LTC1980

1

1980f

APPLICATIO S

DESCRIPTIO

FEATURES

TYPICAL APPLICATIO

■

Handheld Computers

Combination Battery

Charger and DC/DC Converter

The LTC

ing a battery and converting the battery voltage to a

regulated output or simultaneously charging the battery

while powering a system load from an unregulated AC wall

adapter. Combining these features into a single IC pro-

duces a smaller area and lower cost solution compared to

presently available multi-IC solutions. The LTC1980 shares

the discrete components for both the battery charger and

the DC/DC converter thus minimizing size and cost relative

to dual controller solutions. Both the battery charger and

DC/DC converter use a current mode flyback topology for

high efficiency and excellent transient response. Optional

Burst Mode operation and power-down mode allow power

density, efficiency and output ripple to be tailored to the

application.

The LTC1980 provides a complete Li-Ion battery charger

with charge termination timer, preset Li-Ion battery volt-

ages, overvoltage and undervoltage protection, and user-

programmable constant-current charging. Automatic bat-

tery recharging, shorted-cell detection, and open-drain

C/10 and wall plug detect outputs are also provided. User

programming allows NiMH and NiCd battery chemistries

to be charged as well.

Plus DC/DC Converter

Battery Voltage

and Regulating from Wall Adapter Input

Termination, Overvoltage Protection, Shorted-Cell

Detection and Battery Recharge

and Shutdown for High Efficiency

Start-Up with Current Limited Wall Adapter

, LTC and LT are registered trademarks of Linear Technology Corporation.

Burst Mode is a registered trademark of Linear Technology Corporation.

Patents Pending.

LTC1980

•

•

Li-Ion

BATTERY

POWER FLOW

CHARGING

BATTERY

OPERATION

SYSTEM

POWER

LDO/

SWITCH

3.3V

UNREGULATED

WALL ADAPTER

INPUT (3V TO 10V)

1.8V

1.5V

1980 TA01

SYSTEM LOAD

DC/DC

CONVERTERS

BAT-FET

REG-FET

Li-Ion Charger and DC/DC Converter Using One IC

LOAD CURRENT (mA)

10

90

85

80

75

70

65

60

100

1000

1980 G04

FIGURE 5

3.3V Regulator Efficiency vs Load Current