Rainbow Electronics MAX8903A User Manual

General Description

The MAX8903A is an integrated 1-cell Li+ charger and
Smart Power Selector™ with dual (AC adapter and
USB) power inputs. The switch mode charger uses a
high switching frequency to eliminate heat and allow
tiny external components. It can operate with either
separate inputs for USB and AC adapter power, or from
a single input that accepts both. All power switches for
charging and switching the load between battery and
external power are included on-chip. No external
MOSFETs, blocking diodes, or current-sense resistors
are required.

The MAX8903A features optimized smart power control
to make the best use of limited USB or adapter power.
Battery charge current and SYS output current limit are
independently set. Power not used by the system
charges the battery. Charge current and SYS output
current limit can be set up to 2A while USB input 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 protection, while the USB input has a range
of 4.1V to 6.3V with up to 8V protection.

The MAX8903A internally blocks current from the bat­tery and system back to the DC and USB inputs when
no input supply is present. Other features include pre­qual 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 overheat­ing. The MAX8903A is available in a 4mm x 4mm, 28-pin
thin QFN package.

Applications

PDAs, Palmtops, and Wireless Handhelds

Personal Navigation Devices

Smart Cell Phones

Portable Multimedia Players

Mobile Internet Devices

Ultra Mobile PCs

Features

♦ Efficient DC-DC Converter Eliminates Heat

♦ 4MHz Switching for Tiny External Components

♦ Instant On—Works with No Battery or Low

Battery

♦ Dual Current-Limiting Input Circuits—AC Adapter

or USB

Automatic Adapter/USB/Battery Switchover to

Support Load Transients
50mΩ System-to-Battery Switch
Supports USB Spec

♦ Thermistor Monitor

♦ Integrated Current-Sense Resistor

♦ No External MOSFETS or Diodes

♦ 4.1V to 16V Input Operating Voltage Range

MAX8903A

2A 1-Cell Li+ DC-DC Charger for USB*

and Adapter Power

________________________________________________________________

Maxim Integrated Products

1

19-4410; Rev 0; 12/08

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.

EVALUATION KIT

AVAILABLE

Pin Configuration appears at end of data sheet.

Typical Operating Circuit

*Protected by US Patent #6,507,172.

Smart Power Selector is a trademark of Maxim Integrated
Products, Inc.

Ordering Information

+

Denotes a lead(Pb)-free/RoHS-compliant package.

**

EP = Exposed pad.

PART TEMP RANGE PIN-PACKAGE

MAX8903AETI+ -40°C to +85°C

28 Thin QFN-EP**

AC

ADAPTER

OR USB

USB

DC

USB

LX

PWM

STEP-DOWN

CS

SYS

LOAD

CHARGE
CURRENT

CURRENT

CHARGE AND
SYS LOAD
SWITCH

BAT

SYSTEM

LOAD

BATTERY

MAX8903A

GND

MAX8903A

2A 1-Cell Li+ DC-DC Charger for USB*
and Adapter Power

2 _______________________________________________________________________________________

ELECTRICAL CHARACTERISTICS

(VDC= V

USB

= 5V, V

BAT

= 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.

ABSOLUTE MAXIMUM RATINGS

DC, LX, DCM to GND .............................................-0.3V to +20V

DC to SYS .................................................................-6V to +20V

BST to GND ...........................................................-0.3V to +26V

BST TO LX ................................................................-0.3V to +6V

USB to GND .............................................................-0.3V to +9V

USB to SYS..................................................................-6V to +9V

VL to GND ................................................................-0.3V to +6V

THM, IDC, ISET, CT to GND .........................-0.3V to (VL + 0.3V)

DOK, FLT, CEN, UOK, CHG, USUS,

BAT, SYS, IUSB, CS to GND ................................-0.3V to +6V

SYS to BAT ...............................................................-0.3V to +6V

PG, EP (exposed pad) to GND .............................-0.3V to +0.3V

DC Continuous Current (total in two pins)......................2.4A

RMS

USB Continuous Current.......................................................1.6A

LX Continuous Current (total in two pins).......................2.4A

RMS

CS Continuous Current (total in two pins) ......................2.4A

RMS

SYS Continuous Current (total in two pins) .......................3A

RMS

BAT Continuous Current (total in two pins) .......................3A

RMS

Continuous Power Dissipation (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

DC INPUT

DC Operating Range 4.15 16 V

DC Undervoltage Threshold

DC Overvoltage Threshold

DC Supply Current

DC High-Side Resistance 0.15 Ω

DC Low-Side Resistance 0.15 Ω

DC-to-BAT Dropout Resistance 0.31 Ω

DC-to-BAT Dropout Voltage

Switching Frequency

DC Step-Down Output Current­Limit Step Range

DC Step-Down Output Current
Limit

DC Soft-Start Time

PARAMETER CONDITIONS MIN TYP MAX UNITS

When V
rising, 500mV typical hysteresis

When V
hysteresis

Charger enabled, no switching, V

Charger enabled, f = 3MHz, VDC = 5V 15

C har g er enab l ed , V

C har g er enab l ed , V

V

DCM

When SYS regulation and charging stops, V
200mV hysteresis

VDC = 8V, V

V

DC

V

DC

No valid USB input 1 ms

Valid USB input before soft-start 20 µs

goes low, V

DOK

goes high, VDC rising, 500mV typical

DOK

= 0V, V

USUS

= 4V 4

BAT

= 5V, V

= 6V, V

= 3V 3

BAT

= 4V

SYS

DC

= 0V , 100m A U S B m od e ( N ote 2) 1 2

C E N

= 5V , 100m A U S B m od e ( N ote 2) 1 2

C E N

= 5V 0.10 0.25

No valid USB input 3.9 4.0 4.1

Valid USB input 4.0 4.3 4.4

16.5 17 17.5 V

= 5V 2.3 4

SYS

falling,

DC

R

= 3kΩ 1900 2000 2100

IDC

R

= 6kΩ 950 1000 1050

IDC

= 12kΩ 450 500 550

R

IDC

01530mV

0.5 2 A

V

mA

MHz

mA

MAX8903A

2A 1-Cell Li+ DC-DC Charger for USB*

and Adapter Power

_______________________________________________________________________________________ 3

ELECTRICAL CHARACTERISTICS (continued)

(VDC= V

USB

= 5V, V

BAT

= 4V, circuit of Figure 2, TA= -40°C to +85°C, unless otherwise noted. Typical values are at TA= +25°C.)

(Note 1)

DC Output Current
500mA USB Mode
(Note 3)

DC Output Current
100mA USB Mode
(Note 2)

SYS to DC Reverse Current
Blocking

USB INPUT

USB Operating Range 4.1 6.3 V

USB Standoff Voltage 8V

USB Undervoltage Threshold When V

USB Overvoltage Threshold When V

USB Current Limit

Minimum USB to BAT Headroom 0 15 30 mV

USB to SYS Dropout Resistance 0.2 0.35 Ω

USB Soft-Start Time

SYS OUTPUT

Minimum SYS Regulation Voltage I

Regulation Voltage I

Load Regulation I

CS to SYS Resistance VDC = 6V, V

SYS to CS Leakage V

BAT to SYS Resistance VDC = V

BAT to SYS Reverse Regulation
Voltage

SYS Undervoltage Threshold SYS falling, 200mV hysteresis (Note 4) 1.8 1.9 2.0 V

BATTERY CHARGER

BAT Regulation Voltage I

Charger Restart Threshold Change in V

BAT Prequal Threshold V

Prequal Charge Current Percentage of fast-charge current set at ISET 10 %

PARAMETER CONDITIONS MIN TYP MAX UNITS

V

= 0V, V

DCM

V

= 0V, V

DCM

V

= 5.5V, VDC = 0V 0.01 µA

SYS

UOK

UOK

V

= 0V (100mA setting) 90 95 100

IUSB

V

= 5V (500mA setting) 450 475 500

IUSB

I

= I

SYS

BAT

I

= I

SYS

BAT

= 5V (USB suspend mode) 0.115 0.25

V

USUS

V

rising 1 ms

USB

falling below DC UVLO to initiate USB soft-start 20 µs

V

DC

= 1A, V

SYS

= 0A 4.3 4.4 4.5 V

SYS

= 0 to 2A 40 mV/A

SYS

= 5.5V, VDC = VCS = 0V 0.01 µA

SYS

USB

V

= 5V, VDC = 0V, V

USB

= 0mA

BAT

rising, 180mV hysteresis 2.9 3 3.1 V

BAT

= 5V 450 475 500 mA

IUSB

= 0V 90 95 100 mA

IUSB

goes low, V

goes high, V

= 0mA, V

= 0mA, V

< V

BAT

SYS_MIN

= 5V, V

DCM

= 0V, V

BAT

rising, 500mV hysteresis 3.95 4.0 4.05 V

USB

rising, 500mV hysteresis 6.8 6.9 7.0 V

USB

= 0V 1.3 3

CEN

= 5V 0.8 2USB Supply Current

CEN

3.0 V

= 4V, ICS = 1A 0.07 Ω

SYS

= 4.2V, I

IUSB

= 1A 0.05 0.1 Ω

SYS

= 0V, I

= 200mA 50 75 100 mV

SYS

TA = +25°C 4.179 4.2 4.221

= -40°C to +85°C 4.158 4.2 4.242

T

A

from DONE to fast-charge -150 -100 -60 mV

BAT

mA

mA

V

MAX8903A

2A 1-Cell Li+ DC-DC Charger for USB*
and Adapter Power

4 _______________________________________________________________________________________

ELECTRICAL CHARACTERISTICS (continued)

(VDC= V

USB

= 5V, V

BAT

= 4V, circuit of Figure 2, TA= -40°C to +85°C, unless otherwise noted. Typical values are at TA= +25°C.)

(Note 1)

DONE Threshold Percentage of fast-charge, I

R

ISET

ISET Output Voltage 1.5 V

ISET Current Monitor Gain 1.25 mA/A

BAT Leakage Current

Charger Soft-Start Time 1.0 ms

Charger Thermal Limit
Temperature

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

Timer Accuracy -15 +15 %

Timer Extend Current Threshold

Timer Suspend Current Threshold

Charge Done Delay Time

THERMISTOR MONITOR

THM Threshold, Hot When charging is suspended, 1% hysteresis

THM Threshold, Cold When charging is suspended, 1% hysteresis

THM Threshold, Disabled THM function is disabled below this voltage

THM Input Leakage

THERMAL SHUTDOWN, VL, AND LOGIC I/O: CHG, FLT, DOK, UOK, DCM, CEN, USUS, IUSB

Logic-Input Thresholds
(DCM, CEN, USUS, IUSB)

Logic-Input Leakage Current
(DCM, CEN, USUS, IUSB)

PARAMETER CONDITIONS MIN TYP MAX UNITS

Resistor Range 0.6 2.4 kΩ

R

= 600Ω 1800 2000 2200

ISET

R

= 1.2kΩ 900 1000 1100Fast-Charge Current

ISET

= 2.4kΩ 450 500 550

R

ISET

decreasing 10 %

BAT

No DC or USB input 0.05 4

With valid input power, V

Percentage of fast-charge current below which the timer
clock operates at half-speed

Percentage of fast-charge current below which timer
clock pauses

From done threshold detection until charger turns off and
CHG goes high

THM = GND or VL; TA = +25°C -0.1 +0.001 +0.2

THM = GND or VL; T

High level 1.3

Low level 0.4

Hysteresis 50 mV

= 0 to 5.5V

V

INPUT

= 5V 1 6

CEN

40 50 60 %

16 20 24 %

0.27 x
V

0.73 x
V

0.0254
x V

= +85°C 0.01

A

TA = +25°C 0.001 1

T

= +85°C 0.01

A

0.28 x

VL

0.74 x

VL

0.03 x

VL

100 °C

15 s

0.29 x

V

V

V

VL

VL

VL

V

0.75 x
V

0.036 x
V

VL

VL

VL

mA

µA

V

V

V

µA

V

µA

MAX8903A

2A 1-Cell Li+ DC-DC Charger for USB*

and Adapter Power

_______________________________________________________________________________________ 5

ELECTRICAL CHARACTERISTICS (continued)

(VDC= V

USB

= 5V, V

BAT

= 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 T

A

= +25°C. Limits over the operating temperature range are guaranteed by design.

Note 2: For the 100mA USB mode using the DC input, the step-down regulator is turned off and a low-dropout linear regulator is

connected from DC to SYS.

Note 3: For the 500mA USB mode, the actual current drawn from USB is less than the output current due to the input/output current

ratio of the DC-DC converter.

Note 4: For short-circuit protection, SYS sources 25mA below V

SYS

= 400mV, and 50mA for V

SYS

between 400mV and 2V.

Typical Operating Characteristics

(TA = +25°C, unless otherwise noted.)

Logic Output Voltage, Low
(CHG, FLT, DOK, UOK)

Open-Drain Output Leakage
C ur rent, Hi g h (CHG , FLT, DOK, UOK)

VL Output Voltage VDC = V

VL UVLO Threshold VVL falling; 200mV hysteresis 3.2 V

Thermal Shutdown Temperature 160 °C

Thermal Shutdown Hysteresis 15 °C

PARAMETER CONDITIONS MIN TYP MAX UNITS

Sinking 1mA 8 50

Sinking 10mA 80

V

OUT

= 5.5V

= 6V, I

USB

= 0 to 1mA 4.6 5 5.4 V

VL

TA = +25°C 0.001 1

T

= +85°C 0.01

A

mV

µA

BATTERY CHARGER EFFICIENCY

vs. BATTERY VOLTAGE

100

90

80

70

60

50

40

EFFICIENCY (%)

30

20

10

0

VDC = 5V

VDC = 8V

VDC = 12V

I

= 0.15A

BATT

1.0 2.0 2.51.5 3.0 3.5 4.0 4.5 5.0
BATTERY VOLTAGE (V)

I

BATT

I

BATT

= 1.5A

= 1.5A

4.5

4.0

MAX8903A toc01

3.5

3.0

2.5

2.0

1.5

1.0

SWITCHING FREQUENCY (MHz)

0.5

0.0
486 10121416

SWITCHING FREQUENCY

vs. V

DC

V

= 3V

BAT

V

= 4V

BAT

R

ISET

CEN = 0V

DC VOLTAGE (V)

= 1.2kΩ

100

MAX8903A toc02

SYS EFFICIENCY (%)

SYS EFFICIENCY vs. DC VOLTAGE

90

80

70

60

50

40

30

20

10

0

1 10,000

SYS OUTPUT CURRENT (mA)

VDC = 16V

VDC = 11V

VDC = 6V

VDC = 4.5V

100010010

MAX8903A toc03

MAX8903A

2A 1-Cell Li+ DC-DC Charger for USB*
and Adapter Power

6 _______________________________________________________________________________________

Typical Operating Characteristics (continued)

(TA = +25°C, unless otherwise noted.)

0

0.4

0.2

0.8

0.6

1.4

1.2

1.0

1.6

021 34567

USB QUIESCENT CURRENT

vs. USB VOLTAGE

MAX8903A toc04

USB VOLTAGE (V)

USB QUIESCENT CURRENT (mA)

CHARGER
ENABLED

CHARGER
DISABLED

0

40

20

80

60

120

100

140

0231 4567

USB QUIESCENT CURRENT

vs. USB VOLTAGE

MAX8903A toc05

USB VOLTAGE (V)

USB QUIESCENT CURRENT (μA)

USB SUSPEND

0

1.5

1.0

0.5

2.5

2.0

4.5

4.0

3.5

3.0

5.0

01234567

SYS VOLTAGE vs. USB VOLTAGE

MAX8903A toc12

USB VOLTAGE (V)

SYS VOLTAGE (V)

V

USB

FALLING

V

USB

RISING

R

SYS

= 1MΩ

80

70

60

50

40

30

20

BATTERY LEAKAGE CURRENT (nA)

10

BATTERY LEAKAGE CURRENT

vs. BATTERY VOLTAGE

MAX8903A toc06

USB UNCONNECTED

0

0456321

BATTERY VOLTAGE (V)

BATTERY LEAKAGE CURRENT

vs. AMBIENT TEMPERATURE

90

80

70

60

50

40

30

20

BATTERY LEAKAGE CURRENT (nA)

10

0

-40 35 60-15 10 85

NORMALIZED CHARGE CURRENT

vs. AMBIENT TEMPERATURE

1.015
V

= 5V, V

USB

1.010

1.005

1.000

0.995

NORMALIZED CHARGE CURRENT

0.990

0.985

-40 85

TEMPERATURE (°C)

= 4V

BATT

TEMPERATURE (°C)

CHARGE CURRENT

vs. BATTERY VOLTAGE—DC MODE

SET TO 1.5A

BAT

SET TO 1A

DC

BATTERY VOLTAGE (V)

MAX8903A toc09

500

450

400

MAX8903A toc07

350

300

250

200

150

CHARGE CURRENT (mA)

100

50

0

CHARGE CURRENT

vs. BATTERY VOLTAGE—USB

CHARGER ENABLED

SET TO 1.5A

I

BAT

V

= V

IUSB

USB

V

= 0V

IUSB

042135

BATTERY VOLTAGE (V)

1000

900

800

MAX8903A toc08

700

600

500

400

300

CHARGE CURRENT (mA)

200

100

0

CHARGER ENABLED
I
I

042315

BATTERY REGULATION VOLTAGE

vs. AMBIENT TEMPERATURE

4.205

4.200

MAX8903A toc10

4.195

4.190

4.185

BATTERY REGULATION VOLTAGE (V)

4.180

603510-15

-40 85
TEMPERATURE (°C)

603510-15

MAX8903A toc11