Fairchild FAN6751MR service manual

FAN6751MR Highly-Integrated Green-Mode PWM Controller

FAN6751MR — Highly-Integrated Green-Mode PWM Controller

September 2008

Features

 High-Voltage Startup  Low Operating Current: 4mA  Linearly Decreasing PWM Frequency to 18KHz  Fixed PWM Frequency: 65KHz  Peak-current-mode Control  Cycle-by-cycle Current Limiting  Leading-edge Blanking (LEB)  Synchronized Slope Compensation  Internal Open-loop Protection  GATE Output Maximum Voltage Clamp: 18V  V  V

Under-Voltage Lockout (UVLO)

Over-Voltage Protection (OVP)

 Internal Recovery Circuit (OVP, OLP)  Internal Sense Short-Circuit Protection  External Constant Power Limit (Full AC Input

Range)

 Internal OTP Sensor with Hysteresis  Built-in 5ms Soft-Start Function  Built-in VIN Pin Pull HIGH (> 4.7V) Recovery

Function for Second-Side Output OVP

 Brownout Protection with Hysteresis

Description

The highly integrated FAN6751 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 also eliminated. To further reduce power consumption, FAN6751 is manufactured using the BiCMOS process, which allows an operating current of only 4mA.

Built-in synchronized slope compensation achieves stable peak-current-mode control. The proprietary, external line compensation ensures constant output power limit over a wide AC input voltage range, from 90V

to 264VAC.

FAN6751 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 limit, when the controller starts up again. As long as V exceeds ~26V, the internal OVP circuit is triggered.

FAN6751 is available in an 8-pin SOP package.

drops below the UVLO lower

Applications

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

 Power Adapters  Open-frame SMPS

Ordering Information

Operating

Part Number

Temperature

Eco Status

Range

FAN6751MRMY

For Fairchild’s definition of “green” Eco Status, please vis i t : http://www.fairchildsemi.com/company/green/rohs_green.html.

-40°C to +105°C

Green

Package Packing Method

8-Lead, Small Outline

Package (SOP-8)

Tape & Reel

Application Diagram

FAN6751MR — Highly-Integrated Green-Mode PWM Controller

Internal Block Diagram

Figure 1. Typical Application

Figure 2. Functional Block Diagram

Marking Information

FAN6751MR — Highly-Integrated Green-Mode PWM Controller

Pin Configuration

ZXYTT 6751MR TPM

F: Fairchild logo Z: Plant code X: 1 digit year code Y: 1 digit week code TT: 2 digits die run code T: Package type (N:DIP, M:SOP) P: Y=Green package M: Manufacture flow code

Figure 3. Top Mark

SOP-8

GND

Figure 4. Pin Configuration (Top View)

GATE

VDD

SENSE

VIN

Pin Definitions

Pin # Name Description

1 GND Ground.

2 FB

3 NC No connection.

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

5 VIN

6 SENSE

7 VDD

8 GATE The totem-pole output driver. Soft-driving waveform is implemented for improved EMI.

The signal from the external compensation circuit is fed into this pin. The PWM duty cycle is determined in response to the signal on this pin and the current-sense signal on the SENSE pin.

Line-voltage detection. The line-voltage detection is used for brownout protection with hysteresis. Constant output power limit over universal AC input range is also achieved using this VIN pin. It is suggested to add a low pass filter to filter out line ripple on bulk capacitor. VIN pulling high triggers latch protection.

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 VDD exceeds the OVP trigger point.

FAN6751MR — 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.

Symbol Parameter Min. Max. Unit

VDD DC Supply Voltage

VFB FB Pin Input Voltage -0.3 7.0 V

SENSE Pin Input Voltage -0.3 7.0 V

SENSE

VIN Pin Input Voltage -0.3 7.0 V

VIN

VHV HV Pin Input Voltage 500 V

ΘJA

Power Dissipation (T

Thermal Resistance, Junction-to-Air 141

TJ Operating Junction Temperature -40 +150

Storage Temperature Range -55 +150

STG

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

Electrostatic Discharge Capability,

ESD

Human Body Model: JESD22-A114

Electrostatic Discharge Capability, Machine Model: JESD22-A115

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

All pins except HV pin 4 kV

All pins except HV pin 200 V

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