AD7657-1: How to improve noise of CH1?

Hello,

Our customer has a trouble about AD7657-1. Only CH 1 is noisy as compared to other CHs. Do you have any idea about causes ans/or countermeasures?

Best regards,

Akira

Parents
  • Hi Niall-san,

    Yes, I also think it is layput proble. But we confirmed it was different noise level between AD7657 and AD7657-1. Could you please look at the attached file?  They are output wave form of AD7657 and AD7657-1. We can see CH1 of AD7657-1 is noisier than AD7657. They measured same board. Different points are only decoupling capacitor for Vcc lines. 1uF + 10uF are for AD7657. 1uF is for AD7657-1. 1uF is recommended capacitor value. Howeve, we got different result about the noise level. Therefore, our customer concerned that AD7657-1 is sensitive than AD7657 about layout. So, we would like to know that AD7657-1 is sensitive than AD7657 about layout or not. If it is correct, I'll recommend to the customer to use AD7657 instead of AD7657-1. The customer has no time for improve the layout of the board.

    Can you send me a gerber data of evaluation board of AD7657 and AD7657-1? The customer would like to use the gerber data as a reference.

    And, when we use two or three ADC on the board, how ahold we connet analog GND and digital GND? Should we connect analog GND and digital GND of ADC only one point on the board or connect analog GND and digital GND of ADC by each ADC around the ADC?

    Best regards,

    Akira

Reply
  • Hi Niall-san,

    Yes, I also think it is layput proble. But we confirmed it was different noise level between AD7657 and AD7657-1. Could you please look at the attached file?  They are output wave form of AD7657 and AD7657-1. We can see CH1 of AD7657-1 is noisier than AD7657. They measured same board. Different points are only decoupling capacitor for Vcc lines. 1uF + 10uF are for AD7657. 1uF is for AD7657-1. 1uF is recommended capacitor value. Howeve, we got different result about the noise level. Therefore, our customer concerned that AD7657-1 is sensitive than AD7657 about layout. So, we would like to know that AD7657-1 is sensitive than AD7657 about layout or not. If it is correct, I'll recommend to the customer to use AD7657 instead of AD7657-1. The customer has no time for improve the layout of the board.

    Can you send me a gerber data of evaluation board of AD7657 and AD7657-1? The customer would like to use the gerber data as a reference.

    And, when we use two or three ADC on the board, how ahold we connet analog GND and digital GND? Should we connect analog GND and digital GND of ADC only one point on the board or connect analog GND and digital GND of ADC by each ADC around the ADC?

    Best regards,

    Akira

Children
No Data