ASM8P18S42 Datasheet, PDF (1/11 Pages) Alliance Semiconductor Corporation – Voltage Mode PWM Controller with EMI Reduction

June 2005
rev 0.6
ASM8P18S42 / ASM8P18S42ER
ASM8P1843 / ASM8P18S43ER
ASM8P18S44ER / ASM8P18S45ER
Voltage Mode PWM Controller with EMI Reduction
General Description
Features
ASM8P18xx is a high performance, adjustable frequency,
PWM controller with an integrated spread spectrum
modulator for EMI reduction. It contains all the functions
of a standard PWM controller along with a user
configurable spread spectrum modulation with adjustable
spread. ASM8P18xx allows significant system cost
savings by reducing the number of PCB layers and
shielding that are traditionally required to pass EMI
regulation.
ASM8P18xx is the industry’s first general purpose EMI
reduction IC, specifically designed for use in SMPS
systems. ASM8P18xx is compatible to any other 3842
PWM controllers.
ASM8P18xx is capable of driving 1A maximum current
output and it covers a wide supply voltage range from 7V
DC to 30V DC. The PWM frequency is selectable from 40
KHz to 400 KHz.
ASM8P18xx provides under voltage lockout, thermal
shutdown, overload, and undercurrent protection. It is
available in 8-pin MicroSO, P-DIP and SOIC package.
30V maximum operating voltage with CMOS
technology
Adjustable PWM frequencies (40 KHz to 400 KHz)
Maximum Output drive current of 1A.
Wide duty cycle range (0% minimum to 95%
maximum)
Spread spectrum modulation with adjustable spread.
Under voltage lockout with hysteresis.
Low startup current: 275?A maximum
Pin compatible with industry standard 3842 PWM
controller.
Temperature range –40°C to +85°C.
Thermal shutdown, overload and undercurrent
protection.
Frequency skip mode.
Available in 8-pin plastic MicroSO, P-DIP and SOIC
packages.
Applications
Off-line converter
DC-DC converter
Monitor power supply
Computer/DVD/STB power supply
Wireless base station power supply
Telecom power supply
Typical Operating Circuit
VDD
VDD
VIN
FSEL
CT _GND
ASM8P18xx
VREF
RD
COMP
OUT
FB ^ISNS
R1
RC ^CC
R2
R3
RS
From SMPS Output
Alliance Semiconductor
2575 Augustine Drive • Santa Clara, CA • Tel: [phone] • Fax: [phone] •
Notice: The information in this document is subject to change without notice.