EVALUATION KIT AVAILABLE
MAX1870A
Step-Up/Step-Down
Li+ Battery Charger
General Description
The MAX1870A step-up/step-down multichemistry
battery charger charges with battery voltages above
and below the adapter voltage. This highly integrated
charger requires a minimum number of external com-
ponents. The MAX1870A uses a proprietary step-up/
step-down control scheme that provides effi-
cient 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 program-
mable input current limit is included, which avoids over-
loading 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
current 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 consumes
less than 1µA from the battery.
The MAX1870A is available in a 32-pin thin QFN
(5mm x 5mm) package and is specified over the
-40°C to +85°C extended temperature range. The
MAX1870A evaluation kit (MAX1870AEVKIT) is available
to help reduce design time.
Benefits and Features
●
Highly Flexible Input Voltage Range Works with
Affordable AC Adapters
• Step-Up/Step-Down Control Scheme
• Input Voltage from 8V to 28V
• Analog Output Indicates Adapter Current
●
Accurately Charge Li+ or NiCd/NiMH Batteries
• Battery Voltage from 0V to 17.6V
• ±0.5% Charge-Voltage Accuracy
• ±9% Charge-Current Accuracy
• ±8% Input Current-Limit Accuracy
●
Tune Design to Increase Safety and Efficiency
• Programmable Maximum Battery Charge Current
• Analog Inputs Control-Charge Current, Charge
Voltage, and Input-Current Limit
●
32-Pin Thin QFN (5mm x 5mm) Package Saves
Space while Supporting Step-Up and Step-Down
Operation
Typical Operating Circuit
FROM WALL ADAPTER
SYSTEM
LOAD
CSSS
DCIN
VHP
VHN
REF
CLS
CELLS
ASNS
IINP
DBST
CSIP
CSIN
REFIN
SHDN
ICTL
VCTL
LDO
PGND
DLOV
GND
BATT
BLKP
N
CSSP
CSSN
Applications
MAX1870A
DHI
P
●
Notebook and Subnotebook Computers
●
Handheld Terminals
Ordering Information
appears at end of data sheet.
19-3243; Rev 3; 8/15
MAX1870A
Step-Up/Step-Down
Li+ Battery Charger
Absolute Maximum Ratings
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
= +70°C)
32-Pin Thin QFN 5mm x 5mm
(derate 21mW/°C above +70°C) .....................................1.7W
Operating Temperature Range
MAX1870AETJ ............................................... -40°C to +85°C
Storage Temperature Range ............................ -60°C to +150°C
Lead Temperature (soldering, 10s) ................................ +300°C
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.
Package Information
32 TQFN
Package Code
Outline Number
Land Pattern Number
T3255+4
21-0140
90-0012
For the latest package outline information and land patterns (footprints), go to
www.maximintegrated.com/packages.
Note that a “+”,
“#”, or “-” in the package code indicates RoHS status only. Package drawings may show a different suffix character, but the drawing
pertains to the package regardless of RoHS status.
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
= 0°C to +85°C,
unless otherwise noted. Typical
values are at T
A
= +25°C.)
PARAMETER
CHARGE-VOLTAGE REGULATION
VCTL Range
V
VCTL
= V
LDO
(2 cells)
V
VCTL
= V
LDO
(3 cells)
V
VCTL
= V
LDO
(4 cells)
Battery Regulation Voltage
Accuracy
V
VCTL
= V
REFIN
(2 cells)
V
VCTL
= V
REFIN
(3 cells)
V
VCTL
= V
REFIN
(4 cells)
V
VCTL
= V
REFIN
/ 20 (2 cells)
V
VCTL
= V
REFIN
/ 20 (3 cells)
V
VCTL
= V
REFIN
/ 20 (4 cells)
VCTL Default Threshold
VCTL Input Bias Current
VCTL rising
0 < V
VCTL
< V
REFIN
DCIN = 0, V
REFIN
= V
VCTL
= 3.6V
VCTL = DCIN = 0, V
REFIN
= 3.6V
0
-0.5
-0.5
-0.5
-0.8
-0.8
-0.8
-1.2
-1.2
-1.2
4.0
-1
-1
-1
4.1
3.6
+0.5
+0.5
+0.5
+0.8
+0.8
+0.8
+1.2
+1.2
+1.2
4.2
+1
+1
+1
µA
V
%
V
CONDITIONS
MIN
TYP
MAX
UNITS
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│
2
MAX1870A
Step-Up/Step-Down
Li+ Battery Charger
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
= 0°C to +85°C,
unless otherwise noted. Typical
values are at T
A
= +25°C.)
PARAMETER
CHARGE-CURRENT REGULATION
ICTL Range
V
ICTL
= V
REFIN
Quick-Charge-Current Accuracy
Trickle-Charge-Current Accuracy
BATT/CSIP/CSIN Input Voltage
Range
DCIN = 0
CSIP Input Current
ICTL = 0
ICTL = REFIN
DCIN = 0
CSIN Input Current
ICTL Power-Down-Mode
Threshold Voltage
ICTL Input Bias Current
INPUT-CURRENT REGULATION
Charger-Input Current-Limit
Accuracy (V
CSSP
- V
CSSN
)
System-Input Current-Limit
Accuracy (V
CSSP
- V
CSSS
)
CSSP/CSSS/CSSN Input
Voltage Range
CSSP Input Current
CSSS/CSSN Input Current
CLS Input Range
CLS Input Bias Current
IINP Transconductance
IINP Output Current
IINP Output Voltage
CLS = REF
V
CSSP
- V
CSSS
= 102mV, CSSN = CSSP
V
CSSP
- V
CSSN
= 200mV, V
IINP
= 0V
V
CSSP
- V
CSSS
= 200mV, V
IINP
= 0V
V
CSSP
- V
CSSN
= 200mV, IINP float
V
CSSP
- V
CSSS
= 200mV, IINP float
V
CSSP
= V
CSSN
= V
CSSS
= V
DCIN
= 6V
V
CSSP
= V
CSSN
= V
CSSS
= V
DCIN
= 8V, 28V
V
CSSP
= V
CSSN
= V
CSSS
= V
DCIN
= 6V
V
CSSP
= V
CSSN
= V
CSSS
= V
DCIN
= 8V, 28V
-1
-1
V
REF
/ 2
-1
2.5
350
350
3.5
3.5
2.8
CSSS = CSSP
CSSN = CSSP
CLS = REF
CLS = REF x 0.845
CLS = REF
CLS = REF x 0.845
97
81
97
81
8
-1
700
105
88
105
88
113
95
113
95
28
+1
1200
+1
+1
V
REF
+1
3.1
mV
mV
V
µA
µA
V
µA
µA/mV
µA
V
0 < V
ICTL
< V
REFIN
ICTL = DCIN = 0, V
REFIN
= 3.6V
ICTL = 0
ICTL = REFIN
REFIN
/ 100
-1
-1
V
ICTL
= V
REFIN
x 0.8
V
ICTL
= V
REFIN
x 0.583
V
ICTL
= V
REFIN
x 0.0625
0
67
54
39
3.0
0
0.1
0.1
350
0.1
0.1
0.1
REFIN
/ 55
73
59
43
4.5
3.6
79
64
47
6.0
19
2
2
600
2
2
2
REFIN
/ 32
+1
+1
V
µA
µA
µA
mV
V
mV
V
CONDITIONS
MIN
TYP
MAX
UNITS
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Maxim Integrated
│
3
MAX1870A
Step-Up/Step-Down
Li+ Battery Charger
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
= 0°C to +85°C,
unless otherwise noted. Typical
values are at T
A
= +25°C.)
PARAMETER
SUPPLY AND LINEAR REGULATOR
DCIN Input Voltage Range
DCIN Undervoltage Lockout
DCIN Quiescent Current
BATT Input Voltage Range
BATT Input Bias Current
LDO Output Voltage
LDO Load Regulation
LDO Undervoltage Lockout
REFERENCE
REF Output Voltage
REF Load Regulation
REF Undervoltage-Lockout Trip
Point
REFIN Input Range
REFIN UVLO Rising
REFIN UVLO Hysteresis
REFIN Input Bias Current
SWITCHING REGULATOR
Cycle-by-Cycle Step-Up Maximum
Current-Limit Sense Voltage
Cycle-by-Cycle Step-Down
Maximum Current-Limit Sense
Voltage
Step-Down On-Time
Minimum Step-Down Off-Time
Step-Up Off-Time
Minimum Step-Up On-Time
V
DCIN
= 12V, V
BATT
= 16.8V
V
DCIN
= 19V, V
BATT
= 16.8V
V
DCIN
= 18V, V
BATT
= 16.8V
V
DCIN
= 18V, V
BATT
= 16.8V
V
DCIN
= 12V, V
BATT
= 16.8V
V
DCIN
= 12V, V
BATT
= 16.8V
135
135
2.2
0.15
1.6
0.15
150
150
2.4
0.4
1.8
0.3
165
165
2.6
0.50
2.0
0.40
mV
mV
µs
µs
µs
µs
V
DCIN
= 18V
DCIN = 0, V
REFIN
= 3.6V
-1
I
REF
= 0µA
0 < I
REF
< 500µA
V
REF
falling
2.5
1.9
50
50
100
+1
4.076
4.096
5
3.1
4.116
10
3.9
3.6
2.2
V
mV
V
V
V
mV
µA
DCIN = 0
V
BATT
= 2V to 19V
No load
0 < I
LDO
< 10mA
V
DCIN
= 8V, LDO rising
4.00
5.3
DCIN falling
DCIN rising
8.0V < V
DCIN
< 28V
0
0.1
300
5.4
70
5.0
8
4
6.2
6.3
3.5
7.85
6
19
1
500
5.5
150
5.25
28
V
V
mA
V
µA
V
mV
V
CONDITIONS
MIN
TYP
MAX
UNITS
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Maxim Integrated
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4
MAX1870A
Step-Up/Step-Down
Li+ Battery Charger
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
= 0°C to +85°C,
unless otherwise noted. Typical
values are at T
A
= +25°C.)
PARAMETER
MOSFET DRIVERS
VHP - VHN Output Voltage
VHN Load Regulation
DHI On-Resistance High
DHI On-Resistance Low
VHP Input Bias Current
BLKP Input Bias Current
DLOV Supply Current
DBST On-Resistance High
DBST On-Resistance Low
ERROR AMPLIFIERS
GMV Amplifier Loop
Transconductance
GMI Amplifier Loop
Transconductance
GMS Amplifier Loop
Transconductance
VCTL = REFIN, V
BATT
= 16.8V
ICTL = REFIN, V
CSIP
- V
CSIN
= 72mV
V
CLS
= REF, V
CSSP
- V
CSSN
= 102mV, V
CSSP
=
V
CSSS
V
CLS
= REF, V
CSSP
- V
CSSS
= 102mV, V
CSSP
=
V
CSSN
VCTL = REFIN, V
BATT
= 15.8V
VCTL = REFIN, V
BATT
= 17.8V
ICTL = REFIN, V
CSIP
- V
CSIN
= 0mV
ICTL = REFIN, V
CSIP
- V
CSIN
= 150mV
CLS = REF, V
CSSP
= V
CSSN
, V
CSSP
= V
CSSS
CLS = REF, V
CSSP
- V
CSSN
= 200mV,
V
CSSP
- V
CSSS
= 200mV
1.1V < V
CCV
< 3.5V, 1.1V < V
CCS
< 3.5V,
1.1V < V
CCI
< 3.5V
100
300
100
-100
500
µA
150
-150
0.05
1.8
1.2
1.2
50
-50
0.1
2.4
1.7
1.7
0.20
3.0
2.2
µA/mV
2.2
µA
µA
µA/mV
µA/mV
8V < V
VHP
< 28V, no load
0 < I
VHN
< 10mA
I
SOURCE
= 10mA
I
SINK
= 10mA
DCIN = 0
V
DCIN
= 18V
ICTL = 0
V
ICTL
= V
REFIN
= 3.3V
DBST low
I
SOURCE
= 10mA
I
SINK
= 10mA
4.5
5
70
2
1
0.1
1.3
0.1
100
5
2
1
5.5
150
5
3
1
2
2
400
10
5
3
V
mV
Ω
Ω
µA
mA
µA
µA
Ω
Ω
CONDITIONS
MIN
TYP
MAX
UNITS
CCV Output Current
CCI Output Current
CCS Output Current
CCI/CCS/CCV Clamp Voltage
mV
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5
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