Fairchild SG6741A, SG6741A Schematic [ru]

SG6741A Highly Integrated Green-Mode PWM Controller

SG6741A — Highly Integrated Green-Mode PWM Controller

August 2010

Features

 High-Voltage Startup  Low Operating Current: 4mA  Linearly Decreasing PWM Frequency to 18kHz  Frequency Hopping to Reduce EMI Emissions  Peak-Current-Mode Control  Cycle-by-Cycle Current Limiting  Leading-Edge Blanking (LEB)  Synchronized Slope Compensation  GATE Output Maximum Voltage Clamp: 18V  V  V

Over-Voltage Protection (Auto Restart)

Under-Voltage Lockout (UVLO)

 Internal Open-Loop Protection  Constant Power Limit (Full AC Input Range)

Applications

General-purpose switch-mode power supplies and flyback power converters, including:

 Power Adapters  Open-Frame SMPS

Description

The highly integrated SG6741A 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 linearly decrease the switching frequency at light-load conditions. To avoid acoustic-noise problems, the minimum PWM frequency is set above 18KHz. This green-mode function enables the power supply to meet international power conservation requirements. With the internal high-voltage startup circuitry, the power loss due to bleeding resistors is eliminated. To further reduce power consumption, SG6741A is manufactured using the BiCMOS process, which allows an operating current of only 4mA.

SG6741A integrates a frequency-hopping function internally to reduce EMI emission of a power supply with minimum line filters. A 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 90V

SG6741A provides many protection functions. In addition to cycle-by-cycle current limiting, the internal open-loop protection circuit ensures safety when an open-loop or output short-circuit failure occurs. PWM output is disabled until V limit, when the controller starts up again. As long as V exceeds ~26V, the internal OVP circuit is triggered.

SG6741A is available in an 8-pin SOP package.

to 264 VAC.

drops below the UVLO lower

Ordering Information

Part Number

SG6741ASY -40 to +105°C 8-Lead Small Outline Package (SOP) Tape & Reel

Operating

Temperature Range

Package Packing Method

Application Diagram

SG6741A — Highly Integrated Green-Mode PWM Controller

Figure 1. Typical Application

Block Diagram

OSC

Generator

Figure 2. Block Diagram

Marking Information

Pin Configuration

ZXYTT 6741A TPM

GND

SG6741A — Highly Integrated Green-Mode PWM Controller

F: Fairchild Logo Z: Plant Code X: 1-Digit Year Code Y: 1-Digit Week Code TT: 2-Digit Die Run Code T: Package Type (S = SOP) P: Y=Green Package M: Manufacture Flow Code

Figure 3. Top Mark

GATE

Figure 4. Pin Configuration

VDD

SENSE

Pin Definitions

Pin # Name Description

1 GND Ground.

Feedback. The signal from the external compensation circuit is fed into this pin. The PWM duty

2 FB

3 NC No Connection.

4 HV Startup Input. For startup, this pin is pulled HIGH to the line input or bulk capacitor via resistors.

5 RI

6 SENSE

7 VDD

8 GATE Driver Output. Totem-pole output driver. Soft driving waveform is implemented for improved EMI.

cycle is determined in response to the signal on this pin and the current-sense signal on SENSE pin.

Reference Setting. A resistor connected from the RI pin to GND pin provides a constant current source, which determines the center PWM frequency. Increasing the resistance reduces PWM frequency. Using a 26KΩ resistor for R

Current Sense. The sensed voltage is used for peak-current-mode control and cycle-by-cycle current limiting.

Power Supply. The internal protection circuit disables PWM output as long as V OVP trigger point.

results in a 65kHz center PWM frequency.

exceeds the

SG6741A — Highly Integrated Green-Mode PWM Controller

Absolute Maximum Ratings

Stresses exceeding the absolute maximum ratings may damage the device. The device may not function or be operable above the recommended operating conditions and stressing the parts to these levels is not recommended. In addition, extended exposure to stresses above the recommended operating conditions may affect device reliability. The absolute maximum ratings are stress ratings only. All voltage values, except differential voltages, are given with respect to the ground pin.

Symbol Parameter Min. Max. Unit

DC Supply Voltage

VDD

VFB FB Pin Input Voltage -0.3 7.0 V

SENSE Pin Input Voltage -0.3 7.0 V

SENSE

VRI RI Pin Input Voltage -0.3 7.0 V

VHV HV Pin Input Voltage 500 V

ΘJA

Power Dissipation

Thermal Resistance (Junction-to-Air) 141

TJ Operating Junction Temperature -40 +125

Storage Temperature Range -55 +150

STG

TL Lead Temperature (Wave Soldering or IR, 10 Seconds) +260

ESD

Electrostatic Discharge Capability

Notes:

1. All voltage values, except differential voltages, are given with respect to the network ground terminal.

2. Stresses beyond those listed under Absolute Maximum Ratings may cause permanent damage to the device.

(1, 2)

30 V

＜50°C)

400 mW

°C/W

°C

Human Body Model, JESD22-A114, All Pins Except HV Pin

Machine Model, JESD22-A115, All Pins Except HV Pin

4 kV

200 V

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