Pin function description
Pin
1
2
3
4
5
6
7
8
9
10
11
12
Name
VCC
VC
Output
Gnd
Foldback Input
Overvoltage
Protection
Current Sense Input
Demagnetisation Detection
Synchronisation Input
CT
Soft- Start/Dmax/Volta
RP Standby
Description
This pin is the positive supply of the IC. The operating voltage range after
The output high state (VOH) is set by the voltage applied to this pin.
Peak currents up to 750 mA can be sourced or sunk, suitable for driving either MOSFET or bipolar transistors.
The groundpin is a single return, typically connected back to the power source.
The foldback function provides overload protection.
When the overvoltage protection pin receives a voltage greater than 2.5V, the device is disabled and requires a complete restart sequence.
A voltage proportional to the current flowing into the power switch is connected to this input.
A voltage delivered by an auxiliary transformer winding provides to the demagnetisation pin an indication of the magnetisation state of the flyback transformer. A zero voltage detection corresponds to complete core saturation.
The synchronisation input pin can be activated with either a negative pulse going from a level between 0.7V and 3.7V to Gnd or a positive pulse going from a level between 0.7V and 3.7V up to a level higher than 3.7V. The oscillator runs free when Pin 9 is connected to Gnd.
The normal mode oscillator frequency is programmed by the capacitor CT choice together with the Rref resistance value. CT, connected between Pin 10 and Gnd, generates the oscillator sawtooth.
A capacitor, resistor or a voltage source connected to this pin limits the switching
A voltage level applied to the RP Standby pin determines the output power level at which the oscillator will turn into the reduced frequency mode of operation (i.e. standby mode). An internal hysteresis comparator allows to return in the normal mode at a higher output power level.
13
14
15
16
E/A Out
Voltage Feedback
RF Standby
Rref
The error amplifier output is made available for loop compensation.
This is the inverting input of the Error Amplifier. It can be connected to the switching power supply output through an optical (or other) feedback loop.
The reduced frequency or standby frequency programming is made by the RF Standby resistance choice.
Rref sets the internal reference current. The internal reference current ranges from 100 A to 500 A. This requires that 5.0kW £ Rref £ 25kW .
CL 96532076_031.eps 290799
Figure
21