Datasheet

7
LTC1514-3.3/LTC1514-5
APPLICATIONS INFORMATION
WUU
U
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.
TYPICAL APPLICATIONS N
U
3.3V Step-Up/Step-Down Supply with Power Good Output
1
2
3
4
8
7
6
5
SHDN
LBO
LBI
GND
V
OUT

V
IN

C1
+

C1
–
LTC1514-3.3
V
OUT
= 3.3V ±4%
I
OUT
= 15mA, V
IN
> 2V
I
OUT
= 50mA, V
IN
> 3V
V
IN
2V TO 8V
0.22µF
499k
1%
10µF
10µF
806k
1%
100k
1514 TA05
ON OFF
POWER GOOD
3V V
TRIP
+
+
Low Power Battery Backup Supply with Autoswitchover and No Reverse Current
1
2
3
4
8
7
6
5
SHDN
LBO
LBI
GND
V
OUT

V
IN

C1
+

C1
–
LTC1514-5
5V BACKUP SUPPLY
I
OUT
= 15mA
0.1µF
499k
MAIN
5V SUPPLY
10µF
10µF
3-CELL 
NiCd BATTERY
TRICKLE CHARGE
AND LTC1514 I
DD
499k
1%
1.5M
1%
499k
1514 TA03
4.6V V
TRIP
TP0610T
+
+
BACKED-UP
CIRCUITRY
BAT54
1
2
3
4
8
7
6
5
SHDN
LBO
LBI
GND
V
OUT

V
IN

C1
+

C1
–
LTC1514-5
MBR0520L
0.22µF
CHARGE PATH
499k
1%
3-CELL
NiCd
BATTERY
499k
1M
1%
6V
WALL
ADAPTER
INPUT
1514 TA06
EXTERNAL 
POWER GOOD
5V
ON OFF
10µF
+
22µF
+
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.