AMC1311-Q1: Isolated voltage measurement for high voltage applications

Duman Demir

Part Number: AMC1311-Q1

I want to measure output voltage of a DC/DC converter of 3.5kV for input to ADC of microcontroller. Could I use AMC1311-Q1 for this purpose? This IC requires 0-2V as input, so I have to use large voltage divider to scale the high voltage of 3.5kV to 2V. Would there be any problem in doing this? Are there other options available for isolated voltage sensing of such high voltages? Thank you.

over 3 years ago

0 kai klaas69 over 3 years ago

Guru 140200 points

Hi Duman,

take care, the "maximum-rated DC isolation voltage" of AMC1311-Q1 is only 2121V.

Kai

0 Duman Demir over 3 years ago in reply to kai klaas69

Prodigy 132 points

Thanks for your reply. Could you please suggest a relevant device that can withstand the ratings?

+1 Alexander Smith over 3 years ago in reply to Duman Demir

TI__Mastermind 47595 points

Hi Duman,

Can you tell me a little more about your application? What is this DC/DC converter used for?

What are the absolute magnitudes of GND1 and GND2? Both ideally and during failure events?

As Kai said, the maximum-rated DC isolation working voltage is 2.1kV. If there is an issue on the high side where the resistors in the divider are shorted and 3.5kV is connected to GND1 of the AMC1311-Q1 for an extended period of time, there could be an isolation failure, resulting in an open circuit. Please take a look at figure 4 in the datasheet, it shows the life expectancy degradation of the capacitive isolation barrier for different working voltages.

This document details failure for isolation products from TI: https://www.ti.com/lit/wp/slyy081a/slyy081a.pdf

I will consult with my team about your application.

0 kai klaas69 over 3 years ago in reply to Duman Demir

Guru 140200 points

Hi Duman,

another option is to do some analog to digital conversion of 3.5kV voltage (voltage divider -> ADC) directly at the high voltage side and to transmit the digital output signals of ADC (data, clock, strobe, or whatsoever) by the help of high voltage optocouplers.

Even a self-built optocoupler with a simple LED driver at the high voltage side, a TIA on the low voltage side and an inch of air between could be used

Kai

0 Duman Demir over 2 years ago in reply to Alexander Smith

Prodigy 132 points

Thank you Alexander,

I understand your point but what if we take the risk, since resistors are not much vulnerable to short circuit on failure. In the extreme case the IC might be damaged so we can replace the IC as this is not a very demanding application, just a capstone design project in power electronics course.

Best Regards,

Duman

0 kai klaas69 over 2 years ago in reply to Duman Demir

Guru 140200 points

Hi Duman,

if the IC gets damaged you might lose safety isolation

Kai

0 Alexander Smith over 2 years ago in reply to kai klaas69

TI__Mastermind 47595 points

Hi Duman,

I see. Be careful!

Here's a document on failure-modes in isolators. Our products are designed to fail open, so there should be no concern for high voltage on the low side in the event of failure: https://www.ti.com/lit/wp/slyy081a/slyy081a.pdf

But as always, please be very careful and adhere to all safety rules.

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AMC1311-Q1: Isolated voltage measurement for high voltage applications