SG6842JLSZ Datasheet, PDF (1/13 Pages) Fairchild Semiconductor – Highly-Integrated Green-Mode PWM Controller

Highly-Integrated Green-Mode PWM Controller
Product Specification
SG6842J
FEATURES
Green-mode PWM Controller
Low Start-Up Current (8uA)
Low Operating Current (4mA)
Programmable PWM frequency with Jittering
Peak-current-mode Operation
Cycle-by-Cycle Current Limiting
Synchronized Slope Compensation
Leading-Edge Blanking
Constant Output Power Limit (Full AC Input Range)
VDD Over Voltage Protection (OVP)
Programmable Over Temperature Protection (OTP)
Internal Latch Circuit (OTP, OVP) Options
Internal Open-loop Protection
APPLICATIONS
General-purpose switch mode power supplies and
flyback power converters, including:
Notebook Power Adapters
Open-Frame SMPS
DESCRIPTION
The highly integrated SG6842J series of PWM
controllers provides several features to enhance the
performance of flyback converters.
To minimize standby power consumption, a
proprietary green-mode function provides off-time
modulation to continuously decrease the switching
frequency at light-load conditions. To avoid
acoustic-noise problem, the minimum PWM frequency
set above 20kHz. This green-mode function enables the
power supply to easily meet international power
conservation requirements. To further reduce power
consumption, SG6842J is manufactured by using the
BiCMOS process. This allows the lowest start-up current
around 8uA, and the operating current is only 4mA. As a
result, large start-up resistance can be used.
SG6842J integrates frequency jittering function
internally. The frequency jittering function helps reduce
EMI emission of a power supply with minimum line
filters. Also, its built-in synchronized slope compensation
achieves stable peak-current-mode control. The
proprietary internal line compensation ensures constant
output power limit over a wide AC input voltages, from
90VAC to 264VAC.
SG6842J provides many protection functions. In
addition to cycle-by-cycle current limiting, the internal
open-loop protection circuit ensures safety should an open
loop or output short-circuit failure occurs. PWM output is
disabled till V_DD drops below the UVLO lower limit.
Then, the controller starts up again. As long as V_DD
exceeds about 24V, the internal OVP circuit is triggered.
An external NTC thermistor can be applied for
over-temperature protection. For OVP and OTP, the
protection mode can be chosen to be latch off or auto
recovery.
SG6842J is available in an 8-pin DIP or SOP
package.
TYPICAL APPLICATION
© System General Corp.
-1-
Version 1.4(IAO33.0015.B4)
www.sg.com.tw
Feb. 13, 2006