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AD5293 digital potentiometer wiper position not changing in response to programming

Question asked by Anoop on Apr 23, 2012
Latest reply on Jul 23, 2014 by pavanbabut

Hi,

Problem I face is, no matter what i try to program, the digital pot output remains at midscale. I have first written 1806H data, then 07FFH data, which should ideally set the pot to full scale, but it is not responding. I have captured the the SPI signals are all verified to be proper as per the timing diagram given, and RESET pin is maintained high. The captured interface signal waveforms probed at IC pins and the schematic are attached, and sclk frequency used=15Mhz. But no matter what data I program, pot output is always at midcode. Even the RDY pin is not toggling, when i probed it. I even replaced the pot with a fresh one but still the problem persists. To meet the minimum sync high time=400ns, a delay of 1us is used, and RDY pin is left unused.

 

Details on attached files:

1.Writing 1806H.JPG: Captured waveform of writing 1806H data to select normal mode and enable wiper update via digital interface.

BLUE signal: SYNC

GREEN signal: SCLK

VIOLET signal: SDIN

 

2.Writing 07FFH.JPG: Captured waveform of writing 1806H data to select normal mode and enable wiper update via digital interface.

BLUE signal: SYNC

GREEN signal: SCLK

VIOLET signal: SDIN

 

3.Schematic.JPG:

VDD=15V, VSS=-15V

VLOGIC=3.3V

RESET driven to 3.3V

Digital interface signals are driven by an FPGA

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