Rainbow Electronics MAX8724 User Manual
General Description
The MAX1908/MAX8724 highly integrated, multichemistry
battery-charger control ICs simplify the construction of
accurate and efficient chargers. These devices use analog inputs to control charge current and voltage, and can
be programmed by the host or hardwired. The MAX1908/
MAX8724 achieve high efficiency using a buck topology
with synchronous rectification.
The MAX1908/MAX8724 feature input current limiting.
This feature reduces battery charge current when the
input current limit is reached to avoid overloading the AC
adapter when supplying the load and the battery charger
simultaneously. The MAX1908/MAX8724 provide outputs
to monitor current drawn from the AC adapter (DC input
source), battery-charging current, and the presence of
an AC adapter. The MAX1908’s conditioning charge feature provides 300mA to safely charge deeply discharged
lithium-ion (Li+) battery packs.
The MAX1908 includes a conditioning charge feature
while the MAX8724 does not.
The MAX1908/MAX8724 charge two to four series Li+
cells, providing more than 5A, and are available in a
space-saving 28-pin thin QFN package (5mm × 5mm).
An evaluation kit is available to speed designs.
Applications
Notebook and Subnotebook Computers
Personal Digital Assistants
Hand-Held Terminals
Features
♦ ±0.5% Output Voltage Accuracy Using Internal
Reference (0°C to +85°C)
♦ ±4% Accurate Input Current Limiting
♦ ±5% Accurate Charge Current
♦ Analog Inputs Control Charge Current and
Charge Voltage
♦ Outputs for Monitoring
Current Drawn from AC Adapter
Charging Current
AC Adapter Presence
♦ Up to 17.6V Battery-Voltage Set Point
♦ Maximum 28V Input Voltage
♦ >95% Efficiency
♦ Shutdown Control Input
♦ Charges Any Battery Chemistry
Li+, NiCd, NiMH, Lead Acid, etc.
MAX1908/MAX8724
Low-Cost Multichemistry Battery Chargers
________________________________________________________________ Maxim Integrated Products 1
28 27 26 25 24 23 22
IINP
CSSP
CSSN
DHI
BST
LX
DLOV
89101112 13 14
SHDN
ICHG
ACIN
ACOK
REFIN
ICTL
GND
15
16
17
18
19
20
21
VCTL
BATT
CELLS
CSIN
CSIP
PGND
DLO
7
6
5
4
3
2
1
CCV
CCI
CCS
REF
CLS
LDO
DCIN
MAX1908
MAX8724
THIN QFN
TOP VIEW
Pin Configuration
Ordering Information
MAX1908
MAX8724
AC ADAPTER
INPUT
TO EXTERNAL
LOAD
LDO
FROM HOST µP
10µH
0.015Ω
BATT+
DCIN
REFIN
VCTL
ICTL
ACIN
ACOK
SHDN
ICHG
IINP
CCV
CCI
CCS
CELLS
LDO
BST
DLOV
DHI
LX
DLO
PGND
CSIP
CSIN
BATT
REF CLS
GND
CSSP CSSN
0.01Ω
Minimum Operating Circuit
19-2764; Rev 1; 1/04
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
PART TEMP RANGE PIN-PACKAGE
MAX1908ETI -40°C to +85°C 28 Thin QFN
MAX8724ETI -40°C to +85°C 28 Thin QFN
MAX1908/MAX8724
Low-Cost Multichemistry Battery Chargers
2 _______________________________________________________________________________________
ABSOLUTE MAXIMUM RATINGS
ELECTRICAL CHARACTERISTICS
(V
DCIN
= V
CSSP
= V
CSSN
= 18V, V
BATT
= V
CSIP
= V
CSIN
= 12V, V
REFIN
= 3V, V
VCTL
= V
ICTL
= 0.75 x V
REFIN
, CELLS = float, CLS =
REF, V
BST
- VLX= 4.5V, ACIN = GND = PGND = 0, C
LDO
= 1µF, LDO = DLOV, C
REF
= 1µF; CCI, CCS, and CCV are compensated
per Figure 1a; T
A
= 0°C to +85°C, unless otherwise noted. Typical values are at TA= +25°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.
DCIN, CSSP, CSSN, ACOK to GND.......................-0.3V to +30V
BST to GND............................................................-0.3V to +36V
BST to LX..................................................................-0.3V to +6V
DHI to LX...................................................-0.3V to (V
BST
+ 0.3V)
LX to GND .................................................................-6V to +30V
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, ICHG,
IINP, ACIN, REF to GND...........................-0.3V to (V
LDO
+ 0.3V)
DLOV, VCTL, ICTL, REFIN, CELLS, CLS,
LDO, SHDN to GND.................................................-0.3V to +6V
DLOV to LDO.........................................................-0.3V to +0.3V
DLO to PGND .........................................-0.3V to (V
DLOV
+ 0.3V)
LDO Short-Circuit Current...................................................50mA
Continuous Power Dissipation (T
A
= +70°C)
28-Pin Thin QFN (5mm × 5mm)
(derate 20.8mW/°C above +70°C) .........................1666.7mW
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
PARAMETER
SYMBOL
CONDITIONS
MIN
TYP
MAX
UNITS
CHARGE VOLTAGE REGULATION
V
VCTL
= V
REFIN
(2, 3, or 4 cells)
V
VCTL
= V
REFIN
/ 20 (2, 3, or 4 cells)
Battery Regulation Voltage
Accuracy
V
VCTL
= V
LDO
(2, 3, or 4 cells)
%
VCTL Default Threshold V
VCTL
rising 4.0 4.1 4.2 V
REFIN Range (Note 1) 2.5 3.6 V
REFIN Undervoltage Lockout V
REFIN
falling
V
CHARGE CURRENT REGULATION
CSIP-to-CSIN Full-Scale Current-
Sense Voltage
V
ICTL
= V
REFIN
75
mV
V
ICTL
= V
REFIN
-5 +5
V
ICTL
= V
REFIN
x 0.6 -5 +5 Charging Current Accuracy
V
ICTL
= V
LDO
-6 +6
%
ICTL Default Threshold V
ICTL
rising 4.0 4.1 4.2 V
BATT/CSIP/CSIN Input Voltage
Range
0 19 V
V
DCIN
= 0 or V
ICTL
= 0 or SHDN = 0 1
CSIP/CSIN Input Current
Charging
650
µA
Cycle-by-Cycle Maximum Current
Limit
I
MAX
RS2 = 0.015Ω 6.0 6.8 7.5 A
ICTL Power-Down Mode
Threshold Voltage
V
ICTL
rising
REFIN /
100
REFIN /55 REFIN /
33
V
V
VCTL
= V
ICTL
= 0 or 3V -1 +1
ICTL, VCTL Input Bias Current
V
DCIN
= 0, V
VCTL
= V
ICTL
= V
REFIN
= 5V -1 +1
µA
-0.5
-0.5
-0.5
1.20 1.92
71.25
400
+0.5
+0.5
+0.5
78.75
MAX1908/MAX8724
Low-Cost Multichemistry Battery Chargers
_______________________________________________________________________________________ 3
ELECTRICAL CHARACTERISTICS (continued)
(V
DCIN
= V
CSSP
= V
CSSN
= 18V, V
BATT
= V
CSIP
= V
CSIN
= 12V, V
REFIN
= 3V, V
VCTL
= V
ICTL
= 0.75 x V
REFIN
, CELLS = float, CLS =
REF, V
BST
- VLX= 4.5V, ACIN = GND = PGND = 0, C
LDO
= 1µF, LDO = DLOV, C
REF
= 1µF; CCI, CCS, and CCV are compensated
per Figure 1a; T
A
= 0°C to +85°C, unless otherwise noted. Typical values are at TA= +25°C.)
PARAMETER
SYMBOL
CONDITIONS
MIN
TYP
MAX
UNITS
V
DCIN
= 5V, V
REFIN
= 3V -1 +1
REFIN Input Bias Current
V
REFIN
= 5V -1 +1
µA
ICHG Transconductance
V
CSIP
- V
CSIN
= 45mV 2.7 3 3.3
µA/mV
V
CSIP
- V
CSIN
= 75mV -6 +6
V
CSIP
- V
CSIN
= 45mV -5 +5 ICHG Accuracy
V
CSIP
- V
CSIN
= 5mV -40
%
ICHG Output Current V
CSIP
- V
CSIN
= 150mV, V
ICHG
= 0
µA
ICHG Output Voltage V
CSIP
- V
CSIN
= 150mV, ICHG = float 3.5 V
INPUT CURRENT REGULATION
CSSP-to-CSSN Full-Scale
Current-Sense Voltage
72 75 78 mV
V
CLS
= V
REF
-4 +4
Input Current-Limit Accuracy
V
CLS
= V
REF
/ 2
%
CSSP, CSSN Input Voltage
Range
8 28 V
V
DCIN
= 0 0.1 1
CSSP, CSSN Input Current
V
CSSP
= V
CSSN
= V
DCIN
> 8V
600
µA
CLS Input Range 1.6
V
CLS Input Bias Current V
CLS
= 2V -1 +1 µA
IINP Transconductance G
IINP
V
CSSP
- V
CSSN
= 75mV 2.7 3 3.3
µA/mV
V
CSSP
- V
CSSN
= 75mV -5 +5
IINP Accuracy
V
CSSP
- V
CSSN
= 37.5mV
%
IINP Output Current V
CSSP
- V
CSSN
= 150mV, V
IINP
= 0
µA
IINP Output Voltage V
CSSP
- V
CSSN
= 150mV,V
IINP
= float 3.5 V
SUPPLY AND LDO REGULATOR
DCIN Input Voltage Range V
DCIN
8 28 V
V
DCIN
falling 7 7.4
DCIN Undervoltage-Lockout Trip
Point
V
DCIN
rising 7.5
V
DCIN Quiescent Current I
DCIN
8.0V < V
DCIN
< 28V 3.2 6 mA
V
BATT
= 19V, V
DCIN
= 0 1
BATT Input Current I
BATT
V
BATT
= 2V to 19V, V
DCIN
= 19.3V
500
µA
LDO Output Voltage 8V < V
DCIN
< 28V, no load
5.4
V
LDO Load Regulation 0 < I
LDO
< 10mA 34 100 mV
LDO Undervoltage-Lockout Trip
Point
V
DCIN
= 8V
4
V
REFERENCE
REF Output Voltage 0 < I
REF
< 500µA
V
G
ICHG
350
-7.5
350
-7.5
350
200
5.25
3.20
4.072 4.096 4.120
+40
+7.5
REF
+7.5
7.85
5.55
5.15
MAX1908/MAX8724
Low-Cost Multichemistry Battery Chargers
4 _______________________________________________________________________________________
ELECTRICAL CHARACTERISTICS (continued)
(V
DCIN
= V
CSSP
= V
CSSN
= 18V, V
BATT
= V
CSIP
= V
CSIN
= 12V, V
REFIN
= 3V, V
VCTL
= V
ICTL
= 0.75 x V
REFIN
, CELLS = float, CLS =
REF, V
BST
- VLX= 4.5V, ACIN = GND = PGND = 0, C
LDO
= 1µF, LDO = DLOV, C
REF
= 1µF; CCI, CCS, and CCV are compensated
per Figure 1a; T
A
= 0°C to +85°C, unless otherwise noted. Typical values are at TA= +25°C.)
PARAMETER
SYMBOL
CONDITIONS
MIN
TYP
MAX
UNITS
REF Undervoltage-Lockout Trip
Point
V
REF
falling 3.1 3.9 V
TRIP POINTS
BATT Power-Fail Threshold V
DCIN
falling, referred to V
CSIN
50
150 mV
BATT Power-Fail Threshold
Hysteresis
mV
ACIN Threshold ACIN rising
V
ACIN Threshold Hysteresis 0.5% of REF 20 mV
ACIN Input Bias Current V
ACIN
= 2.048V -1 +1 µA
SWITCHING REGULATOR
DHI Off-Time
V
BATT
= 16V, V
DCIN
= 19V,
V
CELLS
= V
REFIN
0.4
µs
DHI Minimum Off-Time
V
BATT
= 16V, V
DCIN
= 17V,
V
CELLS
= V
REFIN
µs
DHI Maximum On-Time 2.5 5 7.5 ms
DLOV Supply Current I
DLOV
DLO low 5 10 µA
BST Supply Current I
BST
DHI high 6 15 µA
BST Input Quiescent Current
V
DCIN
= 0, V
BST
= 24.5V,
V
BATT
= VLX = 20V
0.3 1 µA
LX Input Bias Current V
DCIN
= 28V, V
BATT
= VLX = 20V
500 µA
LX Input Quiescent Current V
DCIN
= 0, V
BATT
= VLX = 20V 0.3 1 µA
DHI Maximum Duty Cycle 99
%
Minimum Discontinuous-Mode
Ripple Current
0.5 A
Battery Undervoltage Charge
Current
V
BATT
= 3V per cell (RS2 = 15mΩ),
MAX1908 only, V
BATT
rising
450 mA
CELLS = GND, MAX1908 only, V
BATT
rising 6.1 6.2 6.3
CELLS = float, MAX1908 only, V
BATT
rising
9.3
Battery Undervoltage Current
Threshold
V
DHI On-Resistance High V
BST
- VLX = 4.5V, I
DHI
= +100mA 4 7 Ω
DHI On-Resistance Low V
BST
- VLX = 4.5V, I
DHI
= -100mA 1 3.5 Ω
DLO On-Resistance High V
DLOV
= 4.5V, I
DLO
= +100mA 4 7 Ω
DLO On-Resistance Low V
DLOV
= 4.5V, I
DLO
= -100mA 1 3.5 Ω
ERROR AMPLIFIERS
GMV Amplifier Transconductance
GMV
V
V C T L
= V
LD O
, V
BAT T
= 16.8V ,
C E LLS = V
RE F IN
µA/mV
GMI Amplifier Transconductance
GMI V
ICTL
= V
RE F IN
, V
CSIP
- V
CSIN
= 75mV 0.5 1 2.0
µA/mV
100
200
2.007 2.048 2.089
0.36
0.24 0.28 0.33
CELLS = V
, MAX1908 only, V
REFIN
BATT
rising 12.2 12.4 12.6
150 300
9.15
0.0625 0.125 0.2500
150
99.9
0.44
9.45
MAX1908/MAX8724
Low-Cost Multichemistry Battery Chargers
_______________________________________________________________________________________ 5
ELECTRICAL CHARACTERISTICS (continued)
(V
DCIN
= V
CSSP
= V
CSSN
= 18V, V
BATT
= V
CSIP
= V
CSIN
= 12V, V
REFIN
= 3V, V
VCTL
= V
ICTL
= 0.75 x V
REFIN
, CELLS = float, CLS =
REF, V
BST
- VLX= 4.5V, ACIN = GND = PGND = 0, C
LDO
= 1µF, LDO = DLOV, C
REF
= 1µF; CCI, CCS, and CCV are compensated
per Figure 1a; T
A
= 0°C to +85°C, unless otherwise noted. Typical values are at TA= +25°C.)
PARAMETER
SYMBOL
CONDITIONS
MIN
TYP
MAX
UNITS
GMS Amplifier Transconductance
GMS V
CLS
= V
REF
, V
CSSP
- V
CSSN
= 75mV 0.5 1 2.0
µA/mV
CCI, CCS, CCV Clamp Voltage 0.25V < V
CCV,CCS,CCI
< 2V
600 mV
LOGIC LEVELS
CELLS Input Low Voltage 0.4 V
CELLS Input Float Voltage CELLS = float
(V
REFIN
/ 2) -
0.2V
V
REFIN
/ 2
( V
R E F IN
/ 2) +
V
CELLS Input High Voltage
V
REFIN
V
CELLS Input Bias Current CELLS = 0 or V
REFIN
-2 +2 µA
ACOK AND SHDN
ACOK Input Voltage Range 0 28 V
ACOK Sink Current V
ACOK
= 0.4V, V
ACIN
= 3V 1 mA
ACOK Leakage Current V
ACOK
= 28V, V
ACIN
= 0 1 µA
SHDN Input Voltage Range 0
V
V
SHDN
= 0 or V
LDO
-1 +1
SHDN Input Bias Current
V
DCIN
= 0, V
SHDN
= 5V -1 +1
µA
SHDN Threshold V
SHDN
falling 22
25
% of
V
REFIN
SHDN Threshold Hysteresis 1
% of
V
REFIN
150 300
- 0.4V
0.2V
LDO
23.5
MAX1908/MAX8724
Low-Cost Multichemistry Battery Chargers
6 _______________________________________________________________________________________
ELECTRICAL CHARACTERISTICS
(V
DCIN
= V
CSSP
= V
CSSN
= 18V, V
BATT
= V
CSIP
= V
CSIN
= 12V, V
REFIN
= 3V, V
VCTL
= V
ICTL
= 0.75 x V
REFIN
, CELLS = FLOAT, CLS =
REF, V
BST
- VLX= 4.5V, ACIN = GND = PGND = 0, C
LDO
= 1µF, LDO = DLOV, C
REF
= 1µF; CCI, CCS, and CCV are compensated
per Figure 1a; T
A
= -40°C to +85°C, unless otherwise noted.) (Note 2)
PARAMETER
CONDITIONS
UNITS
CHARGE VOLTAGE REGULATION
V
VCTL
= V
REFIN
(2, 3, or 4 cells)
V
VCTL
= V
REFIN
/ 20 (2, 3, or 4 cells)
Battery Regulation Voltage
Accuracy
V
VCTL
= V
LDO
(2, 3, or 4 cells)
%
REFIN Range (Note 1) 2.5 3.6 V
REFIN Undervoltage Lockout V
REFIN
falling
V
CHARGE CURRENT REGULATION
CSIP-to-CSIN Full-Scale Current-
Sense Voltage
V
ICTL
= V
REFIN
mV
V
ICTL
= V
REFIN
-6 +6
V
ICTL
= V
REFIN
× 0.6
Charging Current Accuracy
V
ICTL
= V
LDO
%
BATT/CSIP/CSIN Input Voltage
Range
0 19 V
V
DCIN
= 0 or V
ICTL
= 0 or SHDN = 0 1
CSIP/CSIN Input Current
Charging 650
µA
Cycle-by-Cycle Maximum Current
Limit
I
MAX
RS2 = 0.015Ω 6.0 7.5 A
ICTL Power-Down Mode
Threshold Voltage
V
ICTL
rising
REFIN /
100
REFIN /
33
V
ICHG Transconductance
V
CSIP
- V
CSIN
= 45mV 2.7 3.3
µA/mV
V
CSIP
- V
CSIN
= 75mV
V
CSIP
- V
CSIN
= 45mV
ICHG Accuracy
V
CSIP
- V
CSIN
= 5mV -40
%
INPUT CURRENT REGULATION
CSSP-to-CSSN Full-Scale
Current-Sense Voltage
mV
V
CLS
= V
REF
-5 +5
Input Current-Limit Accuracy
V
CLS
= V
REF
/ 2
%
CSSP, CSSN Input Voltage
Range
8 28 V
V
DCIN
= 0 1
CSSP, CSSN Input Current
V
CSSP
= V
CSSN
= V
DCIN
> 8V 600
µA
CLS Input Range 1.6
V
IINP Transconductance G
IINP VCSSP
- V
CSSN
= 75mV 2.7 3.3
µA/mV
V
CSSP
- V
CSSN
= 75mV
IINP Accuracy
V
CSSP
- V
CSSN
= 37.5mV
%
SYMBOL
MIN TYP MAX
-0.6
-0.6
-0.6
70.5
-7.5
-7.5
G
ICHG
-7.5
-7.5
71.25
-7.5
-7.5
-7.5
+0.6
+0.6
+0.6
1.92
79.5
+7.5
+7.5
+7.5
+7.5
+40
78.75
+7.5
REF
+7.5
+7.5
MAX1908/MAX8724
Low-Cost Multichemistry Battery Chargers
_______________________________________________________________________________________ 7
ELECTRICAL CHARACTERISTICS (continued)
(V
DCIN
= V
CSSP
= V
CSSN
= 18V, V
BATT
= V
CSIP
= V
CSIN
= 12V, V
REFIN
= 3V, V
VCTL
= V
ICTL
= 0.75 x V
REFIN
, CELLS = FLOAT, CLS =
REF, V
BST
- VLX= 4.5V, ACIN = GND = PGND = 0, C
LDO
= 1µF, LDO = DLOV, C
REF
= 1µF; CCI, CCS, and CCV are compensated
per Figure 1a; T
A
= -40°C to +85°C, unless otherwise noted.) (Note 2)
PARAMETER
SYMBOL
CONDITIONS
MIN
TYP
MAX
UNITS
SUPPLY AND LDO REGULATOR
DCIN Input Voltage Range
8 28 V
DCIN Quiescent Current I
DCIN
8V < V
DCIN
< 28V 6 mA
V
BATT
= 19V, V
DCIN
= 0 1
BATT Input Current I
BATT
V
BATT
= 2V to 19V, V
DCIN
= 19.3V 500
µA
LDO Output Voltage 8V < V
DCIN
< 28V, no load
V
LDO Load Regulation 0 < I
LDO
< 10mA 100 mV
REFERENCE
REF Output Voltage 0 < I
REF
< 500µA
V
TRIP POINTS
BATT Power-Fail Threshold V
DCIN
falling, referred to V
CSIN
50 150 mV
ACIN Threshold V
ACIN
rising
V
SWITCHING REGULATOR
DHI Off-Time
V
BATT
= 16V, V
DCIN
= 19V,
V
CELLS
= V
REFIN
µs
DHI Minimum Off-Time
V
BATT
= 16V, V
DCIN
= 17V,
V
CELLS
= V
REFIN
µs
DHI Maximum On-Time 2.5 7.5 ms
DHI Maximum Duty Cycle 99 %
Battery Undervoltage Charge
Current
V
BATT
= 3V per cell (RS2 = 15mΩ),
MAX1908 only, V
BATT
rising
450 mA
CELLS = GND, MAX1908 only, V
BATT
rising
CELLS = float, MAX1908 only, V
BATT
rising
Battery Undervoltage Current
Threshold
V
DHI On-Resistance High V
BST
- VLX = 4.5V, I
DHI
= +100mA 7 Ω
DHI On-Resistance Low V
BST
- VLX = 4.5V, I
DHI
= -100mA 3.5 Ω
DLO On-Resistance High V
DLOV
= 4.5V, I
DLO
= +100mA 7 Ω
DLO On-Resistance Low V
DLOV
= 4.5V, I
DLO
= -100mA 3.5 Ω
ERROR AMPLIFIERS
GMV Amplifier Transconductance
GMV
V
V C T L
= V
LD O
, V
BAT T
= 16.8V ,
C E LLS = V
RE F IN
µA/mV
GMI Amplifier Transconductance
GMI V
ICTL
= V
RE F IN
, V
CSIP
- V
CSIN
= 75mV 0.5 2.0
µA/mV
GMS Amplifier Transconductance
GMS V
CLS
= V
REF
, V
CSSP
- V
CSSN
= 75mV 0.5 2.0
µA/mV
CCI, CCS, CCV Clamp Voltage 0.25V < V
CCV,CCS,CCI
< 2V
600 mV
LOGIC LEVELS
CELLS Input Low Voltage 0.4 V
V
DCIN
5.25
4.065
2.007
0.35
0.24
CELLS = V
, MAX1908 only, V
REFIN
150
6.09
9.12
rising 12.18
BATT
0.0625
150
5.55
4.120
2.089
0.45
0.33
6.30
9.45
12.6
0.250
MAX1908/MAX8724
Low-Cost Multichemistry Battery Chargers
8 _______________________________________________________________________________________
ELECTRICAL CHARACTERISTICS (continued)
(V
DCIN
= V
CSSP
= V
CSSN
= 18V, V
BATT
= V
CSIP
= V
CSIN
= 12V, V
REFIN
= 3V, V
VCTL
= V
ICTL
= 0.75 x V
REFIN
, CELLS = FLOAT, CLS =
REF, V
BST
- VLX= 4.5V, ACIN = GND = PGND = 0, C
LDO
= 1µF, LDO = DLOV, C
REF
= 1µF; CCI, CCS, and CCV are compensated
per Figure 1a; T
A
= -40°C to +85°C, unless otherwise noted.) (Note 2)
PARAMETER
SYMBOL
CONDITIONS
MIN
TYP
MAX
UNITS
CELLS Input Float Voltage CELLS = float
(V
REFIN
/ 2) -
0.2V
( V
R E F IN
/ 2) +
V
CELLS Input High Voltage
V
REFIN
V
ACOK AND SHDN
ACOK Input Voltage Range 0 28 V
ACOK Sink Current V
A COK
= 0.4V, V
ACIN
= 3V 1 mA
SHDN Input Voltage Range 0
V
SHDN Threshold V
S HDN
falling 22 25
% of
V
REFIN
Note 1: If both ICTL and VCTL use default mode (connected to LDO), REFIN is not used and can be connected to LDO.
Note 2: Specifications to -40°C are guaranteed by design and not production tested.
LOAD-TRANSIENT RESPONSE
(BATTERY INSERTION AND REMOVAL)
MAX1908 toc01
1ms/div
I
BATT
2A/div
V
BATT
5V/div
V
CCI 500mV/div
V
CCV 500mV/div
ICTL = LDO
VCTL = LDO
CCV
CCI
LOAD-TRANSIENT RESPONSE
(STEP IN-LOAD CURRENT)
MAX1908 toc02
1ms/div
V_BATT
2V/div
V_CCI
500mV/div
V_CCS
500mV/div
16.8V
0
0
LOAD
CURRENT
5A/div
ADAPTER
CURRENT
5A/div
ICTL = LDO
CHARGING CURRENT = 3A
V_BATT = 16.8V
LOAD STEP = 0 TO 4A
I_SOURCE LIMIT = 5A
CCI
CCS
CCI
CCS
V_BATT
2V/div
0
0
0
CHARGE
CURRENT
2A/div
LOAD
CURRENT
5A/div
ADAPTER
CURRENT
5A/div
LOAD-TRANSIENT RESPONSE
(STEP IN-LOAD CURRENT)
MAX1908 toc03
1ms/div
ICTL = LDO
CHARGING CURRENT = 3A
VBATT = 16.8V
LOAD STEP = 0 TO 4A
I_SOURCE LIMIT = 5A
Typical Operating Characteristics
(Circuit of Figure 1, V
DCIN
= 20V, TA= +25°C, unless otherwise noted.)
- 0.4V
0.2V
LDO
MAX1908/MAX8724
Low-Cost Multichemistry Battery Chargers
_______________________________________________________________________________________ 9
INDUCTOR
CURRENT
500mA/div
V
DCIN
10V/div
V
BATT
500mV/div
LINE-TRANSIENT RESPONSE
MAX1908 toc04
10ms/div
ICTL = LDO
VCTL = LDO
ICHARGE = 3A
LINE STEP 18.5V TO 27.5V
-1.0
-0.8
-0.9
-0.6
-0.7
-0.4
-0.5
-0.3
-0.1
-0.2
0
0 2341 567 9810
LDO LOAD REGULATION
MAX1908 toc05
LDO CURRENT (mA)
V
LDO
ERROR (%)
V
LDO
= 5.4V
-0.05
-0.03
-0.04
-0.01
-0.02
0.01
0
0.02
0.04
0.03
0.05
812141610 18 20 22 2624 28
LDO LINE REGULATION
MAX1908 toc06
VIN (V)
V
LDO
ERROR (%)
I
LDO
= 0
V
LDO
= 5.4V
-0.10
-0.07
-0.08
-0.09
-0.06
-0.05
-0.04
-0.03
-0.02
-0.01
0
0 200100 300 400 500
REF VOLTAGE LOAD REGULATION
MAX1908 toc07
REF CURRENT (µA)
V
REF
ERROR (%)
-0.10
-0.04
-0.06
-0.08
-0.02
0
0.02
0.04
0.06
0.08
0.10
-40 10-15 35 60 85
REF VOLTAGE ERROR vs. TEMPERATURE
MAX1908 toc08
TEMPERATURE (°C)
V
REF
ERROR (%)
90
0
0.01 1010.1
EFFICIENCY vs. CHARGE CURRENT
30
10
70
50
100
40
20
80
60
MAX1908 toc09
CHARGE CURRENT (A)
EFFICIENCY (%)
V
BATT
= 16V
V
BATT
= 8V
V
BATT
= 12V
0
100
50
250
200
150
300
350
450
400
500
046281012 14 16 18 20 22
FREQUENCY vs. VIN - V
BATT
MAX1908 toc10
(VIN - V
BATT
) (V)
FREQUENCY (kHz)
I
CHARGE
= 3A
VCTL = ICTL = LDO
3 CELLS
4 CELLS
-0.4
-0.1
-0.3
-0.5
0
0.2
0.3
0.4
0.5
01234
OUTPUT V/I CHARACTERISTICS
MAX1908 toc11
BATT CURRENT (A)
BATT VOLTAGE ERROR (%)
0.1
-0.2
2 CELLS
3 CELLS
4 CELLS
0
0.02
0.01
0.03
0.06
0.07
0.05
0.04
0.08
0 0.2 0.3 0.4 0.50.1 0.6 0.7 0.8 0.9
1.0
BATT VOLTAGE ERROR vs. VCTL
MAX1908 toc12
VCTL/REFIN (%)
BATT VOLTAGE ERROR (%)
4 CELLS
REFIN = 3.3V
NO LOAD
Typical Operating Characteristics (continued)
(Circuit of Figure 1, V
DCIN
= 20V, TA= +25°C, unless otherwise noted.)
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