| SLA Status | Assignee | Support Status |
|---|---|---|
| ⚠ 2046 hours | Harshit.Analog WHong Bryan Mueller Ecoscull kevint SideshS BLorenz ChethanBM RakshithPrasadS mvrablic AbhishekP Cuyler |
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LTC6820
Production
The LTC6820 provides bidirectional SPI communications between two isolated devices through a single twisted-pair connection. Each LTC6820 encodes logic...
Datasheet
LTC6820 on Analog.com
I have two LTC6811 devices on the same PCB, sharing the same SPI bus with separate CS pins for each device. Please see my schematic and PCB layout below.
I configured the POL and PHA pins to high levels to match the LTC6811, and set MSTR to high as well. I first soldered one LTC6820 on the board, and after testing, the waveforms looked perfectly fine. What's puzzling is that when I soldered the second LTC6820, the waveforms became strange and erratic, making no sense.And I'll attach the wave form in the comments.
The test procedure is as follows: pull CS low, transmit the byte 0xAB (binary: 10101011) over SPI, wait for 1ms, then pull CS high. Both the SCK and CS waveforms at the SPI side look clean and correct （MOSI signal was in the picture）. During testing, I only connected one CS line, leaving the second CS pin floating. But the output seems just abnormal. This issue is consistently reproducible — I have four boards with the same design, and every single one exhibits this exact same problem.
