LT1375_15 Datasheet, PDF (1/28 Pages) Linear Technology – 1.5A, 500kHz Step-Down Switching Regulators

LT1375/LT1376
1.5A, 500kHz Step-Down
Switching Regulators
FEATURES
■ Constant 500kHz Switching Frequency
■ Uses All Surface Mount Components
■ Inductor Size Reduced to 5µH
■ Easily Synchronizable
■ Saturating Switch Design: 0.4Ω
■ Effective Supply Current: 2.5mA
■ Shutdown Current: 20µA
■ Cycle-by-Cycle Current Limiting
U
APPLICATIO S
■ Portable Computers
■ Battery-Powered Systems
■ Battery Charger
■ Distributed Power
DESCRIPTIO
The LT^®1375/LT1376 are 500kHz monolithic buck mode
switching regulators. A 1.5A switch is included on the die
along with all the necessary oscillator, control and logic
circuitry. High switching frequency allows a considerable
reduction in the size of external components. The topology
is current mode for fast transient response and good loop
stability. Both fixed output voltage and adjustable parts are
available.
A special high speed bipolar process and new design
techniques achieve high efficiency at high switching fre-
quency. Efficiency is maintained over a wide output cur-
rent range by using the output to bias the circuitry and by
utilizing a supply boost capacitor to saturate the power
switch. A shutdown signal will reduce supply current to
20µA on both parts. The LT1375 can be externally syn-
chronized from 580kHz to 900kHz with logic level inputs.
The LT1375/LT1376 fit into standard 8-pin PDIP and SO
packages, as well as a fused lead 16-pin SO with much
lower thermal resistance. Full cycle-by-cycle short-cir-
cuit protection and thermal shutdown are provided.
Standard surface mount external parts are used, includ-
ing the inductor and capacitors.
For low input voltage applications with 3.3V output, see
LT1507. This is a functionally identical part that can
operate with input voltages between 4.5V and 12V.
, LT, LTC and LTM are registered trademarks of Linear Technology Corporation.
All other trademarks are the property of their respective owners.
TYPICAL APPLICATIO
5V Buck Converter
INPUT
6V^† TO 25V _{C3* +}
10µF TO
50µF
DEFAULT
= ON
BOOST
V_IN
V_SW
LT1376-5 BIAS
SHDN
GND
FB
V_C
C_C
3.3nF
D2
1N914
C2
0.1µF
L1**
5µH
OUTPUT**
5V, 1.25A
D2
1N5818
+ ^C1
100µF, 10V
SOLID
TANTALUM
* RIPPLE CURRENT ≥ I_OUT/2
** INCREASE L1 TO 10µH FOR LOAD CURRENTS ABOVE 0.6A AND TO 20µH ABOVE 1A
† _{FOR INPUT VOLTAGE BELOW 7.5V, SOME RESTRICTIONS MAY APPLY.}
SEE APPLICATIONS INFORMATION.
1375/76 TA01
Efficiency vs Load Current
100
V_OUT = 5V
V_IN = 10V
90 L = 10µH
80
70
60
50
0
0.25 0.50 0.75 1.00 1.25
LOAD CURRENT (A)
1375/76 TA02
13756fd
1