TDA4605-3 Datasheet, PDF (3/20 Pages) Siemens Semiconductor Group – Control IC for Switched-Mode Power Supplies using MOS-Transistor

TDA 4605-3
Pin Definitions and Functions
Pin No.
1
2
3
Function
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).
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.
Input for Primary Voltage Monitoring: In the normal operation V₃ is moving
between the thresholds V_3H and V_3L (V_3H > V₃ > V_3L).
V₃ < V_3L: SMPS is switched OFF (line voltage too low).
V₃ > V_3H : Compensation of the overload point regulation (controlled by pin 2)
starts at V_3H : V_3L = 1.7.
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 V_REF is derived from
the supply voltage also the switching thresholds V_6A , V_6E , V_{6 max} and V_{6 min} for
the supply voltage detector. If V₆ > V_6E then V_REF is switched on and swiched off
when V₆ < V_6A . In addition the logic is only enable for V_{6 min} < V₆ < V_{6 max}.
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.
Semiconductor Group
76