LTC1574
LTC1574-3.3/LTC1574-5
High Efficiency Step-Down
DC/DC Converters
with Internal Schottky Diode
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FEATURES
DESCRIPTION
The LTC®1574 is a family of easy-to-use current mode
DC/DC converters ideally suited for 9V to 5V, 5V to 3.3V
and inverting operation. With an internal 0.9Ω switch (at
a supply voltage of 12V) and a low forward drop Schottky
diode (0.450V typ at 200mA, TA = 25°C), the LTC1574
requires only three external components to construct a
complete high efficiency DC/DC converter.
■
High Efficiency: Up to 94%
■
Usable in Noise-Sensitive Products
■
Peak Inductor Current Independent of Inductor Value
■
Short-Circuit Protection
■
Internal Low Forward Drop Schottky Diode
■
Only Three External Components Required
■
Wide VIN Range: 4V to 18.5V (Absolute Maximum)
Low Dropout Operation
Low-Battery Detector
■
Under no load condition, the LTC1574 draws only 130µA.
In shutdown, it draws a mere 2µA making this converter
ideal for battery-powered applications. In dropout, the
internal P-channel MOSFET switch is turned on continu-
ously allowing the user to maximize the life of the battery
source.
■
■
Pin Selectable Current Limit
■
Internal 0.9Ω Power Switch: VIN = 12V
■
Standby Current: 130µA
■
Active Low Micropower Shutdown
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The maximum inductor current of the LTC1574 family is
pin selectable to either 340mA or 600mA, optimizing
efficiency for a wide range of applications. Operation up to
200kHz permits the use of small surface mount inductors
and capacitors.
APPLICATIONS
■
Inverting Converters
■
Step-Down Converters
■
Memory Backup Supply
■
Portable Instruments
For applications requiring higher output current or ultra-
highefficiency,seetheLTC1148andLTC1265datasheets.
For detailed applications information, see the LTC1174
data sheet.
■
Battery-Powered Equipment
■
Distributed Power Systems
and LTC are registered trademarks and LT is a trademark of Linear Technology Corporation.
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TYPICAL APPLICATION
LTC1574-5 Efficiency
High Efficiency Step-Down Converter
100
V
IN
L = 100µH
5.5V to
16V
V
= 5V
= 0V
OUT
I
PGM
95
90
85
80
75
70
V
= 6V
= 9V
+
IN
5
22µF*
V
35V
IN
12
11
6
7
LB
LB
SHDN
IN
V
IN
10
LTC1574-5
V
OUT
OUT
†
100µH
5V
175mA
3, 14
I
SW
PGM
+
100µF*
10V
GND
2, 4, 13, 15
*
AVX TPSD226K035
1574 TA01
** AVX TPSD107K010
1
10
LOAD CURRENT (mA)
100 200
†
COILTRONICS CTX100-4
1574 TA02
1