TMCS1100EVM: TMCS1100A4QDR

Hi Holly,

would you please check the schematics i sent you, i have purchased the EVM and i am duplicating my schematics with an external load feeding EVM negative voltage. it does not seem to work for me.  would you please let me know what i am missing.  it is for a production board which i need to release in a week.

thanks,

Habib

Habib,

Why do you have a pull down resistor (R956) on the Vout?

NU means not populated.  that is not the issue, the issue is how i connect the negative voltage to the input of the TMCS1100.  below is how i am connecting the negative voltage to the input of TMCS1100.

should i be sensing it on the ground node instead of the negative voltage.  those off pages you are seeing are connected together.

thanks,

Habib

Ok, I see the NU now.

When you say the device is not working can you describe the failure? Is there no output, is the output not what you expect, it it noisy, etc.

Please let me know.

-Holly

the EVM works perfectly for the positive voltages.  the issue is with negative voltages.  the power supply negative terminal cannot connect to the T1A and T2A of the TMCS1100 EVM.  the power supply output sees it as short.  when i have the positive terminal of the power supply connected to the EMV T1A and T2A, it works fine and i see 50mV per amp increase.  do you think i have connected the negative ports correctly as i am showing in the schematics above?  i was thinking maybe below schematic is the correct terminology to measure negative voltages.  if you have a design example to measure negative voltages current, it can help too.  

the issue is how to connect the negative voltage to your EVM to measure the current.  i have no issue with the positive voltages.

So you are using the EVM?

I am not understanding why the power supply is unable to apply a negative voltage to the EVM terminals. 

Based on your schematic though the second option you have proposed makes the most sense as there will not be current on the lower side of those capacitors since they are just there to store charge and then release it. The current will be seen on the upper line like in your second schematic.

Our device has internal voltage isolation so you should be able to apply a positive or negative voltage across the input terminals in any fashion you choose and it will work.

BR,

Holly

Hi Holly,

thanks for your response, but i need to make sure if my schematics is correct.  is there any design example for this chip to measure negative voltages.  and i am also not sure why the EVM ports do not accept the negative voltages, i am using an external power supply to feed the EVM at T1A and T2A ports and my supply senses short as soon as i connect the negative port to it..

thanks,

Habib

Habib,

I do not see anything wrong with your schematic. We do not have any reference designs specifically for measuring with a negative voltage due to the fact that it is not different from measuring where there is a positive voltage. There is an insulation barrier as shown in the block diagram below which means the voltage seen on the input pins does not affect the rest of the circuitry. The ±600V limit is due to the limitations of that barrier.

The schematic you are showing is different from the board you are testing and having issues with?

You are right, you need to put the sensor here in order to measure the current you want.

Best,

Holly

Hi Holly,

thanks, yes. i think we should put it on the zero which is a higher voltage.  i will duplicate it with your EVM and see if that works and will get back to you.

thanks,

Habib