AMC1100EVM: High Voltage Side GND Connection

Manmohan Vishwakarma

Prodigy 130 points

Part Number: AMC1100EVM

Hello,

current measurement circuit:

voltage measurement circuit

I am trying to build the above two circuits...but one thing is very confusing to me

1. in case of current measurement, why GND of high voltage side is connected to sense resistor terminal ?

2. in case of voltage measurement, why GND of high voltage side is connected to neutral of high voltage ?

over 4 years ago

0 Alexander Smith over 4 years ago

TI__Mastermind 47595 points

Hi Manmohan,

This is the ensure that the input voltage stays within the +/-250mV input range of the device. With the negative input connected to the same node that the high voltage side GND is connected to, the positive input is able to swing +/-250mV, from the positive to negative full-scale range, with respect to this node. This ensures that the voltage on the positive input pin does not drift with regards to the GND node which could lead to clipping the output or damaging the device.

0 Manmohan Vishwakarma over 4 years ago in reply to Alexander Smith

Prodigy 130 points

thanks for your reply,

but when positive cycle comes the GND of high voltage side would get positive voltage from (0- 230V),

0 Alexander Smith over 4 years ago in reply to Manmohan Vishwakarma

TI__Mastermind 47595 points

Hi Manmohan,

This is ok. Notice that the high side power supply is also referenced to USH. This means that the GND = VINN = the high voltage GND. VINP = +/-250mV with respect to the high voltage GND, and VDD1 = +5V with respect to the high side ground.

There can be several hundreds of volts between GND1 and GND2, this is known as the isolation working voltage.

This video may help: https://training.ti.com/ti-precision-labs-isolation-introduction-isolated-amplifiers

0 Manmohan Vishwakarma over 4 years ago in reply to Alexander Smith

Prodigy 130 points

Hi alex ,

okay i got it.

one more thing can i use LM7805 and LM7905 to generate positive and negative supply for high voltage side of amplifier...?

i have made a rough schematic...i have not designated parts..

0 Alexander Smith over 4 years ago in reply to Manmohan Vishwakarma

TI__Mastermind 47595 points

Hi Manmohan,

I am not familiar with those parts, so you may want to ask on their E2E forum to be sure. But I do not think so since they do not look isolated to me. You may want to adopt a similar implementation to the one shown on the EVM with the isolated transformer providing power to the high side of the device.

Amplifiers

Amplifiers forum

AMC1100EVM: High Voltage Side GND Connection