EVALUATION KIT AVAILABLE
MAX1757
Stand-Alone, Switch-Mode
Li+ Battery Charger with
Internal 14V Switch
Benefits and Features
•
Stand-Alone Charger Safely Charges Up to Three Li+
Batteries
•
Continuous Voltage and Temperature Monitoring
•
Input Current Limiting
•
±0.8% Battery Regulation Voltage Accuracy
•
Up to 1.5A Programmable Charge Current
Low Power Consumption Extends Battery Life
•
0.1μA Shutdown Battery Current
•
Low-Dropout 98% Duty Cycle
Flexible Input Voltage Range Enables the Use of Low
Cost Wall Adapters
•
Input Voltage Up to 14V
•
Precharges Near-Dead Cells
Fixed 300kHz PWM Oscillator Allows Effective Noise
Filtering
28-Pin SSOP Package Saves Board Space
General Description
The MAX1757 is a switch-mode lithium-ion (Li+) battery
charger that charges one to three cells. It provides a
regulated charging current accurate to ±10% and a
regulated voltage with only a ±0.8% total voltage error
at the battery terminals. The internal high-side switch
delivers a programmable current of up to 1.5A to
charge the battery. The built-in safety timer automati-
cally terminates charging once the adjustable time limit
has been reached.
The MAX1757 regulates the voltage set point and
charging current using two loops that work together to
transition smoothly between voltage and current regula-
tion. An additional control loop monitors the total cur-
rent drawn from the input source (charging + system)
and by automatically reducing battery-charging current
prevents overload of the input supply, allowing the use
of a low-cost wall adapter.
The per-cell battery regulation voltage is set between
4.0V and 4.4V using standard 1% resistors. The number
of cells is set from 1 to 3 by pin strapping. Battery tem-
perature is monitored by an external thermistor to prevent
charging outside the acceptable temperature range.
The MAX1757 is available in a space-saving 28-pin
SSOP package. Use the MAX1757EVKIT to help
reduce design time. For a stand-alone charger with a
28V switch, refer to the MAX1758 data sheet. For a
charger controller capable of up to 4A charging cur-
rent, refer to the MAX1737 data sheet.
•
•
•
•
Ordering Information
PART
MAX1757EAI
TEMP. RANGE
-40°C to +85°C
PIN-PACKAGE
28 SSOP
Typical Operating Circuit
V
IN
6V to 14V
DCIN
REF
MAX1757
ISETOUT
CSSP
CSSN
HSD
LX
BST
VL
ISETIN
PGND
SYSTEM
LOAD
Applications
Li+ Battery Packs
Notebook Computers
Hand-Held Instruments
PDAs
Desktop Cradle Chargers
Pin Configuration
TOP VIEW
VL 1
ISETTIN 2
ISETOUT 3
THM 4
REF 5
GND 6
VADJ 7
BATT 8
HSD 9
HSD 10
CELL 11
TIMER1 12
TIMER2 13
FAULT 14
28 DCIN
27 CSSP
CELL
CS
VADJ
26 CSSN
BATT
25 CCV
THM
24 CCI
MAX1757
23 CCS
22 BST
21 CS
20 LX
19 LX
18 PGND
17 SHDN
CCS
THERM
CCI
Li+ BATTERY
1 TO 3 CELLS
CCV
FASTCHG
TIMER1
FULLCHG
TIMER2
FAULT
16 FULLCHG
15 FASTCHG
ON
OFF
SHDN
GND
SSOP
19-1754; Rev 2; 5/15
MAX1757
Stand-Alone, Switch-Mode
Li+ Battery Charger with
Internal 14V Switch
Absolute Maximum Ratings
BATT, CS, DCIN, CSSP, CSSN, HSD to GND ........-0.3V to +15V
CSSP to CSSN.......................................................-0.6V to +0.6V
BST to GND ............................................................-0.3V to +21V
BST to LX..................................................................-0.3V to +6V
LX to PGND ..............................................-0.6V to (V
HSD
+ 0.3V)
VL,
SHDN,
ISETIN, ISETOUT, REF, VADJ, CELL, TIMER1,
TIMER2, CCI, CCS, CCV, THM to GND ................-0.3V to +6V
FASTCHG, FULLCHG, FAULT
to GND ..................-0.3V to +30V
CS to BATT Current ............................................................±3.5A
PGND to GND .......................................................-0.3V to +0.3V
VL Source Current...............................................................50mA
Continuous Power Dissipation (T
A
= +70°C)
28-Pin SSOP (derate 9.5mW/°C above +70°C) ...........762mW
Operating Temperature Range ...........................-40°C to +85°C
Junction Temperature ......................................................+150°C
Storage Temperature Range .............................-65°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.
Electrical Characteristics
(Circuit of Figure 1, V
DCIN
= V
HSD
= V
CSSP
= V
CSSN
= 12V, V
SHDN
= V
VL
, V
CELL
= GND, V
BATT
= V
CS
= 4.2V, V
VADJ
= V
REF
/2,
V
ISETIN
= V
ISETOUT
= V
REF
, R
THM
= 10kΩ,
T
A
= 0°C to +85°C,
unless otherwise noted. Typical values are at T
A
= +25°C.)
PARAMETER
SUPPLY AND REFERENCE
DCIN Input Voltage Range
DCIN Quiescent Supply Current
DCIN to BATT Dropout
Threshold, DCIN Falling
DCIN to BATT Dropout
Threshold, DCIN Rising
VL Output Voltage
VL Output Load Regulation
REF Output Voltage
REF Line Regulation
REF Load Regulation
SWITCHING REGULATOR
PWM Oscillator Frequency
LX Maximum Duty Cycle
CSSN/CSSP Off-State Leakage
HSD Off-State Leakage
LX Off-State Leakage
HSD to LX On-Resistance
LX to PGND On-Resistance
CS to BATT Current-Sensing
Resistance
BATT, CS Input Current
R
CS
V
REF
6V < V
DCIN
< 14V
Falling edge
Rising edge
6V < V
DCIN
< 14V
I
VL
= 0 to 15mA
6V < V
DCIN
< 14V
6V < V
DCIN
< 14V
I
REF
= 0 to 1mA
f
OSC
Nondropout f
OSC
In dropout, f
OSC
/ 4
V
CSSN
= V
CSSP
= V
DCIN
= 14V, V
SHDN
= GND
V
LX
= PGND, V
HSD
= V
DCIN
= 14V,
V
SHDN
= GND
V
LX
= V
HSD
= V
DCIN
=14V, V
SHDN
= GND
V
BST
= V
LX
+ 4.5V
See
PWM Controller
section
Internal resistor between CS and BATT,
1.5A RMS operating
V
SHDN
= GND, V
BATT
=14V
CELL = REF, V
BATT
= 12V, any charging state
V
BATT
= 14V, done state
270
97
0.075
0.20
5.10
6
5
0.125
0.30
5.40
44
4.20
2
6
300
98
2
0.1
0.1
150
1
110
0.1
280
150
14
7
0.175
0.40
5.70
65
4.221
6
14
330
10
10
10
250
2
170
5
540
270
V
mA
V
V
V
mV
V
mV
mV
kHz
%
µA
µA
µA
mΩ
Ω
mΩ
µA
µA
µA
SYMBOL
CONDITIONS
MIN
TYP
MAX
UNITS
4.179
www.maximintegrated.com
Maxim Integrated | 2
MAX1757
Stand-Alone, Switch-Mode
Li+ Battery Charger with
Internal 14V Switch
Electrical Characteristics (continued)
(Circuit of Figure 1, V
DCIN
= V
HSD
= V
CSSP
= V
CSSN
= 12V, V
SHDN
= V
VL
, V
CELL
= GND, V
BATT
= V
CS
= 4.2V, V
VADJ
= V
REF
/2,
V
ISETIN
= V
ISETOUT
= V
REF
, R
THM
= 10kΩ,
T
A
= 0°C to +85°C,
unless otherwise noted. Typical values are at T
A
= +25°C.)
PARAMETER
SWITCHING REGULATOR
CS to BATT Hard Current Limit
BATT, CS Input Voltage Range
VOLTAGE LIMIT ACCURACY
Battery Regulation Voltage
Absolute Voltage Accuracy
BATT Regulation Voltage
Adjustment Range
ERROR AMPLIFIERS
CCV Amplifier
Transconductance
CCV Amplifier Maximum Output
Current
BATT Full-Scale Charge Current
BATT 1/10-Scale Charge
Current (Note 1)
BATT Charge Current in
Prequalification State
CCI Battery Current Sense Gain
CCI Amplifier Maximum Output
Current
CSSP to CSSN Full-Scale
Current-Sense Voltage
CSSP to CSSN 1/10-Scale
Current-Sense Voltage
CCS Amplifier Transconductance
CCS Amplifier Maximum Output
Current
CCI, CCS Clamp Voltage with
Respect to CCV
CCV Clamp Voltage with
Respect to CCI, CCS
STATE MACHINE
THM Trip Threshold Voltage
THM Low-Temp Current
THM High-Temp Current
THM COLD Threshold
Resistance (Note 2)
THM HOT Threshold Resistance
(Note 2)
www.maximintegrated.com
SYMBOL
CONDITIONS
Instantaneous peak current limit
MIN
2.4
0
TYP
2.7
MAX
3.0
14
UNITS
A
V
V/cell
%
V/cell
V
BATTR
CELL = float, GND, or REF
Not including VADJ resistor tolerances
With 1% VADJ resistors
V
ADJ
= GND
V
ADJ
= REF
4.167
-0.8
-1
3.948
4.386
4.2
4.233
0.8
1
3.979
4.421
4.010
4.453
V
CCV
= 2V
V
CCV
= 2V
0.4
±50
1.35
0.7
1.0
mS
×
cells
µA
1.5
150
150
130
1.65
200
200
240
A
mA
mA
µA/A
µA
V
ISETOUT
= V
REF
/10
V
BATT
< 2.4V per cell
V
CCI
= 2V
V
CCI
= 2V
100
100
60
±100
90
100
10
2.0
115
15
3.0
mV
mV
mS
µA
V
ISETIN
= V
REF
/10
V
CCS
= 2V
V
CCS
= 2V
5
1.0
±100
25
25
200
200
mV
mV
V
TRT
I
TLTC
I
THTC
THM low-temp or high-temp current
V
THM
= 1.4V
V
THM
= 1.4V
Combines THM low-temp current and THM
threshold, V
TRT
/ I
TLTC
Combines THM high-temp current and THM
threshold, V
TRT
/ I
THTC
1.386
46.2
344
26.92
3.819
1.40
49
353
28.70
3.964
1.414
51.5
362
30.59
4.115
V
µA
µA
kΩ
kΩ
Maxim Integrated | 3
MAX1757
Stand-Alone, Switch-Mode
Li+ Battery Charger with
Internal 14V Switch
Electrical Characteristics (continued)
(Circuit of Figure 1, V
DCIN
= V
HSD
= V
CSSP
= V
CSSN
= 12V, V
SHDN
= V
VL
, V
CELL
= GND, V
BATT
= V
CS
= 4.2V, V
VADJ
= V
REF
/2,
V
ISETIN
= V
ISETOUT
= V
REF
, R
THM
= 10kΩ,
T
A
= 0°C to +85°C,
unless otherwise noted. Typical values are at T
A
= +25°C.)
PARAMETER
STATE MACHINE
BATT Undervoltage Threshold
(Note 3)
BATT Overvoltage Threshold
(Note 4)
FULLCHG
BATT Current
Termination Threshold (Note 5)
BATT Recharge Voltage
Threshold (Note 6)
TIMER1 and TIMER2
Oscillation Frequency
Prequalification Timer
Fast-Charge Timer
Full-Charge Timer
Top-Off Timer
Temperature Measurement
Frequency
CONTROL INPUTS/OUTPUTS
SHDN
Input Voltage High
SHDN
Input Voltage Low
VADJ, ISETIN, ISETOUT Input
Voltage Range
VADJ, ISETIN, ISETOUT Input
Bias Current
SHDN
Input Bias Current
CELL Input Bias Current
ISETOUT Shutdown Threshold
Voltage (Note 3)
For 1 cell
CELL Input Voltage
For 2 cells (floating)
For 3 cells
V
VADJ
, V
ISETIN
, V
ISETOUT
= 0 or 4.2V
V
SHDN
= 0 or V
VL
V
CELL
= 0 or V
VL
V
IH
V
IL
0
-50
-1
-5
150
0
1.5
V
REF
- 0.3
220
1.4
0.6
V
REF
50
1
5
300
0.5
2.5
V
REF
+ 0.3
V
V
V
V
nA
µA
µA
mV
2.4
4.55
250
2.5
4.67
330
2.6
4.8
400
V/cell
V/cell
mA
% of
V
BATTR
x
cells
kHz
min
min
min
min
Hz
SYMBOL
CONDITIONS
MIN
TYP
MAX
UNITS
94
95
96
2.1
6.25
81
81
40.5
0.98
2.33
7.5
90
90
45
1.12
2.6
8.75
100
100
49.8
1.32
www.maximintegrated.com
Maxim Integrated | 4
MAX1757
Stand-Alone, Switch-Mode
Li+ Battery Charger with
Internal 14V Switch
Electrical Characteristics (continued)
(Circuit of Figure 1, V
DCIN
= V
HSD
= V
CSSP
= V
CSSN
= 12V, V
SHDN
= V
VL
, V
CELL
= GND, V
BATT
= V
CS
= 4.2V, V
VADJ
= V
REF
/2,
V
ISETIN
= V
ISETOUT
= V
REF
, R
THM
= 10kΩ,
T
A
= 0°C to +85°C,
unless otherwise noted. Typical values are at T
A
= +25°C.)
PARAMETER
CONTROL INPUTS/OUTPUTS
FASTCHG, FULLCHG, FAULT
Output Low Voltage
FASTCHG, FULLCHG, FAULT
Output High Leakage
V
OL
I
SINK
= 5mA
V
FASTCHG
, V
FULLCHG
, V
FAULT
= 28V,
V
SHDN
= GND
0.5
1
V
µA
SYMBOL
CONDITIONS
MIN
TYP
MAX
UNITS
Electrical Characteristics
(Circuit of Figure 1, V
DCIN
= V
HSD
= V
CSSP
= V
CSSN
= 12V, V
SHDN
= V
VL
, V
CELL
= GND, V
BATT
= V
CS
= 4.2V, V
VADJ
= V
REF
/2,
V
ISETIN
= V
ISETOUT
= V
REF
, R
THM
= 10kΩ,
T
A
= -40°C to +85°C,
unless otherwise noted.) (Note 7)
PARAMETER
SUPPLY AND REFERENCE
DCIN Input Voltage Range
VL Output Voltage
REF Output Voltage
REF Line Regulation
SWITCHING REGULATOR
PWM Oscillator Frequency
HSD to LX On-Resistance
LX to PGND On-Resistance
CS to BATT Hard Current Limit
BATT, CS Input Voltage Range
ACCURACY AND ERROR AMPLIFIERS
Absolute Voltage Accuracy
BATT Regulation Voltage
BATT Full-Scale Charge Current
BATT 1/10-Scale Charge
Current (Note 1)
BATT Charge Current in
Prequalification State
CSSP to CSSN Full-Scale
Current-Sense Voltage
CSSP to CSSN 1/10-Scale
Current-Sense Voltage
STATE MACHINE
THM Trip Threshold Voltage
THM Low-Temp Current
BATT Undervoltage Threshold
(Note 3)
BATT Overvoltage Threshold
(Note 4)
www.maximintegrated.com
SYMBOL
CONDITIONS
MIN
6
5.1
TYP
MAX
14
5.7
4.242
6
UNITS
V
V
V
mV
kHz
mΩ
Ω
A
V
6V < V
DCIN
< 14V
6V < V
DCIN
< 14V
f
OSC
Nondropout f
OSC
V
BST
= V
LX
+ 4.5V
Instantaneous peak current limit
4.166
260
340
250
2
2.2
0
3.2
14
0.8
1
4.242
1.7
200
200
115
15
Not including VADJ resistor tolerances
With 1% VADJ resistors
CELL = float, GND, or REF
-0.8
-1
4.158
1.3
%
V/cell
A
mA
mA
mV
mV
V
ISETOUT
= V
REF
/ 10
V
BATT
< 2.4V per cell
100
100
85
V
ISETIN
= V
REF
/ 10
5
V
TRT
I
TLTC
THM low-temp or high-temp current
V
THM
= 1.4V
1.386
46.2
2.4
4.55
1.414
51.5
2.6
4.8
V
µA
V/cell
V/cell
Maxim Integrated | 5
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