1/I
1
Input Common Mode Low
0
V
CMSH
CA1/I
1
Input Common Mode High
V
DCIN
0.2
V
V
CL1
CL1 Turn-On Threshold
95
100
105
mV
TGATE Transition Time:
TG t
r
TGATE Rise Time
C
LOAD
= 3300pF, 10% to 90%
50
90
ns
TG t
f
TGATE Fall Time
C
LOAD
= 3300pF, 10% to 90%
50
90
ns
BGATE Transition Time:
BG t
r
BGATE Rise Time
C
LOAD
= 3300pF, 10% to 90%
50
90
ns
BG t
f
BGATE Fall Time
C
LOAD
= 3300pF, 10% to 90%
40
80
ns
Trip Points
V
TR
DCDIV/LOPWR Threshold
V
DCDIV
or V
LOPWR
Falling
q
1.166
1.19
1.215
V
V
THYS
DCDIV/LOPWR Hysteresis Voltage
V
DCDIV
or V
LOPWR
Rising
30
mV
I
BVT
DCDIV/LOPWR Input Bias Current
V
DCDIV
or V
LOPWR
= 1.19V
20
200
nA
V
TSC
Short-Circuit Comparator Threshold
V
SCP
V
SCN
, V
CC
5V
q
90
100
115
mV
V
FTO
Fast Power Path Turn-Off Threshold
V
DCDIV
Rising from V
CC
6
7
7.9
V
V
OVSD
Overvoltage Shutdown Threshold as a
V
SET
Rising from 0.8V until TGATE and BGATE
107
%
Percent of Programmed Charger Voltage
Stop Switching
DACs
I
RES
IDAC Resolution
Guaranteed Monotonic Above I
MAX
/16
10
bits
IDAC Pulse Period:
t
IP
Normal Mode
6
10
15
s
t
ILOW
Low Current Mode
50
ms
V
RES
VDAC Resolution
Guaranteed Monotonic (5V < V
BAT
< 25V)
11
bits
V
STEP
VDAC Granularity
16
mV
V
OFF
VDAC Offset
(Note 6)
0.8
V
t
VP
VDAC Pulse Period
7
11
16.5
s
LTC1960
4
1960f
ELECTRICAL CHARACTERISTICS
The
q
denotes specifications which apply over the full operating
temperature range (Note 7), otherwise specifications are at T
A
= 25
C. V
DCIN
= 20V, V
BAT1
= 12V, V
BAT2
= 12V unless otherwise noted.
SYMBOL
PARAMETER
CONDITIONS
MIN
TYP
MAX
UNITS
Charge Mux Switches
t
ONC
GCH1/GCH2 Turn-On Time
V
GCHX
V
SCHX
> 3V, V
SCHX
= TBD, C
LOAD
= 3nF
5
10
ms
t
OFFC
GCH1/GCH2 Turn-Off Time
V
GCHX
V
SCHX
< 1V, from Time of
3
7
s
V
CSN
< V
BATX
30mV, V
SCHX
= TBD, C
LOAD
= 3nF
V
CON
CH Gate Clamp Voltage
I
LOAD
= 1
A
GCH1
V
GCH1
V
SCH1
5
5.8
7
V
GCH2
V
GCH2
V
SCH2
5
5.8
7
V
V
COFF
CH Gate Off Voltage
I
LOAD
=10
A
GCH1
V
GCH1
V
SCH1
0.8
0.4
0
V
GCH2
V
GCH2
V
SCH2
0.8
0.4
0
V
V
TOC
CH Switch Reverse Turn-Off Voltage
V
CSN
V
BATX
,
5V
V
BATX
28V
q
5
20
40
mV
V
FC
CH Switch Forward Regulation Voltage V
BATX
V
CSN
,
5V
V
BATX
28V
q
15
35
60
mV
GCH1/GCH2 Active Regulation:
V
GCHX
V
SCHX
= 1.5V
I
OC(SRC)
Max Source Current
2
A
I
OC(SNK)
Max Sink Current
2
A
V
CHMIN
BATX Voltage Below Which
3.5
4.7
V
Charging is Inhibited (Does Not Apply
to Low Current Mode)
PowerPath Switches
t
DLY
Blanking Period after UVLO Trip
Switches Held Off
250
ms
t
PPB
Blanking Period after LOPWR Trip
Switches in 3-Diode Mode
1
sec
t
ONPO
GB1O/GB2O/GDCO Turn-On Time
V
GS
< 3V, from Time of Battery/DC
q
5
10
s
Removal, or LOPWR Indication
t
OFFPO
GB1O/GB2O/GDCO Turn-Off Time
V
GS
> 1V, from Time of Battery/DC
q
3
7
s
Removal, or LOPWR Indication
V
PONO
Output Gate Clamp Voltage
I
LOAD
= 1
A
GB1O
Highest (V
BAT1
or V
SCP
) V
GB1O
4.75
6.25
7
V
GB2O
Highest (V
BAT2
or V
SCP
) V
GB2O
4.75
6.25
7
V
GDCO
Highest (V
DCIN
or V
SCP
) V
GDCO
4.75
6.25
7
V
V
POFFO
Output Gate Off Voltage
I
LOAD
= 25
A
GB1O
Highest (V
BAT1
or V
SCP
) V
GB1O
0.18
0.25
V
GB2O
Highest (V
BAT2
or V
SCP
) V
GB2O
0.18
0.25
V
GDCO
Highest (V
DCIN
or V
SCP
) V
GDCO
0.18
0.25
V
V
TOP
PowerPath Switch Reverse
V
SCP
V
BATX
or V
SCP
V
DCIN
q
5
20
60
mV
Turn-Off Voltage
6V
V
SCP
28V
V
FP
PowerPath Switch Forward
V
BATX
V
SCP
or V
DCIN
V
SCP
q
0
25
50
mV
Regulation Voltage
6V
V
SCP
28V
GDCI/GB1I/GB2I Active Regulation
(Note 4)
I
OP(SRC)
Source Current
4
A
I
OP(SNK)
Sink Current
75
A
LTC1960
5
1960f
SYMBOL
PARAMETER
CONDITIONS
MIN
TYP
MAX
UNITS
t
ONPI
Gate B1I/B2I/DCI Turn-On Time
V
GS
< 3V, C
LOAD
= 3nF (Note 5)
300
s
t
OFFPI
Gate B1I/B2I/DCI Turn-Off Time
V
GS
> 1V, C
LOAD
= 3nF (Note 5)
10
s
V
PONI
Input Gate Clamp Voltage
I
LOAD
= 1
A
GB1I
Highest (V
BAT1
or V
SCP
) V
GB1I
4.75
6.7
7.5
V
GB2I
Highest (V
BAT2
or V
SCP
) V
GB2I
4.75
6.7
7.5
V
GDCI
Highest (V
DCIN
or V
SCP
) V
GDCI
4.75
6.7
7.5
V
V
POFFI
Input Gate Off Voltage
I
LOAD
= 25
A
GB1I
Highest (V
BAT1
or V
SCP
) V
GB1I
0.18
0.25
V
GB2I
Highest (V
BAT2
or V
SCP
) V
GB2I
0.18
0.25
V
GDCI
Highest (V
DCIN
or V
SCP
) V
GDCI
0.18
0.25
V
Logic I/O
I
IH
/I
IL
SSB/SCK/MOSI Input High/Low Current
q
1
1
A
V
IL
SSB/MOSI/SCK Input Low Voltage
q
0.8
V
V
IH
SSB/MOSI/SCK Input High Voltage
q
2
V
V
OL
MISO Output Low Voltage
I
OL
= 1.3mA
q
0.4
V
I
OFF
MISO Output Off-State Leakage Current
V
MISO
= 5V
q
2
A
SPI Timing (See Timing Diagram)
T
WD
Watch Dog Timer
q
1.2
2.5
4.5
sec
t
SSH
SSB High Time
680
ns
t
CYC
SCK Period
C
LOAD
= 200pF R
PULLUP
= 4.7k on MISO
q
2
s
t
SH
SCK High Time
680
ns
t
SL
SCK Low Time
680
ns
t
LD
Enable Lead Time
200
ns
t
LG
Enable Lag Time
200
ns
t
su
Input Data Set-Up Time
q
100
ns
t
H
Input Data Hold Time
q
100
ns
t
A
Access Time (From Hi-Z to Data Active on MISO)
q
125
ns
t
dis
Disable Time (Hold Time to Hi-Z State on MISO)
q
125
ns
t
V
Output Data Valid
C
L
= 200pF, R
PULLUP
= 4.7k on MISO
q
580
ns
t
HO
Output Data Hold
q
0
ns
t
Ir
SCK/MOSI/SSB Rise Time
0.8V to 2V
250
ns
t
If
SCK/MOSI/SSB Fall Time
2V to 0.8V
250
ns
t
Of
MISO Fall Time
2V to 0.4V, C
L
= 200 pF
q
400
ns
Note 1: Absolute Maximum Ratings are those values beyond which the life
of a device may be impaired.
Note 2. Battery voltage must be adequate to drive gates of PowerPath
P-channel FET switches. This does not affect charging voltage of the
battery, which can be zero volts.
Note 3. See Test Circuit.
Note 4. DCIN, BAT1, BAT2 are held at 12V and GDCI, GB1I, GB2I are
forced to 10.5V. SCP is set at 12.0V to measure source current at GDCI,
GB1I and GB2I. SCP is set at 11.9V to measure sink current at GDCI, GB1I
and GB2I.
Note 5. Extrapolated from testing with C
L
= 50pF.
Note 6. VDAC offset is equal to the reference voltage, since
V
OUT
= V
REF
(16mV VDAC
(VALUE)
/2047 + 1).
Note 7. The LTC1960C is guaranteed to meet specified performance from
0
C to 70
C and is designed, characterized and expected to meet specified
performance at 40
C and 85
C, but is not tested at these extended
temperature limits.
ELECTRICAL CHARACTERISTICS
The
q
denotes specifications which apply over the full operating
temperature range (Note 7), otherwise specifications are at T
A
= 25
C. V
DCIN
= 20V, V
BAT1
= 12V, V
BAT2
= 12V unless otherwise noted.
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