19-4410; Rev 5; 9/11
For pricing, delivery, and ordering information, please contact Maxim Direct
at 1-888-629-4642, or visit Maxim’s website at www.maximintegrated.com.
MAX8903A–E/G/H/J/N/Y
2A 1-Cell Li+ DC-DC Chargers
for USB and Adapter Power
EVALUATION KIT AVAILABLE
General Description
The MAX8903A–MAX8903E/MAX8903G/MAX8903H/
MAX8903J/MAX8903N/MAX8903Y are integrated 1-cell
Li+ chargers and Smart Power Selectors™ 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 cur-
rent-sense resistors are required.
The MAX8903_ 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 cur-
rent limit can be set up to 2A while USB input current 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 pro-
tection, while the USB input has a range of 4.1V to 6.3V
with up to 8V protection.
The MAX8903_ 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 MAX8903_ is available in a 4mm x 4mm, 28-pin
thin QFN package.
The various versions of the MAX8903_ allow for design
flexibility to choose key parameters such as system
regulation voltage, battery prequalification threshold,
and battery regulation voltage. The MAX8903B/
MAX8903E/MAX8903G also includes power-enable on
battery detection. See the
Selector Guide
section for
complete details.
Applications
Features
oEfficient DC-DC Converter Eliminates Heat
o4MHz Switching for Tiny External Components
oInstant On—Works with No/Low Battery
oDual Current-Limiting Inputs—AC Adapter or USB
Automatic Adapter/USB/Battery Switchover to
Support Load Transients
50mΩSystem-to-Battery Switch
Supports USB Spec
oThermistor Monitor
oIntegrated Current-Sense Resistor
oNo External MOSFETs or Diodes
o4.1V to 16V Input Operating Voltage Range
Pin Configuration appears at end of data sheet.
Selector Guide appears at end of data sheet.
CHARGE
AND
SYS LOAD
SWITCH
DC SYS
BAT
AC
ADAPTER
OR USB
SYSTEM
LOAD
BATTERY
GND
USB
USB
CHARGE
CURRENT
LOAD
CURRENT
LX CS
PWM
STEP-DOWN
MAX8903_
Typical Operating Circuit
Smart Power Selector is a trademark of Maxim Integrated
Products, Inc.
PDAs, Palmtops, and
Wireless Handhelds
Personal Navigation
Devices
Smart Cell Phones
Portable Multimedia
Players
Mobile Internet Devices
Ultra Mobile PCs
Ordering Information
+
Denotes a lead(Pb)-free/RoHS-compliant package.
*
EP = Exposed pad.
T = Tape and reel.
PART TEMP RANGE PIN-PACKAGE
MAX8903AETI+T
-40°C to +85°C
28 Thin QFN-EP*
MAX8903BETI+T
-40°C to +85°C
28 Thin QFN-EP*
MAX8903CETI+T
-40°C to +85°C
28 Thin QFN-EP*
MAX8903DETI+T
-40°C to +85°C
28 Thin QFN-EP*
MAX8903EETI+T
-40°C to +85°C
28 Thin QFN-EP*
MAX8903GETI+T
-40°C to +85°C
28 Thin QFN-EP*
MAX8903HETI+T
-40°C to +85°C
28 Thin QFN-EP*
MAX8903JETI+T
-40°C to +85°C
28 Thin QFN-EP*
MAX8903NETI+T
-40°C to +85°C
28 Thin QFN-EP*
MAX8903YETI+T
-40°C to +85°C
28 Thin QFN-EP*
Visit www.maximintegrated.com/products/patents for
product patent marking information.
MAX8903A–E/G/H/J/N/Y
2A 1-Cell Li+ DC-DC Chargers
for USB and Adapter Power
2Maxim Integrated
ELECTRICAL CHARACTERISTICS
(VDC = VUSB = 5V, VBAT = 4V, circuit of Figure 2, TA= -40°C to +85°C, unless otherwise noted. Typical values are at TA= +25°C.)
(Note 1)
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.
PARAMETER CONDITIONS MIN TYP MAX UNITS
DC INPUT
DC Operating Range 4.15 16 V
No valid USB input 3.9 4.0 4.1
DC Undervoltage Threshold When VDOK goes low, VDC
rising, 500mV typical hysteresis Valid USB input 4.0 4.3 4.4 V
DC Overvoltage Threshold When VDOK goes high, VDC rising, 500mV typical
hysteresis 16.5 17 17.5 V
Charger enabled, no switching, VSYS = 5V 2.3 4
Charger enabled, f = 3MHz, VDC = 5V 15
C har g er enab l ed , V
C E N = 0V , 100m A U S B m od e ( N ote 2) 1 2
C har g er enab l ed , V
C E N = 5V , 100m A U S B m od e ( N ote 2) 1 2
DC Supply Current
VDCM = 0V, VUSUS = 5V 0.10 0.25
mA
DC High-Side Resistance 0.15 Ω
DC Low-Side Resistance 0.15 Ω
DC-to-BAT Dropout Resistance Assumes a 40mΩ inductor resistance (RL) 0.31 Ω
DC-to-BAT Dropout Voltage When SYS regulation and charging stops, VDC falling,
200mV hysteresis 01530mV
Minimum Off Time (tOFFMIN)100 ns
Minimum On Time (tONMIN) 70 ns
VDC = 8V, VBAT = 4V 4
MAX8903A/B/C/D/E/H/J/Y VDC = 5V, VBAT = 3V 3
VDC = 9V, VBAT = 4V 1
Switching Frequency (fSW)
MAX8903G VDC = 9V, VBAT = 3V 1
MHz
DC Step-Down Output Current-
Limit Step Range 0.5 2 A
RIDC = 3kΩ1900 2000 2100
RIDC = 6kΩ950 1000 1050
DC Step-Down Output Current
Limit (ISDLIM)VDC = 6V, VSYS = 4V
RIDC = 12kΩ450 500 550
mA
ABSOLUTE MAXIMUM RATINGS
DC, LX to GND .......................................................-0.3V to +20V
DCM to GND ..............................................-0.3V to (VDC + 0.3V)
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 (VVL + 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)......................2.4ARMS
USB Continuous Current.......................................................1.6A
LX Continuous Current (total in two pins).......................2.4ARMS
CS Continuous Current (total in two pins) ......................2.4ARMS
SYS Continuous Current (total in two pins) .......................3ARMS
BAT Continuous Current (total in two pins) .......................3ARMS
VL Short Circuit to GND .............................................Continuous
Continuous Power Dissipation (TA= +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
Soldering Temperature (reflow) .......................................+260°C
MAX8903A–E/G/H/J/N/Y
2A 1-Cell Li+ DC-DC Chargers
for USB and Adapter Power
3
Maxim Integrated
PARAMETER CONDITIONS MIN TYP MAX UNITS
No valid USB input 1 ms
DC Soft-Start Time Valid USB input before soft-start 20 µs
DC Output Current
500mA USB Mode (Note 3) VDCM = 0V, VIUSB = 5V 450 475 500 mA
DC Output Current
100mA USB Mode (Note 2) VDCM = 0V, VIUSB = 0V 90 95 100 mA
SYS to DC Reverse Current
Blocking VSYS = 5.5V, VDC = 0V 0.01 µA
USB INPUT
USB Operating Range 4.1 6.3 V
USB Standoff Voltage 8V
USB Undervoltage Threshold When VUOK goes low, VUSB rising, 500mV hysteresis 3.95 4.0 4.05 V
USB Overvoltage Threshold When VUOK goes high, VUSB rising, 500mV hysteresis 6.8 6.9 7.0 V
VIUSB = 0V (100mA setting) 90 95 100
USB Current Limit VIUSB = 5V (500mA setting) 450 475 500 mA
ISYS = IBAT = 0mA, VCEN = 0V 1.3 3
ISYS = IBAT = 0mA, VCEN = 5V 0.8 2
USB Supply Current
VUSUS = 5V (USB suspend mode) 0.115 0.25
mA
Minimum USB to BAT Headroom 0 15 30 mV
USB to SYS Dropout Resistance 0.2 0.35 Ω
VUSB rising 1 ms
USB Soft-Start Time VDC falling below DC UVLO to initiate USB soft-start 20 µs
SYS OUTPUT
MAX8903A/B/E/G/Y 3.0
Minimum SYS Regulation Voltage
(VSYSMIN)
ISYS = 1A,
VBAT < VSYSMIN MAX8903C/D/H/J/N 3.4 V
MAX8903A/C/D/H/N/Y 4.3 4.4 4.5
MAX8903B/E/G 4.265 4.325 4.395Regulation Voltage ISYS = 0A
MAX8903J 4.4 4.5 4.55
V
MAX8903A/C/D/H 40
Load Regulation ISYS = 0 to 2A MAX8903B/E/G/J/N/Y 25 mV/A
CS to SYS Resistance VDC = 6V, VDCM = 5V, VSYS = 4V, ICS = 1A 0.07 Ω
SYS to CS Leakage VSYS = 5.5V, VDC = VCS = 0V 0.01 µA
BAT to SYS Resistance VDC = VUSB = 0V, VBAT = 4.2V, ISYS = 1A 0.05 0.1 Ω
BAT to SYS Reverse Regulation
Voltage VUSB = 5V, VDC = 0V, VIUSB = 0V, ISYS = 200mA 50 75 100 mV
SYS Undervoltage Threshold SYS falling, 200mV hysteresis (Note 4) 1.8 1.9 2.0 V
ELECTRICAL CHARACTERISTICS (continued)
(VDC = VUSB = 5V, VBAT = 4V, circuit of Figure 2, TA= -40°C to +85°C, unless otherwise noted. Typical values are at TA= +25°C.)
(Note 1)
MAX8903A–E/G/H/J/N/Y
2A 1-Cell Li+ DC-DC Chargers
for USB and Adapter Power
4Maxim Integrated
PARAMETER CONDITIONS MIN TYP MAX UNITS
BATTERY CHARGER
TA = +25°C 4.179 4.200 4.221
MAX8903A/B/C/G/H TA = -40°C to +85°C 4.158 4.200 4.242
TA = +25°C 4.079 4.100 4.121
MAX8903D/E TA = -40°C to +85°C 4.059 4.100 4.141
TA = +25°C 4.328 4.350 4.372
MAX8903J TA = -40°C to +85°C 4.307 4.350 4.394
TA = +25°C 4.129 4.150 4.171
BAT Regulation Voltage
(VBATREG) IBAT = 0mA
MAX8903Y/N TA = -40°C to +85°C 4.109 4.150 4.192
V
C har g er Restar t Thr eshol d Change in VBAT from DONE to fast-charge -150 -100 -60 mV
MAX8903A/C/D/H/J/N/Y 2.9 3.0 3.1
BAT Prequal Threshold (VBATPQ)VBAT rising 180mV
hystersis MAX8903B/E/G 2.4 2.5 2.6 V
Prequal Charge Current Percentage of fast-charge current set at ISET 10 %
RISET = 600Ω1800 2000 2200
RISET = 1.2kΩ (MAX8903A/C/D) 900 1000 1100Fast-Charge Current
RISET = 2.4kΩ450 500 550
mA
DONE Threshold (ITERM) Percentage of fast-charge, IBAT decreasing 10 %
RISET Resistor Range 0.6 2.4 kΩ
ISET Output Voltage 1.5 V
ISET Current Monitor Gain 1.25 mA/A
No DC or USB input 0.05 4
BAT Leakage Current With valid input power, VCEN = 5V 3 6 µA
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 CCT = 0.15µF 33 min
Fast-Charge Time CCT = 0.15µF 660 min
MAX8903A/C/D/H/J/N/Y (fixed) 15 s
Top-Off Timer (tTOP-OFF)MAX8903B/E/G, CCT = 0.15µF 132 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 %
ELECTRICAL CHARACTERISTICS (continued)
(VDC = VUSB = 5V, VBAT = 4V, circuit of Figure 2, TA= -40°C to +85°C, unless otherwise noted. Typical values are at TA= +25°C.)
(Note 1)
MAX8903A–E/G/H/J/N/Y
2A 1-Cell Li+ DC-DC Chargers
for USB and Adapter Power
5
Maxim Integrated
PARAMETER CONDITIONS MIN TYP MAX UNITS
THERMISTOR MONITOR
THM Threshold, Hot When charging is suspended, 1% hysteresis 0.27 x
VVL
0.28 x
VVL
0.29 x
VVL V
THM Threshold, Cold When charging is suspended, 1% hysteresis 0.73 x
VVL
0.74 x
VVL
0.75 x
VVL V
THM Threshold, Disabled THM function is disabled below this voltage 0.0254
x VVL
0.03 x
VVL
0.036 x
VVL V
THM Threshold DC, USB Enable MAX8903B/MAX8903E/MAX8903G 0.83 x
VVL
0.87 x
VVL
0.91 x
VVL V
THM = GND or VL;
TA = +25°C -0.100 ±0.001 +0.200
MAX8903A/C/D/H/J/N/Y
THM = GND or VL;
TA = +85°C ±0.010
THM Input Leakage
MAX8903B/E/G THM = GND or VL;
TA = -40°C to +85°C -0.200 ±0.001 +0.200
µA
THERMAL SHUTDOWN, VL, AND LOGIC I/O: CHG, FLT, DOK, UOK, DCM, CEN, USUS, IUSB
High level 1.3
Low level 0.4 V
Logic-Input Thresholds
(DCM, CEN, USUS, IUSB) Hysteresis 50 mV
TA = +25°C -1.000 ±0.001 +1.000
VINPUT = 0V to 5.5V
(MAX8903A/C/D/H/J/N/Y) TA = +85°C ±0.010
Logic-Input Leakage Current
(CEN, USUS, IUSB) VINPUT = 0V to 5.5V
(MAX8903B/E/G) TA = -40°C to +85°C -0.200 ±0.001 +0.200
µA
TA = +25°C 0.001 1
Logic-Input Leakage Current
(DCM)
VDCM = 0V to 16V
VDC = 16V TA = +85°C 0.01 µA
Sinking 1mA 8 50
Logic Output Voltage, Low
(CHG, FLT, DOK, UOK)Sinking 10mA 80 mV
TA = +25°C 0.001 1
Open-Drain Output Leakage
C ur rent, Hi g h (CHG , FLT, DOK, UOK) VOUT = 5.5V TA = +85°C 0.01 µA
ELECTRICAL CHARACTERISTICS (continued)
(VDC = VUSB = 5V, VBAT = 4V, circuit of Figure 2, TA= -40°C to +85°C, unless otherwise noted. Typical values are at TA= +25°C.)
(Note 1)
MAX8903A–E/G/H/J/N/Y
2A 1-Cell Li+ DC-DC Chargers
for USB and Adapter Power
6Maxim Integrated
MAX8903A–E/G/H/J/N/Y
PARAMETER CONDITIONS MIN TYP MAX UNITS
IVL = 0 to 1mA
(MAX8903A/C/D/H/J/N/Y) 4.6 5.0 5.4
VL Output Voltage VDC = VUSB = 6V
IVL = 0 to 10mA
(MAX8903B/E/G) 4.6 5.0 5.4
V
VL UVLO Threshold VVL falling; 200mV hysteresis 3.2 V
Thermal Shutdown Temperature 160 °C
Thermal Shutdown Hysteresis 15 °C
ELECTRICAL CHARACTERISTICS (continued)
(VDC = VUSB = 5V, VBAT = 4V, circuit of Figure 2, TA= -40°C to +85°C, unless otherwise noted. Typical values are at TA= +25°C.)
(Note 1)
Note 1: Limits are 100% production tested at TA= +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 its high-side switch operates as a
linear regulator with a 100mA current limit. The linear regulator’s output is connected to LX and its output current flows
through the inductor into CS and finally 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 VSYS = 400mV, and 50mA for VSYS between 400mV and 2V.
Typical Operating Characteristics
(TA = +25°C, unless otherwise noted.)
MAX8903A/B/C/D/E/H/J/N/Y
BATTERY CHARGER EFFICIENCY
vs. BATTERY VOLTAGE
MAX8903A toc01
BATTERY VOLTAGE (V)
EFFICIENCY (%)
4.54.03.0 3.52.0 2.51.5
10
20
30
40
50
60
70
80
90
100
0
1.0 5.0
VDC = 8V
IBAT = 0.15A IBAT = 1.5A
VDC = 5V
VDC = 12V
MAX8903G BATTERY CHARGER
EFFICIENCY vs. BATTERY VOLTAGE
MAX8903A toc01a
BATTERY VOLTAGE (V)
EFFICIENCY (%)
4.54.03.0 3.52.0 2.51.5
10
20
30
40
50
VDC = 12V
IBATT = 0.15A IBATT = 1.5A
60
70
80
90
100
0
1.0 5.0
VDC = 6V
VDC = 9V
0.0
0.5
1.0
1.5
2.0
2.5
3.0
4.0
3.5
4.5
486 10121416
MAX8903A/B/C/D/E/H/J/N/Y
SWITCHING FREQUENCY vs. VDC
MAX8903A toc02
DC VOLTAGE (V)
SWITCHING FREQUENCY (MHz)
VBAT = 3V
RISET = 1.2kΩ
VCEN = 0V
VBAT = 4V
MAX8903G SWITCHING
FREQUENCY vs. VDC
MAX8903A toc02a
DC VOLTAGE (V)
SWITCHING FREQUENCY (MHz)
14126 8 10
0.2
0.4
0.6
0.8
1.0
1.2
1.4
1.6
0
416
VBAT = 3V
VBAT = 4V
RISET = 1.2kI
VCEN = 0V
MAX8903A/B/C/D/E/H/J/N/Y
SYS EFFICIENCY
vs. SYS OUTPUT CURRENT
MAX8903A toc03
SYS OUTPUT CURRENT (mA)
SYS EFFICIENCY (%)
100010010
10
20
30
40
50
60
70
80
90
100
0
1 10000
VCEN = 1V
VSYS = 4.4V
VDC = 4.5V
VDC = 6V
VDC = 11V
VDC = 16V
MAX8903G SYS EFFICIENCY
vs. SYS OUTPUT CURRENT
MAX8903A toc03a
SYS OUTPUT CURRENT (mA)
SYS EFFICIENCY (%)
100010010
10
20
30
40
50
60
70
80
90
100
0
1 10,000
VDC = 16V
VDC = 12V
VDC = 9V
VDC = 6V
VCEN = 1
0
0.4
0.2
0.8
0.6
1.4
1.2
1.0
1.6
02134567
USB SUPPLY CURRENT
vs. USB VOLTAGE
MAX8903A toc04
USB VOLTAGE (V)
USB SUPPLY CURRENT (mA)
CHARGER
ENABLED
CHARGER
DISABLED
0
40
20
80
60
120
100
140
0231 4567
USB SUPPLY CURRENT
vs. USB VOLTAGE (SUSPEND)
MAX8903A toc05
USB VOLTAGE (V)
USB QUIESCENT CURRENT (µA)
USB SUSPEND
0
20
10
40
30
70
60
50
80
0456321
BATTERY LEAKAGE CURRENT
vs. BATTERY VOLTAGE
MAX8903A toc06
BATTERY VOLTAGE (V)
BATTERY LEAKAGE CURRENT (nA)
NO DC OR USB INPUT
0
20
10
40
30
70
80
60
50
90
-40 35 60-15 10 85
BATTERY LEAKAGE CURRENT
vs. AMBIENT TEMPERATURE
MAX8903A toc07
TEMPERATURE (°C)
BATTERY LEAKAGE CURRENT (nA)
NO DC OR USB INPUT
CHARGE CURRENT
vs. BATTERY VOLTAGE—USB MODE
MAX8903A toc08
BATTERY VOLTAGE (V)
CHARGE CURRENT (mA)
4.03.53.02.52.0
50
100
150
200
250
300
350
400
450
500
0
1.5 4.5
CHARGE ENABLED
IBAT SET TO 1.5A
MAX8903D
VBAT RISING
VIUSB = VUSB
VIUSB = 0V
CHARGE CURRENT
vs. BATTERY VOLTAGE—DC MODE
MAX8903A toc09
BATTERY VOLTAGE (V)
CHARGE CURRENT (mA)
4.03.53.02.52.0
200
400
600
800
1000
1200
0
1.5 4.5
CHARGER ENABLED
IBAT SET TO 1A
IDC SET TO 2A
MAX8903A/C/H
VBAT RISING
Typical Operating Characteristics (continued)
(TA = +25°C, unless otherwise noted.)
MAX8903A–E/G/H/J/N/Y
2A 1-Cell Li+ DC-DC Chargers
for USB and Adapter Power
7
Maxim Integrated
MAX8903A–E/G/H/J/N/Y
2A 1-Cell Li+ DC-DC Chargers
for USB and Adapter Power
8Maxim Integrated
NORMALIZED CHARGE CURRENT
vs. AMBIENT TEMPERATURE
MAX8903A toc10
TEMPERATURE (°C)
NORMALIZED CHARGE CURRENT
603510-15
0.990
0.995
1.000
1.005
1.010
1.015
0.985
-40 85
VUSB = 5V, VBAT = 4V
NORMALIZED BATTERY
REGULATION VOLTAGE
vs. AMBIENT TEMPERATURE
MAX8903A toc11
TEMPERATURE (°C)
NORMALIZED BATTERY REGULATION VOLTAGE (%)
603510-15
99.6
99.7
99.8
99.9
100.0
100.1
100.2
100.3
100.4
100.5
99.5
-40 85
22ppm/°
C0
1.5
1.0
0.5
2.5
2.0
4.5
4.0
3.5
3.0
5.0
01234567
MAX8903A/C/D/H/N/Y
SYS VOLTAGE vs. USB VOLTAGE
MAX8903A toc12
USB VOLTAGE (V)
SYS VOLTAGE (V)
VUSB FALLING
VCEN = 5V
VBAT = 0V
VDC = 0V
VUSB RISING
RSYS = 1MΩ
0
1.0
0.5
2.0
1.5
3.0
2.5
3.5
4.5
4.0
5.0
0 4682 1012141618
MAX8903A/C/D/H/N/Y
SYS VOLTAGE vs. DC VOLTAGE
MAX8903A toc13
DC VOLTAGE (V)
SYS VOLTAGE (V)
VDC RISING
VDC FALLING
VCEN = 5V
VBAT = 0V
VUSB = 0V
SYS VOLTAGE
vs. SYS OUTPUT CURRENT, DC INPUT
MAX8903A toc14
SYS OUTPUT CURRENT (A)
SYS VOLTAGE (V)
1.51.00.5
3.9
4.0
4.1
4.2
4.3
4.4
4.5
4.6
3.8
02.0
VUSB = 0V MAX8903J, VDC = 5.75V
MAX8903N/Y,
VDC = 5.75V
MAX8903A/C/D/H,
VDC = 5.75V
MAX8903B/E/G,
VDC = 5.75V
MAX8903_, VDC = 0V
400300200100
SYS VOLTAGE
vs. SYS OUTPUT CURRENT, USB INPUT
MAX8903A toc15
SYS OUTPUT CURRENT (mA)
SYS VOLTAGE (V)
3.9
4.0
4.1
4.2
4.3
4.4
4.5
4.6
3.8
0 500
VDC = 0V, VBATT = 4V
MAX8903J, VUSB = 5V
MAX8903N/Y,
VUSB = 5V
MAX8903A/C/D/H,
VUSB = 5V
MAX8903B/E/G,
VUSB = 5V
MAX8903_, VUSB = 0V
VL VOLTAGE vs. DC VOLTAGE
MAX8903A toc16
DC VOLTAGE (V)
VL VOLTAGE (V)
18161412108642
1
2
3
4
5
6
0
020
VL WITH
NO LOAD AND
DCDC OFF
(VUSUS = 5V)
VL AND DCDC
WITH
FULL LOAD
(VUSUS = 0V)
VBAT = 3.6V
VUSB = 0V
CHARGE PROFILE—1400mAh BATTERY
ADAPTER INPUT—1A CHARGE
MAX8903A toc17
TIME (min)
VBAT (V)
IBAT (A)
12010060 804020
0.5
1.0
1.5
2.0
2.5
3.0
3.5
4.0
4.5
5.0
5.5
6.0
0
0.2
0.4
0.6
0.8
1.0
1.2
0.0
0 140
VBAT
IDC SET TO 1A
IBAT SET TO 2A
IBAT
MAX8903A/B/C/G/H
Typical Operating Characteristics (continued)
(TA = +25°C, unless otherwise noted.)
MAX8903A–E/G/H/J/N/Y
2A 1-Cell Li+ DC-DC Chargers
for USB and Adapter Power
9
Maxim Integrated
MAX8903A/B/C/G/H
CHARGE PROFILE—1400mAh BATTERY
USB INPUT—500mA CHARGE
TIME (min)
VBAT (V)
IBAT (A)
180160120 14040 60 80 10020
0.5
1.0
1.5
2.0
2.5
3.0
3.5
4.0
4.5
5.0
0
0.05
0.10
0.15
0.20
0.25
0.30
0.35
0.40
0.45
0.50
0
0 200
VBAT
IBAT
MAX8903A toc18
MAX8903A/MAX8903B/MAX8903C
IUSB SET TO 500mA
IBAT SET TO 2A
200ns/div
MAX8903A/B/C/D/E/H/J/N/Y DC SWITCHING
WAVEFORMS—LIGHT LOAD
20mV/div
AC-COUPLED
MAX8903A toc19
500mA/div
0A
5V/div
0V
VOUT
VLX
ILX
RSYS = 44Ω
MAX8903G DC SWITCHING
WAVEFORMS—LIGHT LOAD
MAX8903A toc19a
10V/div
0A
50mV/div
AC-COUPLED
0V
1A/div
VSYS
VLX
ILX
1µs/div
VDC = 9V, L = 2.2µH
CSYS = 22µF,
RSYS = 44I
MAX8903A/B/C/D/E/H/J/N/Y DC SWITCHING
WAVEFORMS—HEAVY LOAD
MAX8903A toc20
200ns/div
VLX
VOUT
ILX
5V/div
0V
20mV/div
AC-COUPLED
500mA/div
0A
RSYS = 5Ω
MAX8903G DC SWITCHING
WAVEFORMS—HEAVY LOAD
MAX8903A toc20a
10V/div
0A
50mV/div
AC-COUPLED
0V
1A/div
VSYS
VLX
ILX
1µs/div
VDC = 9V, L = 2.2µH
CSYS = 22µF, RSYS = 5I
CEN = 1
DC CONNECT WITH
USB CONNECTED (RSYS = 25Ω)
MAX8903A toc21
200
µ
s/div
IDC
VSYS
IUSB
IBAT
2V/div
500mA/div
500mA/div
500mA/div
0A
3.6V
347mA
-IBAT = CHARGING
475mA
-335mA
Typical Operating Characteristics (continued)
(TA = +25°C, unless otherwise noted.)
MAX8903A–E/G/H/J/N/Y
2A 1-Cell Li+ DC-DC Chargers
for USB and Adapter Power
10 Maxim Integrated
400µs/div
DC CONNECT WITH NO USB
(RSYS = 25Ω)
2V/div
MAX8903A toc22
5V/div
1A/div
1A/div
3.6V 3.84V
3.6V 3.44V
CDC
CHARGING CSYS
CHARGING 850mA
-1A
BATTERY
CHARGER
SOFT-START
144mA
0A
VSYS
VBAT
IDC
IBAT
-IBAT = CHARGING
40
µ
s/div
DC DISCONNECT WITH NO USB
(RSYS = 25Ω)
2V/div
MAX8903A toc23
5V/div
1A/div
1A/div
3.6V
3.68V
850mA
-1A 144mA
0A
VSYS
VBAT
IDC
IBAT
3.6V
-IBAT = CHARGING
MAX8903A/C/D/H SYS LOAD TRANSIENT
MAX8903A toc24a
0A
20mV/div
AC-COUPLED
500mA/div
VSYS
4.400V
4.360V
1A
0A
ISYS
100µs/div
MAX8903A
VDC = 10.5V
L = 2.2µH
CSYS = 10µF
RIDC = 3kI (2A)
DCM = HIGH
CEN = 1
MAX8903B/E SYS LOAD TRANSIENT
MAX8903A toc24b
0A
20mV/div
500mA/div
VSYS
4.325V
4.305V
1A
0A
ISYS
100µs/div
MAX8903B
VDC = 10.5V
L = 2.2µH
CSYS = 22µF
RIDC = 3kI (2A)
DCM = HIGH
CEN = 1
MAX8903G SYS LOAD TRANSIENT
MAX8903A toc24c
0A
50mV/div
500mA/div
VSYS
0A
1A
4.325V
4.305V
ISYS
100µs/div
VDC = 9V
L = 2.2µH
CSYS = 22µF
RIDC = 3kI (2A)
DCM = 1
CEN = 1
400
µ
s/div
USB CONNECT WITH NO DC
(RSYS = 25Ω)
2V/div
MAX8903A toc25
5V/div
500mA/div
500mA/div
3.6V
CUSB
CHARGING
BATTERY
CHARGER
SOFT-START
144mA
VSYS
VUSB
IUSB
IBAT
3.5V
3.75V
5V
475mA
-330mA
Typical Operating Characteristics (continued)
(TA = +25°C, unless otherwise noted.)
MAX8903A–E/G/H/J/N/Y
2A 1-Cell Li+ DC-DC Chargers
for USB and Adapter Power
11
Maxim Integrated
Typical Operating Characteristics (continued)
(TA = +25°C, unless otherwise noted.)
100µs/div
USB DISCONNECT WITH NO DC
(RSYS = 25Ω)
2V/div
MAX8903A toc26
5V/div
500mA/div
500mA/div
3.6V
475mA
VSYS
VUSB
IUSB
IBAT
5V
144mA
-330mA
200
µ
s/div
USB SUSPEND
5V/div
MAX8903A toc27
500mA/div
2V/div
500mA/div
475mA
-475mA
VUSUS
IUSB
VSYS
IBAT
3V
0V
0A
3.7V
0A
200
µ
s/div
USB RESUME
5V/div
MAX8903A toc28
500mA/div
2V/div
500mA/div
475mA
-475mA
3V 0V
0A
3.6V
0A
3.6V
3.8V
BATTERY
CHARGER
SOFT-START
CUSB
CHARGING
VUSUS
IUSB
VSYS
IBAT
Pin Description
PIN NAME FUNCTION
1, 2 PG Power Ground for Step-Down Low-Side Synchronous n-Channel MOSFET. Both PG pins must be
connected together externally.
3, 4 DC
DC Power Input. DC is capable of delivering up to 2A to SYS. DC supports both AC adapter and USB
inputs. The DC current limit is set through DCM, IUSB, or IDC depending on the input source used. See
Table 2. Both DC pins must be connected together externally. Connect at least a 4.7µF ceramic capacitor
from DC to PG.
5 DCM
Current-Limit Mode Setting for the DC Power Input. When logic-high, the DC input current limit is set by
the resistance from IDC to GND. When logic-low, the DC input current limit is internally programmed to
500mA or 100mA, as set by the IUSB logic input. There is an internal diode from DCM (anode) to DC
(cathode) as shown in Figure 1.
6 BST High-Side MOSFET Driver Supply. Bypass BST to LX with a 0.1µF ceramic capacitor.
7 IUSB USB Current-Limit Set Input. Drive IUSB logic-low to set the USB current limit to 100mA. Drive IUSB logic-
high to set the USB current limit to 500mA.
8DOK DC Power-OK Output. Active-low open-drain output pulls low when a valid input is detected at DC. DOK
is still valid when the charger is disabled (CEN high).
9VL
Logic LDO Output. VL is the output of an LDO that powers the MAX8903_ internal circuitry and charges
the BST capacitor. Connect a 1µF ceramic capacitor from VL to GND.
10 CT Charge Timer Set Input. A capacitor (CCT) from CT to GND sets the fast-charge and prequal fault timers.
Connect to GND to disable the timer.
11 IDC DC Current-Limit Set Input. Connect a resistor (RIDC) from IDC to GND to program the current limit of the
step-down regulator from 0.5A to 2A when DCM is logic-high.
12 GND Ground. GND is the low-noise ground connection for the internal circuitry.
MAX8903A–E/G/H/J/N/Y
2A 1-Cell Li+ DC-DC Chargers
for USB and Adapter Power
12 Maxim Integrated
Pin Description (continued)
PIN NAME FUNCTION
13 ISET Charge Current Set Input. A resistor (RISET) from ISET to GND programs the fast-charge current up to 2A.
The prequal charge current is 10% of the fast-charge current.
14 CEN Charger Enable Input. Connect CEN to GND to enable battery charging when a valid source is connected
at DC or USB. Connect to VL, or drive high to disable battery charging.
15 USUS USB Suspend Input. Drive USUS logic-high to enter USB suspend mode, lowering USB current to 115µA,
and internally shorting SYS to BAT.
16 THM
Thermistor Input. Connect a negative temperature coefficient (NTC) thermistor from THM to GND.
Connect a resistor equal to the thermistor +25°C resistance from THM to VL. Charging is suspended
when the thermistor is outside the hot and cold limits. Connect THM to GND to disable the thermistor
temperature sensor.
17 USB USB Power Input. USB is capable of delivering 100mA or 500mA to SYS as set by the IUSB logic input.
Connect a 4.7µF ceramic capacitor from USB to GND.
18 FLT Fault Output. Active-low, open-drain output pulls low when the battery timer expires before prequal or
fast-charge completes.
19 UOK USB Power-OK Output. Active-low, open-drain output pulls low when a valid input is detected at USB.
UOK is still valid when the charger is disabled (CEN high).
20, 21 BAT
Battery Connection. Connect to a single-cell Li+ battery. The battery charges from SYS when a valid
source is present at DC or USB. BAT powers SYS when neither DC nor USB power is present, or when the
SYS load exceeds the input current limit. Both BAT pins must be connected together externally.
22 CHG Charger Status Output. Active-low, open-drain output pulls low when the battery is in fast-charge or
prequal. Otherwise, CHG is high impedance.
23, 24 SYS
System Supply Output. SYS connects to BAT through an internal 50mΩ system load switch when DC or
USB are invalid, or when the SYS load is greater than the input current limit.
When a valid voltage is present at DC or USB, SYS is limited to VSYSREG. When the system load (ISYS)
exceeds the DC or USB current limit, SYS is regulated to 50mV below BAT, and both the powered input
and the battery service SYS.
Bypass SYS to GND with an X5R or X7R ceramic capacitor. See Table 6 for the minimum recommended
SYS capacitor (CSYS). Both SYS pins must be connected together externally.
25, 26 CS
70mΩ Current-Sense Input. Connect the step-down inductor from LX to CS. When the step-down
regulator is on, there is a 70mΩ current-sense MOSFET from CS to SYS. When the step-down regulator is
off, the internal CS MOSFET turns off to block current from SYS back to DC.
27, 28 LX Inductor Connection. Connect the inductor between LX and CS. Both LX pins must be connected together
externally.
—EP
Exposed Pad. Connect the exposed pad to GND. Connecting the exposed pad does not remove the
requirement for proper ground connections to the appropriate pins.
MAX8903A–E/G/H/J/N/Y
2A 1-Cell Li+ DC-DC Chargers
for USB and Adapter Power
13
Maxim Integrated
SYS
BATTERY
CONNECTOR
BAT+
BAT-
+
NTC
T
THM
USB
BAT
ISET
Li+ BATTERY
CHARGER
AND SYS LOAD SWITCH
IC
THERMAL
REGULATION
CHARGER
CURRENT-
VOLTAGE
CONTROL
USB
UOK
DC
DOK
DC POWER
MANAGEMENT
PWM
STEP-DOWN
REGULATOR
PWR
OK
USB POWER
MANAGEMENT
CURRENT-
LIMITED
VOLTAGE
REGULATOR
SET
INPUT
LIMIT
PWR
OK VL
CHG
FLT
CT
CHARGE
TERMINATION
AND MONITOR
CHARGE
TIMER
THERMISTOR
MONITOR
(SEE FIGURE 7)
CEN
INPUT AND
CHARGER
CURRENT-LIMIT
SET LOGIC
DCM
DC
IUSB
USUS
IDC
500mA
100mA
USB
LIMIT
DC
LIMIT
AC
ADAPTER
GND
DC MODE
USB
SUSPEND
TO
SYSTEM
LOAD
LX CS
BST
SET
INPUT
LIMIT
PG
EP
MAX8903_
Figure 1. Functional Block Diagram
MAX8903A–E/G/H/J/N/Y
2A 1-Cell Li+ DC-DC Chargers
for USB and Adapter Power
14 Maxim Integrated
Circuit Description
The MAX8903_ is a dual input charger with a 16V input
for a wide range of DC sources and USB inputs. The IC
includes a high-voltage (16V) input DC-DC step-down
converter that reduces charger power dissipation while
also supplying power to the system load. The step-
down converter supplies up to 2A to the system, the
battery, or a combination of both.
A USB charge input can charge the battery and power
the system from a USB power source. When powered
from USB or the DC input, system load current peaks
that exceed what can be supplied by the input are sup-
plemented by the battery.
The MAX8903_ also manages load switching from the
battery to and from an external power source with an
on-chip 50mΩMOSFET. This switch also helps support
load peaks using battery power when the input source
is overloaded.
PG
PG
DC
DC
BST
LX
LX
CS
CS SYS
SYS
BAT
BAT
FLT
UOK
DOK
FAULT
OUTPUT
USB PWR OK
DC PWR OK
TO VL
RPU
4 x 100kΩ
18
19
8
24
23
21
20
1
2
3
4
6
27
28
25
26
17 USB
ISET
IDC
RISET
RIDC
DCM
THM
CEN
IUSB
GND
EP
NTC
10kΩ
USUS
5
9
16
12
CHARGE ON
OFF
100mA
500mA
USB SUSPEND
14
7
15
TO SYSTEM
LOAD
CHG 22 CHARGE
INDICATOR
CDC
4.7µF
CT
CCT
0.15µF
ADAPTER
VBUS
GND
CBST
0.1µF
L1
1µH
13
11
CUSB
4.7µF
USB
(SEE TABLE 5 FOR
INDUCTOR SELECTION)
10
RT
10kΩ
TO DC
1-CELL
LI+
CBAT
10µF
CVL
1µF
CSYS
(SEE TABLE 6 FOR CSYS SELECTION)
VL
MAX8903_
Figure 2. Typical Application Circuit Using a Separate DC and USB Connector
MAX8903A–E/G/H/J/N/Y
2A 1-Cell Li+ DC-DC Chargers
for USB and Adapter Power
15
Maxim Integrated
As shown in Figure 1, the IC includes a full-featured
charger with thermistor monitor, fault timer, charger
status, and fault outputs. Also included are power-OK
signals for both USB and DC. Flexibility is maintained
with adjustable charge current, input current limit, and
a minimum system voltage (when charging is scaled
back to hold the system voltage up).
The MAX8903_ prevents overheating during high ambi-
ent temperatures by limiting charging current when the
die temperature exceeds +100°C.
DC Input—Fast Hysteretic
Step-Down Regulator
If a valid DC input is present, the USB power path is
turned off and power for SYS and battery charging is
supplied by the high-frequency step-down regulator
from DC. If the battery voltage is above the minimum
system voltage (VSYSMIN, Figure 4), the battery charger
connects the system voltage to the battery for lowest
power dissipation. The step-down regulation point is
then controlled by three feedback signals: maximum
step-down output current programmed at IDC, maximum
charger current programmed at ISET, and maximum
PG
PG
DC
DC
BST
LX
LX
CS
CS SYS
SYS
BAT
BAT
FLT
UOK
DOK
FAULT
OUTPUT
USB PWR-OK
DC PWR-OK
TO VL
RPU
4 x 100kΩ
18
19
8
24
23
21
20
1
2
3
4
6
27
28
25
26
17 USB
ISET
IDC
RISET
RIDC
DCM
THM
CEN
IUSB
GND
NTC
10kΩ
USUS
5
9
16
12
CHARGE ON
OFF
100mA
500mA
USB SUSPEND
14
7
15
TO SYSTEM
LOAD
CHG 22 CHARGE
INDICATOR
CDC
4.7µF
L1
1µH
CT
EP
CCT
0.15µF
CBST
0.1µF13
11
10
RT
10kΩ
1-CELL
LI+
CBAT
10µF
CSYS
(SEE TABLE 6 FOR CSYS SELECTION)
VL
MAX8903_
VBUS
D-
D+
ID
GND
CVL
1µF
USB
ADAPTER
DC MODE
499kΩ(SEE TABLE 5 FOR
INDUCTOR VALUE
SELECTION)
Figure 3. Typical Application Circuit Using a Mini 5 Style Connector or Other DC/USB Common Connector
MAX8903A–E/G/H/J/N/Y
2A 1-Cell Li+ DC-DC Chargers
for USB and Adapter Power
16 Maxim Integrated
die temperature. The feedback signal requiring the
smallest current controls the average output current in
the inductor. This scheme minimizes total power dissi-
pation for battery charging and allows the battery to
absorb any load transients with minimum system volt-
age disturbance.
If the battery voltage is below VSYSMIN, the charger does
not directly connect the system voltage to the battery
and the system voltage (VSYS) is slightly above VSYSMIN
as shown in Figure 4. The battery charger independently
controls the battery charging current. VSYSMIN is set to
either 3.0V or 3.4V based on the version of MAX8903_.
See Table 6.
After the battery charges to 50mV above VSYSMIN, the
system voltage is connected to the battery. The battery
fast-charge current then controls the step-down con-
verter to set the average inductor current so that both
the programmed input current limit and fast-charge cur-
rent limit are satisfied.
DC-DC Step-Down Control Scheme
A proprietary hysteretic current PWM control scheme
ensures fast switching and physically tiny external com-
ponents. The feedback control signal that requires the
smallest input current controls the center of the peak
and valley currents in the inductor. The ripple current is
internally set to provide 4MHz operation. When the
input voltage decreases near the output voltage, very
high duty cycle occurs and, due to minimum off-time,
4MHz operation is not achievable. The controller then
provides minimum off-time, peak current regulation.
Similarly, when the input voltage is too high to allow
4MHz operation due to the minimum on-time, the con-
troller becomes a minimum on-time, valley current regu-
lator. In this way, ripple current in the inductor is always
as small as possible to reduce ripple voltage on SYS for
a given capacitance. The ripple current is made to vary
with input voltage and output voltage in a way that
reduces frequency variation. However, the frequency
still varies somewhat with operating conditions. See the
Typical Operating Characteristics
.
DC Mode (DCM)
As shown in Table 2, the DC input supports both AC
adapters (up to 2A) and USB (up to 500mA). With the
DCM logic input set high, the DC input is in adapter
mode and the DC input current limit is set by the resis-
tance from IDC to GND (RIDC). Calculate RIDC accord-
ing to the following equation:
RIDC = 6000V/IDC-MAX
With the DCM logic input set low, the DC input current
limit is internally programmed to 500mA or 100mA as
set by the IUSB logic input. With the IUSB logic input
set high, the DC input current limit is 500mA and the
DC input delivers current to SYS through the step-down
regulator. With the IUSB logic input set low, the DC
input current limit is 100mA. In this 100mA mode, the
step-down regulator is turned off and its high-side
switch operates as a linear regulator with a 100mA cur-
rent limit. The linear regulator’s output is connected to
LX and its output current flows through the inductor into
CS and finally to SYS.
The DCM pin has an internal diode to DC as shown in
Figure 1. To prevent current from flowing from DCM
through the internal diode and to the DC input, DCM
cannot be driven to a voltage higher than DC. The
C O M PO N EN T
( F I G U R ES 2 A N D 3) FUNCTION PART
CDC, CUSB Input filter capacitor 4.7µF ceramic capacitor
CVL VL filter capacitor 1.0µF ceramic capacitor
CSYS SYS output bypass capacitor 10µF ( M AX 8903A/M AX 8903C /M AX 8903D /M AX 8903H /M AX 8903J) or
22µF ( M AX 8903B/M AX 8903E /M AX 8903G/M AX 8903Y ) cer am i c cap aci tor
CBAT Battery bypass capacitor 10µF ceramic capacitor
CCT Charger timing capacitor 0.15µF low TC ceramic capacitor
RPU (X4) Logic output pullup resistors 100kΩ
THM Negative TC thermistor Philips NTC thermistor, P/N 2322-640-63103, 0kΩ ±5% at +25°C
RTTHM pullup resistor 10kΩ
RIDC D C i np ut cur r ent- l i m i t p r og r am m i ng r esi stor 3kΩ ±1%, for 2A limit
RISET Fast-charge current programming resistor 1.2kΩ ±1%, for 1A charging
L1 DC input step-down inductor 1µH inductor with ISAT > 2A
Table 1. External Components List for Figures 2 and 3
MAX8903A–E/G/H/J/N/Y
2A 1-Cell Li+ DC-DC Chargers
for USB and Adapter Power
17
Maxim Integrated
circuit of Figure 3 shows a simple MOSFET and resistor
on DCM to prevent any current from flowing from DCM
through the internal diode to DC. This circuit of Figure 3
allows a microprocessor to drive the gate of the MOS-
FET to any state at any time.
An alternative to the simple MOSFET and resistor on
DCM as shown in Figure 3 is to place a 1MΩresistor in
series with the DCM input to the microprocessor. The
microprocessor can then monitor the DOK output and
make sure that whenever DOK is high DCM is also low.
In the event that DCM is driven to a higher voltage than
DC, the 1MΩseries resistance limits the current from
DCM through the internal diode to DC to a few µA.
USB Input—Linear Regulator
If a valid USB input is present with no valid DC input,
current for SYS and battery charging is supplied by a
low-dropout linear regulator connected from USB to
SYS. The SYS regulation voltage shows the same char-
acteristic as when powering from the DC input (see
Figure 4). The battery charger operates from SYS with
any extra available current, while not exceeding the
maximum-allowed USB current. If both USB and DC
inputs are valid, power is only taken from the DC input.
The maximum USB input current is set by the logic
state of the IUSB input to either 100mA or 500mA.
Power Monitor Outputs (
UOK
,
DOK
)
DOK is an open-drain, active-low output that indicates
the DC input power status. With no source at the USB
pin, the source at DC is considered valid and DOK is
driven low when: 4.15V < VDC < 16V. When the USB
voltage is also valid, the DC source is considered valid
and DOK is driven low when: 4.45V < VDC < 16V. The
higher minimum DC voltage with USB present helps
guarantee cleaner transitions between input supplies. If
the DC power-OK output feature is not required, con-
nect DOK to ground.
UOK is an open-drain, active-low output that indicates
the USB input power status. UOK is low when a valid
source is connected at USB. The source at USB is valid
when 4.1V < VUSB < 6.6V. If the USB power-OK output
feature is not required, connect UOK to ground.
Both the UOK and the DOK circuitry remain active in
thermal overload, USB suspend, and when the charger
is disabled. DOK and UOK can also be wire-ORed
together to generate a single power-OK (POK) output.
Thermal Limiting
When the die temperature exceeds +100°C, a thermal
limiting circuit reduces the input current limit by 5%/°C,
bringing the charge current to 0mA at +120°C. Since
the system load gets priority over battery charging, the
battery charge current is reduced to 0mA before the
input limiter drops the load voltage at SYS. To avoid
false charge termination, the charge termination detect
function is disabled in this mode. If the junction temper-
ature rises beyond +120°C, no current is drawn from
DC or USB, and VSYS regulates at 50mV below VBAT.
System Voltage Switching
DC Input
When charging from the DC input, if the battery is
above the minimum system voltage, SYS is connected
to the battery. Current is provided to both SYS and the
battery, up to the maximum program value. The step-
down output current sense and the charger current
sense provide feedback to ensure the current loop
demanding the lower input current is satisfied. The
advantage of this approach when powering from DC is
that power dissipation is dominated by the step-down
regulator efficiency, since there is only a small voltage
drop from SYS to BAT. Also, load transients can be
absorbed by the battery while minimizing the voltage
disturbance on SYS. If both the DC and USB inputs are
valid, the DC input takes priority and delivers the input
current, while the USB input is off.
After the battery is done charging, the charger is turned
off and the SYS load current is supplied from the DC
input. The SYS voltage is regulated to VSYSREG. The
charger turns on again after the battery drops to the
restart threshold. If the load current exceeds the input
limiter, SYS drops down to the battery voltage and the
50mΩSYS-to-BAT PMOS switch turns on to supply the
extra load current. The SYS-to-BAT switch turns off again
once the load is below the input current limit. The 50mΩ
PMOS also turns on if valid DC input power is removed.
USB Input
When charging from the USB input, the DC input step-
down regulator turns off and a linear regulator from
USB to SYS powers the system and charges the bat-
tery. If the battery is greater than the minimum system
IBAT x RON
VBATREG
VSYSREG
VBAT
VSYSMIN
VSYS
VCEN = 0V
VDC AND/OR VUSB = 5.0V
MAX8903_
Figure 4. SYS Tracking VBAT to the Minimum System Voltage
MAX8903A–E/G/H/J/N/Y
2A 1-Cell Li+ DC-DC Chargers
for USB and Adapter Power
18 Maxim Integrated
voltage, the SYS voltage is connected to the battery.
The USB input then supplies the SYS load and charges
the battery with any extra available current, while not
exceeding the maximum-allowed USB current. Load
transients can be absorbed by the battery while mini-
mizing the voltage disturbance on SYS. When battery
charging is completed, or the charger is disabled, SYS
is regulated to VSYSREG. If both USB and DC inputs are
valid, power is only taken from the DC input.
USB Suspend
Driving USUS high and DCM low turns off charging as
well as the SYS output and reduces input current to
170µA to accommodate USB suspend mode. See
Table 2 for settings.
Charge Enable (
CEN
)
When CEN is low, the charger is on. When CEN is high,
the charger turns off. CEN does not affect the SYS out-
put. In many systems, there is no need for the system
controller (typically a microprocessor) to disable the
charger, because the MAX8903_ smart power selector
circuitry independently manages charging and
adapter/battery power hand-off. In these situations, CEN
may be connected to ground.
Soft-Start
To prevent input transients that can cause instability in
the USB or AC adapter power source, the rate of change
of the input current and charge current is limited. When
an input source is valid, SYS current is ramped from
zero to the set current-limit value in typically 50µs. This
also means that if DC becomes valid after USB, the
SYS current limit is ramped down to zero before switch-
ing from the USB to DC input. At some point, SYS is no
longer able to support the load and may switch over to
BAT. The switchover to BAT occurs when VSYS < VBAT.
This threshold is a function of the SYS capacitor size
and SYS load. The SYS current limit then ramps from
zero to the set current level and SYS supports the load
again as long as the SYS load current is less than the
set current limit.
POWER SOURCE DOK UOK DCM*** IUSB USUS
DC STEP-DOWN
OUTPUT
CURRENT LIMIT
USB INPUT
CURRENT LIMIT
MAXIMUM
CHARGE
CURRENT**
AC Adapter at DC Input L X H X X 6000V/RIDC
Lesser of
1200V/RISET and
6000V/RIDC
L X L L L 100mA
Lesser of
1200V/RISET and
100mA
L X L H L 500mA
Lesser of
1200V/RISET and
500mA
USB Power at DC Input
L X L X H USB suspend
USB input off. DC
input has priority.
0
H L X L L 100mA
Lesser of
1200V/RISET and
100mA
H L X H L 500mA
Lesser of
1200V/RISET and
500mA
USB Power at USB Input,
DC Unconnected
H L X X H USB suspend 0
DC and USB Unconnected H H X X X
No DC input
No USB input 0
Table 2. Input Limiter Control Logic
**
Charge current cannot exceed the input current limit. Charge may be less than the maximum charge current if the total SYS load
exceeds the input current limit.
***
There is an internal diode from DCM (anode) to DC (cathode) as shown in Figure 1. If the DCM level needs to be set by a µP, use
a MOSFET for isolation as shown in FIgure 3.
X = Don’t care.
MAX8903A–E/G/H/J/N/Y
2A 1-Cell Li+ DC-DC Chargers
for USB and Adapter Power
19
Maxim Integrated
When the charger is turned on, the charge current ramps
from 0A to the ISET current value in typically 1.0ms.
Charge current also soft-starts when transitioning to fast-
charge from prequal, when the input power source is
switched between USB and DC, and when changing the
USB charge current from 100mA to 500mA with the IUSB
logic input. There is no di/dt limiting, however, if RISET is
changed suddenly using a switch.
Battery Charger
While a valid input source is present, the battery charg-
er attempts to charge the battery with a fast-charge
current determined by the resistance from ISET to
GND. Calculate the RISET resistance according to the
following equation:
RISET = 1200V/ICHGMAX
Monitoring Charge Current
The voltage from ISET to GND is a representation of the
battery charge current and can be used to monitor the
current charging the battery. A voltage of 1.5V repre-
sents the maximum fast-charge current.
If necessary, the charge current is reduced automati-
cally to prevent the SYS voltage from dropping.
Therefore, a battery never charges at a rate beyond the
capabilities of a 100mA or 500mA USB input, or over-
loads an AC adapter. See Figure 5.
When VBAT is below VBATPQ, the charger enters pre-
qual mode and the battery charges at 10% of the maxi-
mum fast-charge rate until the voltage of the deeply
discharged battery recovers. When the battery voltage
reaches VBATREG and the charge current drops to 10%
of the maximum fast-charge current, the charger enters
the DONE state. The charger restarts a fast-charge
cycle if the battery voltage drops by 100mV.
Charge Termination
When the charge current falls to the termination thresh-
old (ITERM) and the charger is in voltage mode, charg-
ing is complete. Charging continues for a brief 15s
top-off period and then enters the DONE state where
charging stops.
Note that if charge current falls to ITERM as a result of
the input or thermal limiter, the charger does not enter
DONE. For the charger to enter DONE, charge current
must be less than ITERM, the charger must be in volt-
age mode, and the input or thermal limiter must not be
reducing charge current.
Charge Status Outputs
Charge Output (CHG)
CHG is an open-drain, active-low output that indicates
charger status. CHG is low when the battery charger is
in its prequalification and fast-charge states. CHG goes
high impedance if the thermistor causes the charger to
go into temperature suspend mode.
When used in conjunction with a microprocessor (µP),
connect a pullup resistor between CHG and the logic
I/O voltage to indicate charge status to the µP.
Alternatively, CHG can sink up to 20mA for an LED
charge indicator.
Fault Output (FLT)
FLT is an open-drain, active-low output that indicates
charger status. FLT is low when the battery charger has
entered a fault state when the charge timer expires.
This can occur when the charger remains in its prequal
state for more than 33 minutes or if the charger remains
in fast-charge state for more than 660 minutes (see
Figure 6). To exit this fault state, toggle CEN or remove
and reconnect the input source.
When used in conjunction with a microprocessor (µP),
connect a pullup resistor between FLT and the logic I/O
voltage to indicate charge status to the µP.
Alternatively, FLT can sink up to 20mA for an LED fault
indicator. If the FLT output is not required, connect FLT
to ground or leave unconnected.
Charge Timer
A fault timer prevents the battery from charging indefi-
nitely. The fault prequal and fast-charge timers are con-
trolled by the capacitance at CT (CCT).
1.5
0
MONITORING THE BATTERY
CHARGE CURRENT WITH VISET
01200V/RISET
BATTERY CHARGING CURRENT (A)
DISCHARGING
VISET (V)
Figure 5. Monitoring the Battery Charge Current with the
Voltage from ISET to GND
MAX8903A–E/G/H/J/N/Y
2A 1-Cell Li+ DC-DC Chargers
for USB and Adapter Power
20 Maxim Integrated
While in fast-charge mode, a large system load or device
self-heating may cause the MAX8903_ to reduce charge
current. Under these circumstances, the fast-charge
timer is slowed by 2x if the charge current drops below
50% of the programmed fast-charge level, and suspend-
ed if the charge current drops below 20% of the pro-
grammed level. The fast-charge timer is not affected at
any current if the charger is regulating the BAT voltage
at VBATREG (i.e., the charger is in voltage mode).
tC
F
tC
PREQUAL CT
FST CHG CT
=×
µ
=×
33 015
660
min .
min
-0015
15 8903
.
( /////)
µF
tsMAXADHJNY
t
TOP OFF
TO
-=
PPOFF CT
C
FMAX B E G
-=×132 015 8903min .(//)
µ
FAULT
UOK AND/OR DOK = LOW
CHG = HIGH IMPEDANCE
FLT = LOW
ICHG = 0mA
PREQUALIFICATION
UOK AND/OR DOK = LOW
CHG = LOW
FLT = HIGH IMPEDANCE
0 < VBAT < VBATPQ
ICHG ≤ ICHGMAX/10
DONE
UOK AND/OR DOK = 0
CHG = HIGH IMPEDANCE
FLT = HIGH IMPEDANCE
VBATREG + VRSTRT < VBAT < VBATREG
ICHG = 0mA
FAST-CHARGE
UOK AND/OR DOK = LOW
CHG = LOW
FLT = HIGH IMPEDANCE
VBATPQ < VBAT < VBATREG
ICHG ≤ ICHGMAX
NOT READY
UOK AND DOK = HIGH IMPEDANCE
CHG = HIGH IMPEDANCE
FLT = HIGH IMPEDANCE
ICHG = 0mA
TIMER > tPREQUAL
VBAT > VBATPQ
RESET TIMER
VBAT < VBATPQ - 180mV
RESET TIMER = 0
ICHG < ITERM
AND VBAT = VBATREG
AND THERMAL
OR INPUT LIMIT
NOT EXCEEDED;
RESET TIMER
ICHG > ITERM
RESET TIMER
VBAT < VBATREG + VRSTRT
RESET TIMER
TIMER > tTOP-OFF
UOK AND/OR DOK = LOW
CEN = 0
RESET TIMER
CEN = HI OR
REMOVE AND RECONNECT
THE INPUT SOURCE(S)
ANY STATE
TOGGLE CEN OR
REMOVE AND RECONNECT
THE INPUT SOURCE(S)
TIMER > tFSTCHG
(TIMER SLOWED BY 2x IF
ICHG < ICHGMAX/2, AND
PAUSED IF ICHG < ICHGMAX/5 WHILE VBAT < VBATREG)
TOP-OFF
UOK AND/OR DOK = LOW
CHG = HIGH IMPEDANCE
FLT = HIGH IMPEDANCE
VBAT = VBATREG
ICHG = ITERM
TEMPERATURE SUSPEND
ICHG = 0mA
UOK OR DOK PREVIOUS STATE
CHG = HIGH IMPEDANCE
FLT = HIGH IMPEDANCE
ANY CHARGING
STATE
THM NOT OK
TIMER SUSPEND
THM OK
TIMER RESUME
VBAT < VBATPQ - 180mV
RESET TIMER
Figure 6. MAX8903A Charger State Flow Chart
MAX8903A–E/G/H/J/N/Y
2A 1-Cell Li+ DC-DC Chargers
for USB and Adapter Power
21
Maxim Integrated
VL Regulator
VL is a 5V linear regulator that powers the MAX8903’s
internal circuitry and charges the BST capacitor. VL is
used externally to bias the battery’s thermistor. VL takes
its input power from USB or DC. When input power is
available from both USB and DC, VL takes power from
DC. VL is enabled whenever the input voltage at USB
or DC is greater than ~1.5V. VL does not turn off when
the input voltage is above the overvoltage threshold.
Similarly, VL does not turn off when the charger is dis-
abled (CEN = high). Connect a 1µF ceramic capacitor
from VL to GND.
Thermistor Input (THM)
The THM input connects to an external negative tem-
perature coefficient (NTC) thermistor to monitor battery
or system temperature. Charging is suspended when
the thermistor temperature is out of range. The charge
timers are suspended and hold their state but no fault is
indicated. When the thermistor comes back into range,
charging resumes and the charge timer continues from
where it left off. Connecting THM to GND disables the
thermistor monitoring function. Table 3 lists the fault
temperature of different thermistors.
Since the thermistor monitoring circuit employs an exter-
nal bias resistor from THM to VL (RTB, Figure 7), the ther-
mistor is not limited only to 10kΩ(at +25°C). Any
resistance thermistor can be used as long as the value is
equivalent to the thermistor’s +25°C resistance. For
example, with a 10kΩat +25°C thermistor, use 10kΩat
RTB, and with a 100kΩat +25°C thermistor, use 100kΩ.
For a typical 10kΩ(at +25°C) thermistor and a 10kΩ
RTB resistor, the charger enters a temperature suspend
state when the thermistor resistance falls below 3.97kΩ
(too hot) or rises above 28.7kΩ(too cold). This corre-
sponds to a 0°C to +50°C range when using a 10kΩ
NTC thermistor with a beta of 3500. The general relation
of thermistor resistance to temperature is defined by
the following equation:
RR e
TTC C
=× +°
−°
⎛
⎝
⎜⎞
⎠
⎟
⎧
⎨
⎩
⎪
⎫
⎬
25
1
273
1
298
β⎭⎭
⎪
THM
GND
THM
OUT OF
RANGE
DISABLE
CHARGER
VL
CEN
VL
0.74 VL
0.87 VL
0.28 VL
0.03 VL
COLD
HOT
RTB
THERMISTOR
CIRCUITRY
THERMISTOR
DETECTOR
MAX8903B/MAX8903E/
MAX8903G ONLY
ENABLE THM
RT
RTS
RTP
ALTERNATE
THERMISTOR
CONNECTION
RT
ALL COMPARATORS
60mV HYSTERESIS
MAX8903_
Figure 7. Thermistor Monitor Circuitry
Thermistor β (K) 3000 3250 3500 3750 4250
RTB (kΩ) (Figure 7) 10 10 10 10 10
Resistance at +25°C
(kΩ)10 10 10 10 10
Resistance at +50°C
(kΩ)4.59 4.30 4.03 3.78 3.316
Resistance at 0°C (kΩ) 25.14 27.15 29.32 31.66 36.91
Nominal Hot Trip
Temperature (°C) 55 53 50 49 46
Nominal Cold Trip
Temperature (°C) -3 -1 0 2 4.5
Table 3. Fault Temperatures for Different
Thermistors
MAX8903A–E/G/H/J/N/Y
2A 1-Cell Li+ DC-DC Chargers
for USB and Adapter Power
22 Maxim Integrated
where:
RT= The resistance in Ωof the thermistor at tempera-
ture T in Celsius
R25 = The resistance in Ωof the thermistor at +25°C
β= The material constant of the thermistor, which typi-
cally ranges from 3000K to 5000K
T = The temperature of the thermistor in °C
Table 3 shows the MAX8903_ THM temperature limits
for different thermistor material constants.
Some designs might prefer other thermistor temperature
limits. Threshold adjustment can be accommodated by
changing RTB, connecting a resistor in series and/or in
parallel with the thermistor, or using a thermistor with dif-
ferent β. For example, a +45°C hot threshold and 0°C
cold threshold can be realized by using a thermistor
with a βof 4250 and connecting 120kΩin parallel. Since
the thermistor resistance near 0°C is much higher than it
is near +50°C, a large parallel resistance lowers the
cold threshold, while only slightly lowering the hot
threshold. Conversely, a small series resistance raises
the hot threshold, while only slightly raising the cold
threshold. Raising RTB lowers both the cold and hot
thresholds, while lowering RTB raises both thresholds.
Note that since VL is active whenever valid input power
is connected at DC or USB, thermistor bias current
flows at all times, even when charging is disabled (CEN
= high). When using a 10kΩthermistor and a 10kΩ
pullup to VL, this results in an additional 250µA load.
This load can be reduced to 25µA by instead using a
100kΩthermistor and 100kΩpullup resistor.
Power Enable on Battery Detection
The power enabled on battery detection function allows
the MAX8903B/MAX8903E/MAX8903G to automatically
enable/disable the USB and DC power inputs when the
battery is applied/removed. This function utilizes the
battery pack’s integrated thermistor as a sensing mech-
anism to determine when the battery is applied or
removed. With this function, MAX8903B/MAX8903E/
MAX8903G-based systems shut down when the battery
is removed regardless of whether external power is
available at the USB or DC power inputs.
The MAX8903B/MAX8903E/MAX8903G implement the
power enabled on battery detection function with the ther-
mistor detector comparator as shown in Figure 7. If no bat-
tery is present, the absence of the thermistor allows RTB to
pull THM to VL. When the voltage at the THM pin increases
above 87% of VL, it is assumed that the battery has been
removed and the system powers down. However, there is
also the option to bypass this thermistor sensing option
completely, and so retain the ability to remove the battery
and let the system continue to operate with external power.
If the THM pin is tied to GND (voltage at THM is below 3%
of VL), the thermistor option is disabled and the system
does not respond to the thermistor input. In those cases, it
is assumed that the system has its own temperature sens-
ing, and halts changing through CEN when the tempera-
ture is outside of the safe charging range.
Minimum SYS Output Capacitor
Based on the version of the MAX8903_, the SYS load
regulation is either 25mV/A or 40mV/A. The 25mV/A ver-
sions achieve better load regulation by increasing the
feedback loop gain. To ensure feedback stability with
this higher gain, a larger SYS output capacitor is
required. Devices with 25m/V SYS load regulation
require 22µF SYS output capacitor whereas devices
with 40m/V only require 10µF. See Table 6 for more
information about the various versions of the
MAX8903_.
Inductor Selection for
Step-Down DC-DC Regulator
The MAX8903_'s control scheme requires an external
inductor (LOUT) from 1.0µH to 10µH for proper operation.
This section describes the control scheme and the consid-
erations for inductor selection. Table 5 shows recommend-
ed inductors for typical applications. For assistance with
the calculations needed to select the optimum inductor for
a given application, refer to the spreadsheet at:
www.maximintegrated.com/design/tools/calcula-
tors/files/MAX8903-INDUCTOR-DESIGN.xls.
The MAX8903 step-down DC-DC regulator implements a
control scheme that typically results in a constant switch-
ing frequency (fSW). When the input voltage decreases to
a value near the output voltage, high duty cycle operation
occurs and the device can operate at less than fSW due
to minimum off-time (tOFFMIN) constraints. In high duty
cycle operation, the regulator operates with tOFFMIN and
a peak current regulation. Similarly, when the input
voltage is too high to allow fSW operation due to minimum
28-PIN 4mm x 4mm THIN QFN
SINGLE-LAYER PCB MULTILAYER PCB
Continuous
Power
Dissipation
1666.7mW
Derate 20.8mW/°C
above +70°C
2286mW
Derate 28.6mW/°C
above +70°C
θJA 48°C/W 35°C/W
θJC 3°C/W 3°C/W
Table 4. Package Thermal Characteristics
Power Dissipation
MAX8903A–E/G/H/J/N/Y
2A 1-Cell Li+ DC-DC Chargers
for USB and Adapter Power
23
Maxim Integrated
on-time constraints (tONMIN), the regulator becomes a
fixed minimum on-time valley current regulator.
Versions of the MAX8903 with fSW = 4MHz offer the
smallest LOUT while delivering good efficiency with low
input voltages (5V or 9V). For applications that use high
input voltages (12V), the MAX8903G with fSW = 1MHz
is the best choice because of its higher efficiency.
For a given maximum output voltage, the minimum
inductor ripple current condition occurs at the lowest
input voltage that allows the regulator to maintain fSW
operation. If the minimum input voltage dictates an off-
time less than tOFFMIN, then the minimum inductor rip-
ple condition occurs just before the regulator enters
fixed minimum off-time operation. To allow the current-
mode regulator to provide a low-jitter, stable duty factor
operation, the minimum inductor ripple current
(IL_RIPPLE_MIN) should be greater than 150mA in the
minimum inductor ripple current condition. The maxi-
mum allowed output inductance LOUT_MAX is therefore
obtained using the equations (1) and (2) below.
(1)
otherwise,
where tOFF is the off-time, VSYS(MAX) is maximum charger
output voltage, and VDC(MIN) is minimum DC input volt-
age.
(2)
where LOUT
_
MAX is the maximum allowed inductance.
To obtain a small-sized inductor with acceptable core
loss, while providing stable, jitter-free operation at the
advertised fSW, the actual output inductance (LOUT), is
obtained by choosing an appropriate ripple factor K, and
picking an available inductor in the range inductance
yielded by equations (2), (3), and (4). LOUT should also
not be lower than the minimum allowable inductance as
shown in Table 6. The recommended ripple factor ranges
from (0.2 ≤K ≤0.45) for (2A ≥ISDLIM ≥1A) designs.
(3)
where tOFF is the minimum off-time obtained from (1).
(4)
where VDC(MAX) is maximum input voltage, VSYS(MIN) is
the minimum charger output voltage, and tON is the on-
time at high input voltage, as given by the following
equation:
(5)
otherwise,
The saturation current DC rating of the inductor (ISAT)
must be greater than the DC step-down output current
limit (ISDLIM) plus one-half the maximum ripple current,
as given by equation (6).
(6)
where ILRIPPLE_MAX is the greater of the ripple currents
obtained from (7) and (8).
(7)
(8)
PCB Layout and Routing
Good design minimizes ground bounce and voltage gra-
dients in the ground plane, which can result in instability
or regulation errors. The GND and PGs should connect to
the power-ground plane at only one point to minimize the
effects of power-ground currents. Battery ground should
connect directly to the power-ground plane. The ISET
and IDC current-setting resistors should connect directly
to GND to avoid current errors. Connect GND to the
exposed pad directly under the IC. Use multiple tightly
spaced vias to the ground plane under the exposed pad
to help cool the IC. Position input capacitors from DC,
SYS, BAT, and USB to the power-ground plane as close
as possible to the IC. Keep high current traces such as
those to DC, SYS, and BAT as short and wide as possi-
ble. Refer to the MAX8903A Evaluation Kit for a suitable
PCB layout example.
IL VV t
L
RIPPLE MIN T
DC MAX SYS MIN ON
O
ON
__
() ()
=
()
×−
UUT
IL Vt
L
RIPPLE MIN T
SYS MAX OFF
OUT
OFF
__
()
=×
II IL
SAT SDLIM RIPPLE MAX
>+ _
2
⎝
=×tV
Vf
ON
SYS MIN
DC MAX SW
()
()
1
tt if
V
Vf
ON ONMIN
SYS MIN
DC MAX SW
=×
⎛
⎝
⎜⎞
⎠
⎟
()
()
1≤≤ tONMIN,
LVV t
K
OUT MIN t
DC MAX SYS MIN ON
ON
__
() ()
=
()
×
×
−
IISDLIM
LVt
KI
OUT MIN T
SYS MAX OFF
SDLIM
OFF
__
()
=×
×
LVt
I
OUT MAX
SYS MAX OFF
L RIPPLE MIN
_
()
__
=×
=⎛
⎝−1t V
V
OFF
SYS MAX
DC MIN
()
()
⎜⎜ ⎞
⎠
⎟×1
fSW
tt if
V
V
OFF OFFMIN
SYS MAX
DC MIN
=⎛
⎝
⎜⎞
⎠
⎟
−()
()
1××≤
1
ft
SW OFFMIN,
MAX8903A–E/G/H/J/N/Y
2A 1-Cell Li+ DC-DC Chargers
for USB and Adapter Power
24 Maxim Integrated
DC INPUT
VOLTAGE
RANGE
DC STEP-DOWN
OUTPUT
CURRENT LIMIT
(ISDMAX)
PART NUMBER,
SWITCHING
FREQUENCY*
RECOMMENDED INDUCTOR
5V ±10% 2A MAX8903H/J/N/Y, 4MHz
1.0µH, IFSC1008ABER1R0M01, Vishay
2.5mm x 2mm x 1.2mm, 43mΩ (max), 2.6A
or 1.0µH, LQH32PN1R0-NN0, Murata,
3.2mm x 2.5mm x 1.55mm, 54mΩ (max), 2.3A
5V ±10% 1A MAX8903H/J/N/Y, 4MHz
1.5µH inductor, MDT2520-CN1R5M, TOKO
2.5mm x 2.0mm x 1.2mm, 123.5mΩ (max), 1.25A
or 1.5uH Inductor, IFSC1008ABER1R5M01, Vishay
2.5mm x 2mm x 1.2mm, 72mΩ (max), 2.2A
5V ±10% 2A MAX8903A/B/C/D/E,
4MHz
2.2µH inductor, DFE322512C-2R2N, TOKO
3.2mm x 2.5mm x 1.2mm, 91mΩ (max), 2.4A
or 2.2µH inductor, IFSC1515AHER2R2M01, Vishay
3.8mm x 3.8mm x 1.8mm, 45mΩ (max), 3A
5V ±10% 1A MAX8903A/B/C/D/E,
4MHz
2.2µH inductor, IFSC1008ABER2R2M01, Vishay
2.5mm x 2mm x 1.2mm, 90mΩ (max), 2.15A
or 2.2µH Inductor, LQH32PN2R2-NN0, Murata
3.2mm x 2.5mm x 1.55mm, 91mΩ (max), 1.55A
9V ±10% 2A MAX8903H/J/N/Y, 4MHz
1.5uH inductor, IFSC1008ABER1R5M01, Vishay
2.5mm x 2mm x 1.2mm, 72mW (max), 2.2A
or 1.5µH Inductor, VLS4012ET-1R5N, TDK
4mm x 4mm x 1.2mm, 72mW (max), 2.1A
9V ±10% 1A MAX8903H/J/N/Y, 4MHz
2.2µH inductor, IFSC1008ABER2R2M01, Vishay
2.5mm x 2mm x 1.2mm, 90mΩ (max), 2.15A
or 2.2µH inductor, LQH3NPN2R2NJ0, Murata
3mm x 3mm x 1.1mm, 83mΩ (max), 1.15A
Table 5. Recommended Inductor Examples
MAX8903A–E/G/H/J/N/Y
2A 1-Cell Li+ DC-DC Chargers
for USB and Adapter Power
25
Maxim Integrated
DC INPUT
VOLTAGE
RANGE
DC STEP-DOWN
OUTPUT
CURRENT LIMIT
(ISDMAX)
PART NUMBER,
SWITCHING
FREQUENCY*
RECOMMENDED INDUCTOR
9V ±10% 2A MAX8903A/B/C/D/E,
4MHz
2.2µH inductor, DFE322512C-2R2N, TOKO
3.2mm x 2.5mm x 1.2mm, 91mΩ (max), 2.4A
or 2.2µH Inductor, IFSC1515AHER2R2M01, Vishay
3.8mm x 3.8mm x 1.8mm, 45mΩ (max), 3A
9V ±10% 1A MAX8903A/B/C/D/E,
4MHz
2.2µH Inductor, IFSC1008ABER2R2M01, Vishay
2.5mm x 2mm x 1.2mm, 90mΩ (max), 2.15A
or 2.2µH Inductor, LQH3NPN2R2NJ0, Murata
3mm x 3mm x 1.1mm, 83mΩ (max), 1.15A
9V ±10% 2A MAX8903G, 1MHz
4.3uH Inductor, DEM4518C (1235AS-H-4R3M), TOKO
4.7mm x 4.5mm x 1.8mm, 84mΩ (max), 2.0A
or 4.7µH Inductor, IFSC1515AHER4R7M01, Vishay
3.8mm x 3.8mm x 1.8mm, 90mΩ (max), 2.0A
9V ±10% 1A MAX8903G, 1MHz
4.7µH inductor, DEM2818C (1227AS-H-4R7M), TOKO
3.2mm x 2.8mm x 1.8mm, 92mΩ (max), 1.1A
or 4.7µH inductor, IFSC1008ABER4R7M01, Vishay
2.5mm x 2mm x 1.2mm, 212mΩ (max), 1.2A
12V ±10% 2A MAX8903G, 1MHz
4.3µH inductor, DEM4518C (1235AS-H-4R3M), TOKO
4.7mm x 4.5mm x 1.8mm, 84mΩ (max), 2.0A
or 4.7µH inductor, IFSC1515AHER4R7M01, Vishay
3.8mm x 3.8mm x 1.8mm, 90mΩ (max), 2.0A
12V ±10% 1A MAX8903G, 1MHz
6.8µH, IFSC1515AHER6R8M01, Vishay
3.8mm x 3.8mm x 1.8mm, 115mΩ (max), 1.5A
or 6.8µH, LQH44PN6R8MP0, Murata
4mm x 4mm x 1.65mm, 144mΩ (max), 1.34A
Table 5. Recommended Inductor Examples (continued)
*
See the Selector Guide for more information about part numbers.
MAX8903A–E/G/H/J/N/Y
2A 1-Cell Li+ DC-DC Chargers
for USB and Adapter Power
26 Maxim Integrated
Note 5: Typical values. See the
Electrical Characteristics
table for min/max values.
Note 6: Note that this also changes the timing for the prequal and fast-charge timers.
Note 7: See the
Power Enable on Battery Detection
section for details.
Note 8: The MAX8903H is a newer version of the MAX8903C that is a recommended for new designs.
Selector Guide
The MAX8903_ is available in several options designat-
ed by the first letter following the root part number. The
basic architecture and functionality of the
MAX8903A–MAX8903E/MAX8903G/MAX8903Y are the
same. Their differences lie in certain electrical and
operational parameters. Table 6 outlines these differ-
ences.
Table 6. Selector Guide
PARAMETER MAX8903A MAX8903B MAX8903C MAX8903D MAX8903E MAX8903G MAX8903H MAX8903J MAX8903N MAX8903Y
Minimum SYS
Regulation
Voltage
(VSYSMIN)
3.0V 3.0V 3.4V 3.4V 3.0V 3.0V 3.4V 3.4V 3.4V 3.0V
SYS Regulation
Voltage
(VSYSREG)
4.4V 4.325V 4.4V 4.4V 4.325V 4.325V 4.4V 4.5V 4.4V 4.4V
Minimum
Allowable
Inductor
2.2µH 2.2µH 2.2µH 2.2µH 2.2µH 2.2µH 1µH 1µH 1µH 1µH
Switching
Frequency 4MHz 4MHz 4MHz 4MHz 4MHz 1MHz 4MHz 4MHz 4MHz 4MHz
SYS Load
Regulation 40mV/A 25mV/A 40mV/A 40mV/A 25mV/A 25mV/A 40mV/A 25mV/A 25mV/A 25mV/A
Mi ni mum SY S
Outp ut
Capaci tor ( CSYS)
10µF 22µF 10µF 10µF 22µF 22µF 10µF 10µF 22µF 22µF
BAT Regulation
Voltage
(VBATREG)
(Note 5)
4.2V 4.2V 4.2V 4.1V 4.1V 4.2V 4.2V 4.35V 4.15V 4.15V
BAT Prequal
Threshold
(VBATPQ)
(Note 5)
3V 2.5V 3V 3V 2.5V 2.5V 3V 3V 3V 3V
Top-Off Timer
(Note 6) 15s (fixed) 132min 15s (fixed) 15s (fixed) 132min 132min 15s (fixed) 15s (fixed) 15s (fixed) 15s (fixed)
VL Output
Current Rating 1mA 10mA 1mA 1mA 10mA 10mA 1mA 1mA 1mA 1mA
Power-Enable
On Battery
Detection
(Note 7)
No Yes No No Yes Yes No No No No
Comments — — — — — — (Note 8) — — —
MAX8903A–E/G/H/J/N/Y
2A 1-Cell Li+ DC-DC Chargers
for USB and Adapter Power
27
Maxim Integrated
TQFN
TOP VIEW
26
27
25
24
10
9
11
PG
DC
DCM
BST
IUSB
12
PG
BAT
FLT
USB
BAT
THM
USUS
12
CS
4567
2021 19 17 16 15
CS
LX
GND
IDC
CT
VL
DC UOK
3
18
28 8
LX DOK
SYS
23 13 ISET
SYS
22 14 CEN
CHG
+
EP
MAX8903_
Pin Configuration Chip Information
PROCESS: BiCMOS
MAX8903A–E/G/H/J/N/Y
2A 1-Cell Li+ DC-DC Chargers
for USB and Adapter Power
28 Maxim Integrated
PACKAGE TYPE PACKAGE CODE OUTLINE NO. LAND
PATTERN NO.
28 TQFN-EP T2844-1 21-0139 90-0035
Package Information
For the latest package outline information and land patterns (footprints), go to www.maximintegrated.com/packages. Note that a
"+", "#", or "-" in the package code indicates RoHS status only. Package drawings may show a different suffix character, but the draw-
ing pertains to the package regardless of RoHS status.
MAX8903A–E/G/H/J/N/Y
2A 1-Cell Li+ DC-DC Chargers
for USB and Adapter Power
29
Maxim Integrated
Package Information (continued)
For the latest package outline information and land patterns (footprints), go to www.maximintegrated.com/packages. Note that a
"+", "#", or "-" in the package code indicates RoHS status only. Package drawings may show a different suffix character, but the draw-
ing pertains to the package regardless of RoHS status.
Maxim cannot assume responsibility for use of any circuitry other than circuitry entirely embodied in a Maxim product. No circuit patent licenses are
implied. Maxim reserves the right to change the circuitry and specifications without notice at any time. The parametric values (min and max limits) shown in
the Electrical Characteristics table are guaranteed. Other parametric values quoted in this data sheet are provided for guidance.
30
________________________________Maxim Integrated 160 Rio Robles, San Jose, CA 95134 USA 1-408-601-1000
© 2011 Maxim Integrated Products, Inc. The Maxim logo and Maxim Integrated are trademarks of Maxim Integrated Products, Inc.
MAX8903A–E/G/H/J/N/Y
2A 1-Cell Li+ DC-DC Chargers
for USB and Adapter Power
Revision History
REVISION
NUMBER
REVISION
DATE DESCRIPTION PAGES
CHANGED
0 12/08 Initial release —
1 8/09 Added MAX8903C/MAX8903D to data sheet 1–20
2 11/09 Made various corrections 1–7, 9, 11–21
3 10/10 Added MAX8903B, MAX8903E, MAX8903G, and MAX8903Y 1–29
4 5/11 Added MAX8903H and MAX8903J and updated components 1–29
5 9/11 Added the MAX8903N, and removed future product designation for MAX8903J 1–29
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