ASM8P18S42 / ASM8P18S42ER
ASM8P1843 / ASM8P18S43ER
ASM8P18S44ER / ASM8P18S45ER
June 2005
rev 0.6
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
ꢀ 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)
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.
ꢀ Spread spectrum modulation with adjustable spread.
ꢀ Under voltage lockout with hysteresis.
ꢀ Low startup current: 275µA maximum
ꢀ Pin compatible with industry standard 3842 PWM
controller.
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.
ꢀ Temperature range –40°C to +85°C.
ꢀ Thermal shutdown, overload and undercurrent
protection.
ꢀ Frequency skip mode.
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.
ꢀ Available in 8-pin plastic MicroSO, P-DIP and SOIC
packages.
Applications
ꢀ Off-line converter
ꢀ DC-DC converter
ASM8P18xx provides under voltage lockout, thermal
shutdown, overload, and undercurrent protection. It is
available in 8-pin MicroSO, P-DIP and SOIC package.
ꢀ Monitor power supply
ꢀ Computer/DVD/STB power supply
ꢀ Wireless base station power supply
ꢀ Telecom power supply
Typical Operating Circuit
VDD
VIN
VDD
FSEL
GND
CT
ASM8P18xx
VREF
OUT
ISNS
COMP
FB
RD
R3
R1
R2
CC
RC
RS
From SMPS Output
Alliance Semiconductor
2575 Augustine Drive • Santa Clara, CA • Tel: 408.855.4900 • Fax: 408.855.4999 •
Notice: The information in this document is subject to change without notice.