155833 데이터 시트보기 (PDF) - Linear Technology

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155833

Backup Battery Controller with Programmable Output

Linear Technology 

LTC1558-3.3/LTC1558-5

PIN FUNCTIONS

LOBAT (Pin 9): Low-Battery Detector Output. This is an

open-drain output that pulls low when the backup cell

drops below 1V. It gives early warning to the system

controller that the backup cell is getting weak. This pin is

disabled when the LTC1558 is in trickle charge mode.

RESET (Pin 12): System Reset, Active High. This is a TTL-

compatible output driver. It can be used to connect to

systems that require active high logic. The RESET output

will go high whenever RESET is pulled low. If RESET is

externally pulled low, RESET will go high.

BLOCK DIAGRAM

SW

CTL

FB

+

–

VREF

VCC

VREF

–

+

CHARGER

LEVEL SENSE

AND DEBOUNCE

GAS GAUGE

P1

VCC/VBAK

N1

BOOST/BACKUP

LOGIC

RESET

GENERATOR

+

–

VBAK

BACKUP

RESET

RESET

LOBAT

THERMAL

LIMIT

UVLO

DETECTOR

SHDN

SHUTDOWN

LOGIC

U

W

SWITCHING WAVEFORMS

Simplified LTC1558 Connections in a

Battery Backup System

1.2V

NiCd

SW

TO

SYSTEM

CONTROL

BACKUP RESET

LTC1558

VBAK

FB

VCC

QEXT

VBAT

MAIN

BATTERY

+

VIN

R1

CIN

MAIN SYSTEM

REGULATOR

MULTIPLE

POWER

OUTPUTS

R2

FOR MORE DETAILED APPLICATION SCHEMATICS

PLEASE REFER TO THE TYPICAL APPLICATIONS SECTION

1558 SW01

6

BANDGAP

VREF = 1.272V

1558 BD

Cold Power Boot-Up (Main Battery Replaced/Turned On)

RATED BATTERY TERMINAL VOLTAGE

1

VBAT

VBAK

VCC

RESET

BACKUP

2

3

4

RATED VCC VOLTAGE

– 6%

200ms

1558 SW02

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