MAX8903A.pdf
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MAX8903A DS
19-4410; Rev 0; 12/08
2A 1-Cell Li+ DC-DC Charger for USB*
and Adapter Power
General Description
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.
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
50m
Ω
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
Ordering Information
PART
TEMP RANGE
PIN-PACKAGE
MAX8903AETI+
-40°C to +85°C
28 Thin QFN-EP**
+Denotes a lead(Pb)-free/RoHS-compliant package.
**EP = Exposed pad.
Typical Operating Circuit
Applications
PDAs, Palmtops, and Wireless Handhelds
Personal Navigation Devices
Smart Cell Phones
Portable Multimedia Players
Mobile Internet Devices
Ultra Mobile PCs
AC
ADAPTER
OR USB
LX
CS
DC
SYS
LOAD
CURRENT
CHARGE
CURRENT
CHARGE AND
SYS LOAD
SWITCH
SYSTEM
LOAD
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 Directat 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
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
CONDITIONS
MIN
TYP
MAX
UNITS
DC INPUT
DC Operating Range
4.15
16
V
DC Undervoltage Threshold
When V
DOK
goes low, V
DC
rising, 500mV typical hysteresis
Valid USB input
No valid USB input
3.9
4.0
4.1
V
4.0
4.3
4.4
DC Overvoltage Threshold
When V
DOK
goes high, V
DC
rising, 500mV typical
hysteresis
16.5
17
17.5
V
Charger enabled, no switching, V
SYS
= 5V
2.3
4
Charger enabled, f = 3MHz, V
DC
= 5V
15
DC Supply Current
Charger enabled, V
CEN
= 0V, 100mA USB mode (Note 2)
1
2
mA
Charger enabled, V
CEN
= 5V, 100mA USB mode (Note 2)
1
2
V
DCM
= 0V, V
USUS
= 5V
0.10
0.25
DC High-Side Resistance
0.15
Ω
DC Low-Side Resistance
0.15
Ω
DC-to-BAT Dropout Resistance
0.31
Ω
DC-to-BAT Dropout Voltage
When SYS regulation and charging stops, V
DC
falling,
200mV hysteresis
0
15
30
mV
Switching Frequency
V
DC
= 8V, V
BAT
= 4V
4
MHz
V
DC
= 5V, V
BAT
= 3V
3
DC Step-Down Output Current-
Limit Step Range
0.5
2
A
R
IDC
= 3k
Ω
1900
2000
2100
DC Step-Down Output Current
Limit
V
DC
= 6V, V
SYS
= 4V
R
IDC
= 6k
Ω
950
1000
1050
mA
R
IDC
= 12k
Ω
450
500
550
DC Soft-Start Time
No valid USB input
1
ms
Valid USB input before soft-start
20
µs
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
CONDITIONS
MIN
TYP
MAX
UNITS
DC Output Current
500mA USB Mode
(Note 3)
V
DCM
= 0V, V
IUSB
= 5V
450
475
500
mA
DC Output Current
100mA USB Mode
(Note 2)
V
DCM
= 0V, V
IUSB
= 0V
90
95
100
mA
SYS to DC Reverse Current
Blocking
V
SYS
= 5.5V, V
DC
= 0V
0.01
µA
USB INPUT
USB Operating Range
4.1
6.3
V
USB Standoff Voltage
8
V
USB Undervoltage Threshold
When V
UOK
goes low, V
USB
rising, 500mV hysteresis
3.95
4.0
4.05
V
USB Overvoltage Threshold
When V
UOK
goes high, V
USB
rising, 500mV hysteresis
6.8
6.9
7.0
V
USB Current Limit
V
IUSB
= 0V (100mA setting)
90
95
100
mA
V
IUSB
= 5V (500mA setting)
450
475
500
I
SYS
= I
BAT
= 0mA, V
CEN
= 0V
1.3
3
USB Supply Current
I
SYS
= I
BAT
= 0mA, V
CEN
= 5V
0.8
2
mA
V
USUS
= 5V (USB suspend mode)
0.115
0.25
Minimum USB to BAT Headroom
0
15
30
mV
USB to SYS Dropout Resistance
0.2
0.35
Ω
USB Soft-Start Time
V
USB
rising
1
ms
V
DC
falling below DC UVLO to initiate USB soft-start
20
µs
SYS OUTPUT
Minimum SYS Regulation Voltage I
SYS
= 1A, V
BAT
< V
SYS_MIN
3.0
V
Regulation Voltage
I
SYS
= 0A
4.3
4.4
4.5
V
Load Regulation
I
SYS
= 0 to 2A
40
mV/A
CS to SYS Resistance
V
DC
= 6V, V
DCM
= 5V, V
SYS
= 4V, I
CS
= 1A
0.07
Ω
SYS to CS Leakage
V
SYS
= 5.5V, V
DC
= V
CS
= 0V
0.01
µA
BAT to SYS Resistance
V
DC
= V
USB
= 0V, V
BAT
= 4.2V, I
SYS
= 1A
0.05
0.1
Ω
BAT to SYS Reverse Regulation
Voltage
V
USB
= 5V, V
DC
= 0V, V
IUSB
= 0V, I
SYS
= 200mA
50
75
100
mV
SYS Undervoltage Threshold
SYS falling, 200mV hysteresis (Note 4)
1.8
1.9
2.0
V
BATTERY CHARGER
BAT Regulation Voltage
I
BAT
= 0mA
T
A
= +25°C
4.179
4.2
4.221
V
T
A
= -40°C to +85°C
4.158
4.2
4.242
Charger Restart Threshold
Change in V
BAT
from DONE to fast-charge
-150
-100
-60
mV
BAT Prequal Threshold
V
BAT
rising, 180mV hysteresis
2.9
3
3.1
V
Prequal Charge Current
Percentage of fast-charge current set at ISET
10
%
_______________________________________________________________________________________ 3
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
CONDITIONS
MIN
TYP
MAX
UNITS
R
ISET
= 600
Ω
1800
2000
2200
Fast-Charge Current
R
ISET
= 1.2k
Ω
900
1000
1100
mA
R
ISET
= 2.4k
Ω
450
500
550
DONE Threshold
Percentage of fast-charge, I
BAT
decreasing
10
%
R
ISET
Resistor Range
0.6
2.4
k
Ω
ISET Output Voltage
1.5
V
ISET Current Monitor Gain
1.25
mA/A
BAT Leakage Current
No DC or USB input
0.05
4
µA
With valid input power, V
CEN
= 5V
1
6
Charger Soft-Start Time
1.0
ms
Charger Thermal Limit
Temperature
100
°C
Charger Thermal Limit Gain
Charge current = 0 at +120°C
5
%/°C
CHARGER TIMER
Prequalification Time
C
CT
= 0.15µF
33
min
Fast-Charge Time
C
CT
= 0.15µF
660
min
Timer Accuracy
-15
+15
%
Timer Extend Current Threshold
Percentage of fast-charge current below which the timer
clock operates at half-speed
40
50
60
%
Timer Suspend Current Threshold
Percentage of fast-charge current below which timer
clock pauses
16
20
24
%
Charge Done Delay Time
From done threshold detection until charger turns off and
CHG goes high
15
s
THERMISTOR MONITOR
THM Threshold, Hot
When charging is suspended, 1% hysteresis
0.27 x
V
VL
0.28 x
V
VL
0.29 x
V
VL
V
THM Threshold, Cold
When charging is suspended, 1% hysteresis
0.73 x
V
VL
0.74 x
V
VL
0.75 x
V
VL
V
THM Threshold, Disabled
THM function is disabled below this voltage
0.0254
x V
VL
0.03 x
V
VL
0.036 x
V
VL
V
THM Input Leakage
THM = GND or VL; T
A
= +25°C
-0.1
+0.001 +0.2
µA
THM = GND or VL; T
A
= +85°C
0.01
THERMAL SHUTDOWN, VL, AND LOGIC I/O:
CHG
,
FLT
,
DOK
,
UOK
, DCM,
CEN
, USUS, IUSB
High level
1.3
V
Logic-Input Thresholds
(DCM, CEN, USUS, IUSB)
Low level
0.4
Hysteresis
50
mV
Logic-Input Leakage Current
(DCM, CEN, USUS, IUSB)
V
INPUT
= 0 to 5.5V
T
A
= +25°C
0.001
1
µA
T
A
= +85°C
0.01
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
CONDITIONS
MIN
TYP
MAX
UNITS
Logic Output Voltage, Low
(CHG, FLT, DOK, UOK)
Sinking 1mA
8
50
mV
Sinking 10mA
80
Open-Drain Output Leakage
Current, High (CHG, FLT, DOK, UOK)
V
OUT
= 5.5V
T
A
= +25°C
0.001
1
µA
T
A
= +85°C
0.01
VL Output Voltage
V
DC
= V
USB
= 6V, I
VL
= 0 to 1mA
4.6
5
5.4
V
VL UVLO Threshold
V
VL
falling; 200mV hysteresis
3.2
V
Thermal Shutdown Temperature
160
°C
Thermal Shutdown Hysteresis
15
°C
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
SWITCHING FREQUENCY
vs. V
DC
SYS EFFICIENCY vs. DC VOLTAGE
100
4.5
100
90
80
V
DC
= 5V
4.0
3.5
90
80
70
V
DC
= 8V
3.0
V
BAT
= 3V
70
60
50
60
V
DC
= 16V
V
DC
= 11V
V
DC
= 6V
2.5
50
V
BAT
= 4V
2.0
40
30
V
DC
= 12V
40
1.5
30
20
10
I
BATT
= 0.15A
I
BATT
= 1.5A
1.0
20
0.5
R
ISET
= 1.2k
Ω
10
V
DC
= 4.5V
I
BATT
= 1.5A
CEN = 0V
0
0.0
0
1.0
1.5
2.0 2.5
3.0 3.5 4.0 4.5 5.0
4
6
8
10
12
14
16
1
10
100
1000
10,000
BATTERY VOLTAGE (V)
DC VOLTAGE (V)
SYS OUTPUT CURRENT (mA)
_______________________________________________________________________________________ 5
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