CD4070B: went up in smokes

Bram Van Nieuwenhuyze

Part Number: CD4070B

I am building an edge detection. The cyan lines are 12V incomming signals. those signals go strait to the a pin. the b pin gets them delayed using the RC delay. when testing it the ic it did nothing when connecting the vdd and vss. when i set signal to an input it went up in smokes. what could be wrong?

3 months ago

0 Ian Graham 3 months ago

TI__Genius 17731 points

Hi Bram,

1. What's your VCC? This part does not have overvoltage tolerant inputs, so if your VCC is less than 12V, then the input signals could be getting shorted to VCC.

2. This part is not rated to drive a large capacitance. Consider than when the voltage switches on the device, the output pin is effectively shorted while charging/discharging the capacitor. This could pull current far in access to the 10mA limit of the part.

0 Bram Van Nieuwenhuyze 3 months ago in reply to Ian Graham

Prodigy 10 points

1. the Vcc is 12V DC. I remeasured it and got a correct reading of 12V
2. Is there a way I could fix this?

0 Ian Graham 3 months ago in reply to Bram Van Nieuwenhuyze

TI__Genius 17731 points

I recommend removing the capacitor or moving the 4.7 kOhm resistor to between the device and the capacitor.

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CD4070B: went up in smokes