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AD9280 REF range under AD876 mode


Hi,

A customer wants to use AD9280 under AD876 mode for the replacement.

  • REFTF - REFTS: short
  • REFBF - REFBS: short
  • MODE = AGND

When customer applied 1.5V to REFTF and GND to REFBF, he found a mid point of 2V.

that means that the mid point should be 0.75V (1.5/2 V), but he found that the MLB was changed when 2V is applied from Vin. The parts works as if the VREF FS would be 4V.

I have 2 questions;

1. Is the behavior my customer has seen the normal?

2. I think AD9280 seems to have a character like Fig 17 on AD876 DS. Does it have such a limitation?

Could you give me your advice?

Best regards,

Akihiko Hata

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  • Hi Akihiko,

    The AD876-8 Mode of operation is enabled by configuring the AD9280 as shown in datasheet Table 1 and Figure 30. The pin connections listed in your inquiry seem correct with the exception of the REFSENSE pin which also needs to be tied to AVDD. The state of the REFSENSE pin is not referenced in your inquiry. Would it be possible for you to post/attach the AD9280 portion of your schematic so that I can review it?

    Best Regards,

    TonyM

Reply
  • Hi Akihiko,

    The AD876-8 Mode of operation is enabled by configuring the AD9280 as shown in datasheet Table 1 and Figure 30. The pin connections listed in your inquiry seem correct with the exception of the REFSENSE pin which also needs to be tied to AVDD. The state of the REFSENSE pin is not referenced in your inquiry. Would it be possible for you to post/attach the AD9280 portion of your schematic so that I can review it?

    Best Regards,

    TonyM

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