TDA4605-2 Datasheet, PDF (5/23 Pages) Siemens Semiconductor Group – Control IC for Switched-Mode Power Supplies using MOS-Transistors

TDA 4605-2
Pin Definitions and Functions
Pin No.
1
2
3
4
5
6
7
8
Function
Information Input Concerning Secondary Voltage. By comparing the
regulating voltage - obtained from 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 load, 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-circuit. If a voltage level is reached which is derived from the control voltage
at pin 1, the output impulse at pin 5 is terminated. The RC-circuit is used to set
the maximum power of the foldback point.
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.
Ground
Output: Push-pull output for charging or discharging the gate capacity of the
power MOSFET-transistor.
Supply Voltage Input. From the voltage at pin 6 a stable internal reference
voltage V_REF and the switching thresholds V_6A , V_6E , V_{6 max} and V_{6 min} for the
supply voltage detector are derived. If V₆ > V_6E then V_REF is switched on. The
reference voltage will be switched off if V₆ < V_6A . In addition the logic is only
enable, for V_{6 min} < V₆ < V_{6 max} .
Input for Soft-Start and Integrator Circuit. The capacitor connected to ground
causes a slow increase of the duration of the output pulse during start-up and an
integrating response of the control amplifier.
Input for the Feedback of the Oscillator. After the oscillations of the SMPS
started, every transition of the feedback voltage through zero (falling edge)
triggers an output pulse at pin 5. The trigger threshold is at + 50 mV typical.
Version 2.0
5
1 Jul 2002