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