© 2011 Fairchild Semiconductor Corporation

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FSB117H / FSB127H / FSB147H • Rev. 1.0.7

4

Pin Configuration

Figure 3.

Pin Configuration

Pin Definitions

Pin #

Name

Description

1

GND

Ground. This pin internally connects to the SenseFET source and signal ground of the PWM

controller.

2

VDD

Supply voltage of the IC. Typically the holdup capacitor connects from this pin to ground.

Rectifier diode in series with the transformer auxiliary winding connects to this pin to supply bias

during normal operation.

3

FB

Feedback. The signal from the external compensation circuit connects to this pin. The PWM duty

cycle is determined by comparing the signal on this pin and the internal current-sense signal.

4

IPK

Adjust peak current. Typically a resistor connects from this pin to the GND pin to program the

current-limit level. The internal current source (50 µA) introduces voltage drop across the

resistor, which determines the current limit level of pulse-by-pulse current limit.

5

HV

Startup. Typically, resistors in series with diodes from the AC line connect to this pin to supply

internal bias and to charge the external capacitor connected between the VDD pin and the GND

pin during startup. This pin is also used to sense the line voltage for brownout protection and AC

line disconnection detection.

6

Drain

SenseFET drain. This pin is designed to directly drive the transformer.

7

8

F

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