LTC1514-3.3/LTC1514-5
Step-Up/Step-Down Switched
Capacitor DC/DC Converters
with Low-Battery Comparator
FEATURES
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DESCRIPTION
The LTC
廬
1514-3.3/LTC1514-5 are micropower switched
capacitor DC/DC converters that produce a regulated
output voltage by either stepping up or stepping down
the input voltage. Output voltage is fixed at either 3.3V
(LTC1514-3.3) or 5V (LTC1514-5) by an internal resistor
divider.
A unique architecture allows the parts to accommodate
a wide input voltage range (2V to 10V) while maintaining
鹵4%
regulation. Additional circuitry prevents excessive
inrush current and output voltage ripple when large V
IN
to V
OUT
differentials are present.
An internal uncommitted comparator is kept active in
shutdown. The comparator has an open-drain output for
flexible interfacing.
The parts are short-circuit and overtemperature pro-
tected. Battery life is maximized by very low operating
currents (I
CC
= 60碌A typ, 10碌A in shutdown). Both parts
are available in an SO-8 package.
, LTC and LT are registered trademarks of Linear Technology Corporation.
3.3V or 5V Output Voltages
2V to 10V Input Voltage Range
Up to 50mA Output Current
Only Three External Capacitors Required
Soft Start Limits Inrush Current at Turn-On
Low Operating Current: 60碌A
Low Shutdown Current: 10碌A
Shutdown Disconnects Load from V
IN
Short-Circuit and Overtemperature Protected
650kHz Switching Frequency
Low-Battery Comparator Active in Shutdown
Available in SO-8 Package
APPLICATIONS
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Battery-Operated Equipment
Smart Card Readers
Local Power Supplies
Handheld Instruments
Battery Backup Supplies
TYPICAL APPLICATION
5V Step-Up/Step-Down Power Supply with Low-Battery Detect
5.2
100k
1.33M
1%
ON OFF
LOW BAT
1
2
3
499k
1%
4
LTC1514-5
SHDN
LBO
LBI
GND
V
OUT
V
IN
C1
+
C1
鈥?/div>
OUTPUT VOLTAGE (V)
8
7
6
5
0.22碌F
V
OUT
= 5V
I
OUT
= 50mA
5.1
I
OUT
= 10mA
+
10碌F
+
10碌F
1514 TA01
V
IN
4-CELL
NiCd
5.0
4.9
4.8
U
2
U
U
LTC1514-5 Output Voltage
vs Input Voltage
3
4
5
8
6
7
INPUT VOLTAGE (V)
9
10
LT1514 鈥?TA02
1
1
2
3
4
5
6
7
8
