LTC1574
LTC1574-3.3/LTC1574-5
High Efficiency Step-Down
DC/DC Converters
with Internal Schottky Diode
FEATURES
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DESCRIPTION
The LTC
廬
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 0.9鈩?switch (at
a supply voltage of 12V) and a low forward drop Schottky
diode (0.450V typ at 200mA, T
A
= 25擄C), the LTC1574
requires only three external components to construct a
complete high efficiency DC/DC converter.
Under no load condition, the LTC1574 draws only 130碌A.
In shutdown, it draws a mere 2碌A 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.
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.
For applications requiring higher output current or ultra-
high efficiency, see the LTC1148 and LTC1265 data sheets.
For detailed applications information, see the LTC1174
data sheet.
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 V
IN
Range: 4V to 18.5V (Absolute Maximum)
Low Dropout Operation
Low-Battery Detector
Pin Selectable Current Limit
Internal 0.9鈩?Power Switch: V
IN
= 12V
Standby Current: 130碌A
Active Low Micropower Shutdown
APPLICATIONS
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Inverting Converters
Step-Down Converters
Memory Backup Supply
Portable Instruments
Battery-Powered Equipment
Distributed Power Systems
and LTC are registered trademarks and LT is a trademark of Linear Technology Corporation.
TYPICAL APPLICATION
High Efficiency Step-Down Converter
V
IN
5.5V to
16V
12
11
6
100
LTC1574-5 Efficiency
L = 100碌H
V
OUT
= 5V
I
PGM
= 0V
5
V
IN
LB
IN
SHDN
7
10
3, 14
100碌H
鈥?/div>
+
22碌F*
35V
95
EFFICIENCY (%)
90
V
IN
= 9V
85
80
75
70
LB
OUT
LTC1574-5 V
OUT
I
PGM
GND
2, 4, 13, 15
SW
+
5V
175mA
100碌F*
10V
* AVX TPSD226K035
** AVX TPSD107K010
鈥?/div>
COILTRONICS CTX100-4
1574 TA01
1
U
U
U
V
IN
= 6V
10
LOAD CURRENT (mA)
100 200
1574 TA02
1
1
2
3
4
5
6
7
8
