SMB138/A/C

© SUMMIT Microelectronics, Inc. 2004 • 757 N. Mary Avenue • Sunnyvale CA 94085 • Phone 408 523-1000 • FAX 408 523-1266
http://www.summitmicro.com/
3.0 4/5/2008
1
Programmable Switch-mode, USB/AC Input Li+ Battery Charger with TurboCharge™ Mode
and USB “On- the-Go” Power
CONFIDENTIAL
DO NOT COPY
INTRODUCTION

• USB or AC input with programmable input current limiting
• Up to 1.25A continuous charging current from AC adapter
• Up to 750mA charging current from 500mA USB port using
automatic TurboCharge™ mode
• +4.35 to +6.2V input voltage range (+16V tolerant)
• Two product options:
o SMB138A: charger off until I
2
C command initiation,
enable/disable control via I
2
C
o SMB138C: charger powers up in charging mode,
enable/disable control via I
2
C
• USB “On-the-Go” Power support for USB OTG enabled
devices (+5V reverse output @ 200mA)
• Reverse current blocking (<5uA)
• High-efficiency 3MHz voltage-mode step-down regulator
• Integrated frequency compensation
• Internal power MOSFETs and precision current sensing
• High-accuracy float voltage regulation: 1%
• Thermal regulation (current foldback)
• Trickle charging
• Pre-charge and complete-charge (36/240min) safety timers
• Digital programming of all major parameters via I
2
C interface
o Fast charge voltage threshold, float voltage
o Pre-charge, fast charge, termination current
• Status register monitors and flags charger operation
o Charge in-progress/termination
o Charge timer fault
o OC/UV/OV detection/shutdown
• uCSP-19 lead-free package (0.4mm ball pitch)

Applications
• 2.5/3/3G+ GSM/CDMA/WCDMA Phones
• Smartphones/PDAs
• Portable Media Players
• Portable GPS Terminals


The SMB138 is a programmable single-cell lithium-ion/lithium-polymer
battery charger designed for a variety of portable applications. The
device provides a simple and efficient way to charge high-capacity Li-
Ion batteries via a USB or AC adapter input. Unlike conventional
devices, the SMB138’s high-efficiency, switch-mode operation
eliminates the thermal problems of conventional linear solutions. Also
the buck converter architecture effectively multiplies the input current
to increase charge rate for the Li+ cell and uses current limited
supplies like USB more efficiently. The SMB138 also supports USB
On-the-Go devices by providing the required USB-OTG +5V power
supply using the Li-Ion battery as a source.
The SMB138 can switch between USB mode and AC Adapter mode
and works seamlessly in conjunction with a USB controller. Charge
control includes qualification, trickle-charge, pre-charge, constant
current/constant voltage, float voltage and termination/safety settings
that are fully programmable via a serial I
2
C/SMBus and stored in non-
volatile memory making the device truly a flexible solution. Fast
charge current level can be set via I
2
C (limited in USB mode to ensure
100mA or 500mA input). Built-in is reverse-current blocking to prevent
inadvertent cell discharge. High frequency operation and integrated
power FETs contribute to reduced external component count and size.
The SMB138A device requires a user I
2
C command for charging
initiation, whereas the SMB138C device powers up in the charging
mode. The SMB138C offers the option to automatically charge the
battery only when the battery voltage is below a selectable “dead-
battery” threshold.
The SMB138 also offers several features that protect the battery pack
as well as the charger and input circuitry: over-current, under/over-
voltage and thermal protection. Ultra-accurate, 1% battery float
voltage control improves battery capacity utilization. The STAT output
is an interrupt to flag various status/flag events (programmable
selection) and the status register can be read via the serial port. The
SMB138 is available in an ultra-compact lead-free uCSP-19 package
and is rated over the –30C to +85C temperature range.

SYSTEM APPLICATION
FEATURES & APPLICATIONS
Handheld System
USB
USB
USB
500mA
4.35V-5.5V
AC/DC
300-1800mA
4.5V-6.2V
I2C
System
SMB138
Li-Ion
Ch
a
r
g
i
n
g
USB
Total Output
550-1250mA
To system
GN
D
V
B
US
D-
D+
NC
USB-OTG Output
500mA


Figure 1 – Using the SMB138 to charge a single cell Li+ battery from USB or AC Adapter power sources