SMB135

Advanced Information

http://www.summitmicro.com/

2106 1.3 2/21/2006

1

Programmable, USB/AC, Switch-Mode Battery Charger

INTRODUCTION

• Programmable USB/AC Li-Ion battery charger

• High-efficiency current-mode PWM controller

o

750kHz to 1.25MHz switching frequency

o

0% to 100% duty-cycle

• 4.35 to 6.0V input voltage range

• High-accuracy output voltage regulation: 1%

• Low reverse leakage current

interface (with several addresses) and non-volatile

memory

o

Battery voltage set point

o

Pre-charge, fast charge, termination current

o

Fast charge voltage threshold

o

Temperature limits

o

Automatic restart threshold

• Status indicator

•

Stability with ceramic capacitors

• Wide range of protection features

o

Thermal monitor

o

Input/output over-voltage lockout

Applications

• GSM Handsets

• UMTS Handsets

• Portable Media Players

• Digital camcorders/still cameras

• Handheld GPS/PDA’s

The SMB135 is a programmable single-cell lithium-ion/lithium-polymer

battery charger for a variety of portable applications.

The device

provides a simple and efficient way to charge high-capacity Li-Ion

batteries via a USB port or an AC adapter.

Unlike conventional

devices, the SMB135’s high-efficiency operation eliminates large

internal temperature rise and localized hot spot in handheld equipment.

Charge control includes qualification, trickle-charge, pre-charge,

constant current/constant voltage, and termination/safety settings that

are fully programmable via a serial I2C/SMBus making the device truly

a flexible solution. Fast charge current level (one or five unit loads)

can be set via I2C or an input pin (USB500/100). An Enable (EN) pin

is also provided for suspending USB charging and allowing the device

to work in parallel with AC charger, which may already be integrated

into a PMIC device. In this case, the SMB135 does not allow current

to flow back to the USB port.

The SMB135 offers a wide variety of features that protect the battery

pack as well as the charger and input circuitry: over-current,

under/over-voltage and thermal protection. Ultra-precise, 1% accurate,

Kelvin-sensed ADOC™ technology allows accurate control of battery

float voltage and improves battery capacity utilization. Status can be

monitored via the serial port for charge state and fault conditions. In

addition, one LED driver output can be used to signal charge status.

As a protection mechanism, when the junction temperature

approaches approximately 145

°C, the PWM switcher will start to cut

back on the duty cycle, to reduce current.

The SMB135 is available in a space-saving 1.3mm x 2.1mm uCSP

TM

package with lead-free balls and is rated over the -30

°C to +85°C

temperature range.

Figure 1 – Applications block diagram featuring the SMB135 programmable switch-mode battery charger.

SIMPLIFIED APPLICATIONS DRAWING

FEATURES & APPLICATIONS

USB

Controller

D+

D-

VDC

GND

ADC+ ADC-

IN

GND

STAT

R

LIM

LED

6.8uH

SMB135

SENSEH

SENSEL

50-100m

Ω

10uF

Li-Ion

THERM

EN

OUT

USB500/100

SDA

BATT

COMP

C

comp

R

comp

VDDCAP

1uF

4.7uF

SCL

500-700mA

4.35V-6.0V