SC1578 Datasheet, PDF (1/5 Pages) Semtech Corporation – HIGH-EFFICIENCY STEP-DOWN DC-DC CONVERTER

HIGH-EFFICIENCY STEP-DOWN
DC-DC CONVERTER
SC1578
January 29, 1998
TEL:[phone] FAX:[phone] WEB:http://www.semtech.com
DESCRIPTION
The SC1578 is a high performance step-down DC-DC
converter, designed to drive an external P-channel
MOSFET to generate programmable output voltages.
Two main schemes of pulse-skipping and pulse-
frequency modulation are employed to maintain low
quiescent current and high conversion efficiency over
wide ranges of input voltage and loads. The SC1578
delivers 10mA to 2A of output current with 87%-93%
efficiency at V_IN=9V, V_OUT=5V. A current sense
comparator with both inverting and non-inverting inputs
uncommitted is included to provide the crucial function
of either current limit protection or constant output
current control. When the SC1578 is used in a high-
side current sensing step-down constant current
source, the efficiency is typically greater than 90%.
Duty cycle can be adjusted to greater than 90% by
connecting a resistor from the DUTY pin to V_IN.
Quiescent current is about 90µA and can be reduced
to 8µA in shutdown mode. With a switching frequency
range of 90kHz to 280kHz, small size switching
components may be used, which is ideal for battery
powered portable equipment.
FEATURES
• 4V to 24V input voltage operation.
• High efficiency (up to 95%).
• Low quiescent current at 90µA.
• Pulse-skipping and pulse-frequency modulation.
• Inputs-uncommitted current sense comparator.
• Duty cycle adjustable
• 90kHz to 280kHz oscillator frequency
• Power-saving shutdown mode (8µA Typical).
• Push-pull driver output
APPLICATIONS
• Notebook 5V/3.3V main power
• Step-down DC-DC converter module.
• Constant current source for battery chargers.
BLOCK DIAGRAM
ORDERING INFORMATION
DEVICE⁽¹⁾
PACKAGE
SC1578CS
SO-8
Note:
(1) Add suffix ‘TR’ for tape and reel.
PIN CONFIGURATION
ABSOLUTE MAXIMUM RATINGS
Parameter
Symbol Maximum Units
Supply Voltage
V_IN
24
V
Duty Voltage
V_DUTY
20
V
SHDN Voltage
V_SHDN
15
V
Operating
Temperature Range
T_A
0 to 70
°C
Storage Temperature
Range
T_STG
-65 to 150
°C
© 1997 SEMTECH CORP.
652 MITCHELL ROAD NEWBURY PARK CA 91320