Semiconductor Group

76

TDA 4605-3

Pin Definitions and Functions

Pin No.

Function

1

Information Input Concerning Secondary Voltage. By comparing the

regulating voltage - obtained trom the regulating winding of the transformer - with

the internal reference voltage, the output impulse width on pin 5 is adjusted to the

load of the secondary side (normal, overload, short-circuit, no load).

2

Information Input Regarding the Primary Current. The primary current rise in

the primary winding is simulated at pin 2 as a voltage rise by means of external

RC-element. When a voltage level is reached thats derived from the regulating

voltage at pin 1, the output impulse at pin 5 is terminated. The RC-element serves

to set the maximum power at the overload point set.

3

Input for Primary Voltage Monitoring: In the normal operation

between the thresholds

starts at

4

Ground

5

Output: Push-pull output provides

± 1 A for rapid charge and discharge of the

gate capacitance of the power MOS-transistor.

6

Supply Voltage Input: A stable internal reference voltage

the supply voltage also the switching thresholds

the supply voltage detector. If

when

7

Input for Soft-Start. Start-up will begin with short pulses by connecting a

capacitor from pin 7 to ground.

8

Input for the Oscillation Feedback. After starting oscillation, every zero

transition of the feedback voltage (falling edge) through zero (falling edge)

triggers an output pulse at pin 5. The trigger threshold is at + 50 mV typical.