Thanks, Rob Above are the schematics I used. Default settings are used for the application. I didn't use SPI to change new settings. I checked the pins: PD=0, INT/EXT=3.3V, RefT=1.945V, RefB =0.945V. Vcm=1.45V for 16 boards, Vcm=0.36V for 2 boards, Vcm=0.53V for 1 board, Vcm=0.62V for 1 board. 2 boards can turn out to be normal using a power cycle, but the other 2 can't. I can capture the correct data from the chip, the problem is the Vcm output is not correct and can not be used for external Opam for those abnormal boards(1 out of 5). (The layout was already designed to use it.) After I disconnected the Vcm output and added a voltage ladder to create 1.45V for external Opam, the boards worked fine. Just the problem confused me for a while.
↧