19-4410; Rev 0; 12/08
KIT
ATION
EVALU
BLE
AVAILA
2A 1-Cell Li+ DC-DC Charger for USB*
and Adapter Power
General Description
Features
♦
Efficient DC-DC Converter Eliminates Heat
♦
4MHz Switching for Tiny External Components
♦
Instant On—Works with No Battery or Low
Battery
♦
Dual Current-Limiting Input Circuits—AC Adapter
or USB
Automatic Adapter/USB/Battery Switchover to
Support Load Transients
50mΩ System-to-Battery Switch
Supports USB Spec
♦
Thermistor Monitor
♦
Integrated Current-Sense Resistor
♦
No External MOSFETS or Diodes
♦
4.1V to 16V Input Operating Voltage Range
MAX8903A
The MAX8903A is an integrated 1-cell Li+ charger and
Smart Power Selector™ with dual (AC adapter and
USB) power inputs. The switch mode charger uses a
high switching frequency to eliminate heat and allow
tiny external components. It can operate with either
separate inputs for USB and AC adapter power, or from
a single input that accepts both. All power switches for
charging and switching the load between battery and
external power are included on-chip. No external
MOSFETs, blocking diodes, or current-sense resistors
are required.
The MAX8903A features optimized smart power control
to make the best use of limited USB or adapter power.
Battery charge current and SYS output current limit are
independently set. Power not used by the system
charges the battery. Charge current and SYS output
current limit can be set up to 2A while USB input cur-
rent can be set to 100mA or 500mA. Automatic input
selection switches the system from battery to external
power. The DC input operates from 4.15V to 16V with
up to 20V protection, while the USB input has a range
of 4.1V to 6.3V with up to 8V protection.
The MAX8903A internally blocks current from the bat-
tery and system back to the DC and USB inputs when
no input supply is present. Other features include pre-
qual charging and timer, fast charge timer, overvoltage
protection, charge status and fault outputs, power-OK
monitors, and a battery thermistor monitor. In addition,
on-chip thermal limiting reduces battery charge rate
and AC adapter current to prevent charger overheat-
ing. The MAX8903A is available in a 4mm x 4mm, 28-pin
thin QFN package.
Ordering Information
PART
MAX8903AETI+
TEMP RANGE
-40°C to +85°C
PIN-PACKAGE
28 Thin QFN-EP**
+Denotes
a lead(Pb)-free/RoHS-compliant package.
**EP
= Exposed pad.
Typical Operating Circuit
AC
ADAPTER
OR USB
Applications
PDAs, Palmtops, and Wireless Handhelds
Personal Navigation Devices
Smart Cell Phones
Portable Multimedia Players
Mobile Internet Devices
Ultra Mobile PCs
LX
DC
CS
SYS
LOAD
CURRENT
CHARGE AND
SYS LOAD
SWITCH
SYSTEM
LOAD
CHARGE
CURRENT
PWM
STEP-DOWN
USB
USB
BAT
BATTERY
*Protected by US Patent #6,507,172.
Smart Power Selector is a trademark of Maxim Integrated
Products, Inc.
MAX8903A
GND
Pin Configuration appears at end of data sheet.
________________________________________________________________
Maxim Integrated Products
1
For pricing, delivery, and ordering information, please contact Maxim Direct at 1-888-629-4642,
or visit Maxim’s website at www.maxim-ic.com.
2A 1-Cell Li+ DC-DC Charger for USB*
and Adapter Power
MAX8903A
ABSOLUTE MAXIMUM RATINGS
DC, LX, DCM to GND .............................................-0.3V to +20V
DC to SYS .................................................................-6V to +20V
BST to GND ...........................................................-0.3V to +26V
BST TO LX ................................................................-0.3V to +6V
USB to GND .............................................................-0.3V to +9V
USB to SYS..................................................................-6V to +9V
VL to GND ................................................................-0.3V to +6V
THM, IDC, ISET, CT to GND .........................-0.3V to (VL + 0.3V)
DOK, FLT, CEN, UOK, CHG,
USUS,
BAT, SYS, IUSB, CS to GND ................................-0.3V to +6V
SYS to BAT ...............................................................-0.3V to +6V
PG, EP (exposed pad) to GND .............................-0.3V to +0.3V
DC Continuous Current (total in two pins)......................2.4A
RMS
USB Continuous Current.......................................................1.6A
LX Continuous Current (total in two pins).......................2.4A
RMS
CS Continuous Current (total in two pins) ......................2.4A
RMS
SYS Continuous Current (total in two pins) .......................3A
RMS
BAT Continuous Current (total in two pins) .......................3A
RMS
Continuous Power Dissipation (T
A
= +70°C)
28-Pin Thin QFN-EP
Multilayer (derate 28.6mW/°C above +70°C) ..........2286mW
28-Pin Thin QFN-EP
Single-Layer (derate 20.8mW/°C above +70°C)...1666.7mW
Operating Temperature Range ...........................-40°C to +85°C
Junction Temperature Range ............................-40°C to +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
DC
= V
USB
= 5V, V
BAT
= 4V, circuit of Figure 2, T
A
= -40°C to +85°C, unless otherwise noted. Typical values are at T
A
= +25°C.)
(Note 1)
PARAMETER
DC INPUT
DC Operating Range
DC Undervoltage Threshold
DC Overvoltage Threshold
When V
DOK
goes low, V
DC
rising, 500mV typical hysteresis
No valid USB input
Valid USB input
4.15
3.9
4.0
16.5
4.0
4.3
17
2.3
15
1
1
0.10
0.15
0.15
0.31
When SYS regulation and charging stops, V
DC
falling,
200mV hysteresis
V
DC
= 8V, V
BAT
= 4V
V
DC
= 5V, V
BAT
= 3V
0.5
R
IDC
= 3kΩ
V
DC
= 6V, V
SYS
= 4V
No valid USB input
Valid USB input before soft-start
R
IDC
= 6kΩ
R
IDC
= 12kΩ
DC Soft-Start Time
1900
950
450
2000
1000
500
1
20
0
15
4
3
2
2100
1050
550
ms
µs
mA
30
2
2
0.25
Ω
Ω
Ω
mV
MHz
A
mA
16
4.1
4.4
17.5
4
V
V
V
CONDITIONS
MIN
TYP
MAX
UNITS
When V
DOK
goes high, V
DC
rising, 500mV typical
hysteresis
Charger enabled, no switching, V
SYS
= 5V
Charger enabled, f = 3MHz, V
DC
= 5V
DC Supply Current
Charger enabled, V
CEN
= 0V, 100mA USB mode (Note 2)
Charger enabled, V
CEN
= 5V, 100mA USB mode (Note 2)
V
DCM
= 0V, V
USUS
= 5V
DC High-Side Resistance
DC Low-Side Resistance
DC-to-BAT Dropout Resistance
DC-to-BAT Dropout Voltage
Switching Frequency
DC Step-Down Output Current-
Limit Step Range
DC Step-Down Output Current
Limit
2
_______________________________________________________________________________________
2A 1-Cell Li+ DC-DC Charger for USB*
and Adapter Power
ELECTRICAL CHARACTERISTICS (continued)
(V
DC
= V
USB
= 5V, V
BAT
= 4V, circuit of Figure 2, T
A
= -40°C to +85°C, unless otherwise noted. Typical values are at T
A
= +25°C.)
(Note 1)
PARAMETER
DC Output Current
500mA USB Mode
(Note 3)
DC Output Current
100mA USB Mode
(Note 2)
SYS to DC Reverse Current
Blocking
USB INPUT
USB Operating Range
USB Standoff Voltage
USB Undervoltage Threshold
USB Overvoltage Threshold
USB Current Limit
When V
UOK
goes low, V
USB
rising, 500mV hysteresis
When V
UOK
goes high, V
USB
rising, 500mV hysteresis
V
IUSB
= 0V (100mA setting)
V
IUSB
= 5V (500mA setting)
I
SYS
= I
BAT
= 0mA, V
CEN
= 0V
USB Supply Current
Minimum USB to BAT Headroom
USB to SYS Dropout Resistance
USB Soft-Start Time
SYS OUTPUT
Minimum SYS Regulation Voltage
Regulation Voltage
Load Regulation
CS to SYS Resistance
SYS to CS Leakage
BAT to SYS Resistance
BAT to SYS Reverse Regulation
Voltage
SYS Undervoltage Threshold
BATTERY CHARGER
BAT Regulation Voltage
Charger Restart Threshold
BAT Prequal Threshold
Prequal Charge Current
I
BAT
= 0mA
T
A
= +25°C
T
A
= -40°C to +85°C
4.179
4.158
-150
2.9
4.2
4.2
-100
3
10
4.221
4.242
-60
3.1
V
mV
V
%
I
SYS
= 1A, V
BAT
< V
SYS_MIN
I
SYS
= 0A
I
SYS
= 0 to 2A
V
DC
= 6V, V
DCM
= 5V, V
SYS
= 4V, I
CS
= 1A
V
SYS
= 5.5V, V
DC
= V
CS
= 0V
V
DC
= V
USB
= 0V, V
BAT
= 4.2V, I
SYS
= 1A
V
USB
= 5V, V
DC
= 0V, V
IUSB
= 0V, I
SYS
= 200mA
SYS falling, 200mV hysteresis (Note 4)
50
1.8
4.3
3.0
4.4
40
0.07
0.01
0.05
75
1.9
0.1
100
2.0
4.5
V
V
mV/A
Ω
µA
Ω
mV
V
V
USB
rising
V
DC
falling below DC UVLO to initiate USB soft-start
I
SYS
= I
BAT
= 0mA, V
CEN
= 5V
V
USUS
= 5V (USB suspend mode)
0
3.95
6.8
90
450
4.0
6.9
95
475
1.3
0.8
0.115
15
0.2
1
20
4.1
6.3
8
4.05
7.0
100
500
3
2
0.25
30
0.35
mV
Ω
ms
µs
mA
V
V
V
V
mA
CONDITIONS
V
DCM
= 0V, V
IUSB
= 5V
MIN
450
TYP
475
MAX
500
UNITS
mA
MAX8903A
V
DCM
= 0V, V
IUSB
= 0V
90
95
100
mA
V
SYS
= 5.5V, V
DC
= 0V
0.01
µA
Change in V
BAT
from DONE to fast-charge
V
BAT
rising, 180mV hysteresis
Percentage of fast-charge current set at ISET
_______________________________________________________________________________________
3
2A 1-Cell Li+ DC-DC Charger for USB*
and Adapter Power
MAX8903A
ELECTRICAL CHARACTERISTICS (continued)
(V
DC
= V
USB
= 5V, V
BAT
= 4V, circuit of Figure 2, T
A
= -40°C to +85°C, unless otherwise noted. Typical values are at T
A
= +25°C.)
(Note 1)
PARAMETER
R
ISET
= 600Ω
Fast-Charge Current
DONE Threshold
R
ISET
Resistor Range
ISET Output Voltage
ISET Current Monitor Gain
BAT Leakage Current
Charger Soft-Start Time
Charger Thermal Limit
Temperature
Charger Thermal Limit Gain
CHARGER TIMER
Prequalification Time
Fast-Charge Time
Timer Accuracy
Timer Extend Current Threshold
Timer Suspend Current Threshold
Charge Done Delay Time
THERMISTOR MONITOR
THM Threshold, Hot
THM Threshold, Cold
THM Threshold, Disabled
THM Input Leakage
When charging is suspended, 1% hysteresis
When charging is suspended, 1% hysteresis
THM function is disabled below this voltage
THM = GND or VL; T
A
= +25°C
THM = GND or VL; T
A
= +85°C
High level
Logic-Input Thresholds
(DCM,
CEN,
USUS, IUSB)
Logic-Input Leakage Current
(DCM,
CEN,
USUS, IUSB)
Low level
Hysteresis
V
INPUT
= 0 to 5.5V
T
A
= +25°C
T
A
= +85°C
50
0.001
0.01
1
1.3
0.4
0.27 x
V
VL
0.73 x
V
VL
0.0254
x V
VL
-0.1
0.28 x
V
VL
0.74 x
V
VL
0.03 x
V
VL
+0.001
0.01
0.29 x
V
VL
0.75 x
V
VL
0.036 x
V
VL
+0.2
V
V
V
µA
Percentage of fast-charge current below which the timer
clock operates at half-speed
Percentage of fast-charge current below which timer
clock pauses
From done threshold detection until charger turns off and
CHG
goes high
C
CT
= 0.15µF
C
CT
= 0.15µF
-15
40
16
50
20
15
33
660
+15
60
24
min
min
%
%
%
s
Charge current = 0 at +120°C
No DC or USB input
With valid input power, V
CEN
= 5V
R
ISET
= 1.2kΩ
R
ISET
= 2.4kΩ
Percentage of fast-charge, I
BAT
decreasing
0.6
1.5
1.25
0.05
1
1.0
100
5
4
6
CONDITIONS
MIN
1800
900
450
TYP
2000
1000
500
10
2.4
MAX
2200
1100
550
%
kΩ
V
mA/A
µA
ms
°C
%/°C
mA
UNITS
THERMAL SHUTDOWN, VL, AND LOGIC I/O:
CHG, FLT, DOK, UOK,
DCM,
CEN,
USUS, IUSB
V
mV
µA
4
_______________________________________________________________________________________
2A 1-Cell Li+ DC-DC Charger for USB*
and Adapter Power
ELECTRICAL CHARACTERISTICS (continued)
(V
DC
= V
USB
= 5V, V
BAT
= 4V, circuit of Figure 2, T
A
= -40°C to +85°C, unless otherwise noted. Typical values are at T
A
= +25°C.)
(Note 1)
PARAMETER
Logic Output Voltage, Low
(CHG,
FLT, DOK, UOK)
Sinking 1mA
Sinking 10mA
T
A
= +25°C
T
A
= +85°C
4.6
CONDITIONS
MIN
TYP
8
80
0.001
0.01
5
3.2
160
15
5.4
1
MAX
50
UNITS
mV
µA
V
V
°C
°C
MAX8903A
Open-Drain Output Leakage
V
OUT
= 5.5V
Current, High (CHG,
FLT, DOK, UOK)
VL Output Voltage
VL UVLO Threshold
Thermal Shutdown Temperature
Thermal Shutdown Hysteresis
V
VL
falling; 200mV hysteresis
V
DC
= V
USB
= 6V, I
VL
= 0 to 1mA
Note 1:
Limits are 100% production tested at T
A
= +25°C. Limits over the operating temperature range are guaranteed by design.
Note 2:
For the 100mA USB mode using the DC input, the step-down regulator is turned off and a low-dropout linear regulator is
connected from DC to SYS.
Note 3:
For the 500mA USB mode, the actual current drawn from USB is less than the output current due to the input/output current
ratio of the DC-DC converter.
Note 4:
For short-circuit protection, SYS sources 25mA below V
SYS
= 400mV, and 50mA for V
SYS
between 400mV and 2V.
Typical Operating Characteristics
(T
A
= +25°C, unless otherwise noted.)
BATTERY CHARGER EFFICIENCY
vs. BATTERY VOLTAGE
MAX8903A toc01
SWITCHING FREQUENCY
vs. V
DC
MAX8903A toc02
SYS EFFICIENCY vs. DC VOLTAGE
90
80
SYS EFFICIENCY (%)
70
60
50
40
30
20
V
DC
= 6V
V
DC
= 16V
V
DC
= 11V
MAX8903A toc03
100
90
80
EFFICIENCY (%)
70
60
50
40
30
20
10
0
1.0
1.5
2.0
2.5
3.0
3.5
4.0
4.5
I
BATT
= 0.15A
I
BATT
= 1.5A
I
BATT
= 1.5A
V
DC
= 12V
V
DC
= 8V
V
DC
= 5V
4.5
4.0
SWITCHING FREQUENCY (MHz)
3.5
3.0
2.5
2.0
1.5
1.0
0.5
0.0
R
ISET
= 1.2kΩ
CEN = 0V
4
6
8
10
12
14
V
BAT
= 4V
V
BAT
= 3V
100
10
0
16
1
10
V
DC
= 4.5V
100
1000
10,000
5.0
BATTERY VOLTAGE (V)
DC VOLTAGE (V)
SYS OUTPUT CURRENT (mA)
_______________________________________________________________________________________
5
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