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AMC1305M25: RC Filter and Input Offset

Shotaro Sakai
Expert 3500 points
Part Number: AMC1305M25


Hello team,

I have question for datasheet of AMC1305M25 and design with it.

Can you provide me your comment?

1. Does Eo (Offset error) mean the input offset voltage?
* Input offset voltage: Actual value of output after digital signal processing at input 0 V (VIN + = VIN- = 0 V)

2. The AMC1305M does not require an input RC filter for noise suppression of the AD converter, but the EVM has an input RC filter.

Under what conditions do you need an RC filter?

Best regards,

Shotaro

  • 0
    TI__Guru 56532 points

    Hi Sakai-san,

    1. Yes

    2. The AMC1305M is an isolated modulator and does require an RC filter on the input to prevent high frequency signals from aliasing into the sample band of the ADC. We typically recommend a differential RC filter with 10ohm, 10ohm and 10nF. 

  • 0 in reply to Alexander Smith
    TI__Expert 3500 points

    Hello Smith-san,

    Thank you for your reply.

    I know an insolated modulator requires an RC filter. But the EVM user guide mentions the "fc filter is not required in every application".

    What application/input signal fits this case? 

    The application I am discussing is current sensing for AC servo amp. 

    Best regards,

    Shotaro

  • 0 in reply to Shotaro Sakai
    TI__Guru 56532 points

    Hi Sakai-san,

    Ah I see, it would be system specific where there are not high frequency noise signals in the system that may alias into the sample band. This would not apply to specific end equipment's as the system noise will be unique to each system.