19-3670; Rev 0; 4/05
KIT
ATION
EVALU
E
L
B
AVAILA
1A Linear Li+ Battery Chargers with Integrated Pass
FET and Thermal Regulation in 2mm x 2mm TDFN
Features
The MAX8808X/MAX8808Y/MAX8808Z intelligent,
stand-alone constant-current/constant-voltage (CCCV),
thermally regulated linear chargers are designed for
charging a single-cell lithium-ion (Li+) battery. The
MAX8808X/MAX8808Y/MAX8808Z integrate the current-sense circuit, MOS pass element, and thermal-regulation circuitry, and eliminate the reverse-blocking
Schottky diode to create the simplest and smallest
charging solution for handheld equipment.
The MAX8808X functions as a stand-alone charger to
control the charging sequence from the prequalification
state through fast-charge, top-off charge, and fullcharge indication. The MAX8808Y and MAX8808Z eliminate the prequalification state to allow startup into a load
without a battery. Proprietary thermal-regulation circuitry
limits the die temperature when fast-charging or while
exposed to high ambient temperatures, allowing maximum charging current without damaging the IC.
♦ Stand-Alone Linear 1-Cell Li+ Battery Charger
The MAX8808X/MAX8808Y/MAX8808Z achieve high
flexibility by providing an adjustable fast-charge current
with an external resistor. Other features include a battery charging-status indicator (CHG), an active-low control input (EN) for the MAX8808X and MAX8808Z
(active-high control input for the MAX8808Y), and an
active-low input power-source detection output (ACOK).
♦ Tiny 2mm x 2mm 8-Pin TDFN Package, 0.8mm
(max) Height
The MAX8808X/MAX8808Y/MAX8808Z accept a
+4.25V to +15V supply, but disable charging when the
input voltage exceeds +7V to protect against unqualified or faulty AC adapters. The MAX8808X/MAX8808Y/
MAX8808Z operate over the extended temperature
range (-40°C to +85°C) and are available in a compact
8-pin thermally enhanced 2mm x 2mm TDFN package
with 0.8mm (max) height.
♦ No External FET, Reverse Blocking Diode, or
Current-Sense Resistor Required
♦ Programmable Fast-Charge Current (1A max)
♦ Proprietary Die Temperature Regulation Control
(+115°C)
♦ +4.25V to +15V Input Voltage Range with Input
OVP Above +7V
♦ Charge-Current Monitor for Fuel Gauging
♦ Low Dropout Voltage—300mV at 500mA
♦ Input Power-Source Detection Output (ACOK) and
Charge-Enable Input (EN or EN)
♦ Soft-Start Limits Inrush Current
♦ Charge-Status Output (CHG) for LED or
Microprocessor (µP) Interface
Ordering Information
PIN-PACKAGE
TOP
MARK
MAX8808XETA+ 8 TDFN-EP* 2mm x 2mm (T822-1)
AAC
MAX8808YETA+ 8 TDFN-EP* 2mm x 2mm (T822-1)
AAB
MAX8808ZETA+ 8 TDFN-EP* 2mm x 2mm (T822-1)
AAA
PART
All devices specified over the -40°C to +85°C operating range.
+Denotes lead-free package.
*EP = Exposed paddle.
Applications
Typical Operating Circuit
Cellular and Cordless Phones
Smartphones and PDAs
4.25V TO 15V
IN
BATT
Digital Still Cameras and MP3 Players
USB Appliances
CHG
Charging Cradles and Docks
Bluetooth® Equipment
Pin Configuration appears at end of data sheet.
Bluetooth is a registered trademark of Bluetooth SIG.
4.2V
Li+
MAX8808X
MAX8808Y
MAX8808Z
OFF
ON
EN*
ACOK
ISET
VL
GND
*MAX8808Y USES ACTIVE-HIGH LOGIC FOR EN.
________________________________________________________________ Maxim Integrated Products
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.
1
MAX8808X/MAX8808Y/MAX8808Z
General Description
MAX8808X/MAX8808Y/MAX8808Z
1A Linear Li+ Battery Chargers with Integrated Pass
FET and Thermal Regulation in 2mm x 2mm TDFN
ABSOLUTE MAXIMUM RATINGS
IN to GND ...............................................................-0.3V to +16V
VL, BATT, EN, ACOK, CHG to GND.........................-0.3V to +6V
VL, ISET to GND .......................................................-0.3V to +4V
VL to IN................................................................-16.3V to +0.3V
IN to BATT Continuous Current.............................................1.5A
Continuous Power Dissipation (TA = +70°C)
8-Pin 2mm x 2mm TDFN (derate 15.4mW/°C
above +70°C).............................................................1234mW
BATT 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
(VIN = 5V, VBATT = 4.0V, R ACOK = R CHG = 100kΩ to 5V, EN = unconnected (for the MAX8808X and MAX8808Z), EN = VL (for the
MAX8808Y), RISET = 2.8kΩ to GND, CVL = 0.47µF, CBATT = 1µF, TA = -40°C to +85°C, unless otherwise noted. Typical values are at
TA = +25°C.) (Note 1)
PARAMETER
CONDITIONS
MIN
Input Voltage Range
Input Operating Range
ACOK Threshold
VIN - VBATT, 10mV hysteresis (typ)
Overvoltage-Lockout Trip Point
VIN rising, 100mV hysteresis (typ)
IN Input Current
TYP
V
4.25
6.50
V
VIN rising
15
40
60
VIN falling
10
30
45
6.5
7
7.5
Charging (IIN - IBATT)
0.8
2
Disabled
0.23
0.50
IVL = 100µA
3.0
VL Load Regulation
IVL = 100µA to 2mA
-5
VL Undervoltage-Lockout Trip
Point
VVL rising, 100mV hysteresis (typ)
Battery Regulation Voltage
2.74
10
Disabled
1
10
4.200
4.238
1
4.162
2
TA = 0°C to +85°C
418
mV
µA
ARMS
2.2
VBATT = 3.5V
mA
V
1
Minimum BATT Bypass
Capacitance
Fast-Charge Current Loop
System Accuracy
V
V
-30
VIN = 0 to 4V
IBATT = 1mA
mV
0.065
VL Output Voltage
Maximum RMS Charge Current
UNITS
15
OFF state (VIN = VBATT = 4.0V)
BATT Input Current
MAX
0
465
_______________________________________________________________________________________
V
µF/A
512
mA
1A Linear Li+ Battery Chargers with Integrated Pass
FET and Thermal Regulation in 2mm x 2mm TDFN
(VIN = 5V, VBATT = 4.0V, R ACOK = R CHG = 100kΩ to 5V, EN = unconnected (for the MAX8808X and MAX8808Z), EN = VL (for the
MAX8808Y), RISET = 2.8kΩ to GND, CVL = 0.47µF, CBATT = 1µF, TA = -40°C to +85°C, unless otherwise noted. Typical values are at
TA = +25°C.) (Note 1)
PARAMETER
Prequal Charge Current
CONDITIONS
Percentage of the fast-charge current, VBATT = 2.2V,
MAX8808X
MIN
TYP
MAX
UNITS
5
10
15
%
Die Temperature Regulation
Threshold
+115
VBATT Prequal Threshold Voltage
VBATT rising, MAX8808X
Current-Sense Amplifier Gain,
IBATT to IISET
IBATT = 500mA, VISET = 1.4V
Regulator Dropout Voltage
(VIN - VBATT )
VBATT = 4.1V, IBATT = 425mA
EN/EN Logic Input Low Voltage
4.25V < VIN < 6.5V
EN/EN Logic Input High Voltage
4.25V < VIN < 6.5V
1.3
EN Internal Pulldown Resistor
MAX8808X and MAX8808Z only
100
EN Input Leakage Current
MAX8808Y, VEN = 5.5V
CHG Output Low Voltage
I CHG = 5mA
CHG Output High Leakage
Current
V CHG = 5.5V
ACOK Output Low Voltage
I ACOK = 5mA
ACOK Output High Leakage
Current
V ACOK = 5.5V
Full-Battery Detection Current
Threshold
IBATT falling, percentage of the fast-charge current
TA = 0°C to +85°C
°C
2.3
2.5
2.7
V
0.97
1.08
1.19
mA/A
250
430
mV
0.52
V
400
kΩ
V
200
TA = +25°C
1
TA = +85°C
0.002
0.4
TA = +25°C
1
TA = +85°C
0.002
0.4
TA = +25°C
1
TA = +85°C
0.002
5
10
15
µA
V
µA
V
µA
%
Note 1: Specifications are 100% production tested at TA = +25°C. Limits over the operating temperature range are guaranteed by
design and characterization.
_______________________________________________________________________________________
3
MAX8808X/MAX8808Y/MAX8808Z
ELECTRICAL CHARACTERISTICS (continued)
Typical Operating Characteristics
(VIN = 5V, VBATT = 4.0V, ACOK = EN = unconnected, RISET = 2.8kΩ to GND, CIN = 1µF, CBATT = 1µF, CVL = 0.47µF, TA = +25°C,
unless otherwise noted.)
DISABLED-MODE SUPPLY CURRENT
vs. INPUT VOLTAGE
700
1.4
1.2
1.0
0.8
0.6
600
500
400
300
200
0.4
900
800
700
600
MAX8808Y/
MAX8808Z
500
400
MAX8808X
300
200
0.2
100
0
0
2
4
6
8
10
12
14
16
VEN = 5V OR
VEN = 0V
100
0
0
INPUT VOLTAGE (V)
2
4
6
8
10
12
14
16
CHARGE CURRENT
vs. INPUT VOLTAGE HEADROOM
800
700
600
500
400
300
1000
MAX8808X/Y/Z toc05
900
900
800
CHARGE CURRENT (mA)
MAX8808X/Y/Z toc04
1000
CHARGE CURRENT (mA)
0.5 1.0 1.5 2.0 2.5 3.0 3.5 4.0 4.5
VBATT (V)
CHARGE CURRENT
vs. INPUT VOLTAGE
700
600
500
400
300
200
200
100
100
0
0
2
4
6
8
10
12
14
0
(VIN - VBAT) (mV)
BATTERY REGULATION VOLTAGE
vs. AMBIENT TEMPERATURE
CHARGE CURRENT
vs. AMBIENT TEMPERATURE
MAX8808X/Y/Z toc06
4.240
4.230
4.220
4.210
4.200
4.190
4.180
600
500
450
350
4.160
250
-15
10
35
TA (°C)
60
85
VBATT = 3.2V
400
300
4.150
VBATT = 4V
550
4.170
-40
50 100 150 200 250 300 350 400 450 500
VIN (V)
CHARGE CURRENT (mA)
0
BATTERY REGULATION VOLTAGE (V)
0
INPUT VOLTAGE (V)
MAX8808X/Y/Z toc07
0
4
1000
MAX8808X/Y/Z toc03
1.6
SUPPLY CURRENT (µA)
1.8
MAX8808X/Y/Z toc02
800
MAX8808X/Y/Z toc01
2.0
CHARGE CURRENT
vs. BATTERY VOLTAGE
CHARGE CURRENT (mA)
SUPPLY CURRENT
vs. INPUT VOLTAGE
SUPPLY CURRENT (mA)
MAX8808X/MAX8808Y/MAX8808Z
1A Linear Li+ Battery Chargers with Integrated Pass
FET and Thermal Regulation in 2mm x 2mm TDFN
200
-40
-15
10
35
60
TA (°C)
_______________________________________________________________________________________
85
1A Linear Li+ Battery Chargers with Integrated Pass
FET and Thermal Regulation in 2mm x 2mm TDFN
PIN
NAME
FUNCTION
1
IN
Input Supply Voltage. Bypass IN to GND with a 1µF or larger ceramic capacitor to improve line
noise and input transient rejection.
2
VL
Internally Generated Logic Supply for IC. Bypass VL to GND with a 0.47µF ceramic capacitor.
3
GND
Ground. Connect GND and exposed pad to a large copper ground plane for maximum power
dissipation. Connect GND to the exposed paddle directly under the IC.
4
ISET
Charge-Current Program and Fast-Charge Current Monitor. Output current from ISET is 1.08mA
per amp of battery charging current. Set the charging current by connecting a resistor from ISET
to GND. Fast-charge current = 1302V / RISETΩ.
5
CHG
Charging Indicator. CHG is an open-drain output that goes low (LED capable) when charging
begins. CHG is high impedance when the battery current drops below 10% of the fast-charging
current, or when the IC is disabled. Connect a pullup resistor to the µP’s I/O voltage when
interfacing with a µP logic input.
Logic-Level Enable Input. Drive EN high to disable charger. Pull EN low or leave unconnected for
normal operation. EN has an internal 200kΩ pulldown resistor.
6
EN
(MAX8808X/
MAX8808Z)
EN
(MAX8808Y)
Logic-Level Enable Input. Drive EN low to disable charger. Pull EN high for normal operation. EN
has no internal pullup or pulldown resistor.
7
ACOK
Input Status Indicator. ACOK is an open-drain output that asserts low when VIN < +7V and (VIN –
VBATT) ≥ 40mV. ACOK requires an external 100kΩ pullup resistor. ACOK is high impedance
during shutdown.
8
BATT
Li+ Battery Connection. Bypass BATT to GND with a ceramic capacitor of at least 2.2µF per
ampere of charge current.
—
EP
Exposed Paddle. Connect the exposed paddle to a large ground plane for maximum power
dissipation. Connect GND to the exposed paddle directly under the IC.
_______________________________________________________________________________________
5
MAX8808X/MAX8808Y/MAX8808Z
Pin Description
MAX8808X/MAX8808Y/MAX8808Z
1A Linear Li+ Battery Chargers with Integrated Pass
FET and Thermal Regulation in 2mm x 2mm TDFN
exceeds 2.5V, the charger soft-starts as it enters the
fast-charge stage. In the MAX8808X/MAX8808Y/
MAX8808Z, the fast-charge current level is programmed through a resistor from ISET to GND. 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 that the battery is fully
charged. The ICs then enter a constant voltage-regulation mode to maintain the battery at full charge.
Detailed Description
The MAX8808X/MAX8808Y/MAX8808Z chargers use
voltage, current, and thermal-control loops to charge a
single Li+ cell and protect the battery (Figure 1). When
a Li+ battery with a cell voltage below 2.5V is inserted,
the MAX8808X charger enters the prequalification
stage where it precharges that cell with 10% of the
user-programmed fast-charge current (Figure 2). The
CHG indicator output is driven low to indicate entry into
the prequalification state. When battery voltage
4.25V TO 15V
BATT
IN
1µF
1µF
+115°C
OUTPUT DRIVER, CURRENT
SENSE, AND LOGIC
TEMP
SENSOR
ISET
2.8kΩ
VREF
IREF
VI/O
IN
100kΩ
IN
VL
VL
BATT
0.47µF
MAX8808X
MAX8808Y
MAX8808Z
ACOK
EN (MAX8808Y)
UVLO
VI/O
IN
REF
100kΩ
CHG
OVP
ON
EN
(MAX8808X/
MAX8808Z)
LOGIC
REF OK
200kΩ
N
GND
Figure 1. Functional Diagram
6
_______________________________________________________________________________________
1A Linear Li+ Battery Chargers with Integrated Pass
FET and Thermal Regulation in 2mm x 2mm TDFN
AND D
N
< 7V
VIN VBATT A D
E
>
L
VIN ENAB
IC
MAX8808X
VBATT < 2.5V
VIN > 7V OR
VBATT > VIN OR
IC DISABLED
VBATT < 2.4V
MAX8808Y/
MAX8808Z
ASYNCHRONOUS
FROM ANYWHERE
VIN > 7V OR
VBATT > VIN OR
IC DISABLED
V
VIN IN <
> 7
IC VB V AN
EN ATT D
AB AN
LE D
D
PREQUAL
10% CHARGE CURRENT
CHG = LOW
MAX8808X/MAX8808Y/MAX8808Z
SHUTDOWN
CHARGER = OFF
CHG = HIGH
VBATT > 2.5V
FAST-CHARGE
100% CHARGER CURRENT
CHG = LOW
ICHARGE < 10%
OF ISET
ICHARGE > 20%
OF ISET
TOP-OFF
CHG = HIGH
TOP-OFF CONTINUES
TO REGULATE BATT AT
4.2V
Figure 2. Charge-State Diagram
Thermal Regulation
The thermal-regulation loop limits the MAX8808X/
MAX8808Y/MAX8808Z die temperature to +115°C by
reducing the charge current as necessary. This feature
not only protects the ICs from overheating, but also
allows a higher charge current without risking damage
to the system.
EN (MAX8808X/MAX8808Z) and EN
(MAX8808Y) Charger Enable Input
The MAX8808X/MAX8808Z contain an active-low logic
input (EN) used to enable the charger. Drive EN low,
leave floating, or connect to GND to enable the
charge-control circuitry. Drive EN high to disable the
charger-control circuitry. EN has a 200kΩ internal pulldown resistor.
The MAX8808Y contains an active-high enable input
(EN) to enable the charger. Drive EN high to enable the
charge-control circuitry. Drive EN low to disable the
charger-control circuitry. Do not leave EN floating. It
has no internal pullup or pulldown resistor.
ACOK Output
The open-drain ACOK output asserts low when +4.25V
≤ VIN ≤ +7V and VIN - VBATT ≥ 40mV. ACOK requires
an external pullup resistor (100kΩ typ). ACOK is high
impedance during shutdown.
_______________________________________________________________________________________
7
MAX8808X/MAX8808Y/MAX8808Z
1A Linear Li+ Battery Chargers with Integrated Pass
FET and Thermal Regulation in 2mm x 2mm TDFN
VL Internal Voltage Regulator
The MAX8808X/MAX8808Y/MAX8808Z linear chargers
contain an internal linear regulator to supply the power
for the IC. Bypass VL to GND with a 0.47µF ceramic
capacitor. VL is regulated to 3.0V whenever the input
voltage is above the battery voltage.
CHG Charge-Indicator Output
CHG is an open-drain output that indicates charge status. Table 1 describes the state of CHG during different
stages of operation. CHG is suitable for driving a
charge-indication LED. If the MAX8808X/MAX8808Y/
MAX8808Z is used in conjunction with a µP, a pullup
resistor to the logic I/O voltage allows CHG to indicate
charge status to the µP instead of driving an LED.
Soft-Start
The soft-start algorithm activates when entering fastcharge mode. In the MAX8808X, when the prequalification state is complete (V BATT exceeds +2.5V), the
charging current ramps up in 1ms to the full charging
current. This reduces the inrush current on the input
supply. Note that the MAX8808Y and MAX8808Z do not
have a prequalification state and enter soft-start directly
after being enabled.
Applications Information
Charge-Current Selection
The maximum charging current is programmed by an
external resistor connected from ISET to GND (RISET).
Calculate RISET as follows:
RISET = 1302V / IFASTCHG
where IFASTCHG is in Amps and RISET is in Ohms. ISET
can be used to monitor the fast-charge current level.
The output current from ISET is 1.08mA per amp of
charging current. The output voltage at ISET is proportional to the charging current:
VISET = (ICHARGE x RISET) / 930
The voltage at ISET is nominally 1.4V at the selected
fast-charge current, and falls with charging current as
the cell becomes fully charged or as the thermal-regulation circuitry activates.
Capacitor Selection
Connect a ceramic capacitor from BATT to GND for
proper stability. Use a 1µF X5R ceramic capacitor for
most applications. Connect a 1µF ceramic capacitor
from IN to GND. Use a larger input bypass capacitor
for high charging currents to reduce supply noise.
Connect a 0.47µF ceramic capacitor from VL to GND.
Thermal Considerations
The MAX8808X/MAX8808Y/MAX8808Z are available in
a thermally enhanced TDFN package with exposed
paddle. Connect the exposed paddle to a large copper ground plane to provide a thermal contact
between the device and the circuit board for increased
power dissipation. The exposed paddle transfers heat
away from the device, allowing the ICs to charge the
battery with maximum current, while minimizing the
increase in die temperature.
Table 1. CHG States
EN
MAX8808X
EN
MAX8808Y
EN
MAX8808Z
VIN
VBATT
IBATT
CHG
STATE
Shutdown
X
X
X
≤VBATT
≥VIN
0
High-Impedance
Low
—
—
4.25V ≤ VIN ≤ 7V
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