AMC1303M2510: spikes in measurements with the AMC1303M2510

Martin Fertmann

Part Number: AMC1303M2510

Hi,

We have a problem with the AMC1303M2510DWV.

The DOUT of the Delta-Sigma sometimes is 1 (high) for a short time (about 0.2ms), but the input signal is significantly smaller than 250mV. So we get spikes in our measurements.

Is it possible that this is because of problems with the AVDD (EMI)?

We have 100nF + 10µF verry close to the AMC1303M2510DWV, but other ICs use these voltage level too.

Many thanks in advanced.

over 3 years ago

0 Alexander Smith over 3 years ago

TI__Guru 51351 points

Hi Martin,

You're using the version of the AMC1303 with a 10MHz internal clock and you're seeing a high 1's density for 0.2ms, this would be roughly 2000 samples of 1's. Am I understanding correctly?

This could be due to an issue with AVDD or perhaps the CMTI specification of the device is being violated if you are rapidly switching at high voltage. Any additional details you can provide on these two points would help us diagnose the issue.

What OSR are you using in your SDFM?

Can you provide a schematic and/or layout?

0 Martin Fertmann over 3 years ago in reply to Alexander Smith

Prodigy 40 points

Hi,

thank you for your fast answer.

The layout looks like this:

The µC response time is 9,6µs and the filter output period 3,2µs (@ 10MHZ)

The spike looks like the blue upper signal:

0 Martin Fertmann over 3 years ago in reply to Martin Fertmann

Prodigy 40 points

0 Alexander Smith over 3 years ago in reply to Martin Fertmann

TI__Guru 51351 points

Hi Martin,

I do not see where either of your inputs are referred to GND1 of the device. There may be a common-mode input voltage violation (VCM on page 7). If you have a high voltage probe, can you verify if the absolute input voltages are exceeding the specified operating range?

Depending on how your 3.3V VDD1 supply is derived, tying one of the inputs to GND1 may help solve the issue.

CMTI is another possibility. Is what you are measuring switching at high frequency and/or slew rate?

0 Martin Fertmann over 3 years ago in reply to Alexander Smith

Prodigy 40 points

Hi Alexander,

here is a bigger cutout of the circuit.

0 Martin Fertmann over 3 years ago in reply to Martin Fertmann

Prodigy 40 points

I measure a high DC voltage at a switching konverter with about 25 kHz

0 Alexander Smith over 3 years ago in reply to Martin Fertmann

TI__Guru 51351 points

Hi Martin,

I see that R617 is labeled as "open" is this up to date?

If so can you please populate with a 0ohm resistor and confirm that the issue persists?

It may also be a VCM issue as the absolute limit of the input voltages may exceed the specified range. Do you have the ability to supply 5V instead of 3.3V to VDD1?

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AMC1303M2510: spikes in measurements with the AMC1303M2510