AMC1100 Secondary Biasing

Goutham Kuniyil

Prodigy 200 points

Other Parts Discussed in Thread: AMC1100

I made a hardware for AC Voltage sensing based on your application note(SLAA552).

Primary and Secondary is biased with separate 5V DC sources.

The secondary nominal output voltage(center voltage) supposed to be 2.5V but when i tested it is 0.

Kindly help me on this.

Regards

Goutham

over 9 years ago

0 Jose Duenas over 9 years ago

TI__Genius 9975 points

Hello Goutham,

Could you please post a schematic of your circuit and label the nodes where CH1 and CH2 of the oscilloscope where connected?

Best regards,

Jose

0 Goutham Kuniyil over 9 years ago in reply to Jose Duenas

Prodigy 200 points

Hi Jose

Channel 1 is connected to AMC differential out and channel 2 is connected to a step down transformer output(230/12V).

Please find the schematic

Regards

Goutham

0 Jose Duenas over 9 years ago in reply to Goutham Kuniyil

TI__Genius 9975 points

Hello Goutham,

It is hard to read the details in the schematic but it seems that you have two test points in the output of the AMC1100. I imagine you connected the oscilloscope probe on channel 1 between such test points (corresponding to pins 6 and 7 of the AMC1100). If that is the case, then your oscilloscope capture makes perfect sense because the AMC1100 output is differential.

If you would like to see the DC common mode in the AMC1100 output then you need to connect the ground clip of CH1 to pin 5 of the AMC1100 and the probe tip to either pin 6 or 7.

Best regards,

Jose

0 Goutham Kuniyil over 9 years ago in reply to Jose Duenas

Prodigy 200 points

Hi Jose

Thanks. You are correct. I measured between Differential Out.

One more thing secondary i can bias with 5V right? or only 3.3V

Regards

Goutham

0 Jose Duenas over 9 years ago in reply to Goutham Kuniyil

TI__Genius 9975 points

Hello Goutham,

VDD2 can be supplied with a voltage between 2.7 V and 5.5V.

Best,

Jose

0 Goutham Kuniyil over 9 years ago in reply to Jose Duenas

Prodigy 200 points

Thanks Jose

Regards

Goutham

0 Goutham Kuniyil over 9 years ago in reply to Jose Duenas

Prodigy 200 points

Hi Jose

Since i'm taking output at VOUTP and GND2, how will effect on gain?

If input is 50mV output between VOUTP and VOUTN would be 400mV.

How will be across VOUTP and GND2?

Regards

Goutham

0 Jose Duenas over 9 years ago in reply to Goutham Kuniyil

TI__Genius 9975 points

Hello Goutham,

The output of the AMC1100 with respect to GND2 is given by the following equations where Vcm is the common mode output voltage and depends on the supply you are using.

For the case you mention and assuming VDD2 is 5 V, the voltage between VOUTP and GND2 for a 50 mV input is 2.55 V + 0.2 V = 2.75 V.

Best regards,

Jose

0 Goutham Kuniyil over 9 years ago in reply to Jose Duenas

Prodigy 200 points

Hi Jose

Thank you very much for your support.

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AMC1100 Secondary Biasing