7

LTC1514-3.3/LTC1514-5

resistor divider (see Figure 2). Since the low-battery

comparator is kept alive in shutdown, it may be used to

protect batteries against deep discharge by shutting

down the power supply when the battery voltage gets too

low. The open-drain comparator output allows for flex-

ible interfacing between the LBO output and external

logic. LBO pull-up resistors in the 50k to 1M range are

recommended.

3.3V Step-Up/Step-Down Supply with Power Good Output

1

2

3

4

8

7

6

5

SHDN

LBO

LBI

GND

LTC1514-3.3

2V TO 8V

0.22

µF

499k

1%

10

µF

10

µF

806k

1%

100k

1514 TA05

ON OFF

POWER GOOD

+

+

Low Power Battery Backup Supply with Autoswitchover and No Reverse Current

1

2

3

4

8

7

6

5

SHDN

LBO

LBI

GND

LTC1514-5

5V BACKUP SUPPLY

0.1

µF

499k

MAIN

5V SUPPLY

10

µF

10

µF

3-CELL

NiCd BATTERY

TRICKLE CHARGE

499k

1%

1.5M

1%

499k

1514 TA03

TP0610T

+

+

BACKED-UP

CIRCUITRY

BAT54

1

2

3

4

8

7

6

5

SHDN

LBO

LBI

GND

LTC1514-5

MBR0520L

0.22

µF CHARGE PATH

499k

1%

3-CELL

NiCd

BATTERY

499k

1M

1%

6V

WALL

ADAPTER

INPUT

1514 TA06

EXTERNAL

POWER GOOD

5V

ON OFF

10

µF

+

22

µF

+

Battery/External Power Autoswitch Regulator

Information furnished by Linear Technology Corporation is believed to be accurate and reliable.

However, no responsibility is assumed for its use. Linear Technology Corporation makes no represen-

tation that the interconnection of its circuits as described herein will not infringe on existing patent rights.