LTC1574 Datasheet, PDF (1/8 Pages) Linear Technology – High Efficiency Step-Down DC/DC Converters with Internal Schottky Diode

LTC1574
LTC1574-3.3/LTC1574-5
High Efficiency Step-Down
DC/DC Converters
with Internal Schottky Diode
FEATURES
s _{High Efficiency: Up to 94%}
s _{Usable in Noise-Sensitive Products}
s _{Peak Inductor Current Independent of Inductor Value}
s _{Short-Circuit Protection}
s _{Internal Low Forward Drop Schottky Diode}
s _{Only Three External Components Required}
s _{Wide VIN Range: 4V to 18.5V (Absolute Maximum)}
s _{Low Dropout Operation}
s _{Low-Battery Detector}
s _{Pin Selectable Current Limit}
s _{Internal 0.9Ω Power Switch: VIN = 12V}
s _{Standby Current: 130µA}
s _{Active Low Micropower Shutdown}
U
APPLICATIONS
s _{Inverting Converters}
s _{Step-Down Converters}
s _{Memory Backup Supply}
s _{Portable Instruments}
s _{Battery-Powered Equipment}
s _{Distributed Power Systems}
and LTC are registered trademarks and LT is a trademark of Linear Technology Corporation.
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, T_A = 25°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 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.
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.
TYPICAL APPLICATION
V_IN
5.5V to
16V
High Efficiency Step-Down Converter
5
12
LB_IN
V_IN
SHDN ⁷
11 _{LBOUT LTC1574-5 VOUT} 10
6
I_PGM
SW ^{3, 14 100µHâ€} 
GND
2, 4, 13, 15
+ _22µF*
35V
5V
175mA
+ _100µF*
10V
* AVX TPSD226K035
** AVX TPSD107K010
† _{COILTRONICS CTX100-4}
1574 TA01
LTC1574-5 Efficiency
100
L = 100µH
95
V_OUT = 5V
I_PGM = 0V
V_IN = 6V
90
V_IN = 9V
85
80
75
70
1
10
LOAD CURRENT (mA)
100 200
1574 TA02
1