Fairchild SG5842A JA Highly Integrated Green-Mode PWM Controller Data Manual

SG 5842A /SG 5842JA ighly Integrated G reen-M ode PW ontroller

December 2009

SG5842A/SG5842JA — Highly Integrated Green-Mode PWM Controller Features Description

Green-Mode PWM Controller The highly integrated SG5842A/JA series of PWM controllers provides several features to enhance the

Low Startup Current: 14µA

performance of flyback converters. To minimize standby power consumption, a proprietary green-mode function

Low Operating Current: 4m A

provides off-time modulation to continuously decrease

Programmable PWM Frequency with Hopping the switching frequency at light-load conditions. To (SG5842JA) avoid acoustic-noise problems, the minimum PWM

frequency set above 22KHz. This green-mode function

Peak-Current-Mode Control

enables the power supply to meet international power

Cycle-by-Cycle Current Limiting conservation requirements. To further reduce power

consumption, SG5842A/JA is manufactured using the

Synchronized Slope Compensation

Bi CMOS process. This allows a low startup current,

Leading-Edge Blanking (LEB) around 14µA, and an operating current of only 4m A. As

a result, a large startup resistance can be used.

Constant Output Power Limit

The SG5842A/JA built-in synchronized slope

Totem-Pole Output with Soft Driving

compensation achieves stable peak-current-mode

VDD Over-Voltage Protection (OVP) control. SG5842JA integrates a frequency-hopping

function that helps reduce EMI emission of a power

Programmable Over-Temperature Protection (OTP)

supply with minimum line filters.

Internal Latch Circuit (OTP, OVP)

SG5842A/JA provides many protection functions. In

Internal Open-Loop Protection addition to cycle-by-cycle current limiting, the internal

open-loop protection circuit ensures safety should an

VDD Under-Voltage Lockout (UVLO)

open-loop or output short-circuit failure occur. PWM GATE Output Maximum Voltage Clamp: 18V output is disabled until VDD drops below the UVLO lower limit, then the controller starts again. As long as VDD exceeds about 24V, the internal OVP circuit is triggered.

Applications An external NTC thermistor can be applied for over-

temperature protection.

General-purpose switch-mode power supplies and flyback power converters, including: SG5842A/JA is available in an 8-pin DIP or SOP

package.

Notebook Power Adapters Open-Frame SMPS

© 2007 Fairchild Semiconductor Corporation www.fairchildsemi.com SG5842A/SG5842JA • Rev. 1.4.3