19-2890; Rev 2; 8/05
KIT
ATION
EVALU
BLE
AVAILA
Linear Li+ Battery Charger with Integrated Pass FET,
Thermal Regulation, and
ACOK
in 3mm x 3mm TDFN
General Description
The MAX1508 is an intelligent, stand-alone constant-cur-
rent, constant-voltage (CCCV), thermally regulated linear
charger for a single-cell lithium-ion (Li+) battery. The
MAX1508 integrates the current-sense circuit, MOS pass
element, and thermal-regulation circuitry, and also elimi-
nates the reverse-blocking Schottky diode, to create the
simplest and smallest charging solution for hand-held
equipment.
The MAX1508 functions as a stand-alone charger to con-
trol the charging sequence from the prequalification state
through fast-charge, top-off charge, and full-charge indi-
cation. The MAX1508Y and MAX1508Z eliminate the pre-
qualification state to allow startup into a load without a
battery.
Proprietary thermal-regulation circuitry limits the die
temperature to +100°C when fast charging or while
exposed to high ambient temperatures, allowing maxi-
mum charging current without damaging the IC.
The MAX1508 achieves high flexibility by providing an
adjustable fast-charge current by an external resistor.
Other features include the charging status (CHG) of the
battery, an active-low control input (EN) for the
MAX1508 and MAX1508Z (active-high control input for
the MAX1508Y), and an active-low input power-source
detection output (ACOK).
The MAX1508 accepts a +4.25V to +13V supply, but dis-
ables charging when the input voltage exceeds +7V to
protect against unqualified or faulty AC adapters. The
MAX1508 operates over the extended temperature
range (-40°C to +85°C) and is available in a compact
8-pin thermally enhanced 3mm x 3mm thin DFN pack-
age with 0.8mm height.
Features
♦
Stand-Alone Linear 1-Cell Li+ Battery Charger
♦
No External FET, Reverse-Blocking Diode, or
Current-Sense Resistor Required
♦
Programmable Fast-Charge Current (0.8A max)
♦
Proprietary Die-Temperature Regulation Control
(+100°C)
♦
+4.25V to +13V Input Voltage Range with Input
Overvoltage Protection (OVP) Above +7V
♦
Charge-Current Monitor for Fuel Gauging
♦
Low Dropout Voltage—130mV at 0.425A
♦
Input Power-Source Detection Output (ACOK)
♦
Soft-Start Limits Inrush Current
♦
No Prequalification State for the MAX1508Y and
MAX1508Z
♦
Charge Status Output (CHG) for LED or
Microprocessor Interface
♦
Small 3mm x 3mm 8-Pin Thin DFN Package,
0.8mm High
♦
Active-Low Charge Enable (EN) (MAX1508 and
MAX1508Z)
♦
Active-High Charge Enable (EN) (MAX1508Y)
MAX1508/MAX1508Y/MAX1508Z
Ordering Information
PART
MAX1508ETA-T
MAX1508ETA+T
TEMP RANGE PIN-PACKAGE
-40°C to +85°C 8 Thin DFN-EP*
-40°C to +85°C 8 Thin DFN-EP*
TOP
MARK
AHF
AHF
Applications
Cellular and Cordless Phones
PDAs
Digital Cameras and MP3 Players
USB Appliances
Charging Cradles and Docks
Bluetooth™ Equipment
*EP
= Exposed paddle.
+Denotes
lead-free package.
Ordering Information continued at end of data sheet.
Pin Configuration
CHG
BATT
TOP VIEW
8
7
ACOK
6
Typical Operating Circuit appears at end of data sheet.
+
1
VL
MAX1508
MAX1508Y
MAX1508Z
2
IN
3
GND
4
ISET
3mm x 3mm THIN DFN
( ) ARE FOR THE MAX1508Y ONLY
Bluetooth is a trademark of Ericsson.
________________________________________________________________
Maxim Integrated Products
1
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.
EN (EN)
5
Linear Li+ Battery Charger with Integrated Pass FET,
Thermal Regulation, and
ACOK
in 3mm x 3mm TDFN
MAX1508/MAX1508Y/MAX1508Z
ABSOLUTE MAXIMUM RATINGS
IN,
CHG
to GND .....................................................-0.3V to +14V
VL, BATT, ISET,
EN,
EN,
ACOK
to GND ..................-0.3V to +6V
VL to IN...................................................................-14V to +0.3V
IN to BATT Continuous Current.............................................0.9A
Continuous Power Dissipation (T
A
= +70°C)
8-Pin TDFN (derate 24.4mW/°C above +70°C) .........1951mW
Short-Circuit Duration.................................................Continuous
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
(V
IN
= 5V, V
BATT
= 4.0V,
ACOK
=
EN
=
CHG
= unconnected (for the MAX1508 and MAX1508Z), EN = VL (for the MAX1508Y), R
ISET
= 2.8kΩ to GND, C
VL
= 0.47µF, BATT bypassed to GND with 1µF, T
A
= -40°C to +85°C, unless otherwise noted. Typical values are at
T
A
= +25°C.) (Note 1)
PARAMETER
Input Voltage Range
Input Operating Range
ACOK
Trip Point, IN
Overvoltage Lockout Trip Point
V
IN
- V
BATT
, V
IN
rising
V
IN
- V
BATT
, V
IN
falling
V
IN
rising
V
IN
hysteresis
Charging (I
IN
- I
BATT
)
IN Input Current
Disabled,
EN
= VL (MAX1508/MAX1508Z),
EN = GND (MAX1508Y)
OFF state (V
IN
= V
BATT
= 4.0V)
VL Output Voltage
VL Load Regulation
VL Temperature Coefficient
VL Undervoltage Lockout Trip Point
I
VL
= 100µA
I
VL
= 100µA to 2mA
I
VL
= 100µA
V
IN
rising
Hysteresis
V
IN
= 0 to 4V
BATT Input Current
Maximum RMS Charge Current
Battery Regulation Voltage
BATT Removal Detection Threshold
I
BATT
= 0
V
BATT
rising
T
A
= 0°C to +85°C
T
A
= -40°C to +85°C
4.162
4.150
4.4
EN
= VL (MAX1508/MAX1508Z), EN = GND
(MAX1508Y)
3.3
-71
-2
2.95
0.17
3
4
0.8
4.2
4.2
4.67
4.238
4.250
4.9
10
10
µA
A
V
V
-200
CONDITIONS
MIN
0
4.25
20
15
6.5
40
30
7
0.11
1
0.8
2
1.5
0.065
V
mV
mV/°C
V
mA
TYP
MAX
13
6.50
60
45
7.5
UNITS
V
V
mV
V
2
_______________________________________________________________________________________
Linear Li+ Battery Charger with Integrated Pass FET,
Thermal Regulation, and
ACOK
in 3mm x 3mm TDFN
ELECTRICAL CHARACTERISTICS (continued)
(V
IN
= 5V, V
BATT
= 4.0V,
ACOK
=
EN
=
CHG
= unconnected (for the MAX1508 and MAX1508Z), EN = VL (for the MAX1508Y,) R
ISET
= 2.8kΩ to GND, C
VL
= 0.47µF, BATT bypassed to GND with 1µF, T
A
= -40°C to +85°C, unless otherwise noted. Typical values are at
T
A
= +25°C.) (Note 1)
PARAMETER
BATT Removal Detection-Threshold Hysteresis
Minimum BATT Bypass Capacitance
Fast-Charge Current-Loop System Accuracy
Precharge Current System Accuracy
Die-Temperature-Regulation Set Point
V
BATT
Precharge Threshold Voltage
Current-Sense Amplifier Gain, I
SET
to I
BATT
in
Fast-Charge Mode
Regulator Dropout Voltage (V
IN
- V
BATT
)
EN
or EN Logic Input Low Voltage
EN
or EN Logic Input High Voltage
EN
or EN Internal Pulldown Resistor
CHG
Output Low Current
CHG
Output High Leakage Current
ACOK
Output Low Voltage
ACOK
Output High Leakage Current
Full-Battery Detection Current Threshold
(as a Percentage of the Fast-Charge Current)
V
BATT
rising (MAX1508 only)
I
BATT
= 500mA, V
ISET
= 1.4V
V
BATT
= 4.1V, I
BATT
= 425mA
4.25V < V
IN
< 6.5V
4.25V < V
IN
< 6.5V
(MAX1508 and MAX1508Z only)
V
CHG
= 1V
V
CHG
= 13V
I
ACOK
= 0.5mA
V
ACOK
= 5.5V
I
BATT
falling
T
A
= +25°C
T
A
= +85°C
5
0.002
10
15
T
A
= +25°C
T
A
= +85°C
0.002
0.4
1
1.3
100
5
200
12
400
20
1
2.3
0.880
V
BATT
= 3.5V
Percentage of the fast-charge current,
V
BATT
= 2.2V (MAX1508 only)
478
5
CONDITIONS
MIN
TYP
200
1
520
10
100
2.5
0.958
130
2.7
1.035
200
0.52
562
15
MAX
UNITS
mV
µF/A
mA
%
°C
V
mA/A
mV
V
V
kΩ
mA
µA
V
µA
%
MAX1508/MAX1508Y/MAX1508Z
Note 1:
Limits are 100% production tested at T
A
= +25°C.
Limits over operating temperature range are guaranteed through correla-
tion using statistical quality control (SQC) methods.
_______________________________________________________________________________________
3
Linear Li+ Battery Charger with Integrated Pass FET,
Thermal Regulation, and
ACOK
in 3mm x 3mm TDFN
MAX1508/MAX1508Y/MAX1508Z
Typical Operating Characteristics
(V
IN
= 5V, V
BATT
= 4.0V,
ACOK
=
EN
=
CHG
= unconnected, EN = VL (MAX1508Y), R
ISET
= 2.8kΩ to GND, C
IN
= 1µF, C
BATT
=
1µF, C
VL
= 0.47µF, T
A
= +25°C, unless otherwise noted.)
SUPPLY CURRENT
vs. INPUT VOLTAGE
MAX1508 toc01
DISABLED-MODE SUPPLY
CURRENT vs. INPUT VOLTAGE
DISABLED-MODE SUPPLY CURRENT (mA)
CHARGE CURRENT
vs. BATTERY VOLTAGE
MAX1508 toc02
MAX1508 toc03
2.0
I
BATT
= 0
1.5
2.0
600
500
CHARGE CURRENT (mA)
400
300
200
100
EN = VL (MAX1508/1508Z)
EN = GND (MAX1508Y)
1.5
SUPPLY CURRENT (mA)
1.0
1.0
0.5
0.5
0
0
2
4
6
8
10
12
INPUT VOLTAGE (V)
0
0
2
4
6
8
10
12
INPUT VOLTAGE (V)
0
0
1
2
3
4
BATTERY VOLTAGE (V)
CHARGE CURRENT
vs. INPUT VOLTAGE
600
550
500
450
400
350
300
250
200
150
100
50
0
INPUT VOLTAGE (V)
600
550
500
450
400
350
300
250
200
150
100
50
0
MAX1508 toc04
CHARGE CURRENT
vs. INPUT-VOLTAGE HEADROOM
MAX1508 toc05
BATTERY REGULATION VOLTAGE
vs. TEMPERATURE
4.207
4.204
4.201
4.198
4.195
4.192
4.189
4.186
4.183
4.180
MAX1508 toc06
4.210
BATTERY REGULATION VOLTAGE (V)
CHARGE CURRENT (mA)
0 1 2 3 4 5 6 7 8 9 10 11 12 13
CHARGE CURRENT (mA)
0 0.04 0.08 0.12 0.16 0.20 0.24 0.28 0.32 0.36 0.40
V
IN
- V
BATT
(V)
-40
-15
10
35
60
85
TEMPERATURE (°C)
CHARGE CURRENT
vs. AMBIENT TEMPERATURE
MAX1508 toc07
CHARGE CURRENT
vs. AMBIENT TEMPERATURE
900
800
CHARGE CURRENT (mA)
700
600
500
400
300
200
100
0
R
ISET
= 1.87kΩ
-40
-15
10
35
60
85
V
BATT
= 3.6V
V
BATT
= 4.0V
MAX1508 toc09
600
580
CHARGE CURRENT (mA)
560
540
520
500
480
460
440
420
-40
-15
10
35
60
1000
85
AMBIENT TEMPERATURE (°C)
AMBIENT TEMPERATURE (°C)
4
_______________________________________________________________________________________
Linear Li+ Battery Charger with Integrated Pass FET,
Thermal Regulation, and
ACOK
in 3mm x 3mm TDFN
Pin Description
PIN
1
2
3
4
NAME
VL
IN
GND
ISET
FUNCTION
Internally Generated Logic Supply for Chip. Bypass VL to GND with a 0.47µF capacitor.
Input Supply Voltage. Bypass IN to GND with a 1µF capacitor to improve line noise and transient rejection.
Ground. Connect GND and exposed pad to a large copper trace for maximum power dissipation.
Charge-Current Program and Fast-Charge Current Monitor. Output current from ISET is 0.958mA per amp of
battery charging current. The charging current is set by connecting a resistor from ISET to GND. Fast-charge
current = 1461V / R
ISET
Ω.
Logic-Level Enable Input (MAX1508/1508Z). Drive
EN
high to disable charger. Pull
EN
low or float for normal
operation.
EN
has an internal 200kΩ pulldown resistor.
Logic-Level Enable Input (MAX1508Y). Drive EN low to disable charger. Drive EN high for normal operation.
Input Power-Detection Output. The open-drain
ACOK
output asserts low when +4.25V < V
IN
< +7V and V
IN
-
V
BATT
> 40mV.
ACOK
requires an external 100kΩ pullup resistor.
ACOK
is high impedance in shutdown.
Li+ Battery Connection. Bypass BATT to GND with a capacitor of at least 1µF per ampere of charge current.
Charging Indicator, Open-Drain Output.
CHG
goes low (and can turn on an LED) when charging begins.
CHG
is high impedance when the battery current drops below 10% of the fast-charging current, or when
EN
is high. Connect a pullup resistor to the µP’s I/O voltage when interfacing with a µP logic input.
Exposed Pad. Connect exposed pad to a large copper trace for maximum power dissipation. The pad is
internally connected to GND.
MAX1508/MAX1508Y/MAX1508Z
5
EN
EN
6
7
8
ACOK
BATT
CHG
—
PAD
Detailed Description
The MAX1508 charger uses voltage, current, and ther-
mal-control loops to charge a single Li+ cell and to pro-
tect the battery (Figure 1). When a Li+ battery with a cell
voltage below 2.5V is inserted, the MAX1508 charger
enters the prequalification stage where it precharges that
cell with 10% of the user-programmed fast-charge cur-
rent. There is no prequalification stage for the MAX1508Z
and MAX1508Y in order to allow startup into a load with-
out a battery. The
CHG
indicator output is driven low
(Figure 2) to indicate entry into the prequalification state.
Once the cell has passed 2.5V, the charger soft-starts
before it enters the fast-charge stage. The fast-charge
current level is programmed through a resistor from ISET
to ground. As the battery voltage approaches 4.2V, the
charging current is reduced. If the battery current drops
to less than 10% of the fast-charging current, the
CHG
indicator goes high impedance, signaling the battery is
fully charged. At this point the MAX1508 enters a con-
stant voltage-regulation mode to maintain the battery at
full charge. If, at any point while charging the battery, the
die temperature approaches +100°C, the MAX1508
reduces the charging current so the die temperature
does not exceed the temperature-regulation set point.
The thermal-regulation loop limits the MAX1508 die
temperature to +100°C by reducing the charge current
as necessary (see the
Thermal Regulation
section).
This feature not only protects the MAX1508 from over-
heating, but also allows higher charge current without
risking damage to the system.
MAX1508/MAX1508Z
EN
Charger
Enable Input
EN
is a logic input (active low) to enable the charger.
Drive
EN
low, leave floating, or connect to GND to
enable the charger control circuitry. Drive
EN
high to
disable the charger control circuitry.
EN
has a 200kΩ
internal pulldown resistance.
MAX1508Y EN Charger Enable Input
EN is a logic input (active high) to enable the charger.
Drive EN high to enable the charger control circuitry.
Drive EN low to disable the charger control circuitry.
ACOK
Output
Active-Low Output. The open-drain
ACOK
output
asserts low when +4.25V < V
IN
< +7V and V
IN
- V
BATT
> 40mV.
ACOK
requires an external 100kΩ pullup
resistor to the system’s logic I/O voltage.
ACOK
is high
impedance in shutdown.
VL Internal Voltage Regulator
The MAX1508 linear charger contains an internal linear
regulator available on the VL output pin. VL requires a
0.47µF ceramic bypass capacitor to GND. VL is regulat-
ed to 3.3V whenever the input voltage is above 3.5V.
5
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