HT7A3942 Datasheet, PDF (1/11 Pages) Holtek Semiconductor Inc – High Performance Current Mode PWM Controller

HT7A3942
High Performance
Current Mode PWM Controller
Feature
• High performance, low cost current mode PWM
controller especially designed for energy star 2.0
• High-Voltage CMOS process with excellent ESD
protection (>3KV)
• Very low startup current (<20μA) and operating
current
• ±5% trimmed oscillator for precise frequency
control
• Non-audible-noise Green Mode control
• LEB (Leading-Edge Blanking) on CS pin
• Internal slope compensation
• Programmable switching frequency
• Internally trimmed reference with UVLO
(Under Voltage Lockout)
• Cycle-by-Cycle Current Limiting
• Build-in Short-Circuit-Protection(SCP) for
Short-Circuit and Over-Load condition
• 8-Pin SOP package
Applications
• Switching AC-DC adaptor
• Open frames switching power supply
• LCD TV
General Description
The HT7A3942 is a high performance, low cost
Current Mode PWM controller for providing
necessary feature to implement Off-Line application.
By Optimizing for the Energy Star 2.0 spec., the
Power Supply Unit (PSU) implemented using the
HT7A3942 can satisfy the “Energy Star No-Load
Mode” Stand-by Power standard,which is less than
0.3W within all Nameplate Output Power Range of
0~250W. Internally implemented circuits include a
trimmed Oscillator for precise frequency control,
a temperature-compensated Voltage Reference,
Slope Compensation, Leading-Edge Blanking, and
a patented Non-Audible Noise Green Mode Control
Scheme.
The HT7A3942 features a range of various protection
functions such Short-Circuit Protection (SCP, which
can also be used for Over-Load Protection, OLP),
Cycle-by-Cycle Current Limiting and Under Voltage
Lock-Out (UVLO).
Application Circuits
EMI Filter
Flyback Converter
VOUT
GND
GD
RT
10k
CS
VCC
HT7A3942 _COMP
GND
VREF
0.1uF
FOD817
95k
TL431
25k
Rev. 1.00
1
May 27, 2011