Hello,

I have voltage divider circuit with diode clamping. Clamping voltage is 3.3V from Higher side and 0V from lower side. Without clamp voltage divider voltage is 8.48V. Problem is, after connecting Clamping diodes, voltage divider voltage is still to 8.48V only, its not clamping to 3.3V. I have attached circuit for your reference.

Elaborating more: I did simulation in TINA and in simulation it was clamped to 3.3V. In attached schematic i have shown 5V to 3V regulator which is i am using for 3.3V supply. 5V is derived from 24V and that is through switching buck converter and that 24V supply will vary from 8V to 32V. But right now i check this circuit with 24V only.

What will be problem? is there any way to solve this problem?

Regards,
Nandish Jasani.

 

What is your 3.3V source? Can it sink current? The clamp ti 3.3v depends on the 3.3V "source" being able to sink
current...

 

The 3.3V regulator can only pull up. It cannot pull down. Pul a load on the 3.3V. Use a 1k resistor as a 3.3V load.

 

What is your 3.3V source? Can it sink current? The clamp ti 3.3v depends on the 3.3V "source" being able to sink
current...

The positive voltage clamping scheme requires that the clamping voltage source be able to sink current. That is the whole concept of clamping a positive voltage.

 

What is your 3.3V source? Can it sink current? The clamp ti 3.3v depends on the 3.3V "source" being able to sink
current...

I have 3.3V series pass regulator with 5V input. But i have given 5V input through diode and therefore regulator cannot able to sink due to that diode. I put resistor parelle with clamping diodes and now its clamps properly. So thank you for your suggestion.

 

The 3.3V regulator can only pull up. It cannot pull down. Pul a load on the 3.3V. Use a 1k resistor as a 3.3V load.

I have 5 nos of circuit which is having clamping diodes. 3.3V with 1k load is not working rather i put 1k resistor parallel with clamping diode and its clamping properly now. Thank you.

 

The positive voltage clamping scheme requires that the clamping voltage source be able to sink current. That is the whole concept of clamping a positive voltage.

Yes true. As my 3.3V regulators input is 5V through Diode and because of that diode its not sinking current. I put resistor parellel to clamping diodes which will load to 3.3V and then Diode is not clamping voltage.

 

Yes true. As my 3.3V regulators input is 5V through Diode and because of that diode its not sinking current. I put resistor parellel to clamping diodes which will load to 3.3V and then Diode is not clamping voltage.

Are you doing this with real parts, or just trying to simulate it.

 

In reality, a large capacitor across the clamping voltage source will be able to absorb some spike energy, so that could be another option.