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AD5535B channel-to-channel offsets and calibration?

Question asked by mwhitson on Jul 26, 2017
Latest reply on Jul 27, 2017 by rrosario

Working on a custom board with several AD5535B's driving an array of devices for testing, driving the chip in the 0-50V range (VREF=1.0 V).  With the chip in power-on-reset state and all channels zeroed, I observe a steady-state DC output voltage of around 100-300 mV, apparently randomly depending on channel.  This offset seems to be preserved as voltage outputs are commanded on the DAC channels.  I see this both on my own board and on the AD5535B eval board with jumpers set according to UG-730 Fig 2.

 

Is this an expected level of channel-to-channel offset?  I'd assume the behavior of the eval board indicates it's inherent to this high-voltage chip, but it's always possible I've misconfigured the eval board as well as my custom one.

 

If it's normal, any recommendations for calibration procedures beyond compiling a brute-force lookup table?  Should I be able to use a linear correction with offset to scale my inputs, or will I need to compute a nonlinear curve fit?  This is being driven via SPI from a Xilinx Zynq-7000 with SPI cores in the FPGA fabric; if there are any drop-in logic cores that could be of assistance I'd love to know about them.

 

If this isn't normal, any recommendations for tracking down the root cause?

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