January 2003
廬
AS80M1800/1801
EMI Reduction IC for Switching Power Supplies
Overview
AS80M1800
and
AS80M1801
are programmable spread
spectrum frequency modulators designed for Switched
Mode Power Supply (SMPS) applications. These devices
work as companion ICs to the pulse width modulation
(PWM) controller. As such, they can be used as a simple
drop-in solution between the PWM controller and
MOSFET to tackle most EMI problems in the SMPS.
The
AS80M1800
and
AS80M1801
reduce electro-
magnetic interference (EMI) by applying spread spectrum
modulation to the PWM gate drive signal at the gate of the
power MOSFET. Gate drive modulation significantly
reduces the conducted and radiated emissions usually
generated by di/dt and dv/dt switching in a SMPS.
These are the first general purpose EMI reduction ICs
specifically designed for use in SMPS systems. No other
manufacturer to date has a device that can frequency
modulate a PWM train and still maintain the input PWM
content. They can be used in popular DC/DC converter,
and AC/DC inverter and DC/AC inverters designs.
Besides providing EMI reduction functionality, the
AS80M1800
and
AS80M1801
provide additional features
that extend the capabilities of the power system.
Simplified Application Diagram
Vout
From Regulated Output
SS Modulated
Gate Drive
PWM
Controller
PWM_in
AS80M1800
AS80M1801
MOSFET
I_peak
Current Sense
Current Sense
Sense
Resistor
Boost/Flyback configuration
Alliance Semiconductor
2575 Augustine Drvie 鈥?Santa Clara, CA 95054 鈥?Tel: 408.855.4900 鈥?Fax: 408.855.4999 鈥?www.alsc.com
Notice: The information in this document is subject to change without notice.
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