EVALUATION KIT AVAILABLE
MAX1909/MAX8725
Multichemistry Battery Chargers with
Automatic System Power Selector
General Description
The MAX1909/MAX8725 highly integrated control ICs
simplify construction of accurate and efficient multi-
chemistry battery chargers. The MAX1909/MAX8725
use analog inputs to control charge current and volt-
age, and can be programmed by a host microcontroller
(µC) or hardwired. High efficiency is achieved through
use of buck topology with synchronous rectification.
The maximum current drawn from the AC adapter is pro-
grammable to avoid overloading the AC adapter when
supplying the load and the battery charger simultane-
ously. The MAX1909/MAX8725 provide a digital output
that indicates the presence of an AC adapter, and an
analog output that monitors the current drawn from the
AC adapter. Based on the presence or absence of the
AC adapter, the MAX1909/MAX8725 automatically
select the appropriate source for supplying power to the
system by controlling two external p-channel MOSFETs.
Under system control, the MAX1909/MAX8725 allow the
battery to undergo a relearning or conditioning cycle in
which the battery is completely discharged through the
system load and then recharged.
The MAX1909 includes a conditioning charge feature
while the MAX8725 does not. The MAX1909/MAX8725
are available in space-saving 28-pin, 5mm
✕
5mm thin
QFN packages and operate over the extended -40°C to
+85°C temperature range. The MAX1909/MAX8725 are
now available in lead-free packages.
Benefits and Features
•
Precise Measurement Improves Safety and
Performance
•
±0.5% Accurate Charge Voltage (0°C to +85°C)
•
±3% Accurate Input Current Limiting
•
±5% Accurate Charge Current
•
Analog Inputs Control Charge Current and Charge
Voltage
•
Charge Any Battery Chemistry: Li+, NiCd, NiMH,
Lead Acid, etc.
•
Up to 17.65V (max) Battery Voltage
•
Maximum 28V Input Voltage
•
Programmable Charge Current > 4A
•
Intelligent AC Adapter Interface Makes Design Easier
•
Automatic System Power/Source Selection
•
Analog Monitoring of Current Drawn from AC Input
Source
•
Digital Output Indicates AC Adapter Presence
•
Greater than 95% Efficiency Extends Battery Life
Ordering Information
PART
MAX1909ETI
MAX1909ETI+
MAX8725ETI
MAX8725ETI+
TEMP RANGE
-40°C to +85°C
-40°C to +85°C
-40°C to +85°C
-40°C to +85°C
PIN-PACKAGE
28 Thin QFN
28 Thin QFN
28 Thin QFN
28 Thin QFN
Applications
Notebook and Subnotebook Computers
Hand-Held Data Terminals
+Denotes
a lead(Pb)-free/RoHS-compliant package.
Minimum Operating Circuit
P3
AC ADAPTER: INPUT
0.01Ω
SRC
CSSP
CSSN
DHIV
PDL
P2
TO
EXTERNAL LOAD
Pin Configuration
CSSP
CSSN
PDS
SRC
DHI
DHIV
PDL
TOP VIEW
PDS
SRC
DCIN
28
DCIN
LDO
ACIN
REF
GND/PKPRES
ACOK
MODE
27
26
25
24
23
22
21
20
19
DLOV
DLO
PGND
CSIP
CSIN
BATT
MAX8725 ONLY
LDO
LDO
IINP
REF
LDO
MAX1909
VCTL
MAX8725
LDO
ICTL
MODE
DLOV
P1
DHI
1
2
3
4
5
6
7
8
IINP
ACIN
IINP
CLS
ACOK
MAX1909
MAX8725
18
17
16
15
DLO
PGND
PKPRES
CSIP
N1
10μH
GND
CCV
CCI
CCS
REF
0.015Ω
9
CLS
10
ICTL
11
VCTL
12
CCI
13
CCV
14
CCS
CSIN
BATT
GND
THIN QFN
Functional Diagrams appear at end of data sheet.
19-2805; Rev 3; 5/15
MAX1909/MAX8725
Multichemistry Battery Chargers with
Automatic System Power Selector
Absolute Maximum Ratings
DCIN, CSSP, CSSN, SRC, ACOK to GND..............-0.3V to +30V
DHIV ........................................................…SRC + 0.3, SRC - 6V
DHI, PDL, PDS to GND ...............................-0.3V to (V
SRC
+ 0.3)
BATT, CSIP, CSIN to GND .....................................-0.3V to +20V
CSIP to CSIN or CSSP to CSSN or PGND to GND ...-0.3V to +0.3V
CCI, CCS, CCV, DLO, IINP, REF,
ACIN to GND ........................................-0.3V to (V
LDO
+ 0.3V)
DLOV, VCTL, ICTL, MODE, CLS, LDO,
PKPRES
to GND ...................................................-0.3V to +6V
DLOV to LDO.........................................................-0.3V to +0.3V
DLO to PGND ..........................................-0.3V to (DLOV + 0.3V)
LDO Short-Circuit Current...................................................50mA
Continuous Power Dissipation (T
A
= +70°C)
28-Pin TQFN (derate 20.8mW/°C above +70°C) .......1666mW
Operating Temperature Range ...........................-40°C to +85°C
Junction Temperature ......................................................+150°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.
Electrical Characteristics
(Circuit of Figure 1, V
DCIN
= V
CSSP
= V
CSSN
= 18V, V
BATT
= V
CSIP
= V
CSIN
= 12V, V
VCTL
= V
ICTL
= 1.8V, MODE = float, ACIN = 0, CLS =
REF, GND = PGND = 0,
PKPRES
= GND, LDO = DLOV,
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
= 3.6V (3 or 4 cells);
not including VCTL resistor tolerances
V
VCTL
= 3.6V/20 (3 or 4 cells); not including
VCTL resistor tolerances
V
VCTL
= 3.6V (3 or 4 cells); including VCTL
resistor tolerances of 1%
V
VCTL
= VLDO (3 or 4 cells, default
threshold of 4.2V/cell)
VVCTL Default Threshold
VCTL Input Bias Current
CHARGE-CURRENT REGULATION
ICTL Range
CSIP-to-CSIN Full-Scale Current-
Sense Voltage
MAX1909: V
ICTL
= 3.6V (not including ICTL
resistor tolerances)
MAX8725: V
ICTL
= 3.2V (not including ICTL
resistor tolerances)
Charge-Current Accuracy
MAX1909: V
ICTL
= 3.6V x 0.5, MAX8725:
V
ICTL
= 3.2V x 0.5 (not including ICTL
resistor tolerances)
MAX1909: V
ICTL
= 0.9V (not including ICTL
resistor tolerances)
MAX8725: V
ICTL
= 0.18V (not including
ICTL resistor tolerances)
MAX1909
MAX8725
0
0
69.37
-7.5
-5
75.00
3.6
3.2
80.63
+7.5
+5
V
mV
VVCTL rising
VVCTL = 3V
VDCIN = 0, VVCTL = 5V
0
-0.8
-0.8
-1.0
-0.5
4.1
0
0
3.6
+0.8
+0.8
%
+1.0
+0.5
4.3
2.5
12
V
µA
V
SYMBOL
CONDITIONS
MIN
TYP
MAX
UNITS
Battery Regulation Voltage
Accuracy
-5
+5
%
-7.5
-30
+7.5
+30
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Maxim Integrated | 2
MAX1909/MAX8725
Multichemistry Battery Chargers with
Automatic System Power Selector
Electrical Characteristics (continued)
(Circuit of Figure 1, V
DCIN
= V
CSSP
= V
CSSN
= 18V, V
BATT
= V
CSIP
= V
CSIN
= 12V, V
VCTL
= V
ICTL
= 1.8V, MODE = float, ACIN = 0, CLS =
REF, GND = PGND = 0,
PKPRES
= GND, LDO = DLOV,
T
A
= 0°C to +85°C,
unless otherwise noted. Typical values are at T
A
= +25°C.)
PARAMETER
SYMBOL
CONDITIONS
MAX1909: V
ICTL
= 3.6V x 0.5, MAX8725:
V
ICTL
= 3.2V x 0.5 (including ICTL resistor
tolerances of 1%)
V
ICTL
= VLDO (default threshold of 45mV)
V
ICTL
Default Threshold
BATT/CSIP/CSIN Input Voltage
Range
CSIP/CSIN Input Current
ICTL Power-Down Mode
Threshold Voltage
ICTL Power-Up Mode Threshold
Voltage
ICTL Input Bias Current
INPUT CURRENT REGULATION
CSSP-to-CSSN Full-Scale
Current-Sense Voltage
Input Current-Limit
Accuracy
CSSP/CSSN Input Voltage Range
CSSP/CSSN Input Current
CLS Input Range
CLS Input Bias Current
IINP Transconductance
V
CLS
= 2.0V
V
CSSP
- V
CSSN
= 56mV
V
CSSP
- V
CSSN
= 75mV, terminated with
10kΩ
IINP Accuracy
V
CSSP
- V
CSSN
= 56mV, terminated with
10kΩ
V
CSSP
- V
CSSN
= 20mV, terminated with
10kΩ
IINP Output Current
IINP Output Voltage
V
CSSP
- V
CSSN
= 150mV, V
IINP
= 0V
V
CSSP
- V
CSSN
= 150mV, V
IINP
= float
V
CSSP
= V
CSSN
= V
DCIN
> 8.0V
V
DCIN
= 0
1.6
-1
2.7
-7.5
-5
-10
350
3.5
3.0
V
CLS
= REF
V
CLS
= REF x 0.75
V
CLS
= REF x 0.5
72.75
-3
-3
-4
8.0
450
0.1
75.00
77.25
+3
+3
+4
28
730
1
REF
+1
3.3
+7.5
+5
+10
µA
V
%
V
µA
V
µA
mA/V
%
mV
Charging enabled
Charging disabled; V
DCIN
= 0 or V
ICTL
= 0
MAX1909
MAX8725
MAX1909
MAX8725
V
ICTL
= 3V
V
DCIN
= 0V, V
ICTL
= 5V
0.85
0.11
-1
-1
+1
+1
V
ICTL
rising
MIN
-7.0
-5
4.1
0
350
0.1
4.2
TYP
MAX
+7.0
+5
4.3
19
650
1
0.75
0.06
V
V
µA
V
V
µA
UNITS
Charge-Current Accuracy
%
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Maxim Integrated | 3
MAX1909/MAX8725
Multichemistry Battery Chargers with
Automatic System Power Selector
Electrical Characteristics (continued)
(Circuit of Figure 1, V
DCIN
= V
CSSP
= V
CSSN
= 18V, V
BATT
= V
CSIP
= V
CSIN
= 12V, V
VCTL
= V
ICTL
= 1.8V, MODE = float, ACIN = 0, CLS =
REF, GND = PGND = 0,
PKPRES
= GND, LDO = DLOV,
T
A
= 0°C to +85°C,
unless otherwise noted. Typical values are at T
A
= +25°C.)
PARAMETER
DCIN Input Voltage Range
DCIN Undervoltage-Lockout Trip
Point
DCIN Quiescent Current
BATT Input Current
LDO Output Voltage
LDO Load Regulation
LDO Undervoltage-Lockout Trip
Point
REFERENCE
REF Output Voltage
REF Undervoltage-Lockout Trip
Point
TRIP POINTS
BATT POWER_FAIL Threshold
BATT POWER_FAIL Threshold
Hysteresis
ACIN Threshold
ACIN Threshold Hysteresis
ACIN Input Bias Current
SWITCHING REGULATOR
DHI Off-Time
DHI Minimum Off-Time
DLOV Supply Current
Sense Voltage for Minimum
Discontinuous Mode Ripple
Current
Cycle-by-Cycle Current-Limit
Sense Voltage
Sense Voltage for Battery
Undervoltage Charge Current
MAX1909 only, BATT = 3.0V per cell
MAX1909 only, MODE = float (3 cell),
V
BATT
rising
MAX1909 only, MODE = LDO (4 cell),
V
BATT
rising
DHIV Output Voltage
With respect to SRC
3
9.18
12.235
-4.5
-5.0
I
DLOV
V
BATT
= 16.0V, V
DCIN
= 19V, V
MODE
= 3.6V
V
BATT
= 16.0V, V
DCIN
= 17V, V
MODE
= 3.6V
DLO low
360
260
400
300
5
7.5
440
350
10
ns
ns
µA
mV
V
ACIN
= 2.048V
ACIN rising
V
DCIN
- V
BATT
, VDCIN falling
50
100
2.007
10
-1
100
200
2.048
20
150
300
2.089
30
+1
mV
mV
V
mV
µA
Ref
0 < I
REF
< 500µA
REF falling
4.2023
4.2235
3.1
4.2447
3.9
V
V
I
DCIN
I
BATT
SYMBOL
V
DCIN
DCIN falling
DCIN rising
8.0V < V
DCIN
< 28V
V
BATT
= 19V, V
DCIN
= 0V, or ICTL = 0V
V
BATT
= 16.8V, V
DCIN
= 19V, ICTL = 0V
V
BATT
= 2V to 19V, V
DCIN
> V
BATT
+ 0.3V
8.0V < V
DCIN
< 28V, no load
0 < I
LDO
< 10mA
V
DCIN
= 8.0V
3.20
5.25
CONDITIONS
MIN
8.0
7
7.4
7.5
2.7
0.1
0.1
200
5.4
80
4
7.85
6
1
1
500
5.55
115
5.15
V
mV
V
µA
TYP
MAX
28
UNITS
V
V
mA
SUPPLY AND LINEAR REGULATOR
97
4.5
6
9.42
mV
mV
Battery Undervoltage Threshold
V
12.565
-5.5
V
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Maxim Integrated | 4
MAX1909/MAX8725
Multichemistry Battery Chargers with
Automatic System Power Selector
Electrical Characteristics (continued)
(Circuit of Figure 1, V
DCIN
= V
CSSP
= V
CSSN
= 18V, V
BATT
= V
CSIP
= V
CSIN
= 12V, V
VCTL
= V
ICTL
= 1.8V, MODE = float, ACIN = 0, CLS =
REF, GND = PGND = 0,
PKPRES
= GND, LDO = DLOV,
T
A
= 0°C to +85°C,
unless otherwise noted. Typical values are at T
A
= +25°C.)
PARAMETER
DHIV Sink Current
DHI On-Resistance Low
DHI On-Resistance High
DLO On-Resistance High
DLO On-Resistance Low
ERROR AMPLIFIERS
GMV Loop Transconductance
GMI Loop Transconductance
GMS Loop Transconductance
CCI/CCS/CCV Clamp Voltage
LOGIC LEVELS
MODE Input Low Voltage
MODE Input Middle Voltage
MODE Input High Voltage
MODE Input Bias Current
ACOK AND
PKPRES
ACOK Input Voltage Range
ACOK Sink Current
ACOK Leakage Current
PKPRES
Input Voltage
Range
PKPRES
Input Bias Current
PKPRES
Battery Removal Detect
Threshold
PKPRES
Hysteresis
PDS, PDL SWITCH CONTROL
PDS Switch Turn-Off Threshold
PDS Switch Threshold Hysteresis
PDS Output Low Voltage, PDS
Below SRC
PDS Turn-On Current
PDS Turn-Off Current
PDL Switch Turn-On Threshold
PDL Switch Threshold Hysteresis
V
DCIN
- V
BATT
, V
DCIN
falling
V
DCIN
- V
BATT
I
PDS
= 0A
PDS = SRC
V
PDS
= V
SRC
- 2V, V
DCIN
= 16V
V
DCIN
- V
BATT
, V
DCIN
falling
V
DCIN
- V
BATT
50
100
8
6
10
50
100
100
200
10
12
50
100
200
150
300
150
300
12
mV
mV
V
mA
mA
mV
mV
MAX8725,
PKPRES
rising
MAX8725
V
ACOK
= 0.4V, ACIN = 1.5V
V
ACOK
= 28V, ACIN = 2.5V
0
-1
55
1
0
1
1
LDO
+1
28
V
mA
µA
V
µA
% of
LDO
%
MODE = 0V or 3.6V
1.6
2.8
-2
+2
1.8
0.8
2.0
V
V
V
µA
VCTL = 3.6, V
BATT
= 16.8V, MODE = LDO
VCTL = 3.6, V
BATT
= 12.6V, MODE = FLOAT
MAX1909: ICTL = 3.6V, MAX8725: V
ICTL
=
3.2V, V
CSSP
- V
CSIN
= 75mV
V
CLS
= 2.048V, V
CSSP
- V
CSSN
= 75mV
0.25V < V
CCV
< 2.0V, 0.25V < V
CCI
< 2.0V,
0.25V < V
CCS
< 2.0V
0.0625
0.0833
0.5
0.5
150
0.125
0.167
1
1
300
0.2500
0.3330
2
2
600
mA/V
mA/V
mA/V
mV
DHI = V
DHIV
, I
DHI
= -10mA
DHI = V
CSSN
, I
DHI
= 10mA
V
DLOV
= 4.5V, IDLO = +100mA
V
DLOV
= 4.5V, IDLO = -100mA
SYMBOL
CONDITIONS
MIN
10
2
2
3
1
5
4
7
3
TYP
MAX
UNITS
mA
Ω
Ω
Ω
Ω
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