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sinara-hw / Fast_Servo

High speed low latency servo (Stabilizer-compatible) module
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DAC Output Discrepency between Channels #62

Open linuswck opened 1 week ago

linuswck commented 1 week ago

Description

DAC Output 0 and DAC Output 1 should have the same output voltage range but it is not. I suspect there is something wrong with the DAC AFE Stage.

The prototype board we received has the ADA4930-2YCPZ used as a differential to single end converter but the differential to single end operation is not specified in the OpAmp datasheet. image

Point of Measurement

Measurements are taken with Fluke 87V at the AD9117-2 output resistors and DAC SMA Output Port. image image

Measurement Result

AD9117-2 Output DAC SMA Output Unsigned Data
Channel 0 -427.8mV -157mV 0x0000
Channel 1 -426.1mV -163mV 0x0000
Channel 0 429.2mV 258mV 0x3FFF
Channel 1 424.3mV 323mV 0x3FFF

Note1: AD9117-2 DAC is set to receive unsigned data before the measurements are taken. Note2: This behavior also exists on another unmodified, freshly opened fast servo board.

Edited: Add Note2.

gkasprow commented 1 week ago

Every opamp is specified for diff to SE conversion.