MAX8903GETI [MAXIM]
2A 1-Cell Li DC-DC Chargers for USB and Adapter Power Thermistor Monitor; 2A 1节锂DC-DC充电器，用于USB和适配器电源热敏电阻监控器
| 型号： | MAX8903GETI |
| 厂家： | 
MAXIM INTEGRATED PRODUCTS |
| 描述： | 2A 1-Cell Li DC-DC Chargers for USB and Adapter Power Thermistor Monitor |
| 文件： | 总30页 (文件大小：1298K) |
| 中文： | 中文翻译 | 下载： | 下载PDF数据表文档文件 |
19-4410; Rev 4; 5/11
2A 1-Cell Li+ DC-DC Chargers for USB
and Adapter Power
MX8903A–EGHJ/Y
General Description
Features
o Efficient DC-DC Converter Eliminates Heat
The MAX8903A–MAX8903E/MAX8903G/MAX8903H/
MAX8903J/MAX8903Y are integrated 1-cell Li+ charg-
ers 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 current-sense resistors
are required.
o 4MHz Switching for Tiny External Components
o Instant On—Works with No/Low Battery
o Dual Current-Limiting Inputs—AC Adapter or USB
Automatic Adapter/USB/Battery Switchover to
Support Load Transients
50mΩ System-to-Battery Switch
Supports USB Spec
o Thermistor Monitor
o Integrated Current-Sense Resistor
o No External MOSFETs or Diodes
o 4.1V to 16V Input Operating Voltage Range
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.
Ordering Information
PART
TEMP RANGE
-40°C to +85°C
-40°C to +85°C
-40°C to +85°C
-40°C to +85°C
-40°C to +85°C
-40°C to +85°C
-40°C to +85°C
-40°C to +85°C
-40°C to +85°C
PIN-PACKAGE
28 Thin QFN-EP*
28 Thin QFN-EP*
28 Thin QFN-EP*
28 Thin QFN-EP*
28 Thin QFN-EP*
28 Thin QFN-EP*
28 Thin QFN-EP*
28 Thin QFN-EP*
28 Thin QFN-EP*
MAX8903AETI+T
MAX8903BETI+T
MAX8903CETI+T
MAX8903DETI+T
MAX8903EETI+T
MAX8903GETI+T
MAX8903HETI+T
MAX8903JETI+T**
MAX8903YETI+T
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.
+Denotes a lead(Pb)-free/RoHS-compliant package.
*EP = Exposed pad.
**Future product—contact factory for availability.
T = Tape and reel.
Typical Operating Circuit
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.
AC
ADAPTER
OR USB
LX
CS
DC
SYS
LOAD
CURRENT
CHARGE
CURRENT
CHARGE
AND
SYS LOAD
SWITCH
SYSTEM
LOAD
Applications
PDAs, Palmtops, and
Wireless Handhelds
Portable Multimedia
Players
PWM
STEP-DOWN
Personal Navigation
Devices
Smart Cell Phones
Mobile Internet Devices
Ultra Mobile PCs
BAT
BATTERY
USB
USB
MAX8903_
GND
Selector Guide appears at end of data sheet.
Smart Power Selector is a trademark of Maxim Integrated
Products, Inc.
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 Chargers for USB
and Adapter Power
ABSOLUTE MAXIMUM RATINGS
DC, LX to GND .......................................................-0.3V to +20V
LX Continuous Current (total in two pins).......................2.4A
RMS
RMS
RMS
RMS
DCM to GND ..............................................-0.3V to (V
+ 0.3V)
CS Continuous Current (total in two pins) ......................2.4A
SYS Continuous Current (total in two pins) .......................3A
BAT Continuous Current (total in two pins) .......................3A
DC
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
VL Short Circuit to GND .............................................Continuous
Continuous Power Dissipation (T = +70°C)
A
28-Pin Thin QFN-EP
Multilayer (derate 28.6mW/°C above +70°C) ..........2286mW
28-Pin Thin QFN-EP
THM, IDC, ISET, CT to GND........................-0.3V to (V + 0.3V)
VL
DOK, FLT, CEN, UOK, CHG, USUS,
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
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
USB Continuous Current.......................................................1.6A
RMS
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
(Note 1)
= V
= 5V, V
= 4V, circuit of Figure 2, T = -40°C to +85°C, unless otherwise noted. Typical values are at T = +25°C.)
BAT A A
DC
USB
MX8903A–EGHJ/Y
PARAMETER
CONDITIONS
MIN
TYP
MAX
UNITS
DC INPUT
DC Operating Range
4.15
3.9
16
4.1
4.4
V
V
No valid USB input
Valid USB input
4.0
4.3
When V
goes low, V
DC
DOK
DC Undervoltage Threshold
DC Overvoltage Threshold
rising, 500mV typical hysteresis
4.0
When V goes high, V
hysteresis
rising, 500mV typical
DC
DOK
16.5
17
17.5
4
V
Charger enabled, no switching, V
= 5V
2.3
15
SYS
Charger enabled, f = 3MHz, V
= 5V
DC
DC Supply Current
mA
Charger enabled, V
Charger enabled, V
= 0V, 100mA USB mode (Note 2)
= 5V, 100mA USB mode (Note 2)
1
2
2
C EN
C EN
1
V
= 0V, V
= 5V
USUS
0.10
0.15
0.15
0.31
0.25
DCM
DC High-Side Resistance
DC Low-Side Resistance
DC-to-BAT Dropout Resistance
Ω
Ω
Ω
Assumes a 40mΩ inductor resistance (R )
L
When SYS regulation and charging stops, V
200mV hysteresis
falling,
DC
DC-to-BAT Dropout Voltage
0
15
30
mV
Minimum Off Time (t
Minimum On Time (t
)
100
70
4
ns
ns
OFFMIN
)
ONMIN
V
V
V
V
= 8V, V
= 5V, V
= 9V, V
= 9V, V
= 4V
= 3V
= 4V
= 3V
DC
DC
DC
DC
BAT
BAT
BAT
BAT
MAX8903A/B/C/D/E/H/J/Y
MAX8903G
3
Switching Frequency (f
)
MHz
SW
1
1
DC Step-Down Output Current-
Limit Step Range
0.5
2
A
R
IDC
R
IDC
R
IDC
= 3kΩ
= 6kΩ
= 12kΩ
1900
950
2000
1000
500
2100
1050
550
DC Step-Down Output Current
V
= 6V, V
= 4V
SYS
mA
DC
Limit (I
)
SDLIM
450
2
_______________________________________________________________________________________
2A 1-Cell Li+ DC-DC Chargers for USB
and Adapter Power
MX8903A–EGHJ/Y
ELECTRICAL CHARACTERISTICS (continued)
(V
= V
= 5V, V
= 4V, circuit of Figure 2, T = -40°C to +85°C, unless otherwise noted. Typical values are at T = +25°C.)
DC
USB
BAT
A
A
(Note 1)
PARAMETER
CONDITIONS
MIN
TYP
1
MAX
UNITS
ms
No valid USB input
DC Soft-Start Time
Valid USB input before soft-start
20
µs
DC Output Current
500mA USB Mode (Note 3)
V
V
V
= 0V, V
= 0V, V
= 5V
= 0V
= 0V
450
90
475
95
500
100
mA
mA
µA
DCM
DCM
IUSB
IUSB
DC Output Current
100mA USB Mode (Note 2)
SYS to DC Reverse Current
Blocking
= 5.5V, V
0.01
SYS
DC
USB INPUT
USB Operating Range
USB Standoff Voltage
USB Undervoltage Threshold
USB Overvoltage Threshold
4.1
6.3
8
V
V
V
V
When V
When V
goes low, V
rising, 500mV hysteresis
3.95
6.8
90
4.0
6.9
95
4.05
7.0
100
500
3
UOK
UOK
USB
goes high, V
rising, 500mV hysteresis
USB
V
V
= 0V (100mA setting)
= 5V (500mA setting)
IUSB
IUSB
USB Current Limit
mA
450
475
1.3
0.8
0.115
15
I
I
= I
= 0mA, V
= 0mA, V
= 0V
SYS
SYS
BAT
BAT
CEN
CEN
USB Supply Current
mA
= I
= 5V
2
V
= 5V (USB suspend mode)
0.25
30
USUS
Minimum USB to BAT Headroom
USB to SYS Dropout Resistance
0
mV
Ω
0.2
1
0.35
V
V
rising
ms
µs
USB
USB Soft-Start Time
falling below DC UVLO to initiate USB soft-start
20
DC
SYS OUTPUT
MAX8903A/MAX8903B/MAX8903E/
MAX8903G/MAX8903Y
3.0
3.4
4.4
Minimum SYS Regulation Voltage
I
V
= 1A,
< V
BAT
SYS
V
V
(V
SYSMIN
)
SYSMIN MAX8903C/MAX8903D/MAX8903H/
MAX8903J
MAX8903A/MAX8903C/
MAX8903D/MAX8903H/MAX8903Y
4.3
4.5
Regulation Voltage
I
= 0A
MAX8903B/MAX8903E/
MAX8903G
SYS
4.265
4.325
4.5
4.395
MAX8903J
MAX8903A/MAX8903C/
MAX8903D/MAX8903H
40
Load Regulation
I
= 0 to 2A
mV/A
SYS
MAX8903B/MAX8903E/
MAX8903G/MAX8903J/MAX8903Y
25
CS to SYS Resistance
SYS to CS Leakage
V
V
V
= 6V, V
= 5V, V
= 4V, I = 1A
0.07
0.01
0.05
Ω
µA
Ω
DC
SYS
DC
DCM
SYS
CS
= 5.5V, V
= V = 0V
CS
DC
BAT to SYS Resistance
= V
= 0V, V
= 4.2V, I = 1A
SYS
0.1
100
2.0
USB
BAT
BAT to SYS Reverse Regulation
Voltage
V
= 5V, V
= 0V, V
= 0V, I = 200mA
SYS
50
75
mV
V
USB
DC
IUSB
SYS Undervoltage Threshold
SYS falling, 200mV hysteresis (Note 4)
1.8
1.9
_______________________________________________________________________________________
3
2A 1-Cell Li+ DC-DC Chargers for USB
and Adapter Power
ELECTRICAL CHARACTERISTICS (continued)
(V
= V
= 5V, V
= 4V, circuit of Figure 2, T = -40°C to +85°C, unless otherwise noted. Typical values are at T = +25°C.)
BAT A A
DC
USB
(Note 1)
PARAMETER
CONDITIONS
MIN
TYP
MAX
UNITS
BATTERY CHARGER
MAX8903A/
T
= +25°C
4.179
4.158
4.200
4.200
4.221
4.242
A
MAX8903B/
MAX8903C/
MAX8903G/
MAX8903H
T
= -40°C to +85°C
A
BAT Regulation Voltage
T
T
T
T
T
T
= +25°C
4.079
4.059
4.328
4.307
4.129
4.109
-150
4.100
4.100
4.350
4.350
4.150
4.150
-100
4.121
4.141
4.372
4.394
4.171
4.192
-60
A
A
A
A
A
A
MAX8903D/
MAX8903E
I
= 0mA
V
BAT
(V
BATREG
)
= -40°C to +85°C
= +25°C
MAX8903J
MAX8903Y
= -40°C to +85°C
= +25°C
= -40°C to +85°C
Charger Restart Threshold
BAT Prequal Threshold (V
Prequal Charge Current
Fast-Charge Current
Change in V
from DONE to fast-charge
mV
V
BAT
MX8903A–EGHJ/Y
MAX8903A/MAX8903C/MAX8903D/
MAX8903H/MAX8903J/MAX8903Y
2.9
2.4
3.0
3.1
2.6
V
rising
BAT
)
BATPQ
180mV hystersis
MAX8903B/MAX8903E/MAX8903G
2.5
10
Percentage of fast-charge current set at ISET
%
R
R
R
= 600Ω
1800
900
2000
1000
500
10
2200
1100
550
ISET
ISET
ISET
= 1.2kΩ (MAX8903A/MAX8903C/MAX8903D)
= 2.4kΩ
mA
450
DONE Threshold (I
)
Percentage of fast-charge, I
decreasing
BAT
%
kΩ
TERM
R
ISET
Resistor Range
0.6
2.4
ISET Output Voltage
1.5
1.25
0.05
3
V
ISET Current Monitor Gain
BAT Leakage Current
Charger Soft-Start Time
mA/A
No DC or USB input
4
6
µA
With valid input power, V
= 5V
CEN
1.0
ms
°C
Charger Thermal Limit
Temperature
100
5
Charger Thermal Limit Gain
CHARGER TIMER
Charge current = 0 at +120°C
%/°C
Prequalification Time
Fast-Charge Time
C
C
= 0.15µF
= 0.15µF
33
min
min
CT
CT
660
MAX8903A/MAX8903C/MAX8903D/MAX8903H/
MAX8903J/MAX8903Y (fixed)
15
s
Top-Off Timer (t
Timer Accuracy
)
TOP-OFF
MAX8903B/MAX8903E/MAX8903G, C = 0.15µF
CT
132
min
%
-15
40
+15
60
Percentage of fast-charge current below which the timer
clock operates at half-speed
Timer Extend Current Threshold
Timer Suspend Current Threshold
50
20
%
%
Percentage of fast-charge current below which timer
clock pauses
16
24
4
_______________________________________________________________________________________
2A 1-Cell Li+ DC-DC Chargers for USB
and Adapter Power
MX8903A–EGHJ/Y
ELECTRICAL CHARACTERISTICS (continued)
(V
= V
= 5V, V
= 4V, circuit of Figure 2, T = -40°C to +85°C, unless otherwise noted. Typical values are at T = +25°C.)
BAT A A
DC
USB
(Note 1)
PARAMETER
CONDITIONS
MIN
TYP
MAX
UNITS
THERMISTOR MONITOR
0.27 x
0.28 x 0.29 x
THM Threshold, Hot
When charging is suspended, 1% hysteresis
When charging is suspended, 1% hysteresis
THM function is disabled below this voltage
MAX8903B/MAX8903E/MAX8903G
V
V
V
V
V
V
V
VL
VL
VL
0.73 x
0.74 x 0.75 x
THM Threshold, Cold
V
V
V
VL
VL
VL
0.0254 0.03 x 0.036 x
x V
THM Threshold, Disabled
THM Threshold DC, USB Enable
V
V
VL
VL
VL
0.83 x
0.87 x 0.91 x
V
V
V
VL
VL
VL
THM = GND or VL;
= +25°C
-0.100
0.001 +0.200
0.010
MAX8903A/MAX8903C/
MAX8903D/MAX8903H/
MAX8903J/MAX8903Y
T
A
THM = GND or VL;
= +85°C
THM Input Leakage
µA
T
A
MAX8903B/MAX8903E/
MAX8903G
THM = GND or VL;
= -40°C to +85°C
-0.200
0.001 +0.200
T
A
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
V
= 0V to 5.5V
INPUT
T
T
= +25°C
= +85°C
-1.000
0.001 +1.000
0.010
A
(MAX8903A/MAX8903C/
MAX8903D/MAX8903H/
MAX8903J/MAX8903Y)
A
Logic-Input Leakage Current
(CEN, USUS, IUSB)
µA
V
= 0V to 5.5V
INPUT
(MAX8903B/MAX8903E/
MAX8903G)
T
A
= -40°C to +85°C
-0.200
0.001 +0.200
T
T
= +25°C
= +85°C
0.001
0.01
8
1
50
1
A
Logic-Input Leakage Current
(DCM)
V
V
= 0V to 16V
DCM
µA
mV
µA
= 16V
DC
A
Sinking 1mA
Sinking 10mA
Logic Output Voltage, Low
(CHG, FLT, DOK, UOK)
80
T
T
= +25°C
= +85°C
0.001
0.01
A
Open-Drain Output Leakage
Current, High (CHG, FLT, DOK, UOK)
V
= 5.5V
OUT
A
_______________________________________________________________________________________
5
2A 1-Cell Li+ DC-DC Chargers for USB
and Adapter Power
ELECTRICAL CHARACTERISTICS (continued)
(V
= V
= 5V, V
= 4V, circuit of Figure 2, T = -40°C to +85°C, unless otherwise noted. Typical values are at T = +25°C.)
DC
USB
BAT
A
A
(Note 1)
PARAMETER
CONDITIONS
= 0 to 1mA
MIN
TYP
MAX
UNITS
I
VL
(MAX8903A/MAX8903C/
MAX8903D/MAX8903H/
MAX8903J/MAX8903Y)
4.6
5.0
5.4
VL Output Voltage
V
V
= V
= 6V
USB
V
DC
VL
I
VL
= 0 to 10mA
(MAX8903B/MAX8903E/
MAX8903G)
4.6
5.0
5.4
VL UVLO Threshold
falling; 200mV hysteresis
3.2
160
15
V
Thermal Shutdown Temperature
Thermal Shutdown Hysteresis
°C
°C
Note 1: Limits are 100% production tested at T = +25°C. Limits over the operating temperature range are guaranteed by design.
A
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.
MX8903A–EGHJ/Y
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
= 400mV, and 50mA for V
between 400mV and 2V.
SYS
SYS
Typical Operating Characteristics
(T = +25°C, unless otherwise noted.)
A
BATTERY CHARGER EFFICIENCY
SWITCHING FREQUENCY
MAX8903G BATTERY CHARGER
EFFICIENCY vs. BATTERY VOLTAGE
vs. BATTERY VOLTAGE
vs. V
DC
100
100
90
80
70
60
50
40
30
20
10
0
4.5
4.0
3.5
3.0
2.5
2.0
1.5
1.0
0.5
0.0
90
80
V
= 6V
DC
V
= 5V
DC
70
60
50
40
30
20
10
0
V
= 9V
V
= 3V
= 4V
DC
BAT
V
= 8V
DC
V
BAT
V
= 12V
V
= 12V
I
DC
DC
I
= 0.15A
= 1.5A
I
= 0.15A
I
= 1.5A
BAT
BATT
BATT
BAT
R
V
= 1.2kΩ
= 0V
ISET
CEN
1.0 1.5 2.0 2.5 3.0 3.5 4.0 4.5 5.0
BATTERY VOLTAGE (V)
1.0 1.5 2.0 2.5 3.0 3.5 4.0 4.5 5.0
BATTERY VOLTAGE (V)
4
6
8
10
12
14
16
DC VOLTAGE (V)
6
_______________________________________________________________________________________
2A 1-Cell Li+ DC-DC Chargers for USB
and Adapter Power
MX8903A–EGHJ/Y
Typical Operating Characteristics (continued)
(T = +25°C, unless otherwise noted.)
A
SYS EFFICIENCY
vs. SYS OUTPUT CURRENT
MAX8903G SYS EFFICIENCY
vs. SYS OUTPUT CURRENT
MAX8903G SWITCHING
FREQUENCY vs. V
DC
100
90
80
70
60
50
40
30
20
10
0
100
90
80
70
60
50
40
30
20
10
0
1.6
1.4
1.2
1.0
0.8
0.6
0.4
0.2
0
V
V
= 1V
= 4.4V
CEN
SYS
V
= 1
CEN
V
= 16V
DC
V
= 11V
DC
V
= 12V
V
= 4V
DC
BAT
V
= 16V
DC
V
= 9V
V
= 3V
DC
BAT
V
= 6V
DC
V
DC
= 6V
R
V
= 1.2kI
= 0V
ISET
CEN
V
= 4.5V
1000
DC
1
10
100
10000
1
10
100
1000
10,000
4
6
8
10
12
14
16
SYS OUTPUT CURRENT (mA)
SYS OUTPUT CURRENT (mA)
DC VOLTAGE (V)
USB SUPPLY CURRENT
vs. USB VOLTAGE
BATTERY LEAKAGE CURRENT
vs. BATTERY VOLTAGE
USB SUPPLY CURRENT
vs. USB VOLTAGE (SUSPEND)
1.6
1.4
1.2
1.0
0.8
0.6
0.4
0.2
0
80
70
60
50
40
30
20
10
0
140
120
100
80
CHARGER
ENABLED
60
40
CHARGER
DISABLED
20
NO DC OR USB INPUT
USB SUSPEND
0
0
1
2
3
4
5
6
7
0
1
2
3
4
5
6
0
1
2
3
4
5
6
7
USB VOLTAGE (V)
BATTERY VOLTAGE (V)
USB VOLTAGE (V)
CHARGE CURRENT
vs. BATTERY VOLTAGE—USB MODE
BATTERY LEAKAGE CURRENT
vs. AMBIENT TEMPERATURE
CHARGE CURRENT
vs. BATTERY VOLTAGE—DC MODE
500
450
400
350
300
250
200
150
100
50
90
80
70
60
50
40
30
20
10
0
1200
1000
800
600
400
200
0
CHARGER ENABLED
CHARGE ENABLED
I
I
SET TO 1A
SET TO 2A
I
SET TO 1.5A
BAT
BAT
MAX8903D
DC
MAX8903A/MAX8903C
RISING
V
RISING
BAT
V
BAT
V
= V
USB
IUSB
V
= 0V
IUSB
NO DC OR USB INPUT
0
1.5
2.0
2.5
3.0
3.5
4.0
4.5
1.5
2.0
2.5
3.0
3.5
4.0
4.5
-40
-15
10
35
60
85
BATTERY VOLTAGE (V)
BATTERY VOLTAGE (V)
TEMPERATURE (°C)
_______________________________________________________________________________________
7
2A 1-Cell Li+ DC-DC Chargers for USB
and Adapter Power
Typical Operating Characteristics (continued)
(T = +25°C, unless otherwise noted.)
A
MAX8903A/C
NORMALIZED CHARGE CURRENT
vs. AMBIENT TEMPERATURE
1.015
BATTERY REGULATION VOLTAGE
vs. AMBIENT TEMPERATURE
SYS VOLTAGE vs. USB VOLTAGE
5.0
4.5
4.0
3.5
3.0
2.5
2.0
1.5
1.0
0.5
0
100.5
100.4
100.3
100.2
100.1
100.0
99.9
V
V
V
= 5V
= 0V
= 0V
CEN
BAT
DC
V
= 5V, V = 4V
BAT
USB
1.010
1.005
1.000
0.995
0.990
0.985
V
FALLING
USB
V
RISING
USB
99.8
99.7
99.6
R
= 1MΩ
SYS
22ppm/°C
99.5
0
1
2
3
4
5
6
7
-40
-15
10
35
60
85
-40
-15
10
35
60
85
USB VOLTAGE (V)
TEMPERATURE (°C)
TEMPERATURE (°C)
MX8903A–EGHJ/Y
MAX8903A/MAX8903C/MAX8903D
SYS VOLTAGE vs. DC VOLTAGE
SYS VOLTAGE
vs. SYS OUTPUT CURRENT
SYS VOLTAGE
vs. SYS OUTPUT CURRENT, USB INPUT
5.0
4.5
4.0
3.5
3.0
2.5
2.0
1.5
1.0
0.5
0
4.50
4.40
4.30
4.20
4.10
4.00
3.90
3.80
4.41
4.40
4.39
4.38
4.37
4.36
4.35
4.34
4.33
4.32
4.31
4.30
MAX8903A/MAX8903C/MAX8903D
= 5.75V
V
= 5V
USB
V
DC
MAX8903A/MAX8903C/
MAX8903D
V
RISING
DC
MAX8903B/MAX8903E
= 5.75V
V
DC
USB AND DC
UNCONNECTED
V
FALLING
DC
V
BATT
= 4V
MAX8903B/MAX8903E
V
CEN
V
BAT
V
USB
= 5V
= 0V
= 0V
0
2
4
6
8
10 12 14 16 18
0
0.5
1.0
1.5
2.0
0
100
200
300
400
500
DC VOLTAGE (V)
SYS OUTPUT CURRENT (A)
SYS OUTPUT CURRENT (mA)
CHARGE PROFILE—1400mAh BATTERY
VL VOLTAGE vs. DC VOLTAGE
ADAPTER INPUT—1A CHARGE
MAX8903A toc17
6
5
4
3
2
1
0
6.0
5.5
5.0
4.5
4.0
3.5
3.0
2.5
2.0
1.5
1.0
0.5
0
1.2
1.0
0.8
0.6
0.4
0.2
0.0
I
SET TO 1A
SET TO 2A
DC
I
BAT
V
BAT
I
BAT
MAX8903A/MAX8903B/MAX8903C
0
2
4
6
8
10 12 14 16 18
0
20
40
60
80
100 120 140
DC VOLTAGE (V)
TIME (min)
8
_______________________________________________________________________________________
2A 1-Cell Li+ DC-DC Chargers for USB
and Adapter Power
MX8903A–EGHJ/Y
Typical Operating Characteristics (continued)
(T = +25°C, unless otherwise noted.)
A
MAX8903A/B/C/D/E/H/J/Y DC SWITCHING
CHARGE PROFILE—1400mAh BATTERY
USB INPUT—500mA CHARGE
WAVEFORMS—LIGHT LOAD
MAX8903A toc19
MAX8903A toc18
5.0
4.5
4.0
3.5
3.0
2.5
2.0
1.5
1.0
0.5
0
0.500
0.450
0.400
0.350
0.300
0.250
0.200
0.150
0.100
0.050
0
20mV/div
AC-COUPLED
V
OUT
V
BAT
5V/div
0V
V
LX
LX
I
BAT
I
MAX8903A/MAX8903B/MAX8903C
SET TO 500mA
500mA/div
0A
I
USB
R
SYS
= 44Ω
I
SET TO 2A
BAT
200ns/div
0
20 40 60 80 100 120 140 160 180 200
TIME (min)
MAX8903A/B/C/D/E/H/J/Y DC SWITCHING
MAX8903G DC SWITCHING
WAVEFORMS—HEAVY LOAD
WAVEFORMS—LIGHT LOAD
MAX8903A toc20
MAX8903A toc19a
20mV/div
50mV/div
AC-COUPLED
AC-COUPLED
V
V
SYS
OUT
V
= 9V, L = 2.2µH
DC
C
R
= 22µF,
= 44I
SYS
SYS
5V/div
0V
V
I
V
10V/div
LX
LX
0V
1A/div
LX
I
LX
0A
500mA/div
0A
R
= 5Ω
SYS
200ns/div
1µs/div
DC CONNECT WITH
USB CONNECTED (R = 25Ω)
MAX8903G DC SWITCHING
WAVEFORMS—HEAVY LOAD
SYS
MAX8903A toc21
MAX8903A toc20a
3.6V
2V/div
V
50mV/div
SYS
V
SYS
AC-COUPLED
V
= 9V, L = 2.2µH
I
DC
DC
500mA/div
347mA
C
SYS
= 22µF, R = 5I
SYS
CEN = 1
10V/div
0V
475mA
500mA/div
V
I
LX
I
USB
-I = CHARGING
BAT
0A
I
-335mA
BAT
500mA/div
LX
1A/div
0A
200µs/div
1µs/div
_______________________________________________________________________________________
9
2A 1-Cell Li+ DC-DC Chargers for USB
and Adapter Power
Typical Operating Characteristics (continued)
(T = +25°C, unless otherwise noted.)
A
DC CONNECT WITH NO USB
DC DISCONNECT WITH NO USB
(R = 25Ω)
(R
SYS
= 25Ω)
SYS
MAX8903A toc22
MAX8903A toc23
3.84V
3.68V
3.6V
3.6V
3.6V
3.6V
2V/div
5V/div
2V/div
5V/div
V
V
SYS
SYS
3.44V
V
V
BAT
BAT
C
DC
C
SYS
CHARGING
CHARGING
850mA
1A/div
1A/div
1A/div
1A/div
I
0A
0A
DC
850mA
-1A
I
DC
-I = CHARGING
BAT
I
BAT
I
144mA
BAT
144mA
-I = CHARGING
BATTERY
CHARGER
SOFT-START
-1A
BAT
400µs/div
40µs/div
MX8903A–EGHJ/Y
MAX8903A/C/D/H/Y SYS LOAD TRANSIENT
MAX8903B/E SYS LOAD TRANSIENT
MAX8903A toc24a
MAX8903A toc24b
MAX8903B
V
= 10.5V
DC
L = 2.2µH
4.400V
C
SYS
= 22µF
MAX8903A
V
4.325V
R
= 3kI (2A)
SYS
IDC
20mV/div
AC-COUPLED
V
= 10.5V
DCM = HIGH
CEN = 1
DC
V
I
SYS
4.360V
1A
20mV/div
L = 2.2µH
4.305V
C
= 10µF
SYS
R
= 3kI (2A)
IDC
1A
DCM = HIGH
CEN = 1
I
SYS
SYS
500mA/div
0A
0A
500mA/div
0A
0A
100µs/div
100µs/div
USB CONNECT WITH NO DC
(R
= 25Ω)
MAX8903G SYS LOAD TRANSIENT
SYS
MAX8903A toc25
MAX8903A toc24c
3.6V
3.75V
2V/div
5V/div
V
4.325V
= 9V
SYS
3.5V
USB
5V
4.305V
50mV/div
V
SYS
V
USB
V
DC
C
L = 2.2µH
CHARGING
475mA
C
= 22µF
SYS
500mA/div
500mA/div
R
= 3kI (2A)
IDC
1A
I
USB
DCM = 1
CEN = 1
I
SYS
I
BAT
144mA
BATTERY
CHARGER
SOFT-START
500mA/div
0A
0A
-330mA
400µs/div
100µs/div
10 ______________________________________________________________________________________
2A 1-Cell Li+ DC-DC Chargers for USB
and Adapter Power
MX8903A–EGHJ/Y
Typical Operating Characteristics (continued)
(T = +25°C, unless otherwise noted.)
A
USB DISCONNECT WITH NO DC
(R = 25Ω)
USB SUSPEND
USB RESUME
SYS
MAX8903A toc26
MAX8903A toc27
MAX8903A toc28
0V
0V
3.6V
3V
3V
V
V
2V/div
5V/div
5V/div
5V/div
USUS
USUS
V
SYS
C
USB
CHARGING
500mA/div
500mA/div
V
USB
475mA
475mA
3.6V
5V
I
0A
0A
USB
I
USB
475mA
3.8V
3.6V
V
V
SYS
SYS
500mA/div
500mA/div
2V/div
2V/div
3.7V
I
USB
I
I
BAT
BAT
-330mA
144mA
I
BAT
0A
-475mA
-475mA
0A
BATTERY
CHARGER
500mA/div
500mA/div
SOFT-START
100µs/div
200µs/div
200µs/div
Pin Description
PIN
NAME
FUNCTION
Power Ground for Step-Down Low-Side Synchronous n-Channel MOSFET. Both PG pins must be
connected together externally.
1, 2
PG
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.
3, 4
DC
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.
5
DCM
6
7
BST
High-Side MOSFET Driver Supply. Bypass BST to LX with a 0.1µF ceramic capacitor.
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.
IUSB
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).
8
9
DOK
VL
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.
Charge Timer Set Input. A capacitor (C ) from CT to GND sets the fast-charge and prequal fault timers.
CT
Connect to GND to disable the timer.
10
CT
DC Current-Limit Set Input. Connect a resistor (R ) from IDC to GND to program the current limit of the
IDC
step-down regulator from 0.5A to 2A when DCM is logic-high.
11
12
IDC
GND
Ground. GND is the low-noise ground connection for the internal circuitry.
______________________________________________________________________________________ 11
2A 1-Cell Li+ DC-DC Chargers for USB
and Adapter Power
Pin Description (continued)
PIN
NAME
FUNCTION
Charge Current Set Input. A resistor (R
The prequal charge current is 10% of the fast-charge current.
) from ISET to GND programs the fast-charge current up to 2A.
ISET
13
ISET
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.
14
15
CEN
USB Suspend Input. Drive USUS logic-high to enter USB suspend mode, lowering USB current to 115µA,
and internally shorting SYS to BAT.
USUS
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.
16
THM
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.
17
18
19
USB
FLT
Fault Output. Active-low, open-drain output pulls low when the battery timer expires before prequal or
fast-charge completes.
MX8903A–EGHJ/Y
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).
UOK
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.
20, 21
22
BAT
Charger Status Output. Active-low, open-drain output pulls low when the battery is in fast-charge or
prequal. Otherwise, CHG is high impedance.
CHG
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 V . When the system load (I
SYSREG
)
SYS
exceeds the DC or USB current limit, SYS is regulated to 50mV below BAT, and both the powered input
and the battery service SYS.
23, 24
SYS
Bypass SYS to GND with a 10µF (MAX8903A/MAX8903C/MAX8903D/MAX8903H/MAX8903J/MAX8903Y)
or 22µF (MAX8903B/MAX8903E/MAX8903G/MAX8903Y) X5R or X7R ceramic capacitor. Both SYS pins
must be connected together externally.
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.
25, 26
CS
Inductor Connection. Connect the inductor between LX and CS. Both LX pins must be connected together
externally.
27, 28
—
LX
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.
12 ______________________________________________________________________________________
2A 1-Cell Li+ DC-DC Chargers for USB
and Adapter Power
MX8903A–EGHJ/Y
PG
LX
BST
CS
MAX8903A–
MAX8903E
MAX8903G
MAX8903Y
DC POWER
MANAGEMENT
TO
SYSTEM
LOAD
DC
SYS
ISET
AC
ADAPTER
PWR
OK
Li+ BATTERY
CHARGER
AND SYS LOAD SWITCH
PWM
STEP-DOWN
REGULATOR
DOK
CHARGER
CURRENT-
VOLTAGE
CONTROL
BATTERY
CONNECTOR
SET
INPUT
LIMIT
BAT
BAT+
+
BAT-
NTC
USB POWER
MANAGEMENT
USB
UOK
T
USB
THERMISTOR
MONITOR
(SEE FIGURE 7)
THM
VL
PWR
OK
CURRENT-
LIMITED
VOLTAGE
IC
THERMAL
REGULATION
REGULATOR
CHG
CHARGE
TERMINATION
AND MONITOR
SET
INPUT
LIMIT
DC
DCM
IUSB
FLT
CT
DC MODE
500mA
CHARGE
TIMER
INPUT AND
USB
CHARGER
CURRENT-LIMIT
SET LOGIC
LIMIT
100mA
USUS
IDC
USB
SUSPEND
CEN
GND
DC
EP
LIMIT
Figure 1. Functional Block Diagram
______________________________________________________________________________________ 13
2A 1-Cell Li+ DC-DC Chargers for USB
and Adapter Power
R
PU
4 x 100kΩ
TO VL
1
2
PG
PG
18
19
8
FAULT
FLT
UOK
DOK
CHG
MAX8903A–
MAX8903E
MAX8903G
MAX8903Y
OUTPUT
C
DC
4.7µF
USB PWR OK
DC PWR OK
3
DC
DC
ADAPTER
4
6
22
CHARGE
INDICATOR
BST
C
0.1µF
BST
R
R
ISET
27 LX
LX
13
11
ISET
IDC
28
IDC
L1
1µH
25 CS
26 CS
(SEE TABLE 5 FOR
INDUCTOR SELECTION)
SYS 24
TO SYSTEM
LOAD
C
SYS
MX8903A–EGHJ/Y
23
SYS
10µF (MAX8903A/MAX8903C/MAX8903D/MAX8903H/MAX8903J)
22µF (MAX8903B/MAX8903E/MAX8903G/MAX8903Y)
USB
BAT
BAT
21
20
17 USB
VBUS
C
4.7µF
C
10µF
USB
BAT
1-CELL
LI+
GND
5
TO DC
DCM
9
VL
14
OFF
CHARGE ON
C
1µF
VL
CEN
R
T
10kΩ
16
500mA
100mA
7
THM
IUSB
NTC
10kΩ
USB SUSPEND
15
USUS
12
10
CT
GND
C
CT
EP
0.15µF
Figure 2. Typical Application Circuit Using a Separate DC and USB Connector
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.
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.
The MAX8903_ also manages load switching from the
battery to and from an external power source with an
on-chip 50mΩ MOSFET. This switch also helps support
load peaks using battery power when the input source
is overloaded.
14 ______________________________________________________________________________________
2A 1-Cell Li+ DC-DC Chargers for USB
and Adapter Power
MX8903A–EGHJ/Y
R
PU
4 x 100kΩ
TO VL
1
2
PG
PG
18
19
8
FAULT
FLT
UOK
DOK
CHG
MAX8903A–
MAX8903E
MAX8903G
MAX8903Y
OUTPUT
C
DC
4.7µF
USB PWR-OK
DC PWR-OK
3
DC
DC
VBUS
4
6
D-
22
CHARGE
INDICATOR
BST
D+
C
0.1µF
BST
R
R
ISET
27 LX
LX
13
11
ID
ISET
IDC
GND
28
IDC
L1
1µH
25 CS
26 CS
SYS 24
TO SYSTEM
LOAD
499kΩ
C
SYS
23
SYS
(SEE TABLE 5 FOR
INDUCTOR VALUE
SELECTION)
10µF (MAX8903A/MAX8903C/MAX8903D/MAX8903H/MAX8903J)
22µF (MAX8903B/MAX8903E/MAX8903Y)
BAT
BAT
21
20
17 USB
C
BAT
1-CELL
LI+
USB
ADAPTER
DC MODE
10µF
5
DCM
9
VL
14
OFF
CHARGE ON
C
1µF
VL
CEN
R
T
10kΩ
16
500mA
100mA
7
THM
IUSB
NTC
10kΩ
USB SUSPEND
15
USUS
12
10
CT
GND
C
CT
EP
0.15µF
Figure 3. Typical Application Circuit Using a Mini 5 Style Connector or Other DC/USB Common Connector
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).
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 (V
, Figure 4), the battery charger
SYSMIN
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
The MAX8903_ prevents overheating during high ambi-
ent temperatures by limiting charging current when the
die temperature exceeds +100°C.
______________________________________________________________________________________ 15
2A 1-Cell Li+ DC-DC Chargers for USB
and Adapter Power
Table 1. External Components List for Figures 2 and 3
COMPONENT
(FIGURES 2 AND 3)
FUNCTION
PART
C
, C
Input filter capacitor
4.7µF ceramic capacitor
1.0µF ceramic capacitor
DC USB
C
VL filter capacitor
VL
10µF (MAX8903A/MAX8903C/MAX8903D/MAX8903H/MAX8903J) or
22µF (MAX8903B/MAX8903E/MAX8903G/MAX8903Y) ceramic capacitor
C
SYS output bypass capacitor
SYS
C
Battery bypass capacitor
Charger timing capacitor
Logic output pullup resistors
Negative TC thermistor
10µF ceramic capacitor
BAT
C
0.15µF low TC ceramic capacitor
CT
R
(X4)
100kΩ
PU
THM
Philips NTC thermistor, P/N 2322-640-63103, 0kΩ 5% at +25°C
R
THM pullup resistor
10kΩ
T
DC input current-limit programming
Fast-charge current programming
R
3kΩ 1%, for 2A limit
1.2kΩ 1%, for 1A charging
IDC
R
ISET
L1
DC input step-down inductor
1µH inductor with I
> 2A
SAT
MX8903A–EGHJ/Y
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.
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.
If the battery voltage is below V , the charger does
SYSMIN
not directly connect the system voltage to the battery
and the system voltage (V ) is slightly above V
SYS
SYSMIN
as shown in Figure 4. The battery charger independently
controls the battery charging current. V is set to
3.0V in the MAX8903A/MAX8903B/MAX8903E/
MAX8903G/MAX8903Y and 3.4V for MAX8903C/
MAX8903D/MAX8903H/MAX8903J.
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-
SYSMIN
After the battery charges to 50mV above V
, the
tance from IDC to GND (R
). Calculate R
accord-
SYSMIN
IDC
IDC
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.
ing to the following equation:
R
IDC
= 6000V/I
DC-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.
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
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
16 ______________________________________________________________________________________
2A 1-Cell Li+ DC-DC Chargers for USB
and Adapter Power
MX8903A–EGHJ/Y
cannot be driven to a voltage higher than DC. The
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
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.
when 4.1V < V
< 6.6V. If the USB power-OK output
USB
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.
An alternative to the simple MOSFET and resistor on
DCM as shown in Figure 3 is to place a 1MΩ resistor 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 1MΩ series resistance limits the current from
DCM through the internal diode to DC to a few µA.
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
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.
DC or USB, and V
regulates at 50mV below V
.
SYS
BAT
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.
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 < V
< 16V. When the USB
DC
voltage is also valid, the DC source is considered valid
and DOK is driven low when: 4.45V < V < 16V. The
DC
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.
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 V
. The
V
SYSREG
SYSREG
V
BATREG
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
50mΩ SYS-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.
MAX8903A–
MAX8903E
MAX8903G
MAX8903Y
V
SYS
I
x R
ON
BAT
V
SYSMIN
V
V
= 0V
AND/OR V
CEN
= 5.0V
DC
USB
V
BAT
USB Input
When charging from the USB input, the DC input step-
down regulator turns off and a linear regulator from
Figure 4. SYS Tracking V
to the Minimum System Voltage
BAT
______________________________________________________________________________________ 17
2A 1-Cell Li+ DC-DC Chargers for USB
and Adapter Power
Table 2. Input Limiter Control Logic
DC STEP-DOWN
OUTPUT
CURRENT LIMIT
MAXIMUM
CHARGE
CURRENT**
USB INPUT
CURRENT LIMIT
POWER SOURCE
DOK
UOK DCM*** IUSB USUS
Lesser of
1200V/R
6000V/R
and
AC Adapter at DC Input
L
L
X
X
H
L
X
L
X
L
6000V/R
IDC
ISET
IDC
Lesser of
100mA
1200V/R
and
USB input off. DC
input has priority.
ISET
100mA
USB Power at DC Input
Lesser of
1200V/R
and
L
L
X
X
L
L
L
X
H
X
L
L
H
L
500mA
ISET
500mA
USB suspend
0
Lesser of
H
100mA
500mA
1200V/R
and
ISET
MX8903A–EGHJ/Y
100mA
USB Power at USB Input,
DC Unconnected
Lesser of
1200V/R
ISET
No DC input
H
L
X
H
L
and
500mA
H
H
L
X
X
X
X
H
X
USB suspend
No USB input
0
0
DC and USB Unconnected
H
**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.
USB to SYS powers the system and charges the bat-
tery. If the battery is greater than the minimum system
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
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
is regulated to V
. If both USB and DC inputs are
SYSREG
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.
BAT. The switchover to BAT occurs when V
< V
.
BAT
SYS
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-
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
18 ______________________________________________________________________________________
2A 1-Cell Li+ DC-DC Chargers for USB
and Adapter Power
MX8903A–EGHJ/Y
again as long as the SYS load current is less than the
mum fast-charge rate until the voltage of the deeply
discharged battery recovers. When the battery voltage
set current limit.
reaches V
and the charge current drops to 10%
BATREG
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
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-
logic input. There is no di/dt limiting, however, if R
changed suddenly using a switch.
is
ISET
old (I
) and the charger is in voltage mode, charg-
TERM
ing is complete. Charging continues for a brief 15s
top-off period and then enters the DONE state where
charging stops.
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
Note that if charge current falls to I
as a result of
TERM
the input or thermal limiter, the charger does not enter
DONE. For the charger to enter DONE, charge current
GND. Calculate the R
following equation:
resistance according to the
ISET
must be less than I
, the charger must be in volt-
TERM
age mode, and the input or thermal limiter must not be
reducing charge current.
R
= 1200V/I
CHGMAX
ISET
Monitoring Charge Current
Charge Status Outputs
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.
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.
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 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.
When V
is below V
, the charger enters pre-
BATPQ
BAT
qual mode and the battery charges at 10% of the maxi-
MONITORING THE BATTERY
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.
CHARGE CURRENT WITH V
ISET
1.5
ISET
0
V
(V)
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.
0
BATTERY CHARGING CURRENT (A)
DISCHARGING
1200V/R
ISET
Charge Timer
A fault timer prevents the battery from charging indefi-
nitely. The fault prequal and fast-charge timers are con-
Figure 5. Monitoring the Battery Charge Current with the
Voltage from ISET to GND
trolled by the capacitance at CT (C ).
CT
______________________________________________________________________________________ 19
2A 1-Cell Li+ DC-DC Chargers for USB
and Adapter Power
CEN = HI OR
NOT READY
REMOVE AND RECONNECT
UOK AND DOK = HIGH IMPEDANCE
THE INPUT SOURCE(S)
CHG = HIGH IMPEDANCE
FLT = HIGH IMPEDANCE
ANY STATE
I
= 0mA
CHG
UOK AND/OR DOK = LOW
CEN = 0
RESET TIMER
TOGGLE CEN OR
REMOVE AND RECONNECT
THE INPUT SOURCE(S)
PREQUALIFICATION
UOK AND/OR DOK = LOW
CHG = LOW
TIMER > t
PREQUAL
FLT = HIGH IMPEDANCE
FAULT
0 < V < V
BAT
BATPQ
UOK AND/OR DOK = LOW
CHG = HIGH IMPEDANCE
FLT = LOW
I
≤ I
/10
CHG CHGMAX
V
BAT
< V
BATPQ
- 180mV
V
> V
BAT BATPQ
I
= 0mA
CHG
RESET TIMER = 0
RESET TIMER
TIMER > t
FSTCHG
(TIMER SLOWED BY 2x IF
< I /2, AND
FAST-CHARGE
UOK AND/OR DOK = LOW
CHG = LOW
I
CHG CHGMAX
V
< V
- 180mV
RESET TIMER
BAT
BATPQ
PAUSED IF I
< I
/5 WHILE V < V
)
CHG CHGMAX
BAT
BATREG
FLT = HIGH IMPEDANCE
MX8903A–EGHJ/Y
V
< V < V
BAT BATREG
BATPQ
I
≤ I
CHG CHGMAX
I
< I
CHG TERM
AND V = V
BAT
BATREG
I
> I
CHG TERM
AND THERMAL
OR INPUT LIMIT
NOT EXCEEDED;
RESET TIMER
RESET TIMER
ANY CHARGING
STATE
TOP-OFF
UOK AND/OR DOK = LOW
CHG = HIGH IMPEDANCE
FLT = HIGH IMPEDANCE
THM OK
TIMER RESUME
THM NOT OK
TIMER SUSPEND
V
BAT
< V
+ V
BATREG RSTRT
RESET TIMER
V
= V
BATREG
BAT
I
= I
CHG TERM
TEMPERATURE SUSPEND
= 0mA
UOK OR DOK PREVIOUS STATE
CHG = HIGH IMPEDANCE
FLT = HIGH IMPEDANCE
I
CHG
TIMER > t
TOP-OFF
DONE
UOK AND/OR DOK = 0
CHG = HIGH IMPEDANCE
FLT = HIGH IMPEDANCE
V
+ V < V < V
RSTRT BAT BATREG
BATREG
I
= 0mA
CHG
Figure 6. MAX8903A Charger State Flow Chart
C
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
CT
t
= 33min ×
PREQUAL
0.15µF
C
CT
t
= 660min ×
FST−CHG
0.15µF
t
= 15s (MAX8903A/MAX8903C/MAX8903D/
TOP−OFF
MAX8903H/MAX8903J /MAX8903Y
C
CT
t
= 132min ×
(MAX8903B MAX8903E
MAX8903G)
at V
(i.e., the charger is in voltage mode).
BATREG
TOP−OFF
0.15µF
20 ______________________________________________________________________________________
2A 1-Cell Li+ DC-DC Chargers for USB
and Adapter Power
MX8903A–EGHJ/Y
CEN
MAX8903A–
VL
THERMISTOR
CIRCUITRY
MAX8903E
MAX8903G
MAX8903Y
VL
MAX8903B/MAX8903E/
MAX8903G ONLY
THERMISTOR
DETECTOR
0.87 VL
R
TB
ALTERNATE
THERMISTOR
CONNECTION
0.74 VL
COLD
THM
R
TS
THM
0.28 VL
0.03 VL
OUT OF
RANGE
HOT
R
TP
R
T
DISABLE
CHARGER
ENABLE THM
R
T
ALL COMPARATORS
60mV HYSTERESIS
GND
Figure 7. Thermistor Monitor Circuitry
Thermistor Input (THM)
Table 3. Fault Temperatures for Different
Thermistors
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.
Thermistor β (K)
(kΩ) (Figure 7)
3000 3250 3500 3750 4250
R
10
10
10
10
10
TB
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
Since the thermistor monitoring circuit employs an exter-
Nominal Hot Trip
Temperature (°C)
55
-3
53
-1
50
0
49
2
46
nal bias resistor from THM to VL (R , Figure 7), the ther-
TB
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 10kΩ at +25°C thermistor, use 10kΩ at
Nominal Cold Trip
Temperature (°C)
4.5
VL Regulator
R , and with a 100kΩ at +25°C thermistor, use 100kΩ.
TB
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.
For a typical 10kΩ (at +25°C) thermistor and a 10kΩ
resistor, the charger enters a temperature suspend
R
TB
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:
⎧
⎫
⎬
1
1
⎛
⎞
β
−
⎨
⎜
⎝
⎟
⎠
T+273°C
298°C
⎪
⎩
⎪
⎭
R
= R × e
25
T
______________________________________________________________________________________ 21
2A 1-Cell Li+ DC-DC Chargers for USB
and Adapter Power
where:
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.
R = The resistance in Ω of the thermistor at tempera-
T
ture T in Celsius
R
= The resistance in Ω of the thermistor at +25°C
25
β = The material constant of the thermistor, which typi-
cally ranges from 3000K to 5000K
T = The temperature of the thermistor in °C
Power Dissipation
Table 3 shows the MAX8903A–MAX8903E/MAX8903Y
THM temperature limits for different thermistor material
constants.
Table 4. Package Thermal Characteristics
28-PIN 4mm x 4mm THIN QFN
Some designs might prefer other thermistor temperature
limits. Threshold adjustment can be accommodated by
SINGLE-LAYER PCB
MULTILAYER PCB
changing R , connecting a resistor in series and/or in
TB
1666.7mW
2286mW
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 β of 4250 and connecting 120kΩ in 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
Continuous
Power
Dissipation
Derate 20.8mW/°C
above +70°C
Derate 28.6mW/°C
above +70°C
θ
θ
48°C/W
3°C/W
35°C/W
3°C/W
JA
JC
MX8903A–EGHJ/Y
Minimum SYS Output Capacitor
The MAX8903B/MAX8903E/MAX8903G have a SYS
load regulation of 25mV/A versus a load regulation of
40mV/A on the MAX8903A/MAX8903C/MAX8903D/
MAX8903Y. To achieve tighter load regulation, the loop
gain on the MAX8903B/MAX8903E/MAX8903G is high-
er. To ensure feedback loop stability with higher gain, a
larger SYS output capacitor is required (see Table 7).
threshold. Raising R
lowers both the cold and hot
TB
thresholds, while lowering R raises both thresholds.
TB
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 10kΩ thermistor and a 10kΩ
pullup to VL, this results in an additional 250µA load.
This load can be reduced to 25µA by instead using a
100kΩ thermistor and 100kΩ pullup resistor.
Inductor Selection for
Step-Down DC-DC Regulator
The MAX8903_'s control scheme requires an external
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.
inductor (L
) from 1.0µH to 10µH for proper opera-
OUT
tion. This section describes the control scheme and the
considerations for inductor selection. Table 5 shows
recommended 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.maxim-ic.com/tools/other/soft-
ware/MAX8903-inductor-design.xls.
The MAX8903 step-down DC-DC regulator implements a
control scheme that typically results in a constant switch-
ing frequency (f ). When the input voltage decreases to
SW
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-
a value near the output voltage, high duty cycle operation
occurs and the device can operate at less than f
due
SW
to minimum off-time (t
) constraints. In high duty
OFFMIN
tery is present, the absence of the thermistor allows R to
TB
cycle operation, the regulator operates with t
and
OFFMIN
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
a peak current regulation. Similarly, when the input volt-
age is too high to allow f operation due to minimum on-
SW
time constraints (t
), the regulator becomes a fixed
ONMIN
minimum on-time valley current regulator.
22 ______________________________________________________________________________________
2A 1-Cell Li+ DC-DC Chargers for USB
and Adapter Power
MX8903A–EGHJ/Y
Versions of the MAX8903 with f
= 4MHz offer the
SW
V
− V
SYS(MIN)
× t
(
)
DC(MAX)
ON
smallest L
while delivering good efficiency with low
OUT
(4)
L
=
OUT _MIN_ t
ON
input voltages (5V or 9V). For applications that use high
K × I
SDLIM
input voltages (12V), the MAX8903G with f
is the best choice because of its higher efficiency.
= 1MHz
SW
where V
is maximum input voltage, V
the minimum charger output voltage, and t
time at high input voltage, as given by the following
equation:
is
DC(MAX)
SYS(MIN)
is the on-
ON
For a given maximum output voltage, the minimum
inductor ripple current condition occurs at the lowest
input voltage that allows the regulator to maintain f
SW
operation. If the minimum input voltage dictates an off-
time less than t , then the minimum inductor rip-
⎛
⎞
V
1
f
SW
SYS(MIN)
OFFMIN
(5)
t
= t
if
×
≤ t
,
⎜
⎟
ON
ONMIN
ONMIN
V
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
⎝
⎠
DC(MAX)
otherwise,
V
1
SYS(MIN)
t
=
×
ON
V
f
SW
DC(MAX)
(I
) should be greater than 150mA in the
L_RIPPLE_MIN
minimum inductor ripple current condition. The maxi-
mum allowed output inductance L is therefore
The saturation current DC rating of the inductor (I
)
SAT
OUT_MAX
must be greater than the DC step-down output current
obtained using the equations (1) and (2) below.
limit (I ) plus one-half the maximum ripple current,
SDLIM
as given by equation (6).
⎛
⎞
⎟
V
1
SYS(MAX)
(1)
t
= t
if 1−
×
≤ t
,
IL
⎜
OFF
OFFMIN
OFFMIN
RIPPLE_MAX
2
V
f
SW
I
> I
+
⎝
⎠
DC(MIN)
SAT
SDLIM
(6)
otherwise,
where IL
is the greater of the ripple currents
RIPPLE_MAX
obtained from (7) and (8).
⎛
⎞
V
1
f
SW
SYS(MAX)
t
= 1−
⎜
×
⎟
OFF
V
⎝
⎠
V
× t
OFF
DC(MIN)
SYS(MAX)
(7)
(8)
IL
=
RIPPLE _MIN_ T
OFF
L
OUT
where t
is the off-time, V
is maximum charger
OFF
SYS(MAX)
output voltage, and V
age.
is minimum DC input volt-
DC(MIN)
V
− V
× t
ON
(
)
DC(MAX)
SYS(MIN)
IL
=
RIPPLE _MIN_ T
ON
L
V
× t
OUT
SYS(MAX)
OFF
L
=
OUT _MAX
(2)
I
L _RIPPLE _MIN
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.
where L
is the maximum allowed inductance.
OUT_MAX
To obtain a small-sized inductor with acceptable core
loss, while providing stable, jitter-free operation at the
advertised f , the actual output inductance (L
), is
OUT
SW
obtained by choosing an appropriate ripple factor K, and
picking an available inductor in the range inductance
yielded by equations (2), (3), and (4). L
should also
OUT
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 ≥ I
designs.
≥ 1A)
S
DLIM
V
× t
SYS(MAX)
OFF
L
=
OUT _MIN_ T
OFF
(3)
K × I
SDLIM
where t
is the minimum off-time obtained from (1).
OFF
______________________________________________________________________________________ 23
2A 1-Cell Li+ DC-DC Chargers for USB
and Adapter Power
Table 5. Recommended Inductor Examples
DC STEP-DOWN
OUTPUT
CURRENT LIMIT
DC INPUT
VOLTAGE
RANGE
PART NUMBER,
SWITCHING
FREQUENCY*
RECOMMENDED INDUCTOR
(I
)
SDMAX
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%
5V 10%
5V 10%
5V 10%
9V 10%
9V 10%
2A
MAX8903H/J/Y, 4MHz
MAX8903H/J/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
1A
2A
1A
2A
1A
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
MAX8903A/B/C/D/E,
4MHz
MX8903A–EGHJ/Y
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
MAX8903A/B/C/D/E,
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
MAX8903H/J/Y, 4MHz
MAX8903H/J/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
24 ______________________________________________________________________________________
2A 1-Cell Li+ DC-DC Chargers for USB
and Adapter Power
MX8903A–EGHJ/Y
Table 5. Recommended Inductor Examples (continued)
DC STEP-DOWN
OUTPUT
CURRENT LIMIT
DC INPUT
VOLTAGE
RANGE
PART NUMBER,
SWITCHING
FREQUENCY*
RECOMMENDED INDUCTOR
(I
)
SDMAX
2.2µH inductor, DFE3225±2C-2R2N, TOKO
3.2mm x 2.5mm x ±.2mm, 9±mΩ (max), 2.4A
or 2.2µH Inductor, IFSC±5±5AHER2R2M1±, Vishay
3.8mm x 3.8mm x ±.8mm, 45mΩ (max), 3A
MAX8913A/B/C/D/E,
4MHz
9V ±±10
9V ±±10
9V ±±10
9V ±±10
±2V ±±10
±2V ±±10
2A
2.2µH Inductor, IFSC±118ABER2R2M1±, Vishay
2.5mm x 2mm x ±.2mm, 91mΩ (max), 2.±5A
or 2.2µH Inductor, LQH3NPN2R2NJ1, Murata
3mm x 3mm x ±.±mm, 83mΩ (max), ±.±5A
MAX8913A/B/C/D/E,
4MHz
±A
2A
±A
2A
±A
4.3uH Inductor, DEM45±8C (±235AS-H-4R3M), TOKO
4.7mm x 4.5mm x ±.8mm, 84mΩ (max), 2.1A
or 4.7µH Inductor, IFSC±5±5AHER4R7M1±, Vishay
3.8mm x 3.8mm x ±.8mm, 91mΩ (max), 2.1A
MAX8913G, ±MHz
MAX8913G, ±MHz
MAX8913G, ±MHz
MAX8913G, ±MHz
4.7µH inductor, DEM28±8C (±227AS-H-4R7M), TOKO
3.2mm x 2.8mm x ±.8mm, 92mΩ (max), ±.±A
or 4.7µH inductor, IFSC±118ABER4R7M1±, Vishay
2.5mm x 2mm x ±.2mm, 2±2mΩ (max), ±.2A
4.3µH inductor, DEM45±8C (±235AS-H-4R3M), TOKO
4.7mm x 4.5mm x ±.8mm, 84mΩ (max), 2.1A
or 4.7µH inductor, IFSC±5±5AHER4R7M1±, Vishay
3.8mm x 3.8mm x ±.8mm, 91mΩ (max), 2.1A
6.8µH, IFSC±5±5AHER6R8M1±, Vishay
3.8mm x 3.8mm x ±.8mm, ±±5mΩ (max), ±.5A
or 6.8µH, LQH44PN6R8MP1, Murata
4mm x 4mm x ±.65mm, ±44mΩ (max), ±.34A
*See the Selector Guide for more information about part numbers.
______________________________________________________________________________________ 25
2A 1-Cell Li+ DC-DC Chargers for USB
and Adapter Power
MAX8903A–MAX8903E/MAX8903G/MAX8903Y are the
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
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 MAX8903Y
Minimum SYS
Regulation
Voltage
3.0V
3.0V
3.4V
3.4V
3.0V
3.0V
3.4V
3.4V
3.0V
(V
SYSMIN
)
SYS Regulation
Voltage
4.4V
4.325V
2.2µH
4.4V
4.4V
4.325V
2.2µH
4.325V
2.2µH
4.4V
1µH
4.5V
1µH
4.4V
1µH
(V
)
SYSREG
Minimum
Allowable
Inductor
2.2µH
2.2µH
2.2µH
MX8903A–EGHJ/Y
Switching
Frequency
4MHz
4MHz
4MHz
4MHz
4MHz
1MHz
4MHz
4MHz
4MHz
SYS Load
40mV/A
25mV/A
40mV/A
40mV/A
25mV/A
25mV/A
40mV/A
25mV/A
25mV/A
Minimum SYS
Output
10µF
22µF
10µF
10µF
22µF
22µF
10µF
10µF
22µF
Capacitor
BAT Regulation
Voltage
4.2V
4.2V
4.2V
4.1V
4.1V
4.2V
4.2V
4.35V
4.15V
(V
BATREG
)
(Note 5)
BAT Prequal
Threshold
3V
2.5V
3V
3V
2.5V
2.5V
3V
3V
3V
(V
BATPQ
)
(Note 5)
Top-Off Timer
(Note 6)
15s (fixed)
1mA
132min
10mA
15s (fixed)
1mA
15s (fixed)
1mA
132min
10mA
132min
10mA
15s (fixed) 15s (fixed) 15s (fixed)
VL Output
1mA
1mA
1mA
Power-Enable
On Battery
Detection
No
—
Yes
—
No
—
No
—
Yes
—
Yes
—
No
No
No
(Note 7)
Comments
(Note 8)
—
—
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.
26 ______________________________________________________________________________________
2A 1-Cell Li+ DC-DC Chargers for USB
and Adapter Power
MX8903A–EGHJ/Y
Pin Configuration
Chip Information
PROCESS: BiCMOS
TOP VIEW
21 20 19 18 17 16 15
14
13
22
CEN
ISET
CHG
SYS 23
12 GND
24
25
26
27
28
SYS
CS
CS
LX
MAX8903_
IDC
CT
11
10
9
VL
EP
6
8
DOK
LX
+
1
2
3
4
5
7
TQFN
4mm x 4mm
______________________________________________________________________________________ 27
2A 1-Cell Li+ DC-DC Chargers for USB
and Adapter Power
Package Information
For the latest package outline information and land patterns (footprints), go to www.maxim-ic.com/packages. Note that a "+", "#", or
"-" in the package code indicates RoHS status only. Package drawings may show a different suffix character, but the drawing per-
tains to the package regardless of RoHS status.
LAND
PATTERN NO.
PACKAGE TYPE
PACKAGE CODE
OUTLINE NO.
21-0139
90-0035
28 TQFN-EP
T2844-1
MX8903A–EGHJ/Y
28 ______________________________________________________________________________________
2A 1-Cell Li+ DC-DC Chargers for USB
and Adapter Power
MX8903A–EGHJ/Y
Package Information (continued)
For the latest package outline information and land patterns (footprints), go to www.maxim-ic.com/packages. Note that a "+", "#", or
"-" in the package code indicates RoHS status only. Package drawings may show a different suffix character, but the drawing per-
tains to the package regardless of RoHS status.
______________________________________________________________________________________ 29
2A 1-Cell Li+ DC-DC Chargers for USB
and Adapter Power
Revision History
REVISION
NUMBER
REVISION
DATE
PAGES
CHANGED
DESCRIPTION
0
1
2
3
4
12/08
8/09
Initial release
—
1–20
Added MAX8903C/MAX8903D to data sheet
Made various corrections
11/09
10/10
5/11
1–7, 9, 11–21
1–29
Added MAX8903B, MAX8903E, MAX8903G, and MAX8903Y
Added MAX8903H and MAX8903J and updated components
1–29
MX8903A–EGHJ/Y
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.
30 ____________________Maxim Integrated Products, 120 San Gabriel Drive, Sunnyvale, CA 94086 408-737-7600
© 2011 Maxim Integrated Products
Maxim is a registered trademark of Maxim Integrated Products, Inc.
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