AD9238 wrong output

Hi eavtech,

Thanks for your interest in AD9238.

Since the SHARED_REF is enabled, can you confirm that REFT_A is externally shorted to REFT_B, and REFB_A to REFB_B?

Please check the measured voltages in REFT_A, REFB_A, REFT_B, and REFB_A. Can you provide schematics for better understanding of the issue?

Regards,

Xavier

Hi Jxav,

thank you for supporting. Yes, SHARED_REF is enabled (short to 3v3) and REFT_A is externally shorted to REFT_B, also REFB_A shorted to REFB_B.

What voltage should I expected see in REFT and REFB?

Sure, below is the printscreen of AD928 SCH used on my board.

Please, consider R31 = 0 R and not 4k7.

Hi eavtech,

The expected values of REFT and REFB are in the formulas in the attached figure. You can also browse the page 16 of the datasheet in the link AD9238 (Rev. C) (analog.com).

Based from the values of AVDD = 3.3V and VREF = 1V, it is expected that REFT is equal to 0.5(3.3V+1V) = 2.15V and REFB is equal to 0.5(3.3V-1V) = 1.15V with a span of 2Vpp.

Regards,

Xavier

Thank you for supporting. I've found the issue. There was a short circuit on board data connector and it causing a short on B channel pins bit 10 and bit 11 due by hand soldering.

Thank you for supporting. I've found the issue. There was a short circuit on board data connector and it causing a short on B channel pins bit 10 and bit 11 due by hand soldering.

Hi eavtech,

You are welcome. Always happy to help.

Regards,

Xavier