Philips CDR775 Service Manual page 54

GB 54 8. CDR775
Pin function description
Pin Name Description
1 VCC This pin is the positive supply of the IC. The operating voltage range after start-up is 9.0 to 14.5 V.
2 VC The output high state (VOH) is set by the voltage applied to this pin.
3 Output Peak currents up to 750 mA can be sourced or sunk, suitable for driving either MOSFET or bipolar transistors.
4 Gnd The groundpin is a single return, typically connected back to the power source.
5 Foldback Input The foldback function provides overload protection.
6 Overvoltage When the overvoltage protection pin receives a voltage greater than 2.5V, the device is disabled and requires a
Protection complete restart sequence.
7 Current Sense A voltage proportional to the current flowing into the power switch is connected to this input.
Input
8 Demagnetisation A voltage delivered by an auxiliary transformer winding provides to the demagnetisation pin an indication of the
Detection magnetisation state of the flyback transformer. A zero voltage detection corresponds to complete core
saturation.
9 Synchronisation The synchronisation input pin can be activated with either a negative pulse going from a level between 0.7V and
Input 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.
10 C The normal mode oscillator frequency is programmed by the capacitor CT choice together with the Rref
T
resistance value. CT, connected between Pin 10 and Gnd, generates the oscillator sawtooth.
11 Soft- A capacitor, resistor or a voltage source connected to this pin limits the switching duty-cycle. This pin can be
Start/Dmax/Volta used as a voltage mode control input. By connecting Pin 11 to Ground, the MC44603 can be shut down.
ge-Mode
12 RP Standby 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 E/A Out The error amplifier output is made available for loop compensation.
14 Voltage This is the inverting input of the Error Amplifier. It can be connected to the switching power supply output
Feedback through an optical (or other) feedback loop.
15 RF Standby The reduced frequency or standby frequency programming is made by the RF Standby resistance choice.
16 Rref
Rref sets the internal reference current. The internal reference current ranges from 100µA to 500µA. This
requires that 5.0kΩ ≤ Rref ≤ 25kΩ.
Faultfinding Guide
Figure 8-12
CL 96532076_031.eps
290799