TCA505BG Datasheet, PDF (8/18 Pages) Siemens Semiconductor Group – IC for Inductive Proximity Switches with Short-Circuit Protection

TCA 505 BG
Pin 14; B
This pin serves for limiting the base voltage of the internal output-stage transistors. If this pin
is connected to VREF for example, it is possible to set a constant output current (IQ = VREF /
external resistor) that is independent of the supply voltage by means of an external resistor
across Q2 (or Q4) and ground (watch out for power dissipation!).
Pin 15; CD
A capacitor on this pin delays the activation of the outputs after the supply voltage is applied
(turn-ON delay). In this way erroneous pulses are prevented on the output during buildup of
the oscillator.
If VS falls to less than 3.6 to 4 V, the outputs are not inhibited until after a turn-OFF delay time,
this also being determined by CD. In this way the delayed turn-ON operation described above
is suppressed if there are just short glitches (voltage dips) on VS. This is of particular advantage
for large core diameters, because in such cases a relativity long turn-ON delay has to be
selected and the delayed twin-on operation would otherwise be activated each time there was
a brief voltage dip.
The capacitor CD also sets the turn-off delay and the pause duration in short-circuit operation.
The sample / pause ratio is approx. 1:200 (see pin SC).
If these functions can be dispensed with, CD can remain open.
Pin 16; VT
If this pin is connected to + VS, the supply voltage of the IC (when used as a two-wire proximity
switch) can be generated by switching the outputs. The quiescent current can then be kept low.
This mode is primarily suitable for AC switches with power supply by phase-control.
The switching of the outputs is made in a VS range of 6 to 8 V. At 8 V the outputs are turned
on, until VS falls to 6 V. At 6 V the outputs are inhibited, until VS again reaches 8 V. In this mode
VS should not exceed 14 V or fall below 4 V.
Semiconductor Group
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