General Description
The MAX1870A step-up/step-down multichemistry bat-
tery charger charges with battery voltages above and
below the adapter voltage. This highly integrated
charger requires a minimum number of external compo-
nents. The MAX1870A uses a proprietary step-up/step-
down control scheme that provides efficient charging.
Analog inputs control charge current and voltage, and
can be programmed by the host or hardwired.
The MAX1870A accurately charges two to four lithium-
ion (Li+) series cells at greater than 4A. A programma-
ble input current limit is included, which avoids
overloading the AC adapter when supplying the load
and the battery charger simultaneously. This reduces
the maximum adapter current, which reduces cost. The
MAX1870A provides analog outputs to monitor the cur-
rent drawn from the AC adapter and charge current. A
digital output indicates the presence of an AC adapter.
When the adapter is removed, the MAX1870A con-
sumes less than 1A from the battery.
The MAX1870A is available in a 32-pin thin QFN (5mm
x 5mm) package and is specified over the -40C to
+85C extended temperature range. The MAX1870A
evaluation kit (MAX1870AEVKIT) is available to help
reduce design time.
Applications
Notebook and Subnotebook Computers
Hand-Held Terminals
Features
Patented Step-Up/Step-Down Control Scheme*
0.5% Charge-Voltage Accuracy
9% Charge-Current Accuracy
8% Input Current-Limit Accuracy
Programmable Maximum Battery Charge Current
Analog Inputs Control Charge Current, Charge
Voltage, and Input Current Limit
Analog Output Indicates Adapter Current
Input Voltage from 8V to 28V
Battery Voltage from 0 to 17.6V
Charges Li+ or NiCd/NiMH Batteries
Tiny 32-Pin Thin QFN (5mm x 5mm) Package
MAX1870A
Step-Up/Step-Down
Li+ Battery Charger
________________________________________________________________
Maxim Integrated Products
1
Ordering Information
MAX1870A
REFIN
DCIN
CSSP
CSSN
DHI
DBST
CSIP
CSIN
BATT
SHDN
ASNS
VCTL
IINP
PGND
SYSTEM
LOAD
N
P
GND
ICTL
CLS
CELLS
FROM WALL ADAPTER
CSSS
VHN
VHP
BLKP
REF
LDO
DLOV
Typical Operating Circuit
19-3243; Rev 0; 4/04
For pricing, delivery, and ordering information, please contact Maxim/Dallas Direct! at
1-888-629-4642, or visit Maxim's website at www.maxim-ic.com.
EVALUATION KIT
AVAILABLE
Pin Configuration appears at end of data sheet.
PART
TEMP RANGE
PIN-PACKAGE
MAX1870AETJ
-40C to +85C
32 Thin QFN
*Protected by U.S. Patent No. 6,087,816.
MAX1870A
Step-Up/Step-Down
Li+ Battery Charger
2
_______________________________________________________________________________________
ABSOLUTE MAXIMUM RATINGS
ELECTRICAL CHARACTERISTICS
(Circuit of Figure 2, V
DCIN
= V
CSSP
= V
CSSN
= V
CSSS
= V
VHP
= 18V, V
BATT
= V
CSIP
= V
CSIN
= V
BLKP
= 12V, V
REFIN
= 3.0V, V
ICTL
=
0.75 x V
REFIN
, VCTL = LDO, CELLS = FLOAT, GND = PGND = 0, V
DLOV
= 5.4V,
T
A
= 0C to +85C, unless otherwise noted. Typical
values are at T
A
= +25C.)
Stresses beyond those listed under "Absolute Maximum Ratings" may cause permanent damage to the device. These are stress ratings only, and functional
operation of the device at these or any other conditions beyond those indicated in the operational sections of the specifications is not implied. Exposure to
absolute maximum rating conditions for extended periods may affect device reliability.
DCIN, CSSP, CSSS, CSSN,
VHP, VHN, DHI to GND ......................................-0.3V to +30V
VHP, DHI to VHN .....................................................-0.3V to +6V
BATT, CSIP, CSIN, BLKP to GND ..........................-0.3V to +20V
CSIP to CSIN, CSSP to CSSN,
CSSP to CSSS, PGND to GND ..........................-0.3V to +0.3V
CCI, CCS, CCV, REF, IINP to GND ..........-0.3V to (V
LDO
+ 0.3V)
DBST to GND..........................................-0.3V to (V
DLOV
+ 0.3V)
DLOV, VCTL, ICTL, REFIN, CELLS,
CLS, LDO, ASNS, SHDN to GND .........................-0.3V to +6V
LDO Current........................................................................50mA
Continuous Power Dissipation (T
A
= +70C)
32-Pin Thin QFN 5mm x 5mm
(derate 21mW/C above +70C) ......................................1.7W
Operating Temperature Range
MAX1870AETJ .................................................-40C to +85C
Storage Temperature Range .............................-60C to +150C
Lead Temperature (soldering, 10s) ................................ +300C
PARAMETER
CONDITIONS
MIN
TYP
MAX
UNITS
CHARGE-VOLTAGE REGULATION
VCTL Range
0
3.6
V
V
VCTL
= V
LDO
(2 cells)
-0.5
+0.5
V
VCTL
= V
LDO
(3 cells)
-0.5
+0.5
V
VCTL
= V
LDO
(4 cells)
-0.5
+0.5
V
VCTL
= V
REFIN
(2 cells)
-0.8
+0.8
V
VCTL
= V
REFIN
(3 cells)
-0.8
+0.8
V
VCTL
= V
REFIN
(4 cells)
-0.8
+0.8
V
VCTL
= V
REFIN
/ 20 (2 cells)
-1.2
+1.2
V
VCTL
= V
REFIN
/ 20 (3 cells)
-1.2
+1.2
Battery Regulation Voltage
Accuracy
V
VCTL
= V
REFIN
/ 20 (4 cells)
-1.2
+1.2
%
VCTL Default Threshold
VCTL rising
4.0
4.1
4.2
V
0 < V
VCTL
< V
REFIN
-1
+1
DCIN = 0, V
REFIN
= V
VCTL
= 3.6V
-1
+1
VCTL Input Bias Current
VCTL = DCIN = 0, V
REFIN
= 3.6V
-1
+1
A
CHARGE-CURRENT REGULATION
ICTL Range
0
3.6
V
V
ICTL
= V
REFIN
67
73
79
V
ICTL
= V
REFIN
x 0.8
54
59
64
Quick-Charge-Current Accuracy
V
ICTL
= V
REFIN
x 0.583
39
43
47
mV
Trickle-Charge-Current Accuracy
V
ICTL
= V
REFIN
x 0.0625
3.0
4.5
6.0
mV
BATT/CSIP/CSIN Input Voltage
Range
0
19
V
DCIN = 0
0.1
2
ICTL = 0
0.1
2
CSIP Input Current
ICTL = REFIN
350
600
A
MAX1870A
Step-Up/Step-Down
Li+ Battery Charger
_______________________________________________________________________________________
3
PARAMETER
CONDITIONS
MIN
TYP
MAX
UNITS
DCIN = 0
0.1
2
ICTL = 0
0.1
2
CSIN Input Current
ICTL = REFIN
0.1
2
A
ICTL Power-Down-Mode
Threshold Voltage
REFIN /
100
REFIN /
55
REFIN /
32
V
0 < V
ICTL
< V
REFIN
-1
+1
ICTL Input Bias Current
ICTL = DCIN = 0, V
REFIN
= 3.6V
-1
+1
A
INPUT-CURRENT REGULATION
CLS = REF
97
105
113
Charger-Input Current-Limit
Accuracy (V
CSSP
- V
CSSN
)
CSSS = CSSP
CLS = REF x 0.845
81
88
95
mV
CLS = REF
97
105
113
System-Input Current-Limit
Accuracy (V
CSSP
- V
CSSS
)
CSSN = CSSP
CLS = REF x 0.845
81
88
95
mV
CSSP/CSSS/CSSN Input Voltage
Range
8
28
V
V
CSSP
= V
CSSN
= V
CSSS
= V
DCIN
= 6V
-1
+1
CSSP Input Current
V
CSSP
= V
CSSN
= V
CSSS
= V
DCIN
= 8V, 28V
700
1200
A
V
CSSP
= V
CSSN
= V
CSSS
= V
DCIN
= 6V
-1
+1
CSSS/CSSN Input Current
V
CSSP
= V
CSSN
= V
CSSS
= V
DCIN
= 8V, 28V
-1
+1
A
CLS Input Range
V
REF
/ 2
V
REF
V
CLS Input Bias Current
CLS = REF
-1
+1
A
IINP Transconductance
V
CSSP
- V
CSSS
= 102mV, CSSN = CSSP
2.5
2.8
3.1
A/mV
V
CSSP
- V
CSSN
= 200mV, V
IINP
= 0V
350
IINP Output Current
V
CSSP
- V
CSSS
= 200mV, V
IINP
= 0V
350
A
V
CSSP
- V
CSSN
= 200mV, IINP float
3.5
IINP Output Voltage
V
CSSP
- V
CSSS
= 200mV, IINP float
3.5
V
SUPPLY AND LINEAR REGULATOR
DCIN Input Voltage Range
8
28
V
DCIN falling
4
6.2
DCIN Undervoltage Lockout
DCIN rising
6.3
7.85
V
DCIN Quiescent Current
8.0V < V
DCIN
< 28V
3.5
6
mA
BATT Input Voltage Range
0
19
V
DCIN = 0
0.1
1
BATT Input Bias Current
VBATT = 2V to 19V
300
500
A
LDO Output Voltage
No load
5.3
5.4
5.5
V
LDO Load Regulation
0 < I
LDO
< 10mA
70
150
mV
LDO Undervoltage Lockout
V
DCIN
= 8V, LDO rising
4.00
5.0
5.25
V
ELECTRICAL CHARACTERISTICS (continued)
(Circuit of Figure 2, V
DCIN
= V
CSSP
= V
CSSN
= V
CSSS
= V
VHP
= 18V, V
BATT
= V
CSIP
= V
CSIN
= V
BLKP
= 12V, V
REFIN
= 3.0V, V
ICTL
=
0.75 x V
REFIN
, VCTL = LDO, CELLS = FLOAT, GND = PGND = 0, V
DLOV
= 5.4V,
T
A
= 0C to +85C, unless otherwise noted. Typical
values are at T
A
= +25C.)
MAX1870A
Step-Up/Step-Down
Li+ Battery Charger
4
_______________________________________________________________________________________
PARAMETER
CONDITIONS
MIN
TYP
MAX
UNITS
REFERENCE
REF Output Voltage
I
REF
= 0A
4.076
4.096
4.116
V
REF Load Regulation
0 < I
REF
< 500A
5
10
mV
REF Undervoltage-Lockout Trip
Point
V
REF
falling
3.1
3.9
V
REFIN Input Range
2.5
3.6
V
REFIN UVLO Rising
1.9
2.2
V
REFIN UVLO Hysteresis
50
mV
V
DCIN
= 18V
50
100
REFIN Input Bias Current
DCIN = 0, V
REFIN
= 3.6V
-1
+1
A
SWITCHING REGULATOR
C ycl e- b y- C ycl e S tep - U p M axi m um
C ur r ent- Li m i t S ense V ol tag e
V
DCIN
= 12V, V
BATT
= 16.8V
135
150
165
mV
C ycl e- b y- C ycl e S tep - D ow n
M axi m um C ur r ent- Li m i t S ense
V ol tag e
V
DCIN
= 19V, V
BATT
= 16.8V
135
150
165
mV
Step-Down On-Time
V
DCIN
= 18V, V
BATT
= 16.8V
2.2
2.4
2.6
s
Minimum Step-Down Off-Time
V
DCIN
= 18V, V
BATT
= 16.8V
0.15
0.4
0.50
s
Step-Up Off-Time
V
DCIN
= 12V, V
BATT
= 16.8V
1.6
1.8
2.0
s
Minimum Step-Up On-Time
V
DCIN
= 12V, V
BATT
= 16.8V
0.15
0.3
0.40
s
MOSFET DRIVERS
VHP - VHN Output Voltage
8V < V
VHP
< 28V, no load
4.5
5
5.5
V
VHN Load Regulation
0 < I
VHN
< 10mA
70
150
mV
DHI On-Resistance High
I
SOURCE
= 10mA
2
5
DHI On-Resistance Low
I
SINK
= 10mA
1
3
DCIN = 0
0.1
1
A
VHP Input Bias Current
V
DCIN
= 18V
1.3
2
mA
ICTL = 0
0.1
2
BLKP Input Bias Current
V
ICTL
= V
REFIN
= 3.3V
100
400
A
DLOV Supply Current
DBST low
5
10
A
DBST On-Resistance High
I
SOURCE
= 10mA
2
5
DBST On-Resistance Low
I
SINK
= 10mA
1
3
ERROR AMPLIFIERS
GMV Amplifier Loop
Transconductance
V C TL = RE FIN , V
BAT T
= 16.8V
0.05
0.1
0.20
A/mV
GMI Amplifier Loop
Transconductance
ICTL = REFIN, V
CSIP
- V
CSIN
= 72mV
1.8
2.4
3.0
A/mV
ELECTRICAL CHARACTERISTICS (continued)
(Circuit of Figure 2, V
DCIN
= V
CSSP
= V
CSSN
= V
CSSS
= V
VHP
= 18V, V
BATT
= V
CSIP
= V
CSIN
= V
BLKP
= 12V, V
REFIN
= 3.0V, V
ICTL
=
0.75 x V
REFIN
, VCTL = LDO, CELLS = FLOAT, GND = PGND = 0, V
DLOV
= 5.4V,
T
A
= 0C to +85C, unless otherwise noted. Typical
values are at T
A
= +25C.)
MAX1870A
Step-Up/Step-Down
Li+ Battery Charger
_______________________________________________________________________________________
5
PARAMETER
CONDITIONS
MIN
TYP
MAX
UNITS
V
CLS
= REF, V
CSSP
- V
CSSN
= 102mV, V
CSSP
= V
CSSS
1.2
1.7
2.2
GMS Amplifier Loop
Transconductance
V
CLS
= REF, V
CSSP
- V
CSSS
= 102mV, V
CSSP
= V
CSSN
1.2
1.7
2.2
A/mV
VCTL = REFIN, V
BATT
= 15.8V
50
CCV Output Current
VCTL = REFIN, V
BATT
= 17.8V
-50
A
ICTL = REFIN, V
CSIP
- V
CSIN
= 0mV
150
CCI Output Current
ICTL = REFIN, V
CSIP
- V
CSIN
= 150mV
-150
A
CLS = REF, V
CSSP
= V
CSSN
, V
CSSP
= V
CSSS
100
CCS Output Current
CLS = REF, V
CSSP
- V
CSSN
= 200mV,
V
CSSP
- V
CSSS
= 200mV
-100
A
CCI/CCS/CCV Clamp Voltage
1.1V < V
CCV
< 3.5V, 1.1V < V
CCS
< 3.5V,
1.1V < V
CCI
< 3.5V
100
300
500
mV
LOGIC LEVELS
ASNS Output-Voltage Low
V
IINP
= GND,
I
SINK
= 1mA
0.4
V
ASNS Output-Voltage High
V
IINP
= 4V, I
SOURCE
= 1mA
LDO -
0.5
V
V
IINP
rising
1.1
1.15
1.2
V
ASNS Current Detect
Hysteresis
50
mV
V
SHDN
= 0 to V
REFIN
-1
+1
SHDN Input Bias Current
DCIN = 0, V
REFIN
= 5V, V
SHDN
= 0 to V
REFIN
-1
+1
A
SHDN Threshold
SHDN falling, V
REFIN
= 2.8V to 3.6V
22
23.5
25
% of
REFIN
SHDN Hysteresis
1
% of
REFIN
CELLS Input Low Voltage
0.75
V
CELLS Float Voltage
40
50
60
% of
REFIN
CELLS Input High Voltage
RE FIN -
0.75V
V
CELLS Input Bias Current
CELLS = 0 to REFIN
-2
+2
A
ELECTRICAL CHARACTERISTICS (continued)
(Circuit of Figure 2, V
DCIN
= V
CSSP
= V
CSSN
= V
CSSS
= V
VHP
= 18V, V
BATT
= V
CSIP
= V
CSIN
= V
BLKP
= 12V, V
REFIN
= 3.0V, V
ICTL
=
0.75 x V
REFIN
, VCTL = LDO, CELLS = FLOAT, GND = PGND = 0, V
DLOV
= 5.4V,
T
A
= 0C to +85C, unless otherwise noted. Typical
values are at T
A
= +25C.)
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