© 2010 Fairchild Semiconductor Corporation

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FL6300A • Rev. 1.0.1

3

Pin Configuration

GND

DET

NC

CS

1

2

3

4

8

7

6

5

FB

GATE

HV

Figure 4. Pin Assignments

Pin Definitions

Pin #

Name

Description

1

DET

This pin is connected to an auxiliary winding of the transformer via resistors of the divider for the

following purposes:

-

Generates a zero-current detection (ZCD) signal once the secondary-side switching current

falls to zero.

-

Produces an offset voltage to compensate the threshold voltage of the peak current limit to

provide a constant power limit. The offset is generated in accordance with the input voltage

when PWM signal is enabled.

-

Detects the valley voltage of the switching waveform to achieve the valley voltage switching

and minimize the switching losses.

A voltage comparator and a 2.5V reference voltage develop an output OVP protection. The ratio

of the divider determines what output voltage to stop gate, as an optical coupler and secondary

shunt regulator are used.

2

FB

The feedback pin should to be connected to the output of the error amplifier for achieving the

voltage control loop. The FB pin should be connected to the output of the optical coupler if the

error amplifier is equipped at the secondary-side of the power converter.

For primary-side control applications, FB is applied to connect a RC network to the ground for

feedback-loop compensation.

The input impedance of this pin is a 5k

Ω equivalent resistance. A one-third (1/3) attenuator

connected between the FB and the PWM circuit is used for the loop-gain attenuation. FL6300A

performs an open-loop protection (OLP) once the FB voltage is higher than a threshold voltage

(around 4.2V) for more than 55ms.

3

CS

Input to the comparator of the over-current protection. A resistor senses the switching current

and the resulting voltage is applied to this pin for the cycle-by-cycle current limit.

4

GND

GND is recommended.

5

GATE

Totem-pole output generates the PWM signal to drive the external power MOSFET. The

clamped gate output voltage is 18V.

6

Power supply. The threshold voltages for startup and turn-off are 16V and 10V, respectively.

The startup current is less than 20µA and the operating current is lower than 4.5mA.

7

NC

No connect

8

HV

High-voltage startup