How to use tactile switch as a ON-OFF button

[tapasxplore]

Hi,

I am planning to use tactile switch to turn ON & OFF the circuit, can any one of you suggest IC for the same. I am not using any micro-controller in my circuit. I am thinking of using TPS3422 single channel push button controller, but after reading the datasheet, we can see there are two ports RST(invert) and Reset in the TPS3422, so how we can use TPS3422 without controller.

Regards,
Tapas

[ebclr]

or

[CJay]

[Bushougoma]

You can use an SR latch it just requires a single quad NAND gate IC (tie the 2 unused NAND gates inputs directly to power or ground). Pull the S input low with the R input high and the Q output will go high. Pull the R input low with the S input high and the Q output will go low. High = output connected to VCC or Logic 1. Low= output connected to GND or Logic 0. Note that NAND gates can't source or sink much current (25 mA max) for the TI SN74HC00 so be sure to check the datasheet. Driving larger loads will require an external transistor or MOSFET.



The SR latch follows the following truth table:

----------
S  R   Q
----------
0  0   not allowed
0  1   1
1  0   0
1  1   no change

You could also use a 555 timer in bistable mode you can use two tactile switches one for ON and another for OFF (not shown) or a single tactile switch for ON and OFF as shown in this schematic. The 555 is capable of sourcing or sinking 200 mA max so you can drive larger loads without an external transistor or MOSFET.