LT1572 Datasheet, PDF (1/12 Pages) Linear Technology – 100kHz, 1.25A Switching Regulator with Catch Diode

FEATURES
s _{Catch Diode Included in Package}
s _{Wide Input Voltage Range: 3V to 30V}
s _{Low Quiescent Current: 6mA}
s _{Internal 1.25A Switch}
s _{Very Few External Parts Required}
s _{Self-Protected Against Overloads}
s _{Operates in Nearly All Switching Topologies}
s _{Shutdown Mode Draws Only 50µA Typical Current}
s _{Can Be Externally Synchronized}
APPLICATI S
s _{3.3V-to-5V and 5V-to-12V Boost Converters}
s _{Negative-to-Positive Converter}
s _{SEPIC Converter (Input Can Be Greater or}
Less Than Output)
s _{Battery Charger}
LT1572
100kHz, 1.25A Switching
Regulator with Catch Diode
DESCRIPTIO
The LT^®1572 is a 1.25A 100kHz monolithic switching
regulator with on-board switch and catch diode included
in one package. It combines an LT1172 with a 1A Schottky
catch diode. The LT1572 can be operated in all standard
switching configurations, including boost, buck, SEPIC,
flyback, forward, inverting and “Cuk”. All necessary con-
trol, oscillator and protection circuitry is included on the
die with the high efficiency switch. This makes the part
extremely easy to use and provides “bustproof” operation
similar to that obtained with 3-pin linear regulators.
The LT1572 operates with supply voltages from 3V to 30V
and draws only 6mA quiescent current. It can deliver load
power up to 15W with no external power devices. By
utilizing a current mode switching technique, the LT1572
achieves excellent response to load and line transients.
The LT1572 has many unique features not found on the
more difficult to use control chips presently available. It
uses adaptive anti-sat switch drive to allow very wide
ranging load currents with no loss in efficiency. An exter-
nally activated shutdown mode reduces total supply cur-
rent to 50µA typical for standby operation. External syn-
chronizing of switching frequency is possible, with a range
of 120kHz to 160kHz.
, LTC and LT are registered trademarks of Linear Technology Corporation.
TYPICAL APPLICATI
V_IN
4.5V
TO 10V
5V-to-12V Boost Converter
C3
100µF
10V
L1*
50µH
*COILTRONICS CTX50-2
**AVX TPS OR SPRAGUE 593D
9
11 2 15
†_{ALWAYS CONNECT BOTH ANODE (2, 15)}
V_IN
V_SW ANODE^† ₃ ^{AND CATHODE (3, 14) PINS}
CATHODE^† 14
LT1572
FB
R1
10.7k
1%
12V
0.25A
E1 E2 GND ^VC
10 12 4, 13 5
R3
1k
C1
1µF
R2
1.24k
1%
C2**
100µF
16V
LT1572 • TA01
Boost Converter Efficiency
100
BOOST CONVERTER
V_IN = 5V
90 ^{VOUT = 12V}
80
70
60
50
0
50 100 150 200 250
L0AD CURRENT (mA)
LT1572 • TA01
1