AMC1300B-Q1: Error from input filter

Kento Adachi

Part Number: AMC1300B-Q1
Other Parts Discussed in Thread: AMC3301

Hello experts,

My customer would like to use AMC1300B or AMC3301 for isolated current sensing with a shunt resistor, and he is worrying about the error from input filter.

As discussed 8.1.3 in the link below, input filter creates additional error for a non-isolated current sensing amplifier.

INAx181 Bidirectional,Low- and High-Side Voltage Output,Current-Sense Amplifiers datasheet (Rev. H)

So, could you answer the following questions?

1. Does input filter create additonal error also for an isolated current sense amplifier like AMC1300B or AMC3301?

2. If No.1 is yes, could you give me a equation to calculate the error like the equation below to estimate the error?

Regards,

Kento

over 1 year ago

+1 Alexander Smith over 1 year ago

TI__Guru 54442 points

Hi Adachi-san,

Yes, I would expect the input filter to introduce a small DC error to the input measurement, caused by the voltage drop across the filter resistors.

This would be dependent on the tolerance of the input filter resistors that are effectively in series with the differential input impedance of the device.

We generally recommend 10ohm, 10ohm, and 10nF input filter to these devices. The introduced error should be quite low when the differential input impedance of 22kOhm typ (see FAQ below on variation) is considered.

Please see this excel calculator for additional help with the calculation: https://www.ti.com/lit/zip/sbar020

FAQ: https://e2e.ti.com/support/amplifiers-group/amplifiers/f/amplifiers-forum/1023946/faq-does-ti-provide-guidance-on-input-resistance-variation-due-to-manufacturing-process-temperature-drift-and-lifetime-for-isolated-converters

0 Kento Adachi over 1 year ago in reply to Alexander Smith

TI__Expert 3315 points

Hello Alex,

Thanks for your kind reply.

I understood the introduced error should be quite low when we use 10ohm, 10ohm, and 10nF input filter. I'll recommend this configuration to my customer.

Regards,

Kento

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AMC1300B-Q1: Error from input filter