SG5842A Datasheet, PDF (1/14 Pages) Fairchild Semiconductor – Highly Integrated Green-Mode PWM Controller

Highly Integrated Green-Mode PWM Controller
FEATURES
„ Green-Mode PWM Controller
„ Low Start-up Current (14µA)
„ Low Operating Current (4mA)
„ Programmable PWM Frequency with Hopping
(5842JA)
„ Peak-Current-Mode Control
„ Cycle-by-Cycle Current Limiting
„ Synchronized Slope Compensation
„ Leading-Edge Blanking
„ Constant Output Power Limit
„ Totem Pole Output with Soft Driving
„ V_DD Over-Voltage Protection (OVP)
„ Programmable Over-Temperature Protection (OTP)
„ Internal Latch Circuit (OTP, OVP)
„ Internal Open-Loop Protection
„ V_DD Under-Voltage Lockout (UVLO)
„ GATE Output Maximum Voltage Clamp (18V)
APPLICATIONS
General-purpose switch mode power supplies and flyback
power converters, including:
„ Notebook Power Adapters
„ Open-Frame SMPS
DESCRIPTION
The highly integrated SG5842A/JA series of PWM
controllers provides several features to enhance the
performance of flyback converters.
Product Specification
SG5842A/JA
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 22KHz. This
green-mode function enables the power supply to meet
international power conservation requirements. To further
reduce power consumption, SG5842A/JA is
manufactured using the BiCMOS process. This allows a
low start-up current, around 14µA, and an operating
current of only 4mA. As a result, a large start-up
resistance can be used.
The SG5842A/JA built-in synchronized slope
compensation achieves stable peak-current-mode control.
SG5842JA integrates a frequency hopping function that
helps reduce EMI emission of a power supply with
minimum line filters.
SG5842A/JA 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 occur. PWM output is
disabled until V_DD drops below the UVLO lower limit,
then the controller starts 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.
SG5842A/JA is available in an 8-pin DIP or SOP package.
TYPICAL APPLICATION
SG5842A/JA
© System General Corp.
-1-
Version 1.4.2 (IAO33.0026.B6)
www.sg.com.tw • www.fairchildsemi.com
October 30, 2007