TDA4605-3 Datasheet, PDF (6/20 Pages) Siemens Semiconductor Group – Control IC for Switched-Mode Power Supplies using MOS-Transistor

TDA 4605-3
Block Diagram
Pin 1
The regulating voltage forwarded to this pin is compared with a stable internal reference voltage V_R
in the regulating and overload amplifier. The output of this stage is fed to the stop comparator. If
the control voltage is rather small at pin 1 an additional current is added by means of current source
which is controlled according the level at pin 7. This additional current is virtually reducing the
control voltage present at pin 1.
Pin 2
A voltage proportional to the drain current of the switching transistor is generated there by the
external RC-combination in conjunction with the primary current transducer. The output of this
transducer is controlled by the logic and referenced to the internal stable voltage V_2B . If the voltage
V₂ exceeds the output voltage of the regulations amplifier, the logic is reset by the stop comparator
and consequently the output of pin 5 is switched to low potential. Further inputs for the logic stage
are the output for the start impulse generator with the stable reference potential V_ST and the
supply voltage motor.
Pin 3
The down divided primary voltage applied there stabilizes the overload point. In addition the logic is
disabled in the event of low voltage by comparison with the internal stable voltage V_V in the primary
voltage monitor block.
Pin 4
Ground
Pin 5
In the output stage the output signals produced by the logic are shifted to a level suitable for MOS-
power transistors.
Pin 6
From the supply voltage V₆ are derived a stable internal references V_REF and the switching
threshold V_6A , V_6E , V_{6 max} and V_{6 min} for the supply voltage monitor. All references values (V_R ,
V_2B , V_ST) are derived from V_REF . If V₆ > V_VE , the V_REF is switched on and switched off when V₆ <
V _6A . In addition, the logic is released only for V_{6 min} < V₆ < V_{6 max} .
Pin 7
The output of the overload amplifier is connected to pin 7. A load on this output causes a reduction
in maximal impulse duration. This function can be used to implement a soft start, when pin 7 is
connected to ground by a capacitor.
Semiconductor Group
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