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DS90UB928Q-Q1: I2C function could not work under low temp

Andy Jin
Intellectual 530 points

Part Number: DS90UB928Q-Q1

Hi Expert,

A project completed PV environment testing and found that the I2C of DS90UB928 cannot work in low-temperature environments. DS90UB981 cannot configure the I2C of DS90UB928, and the lock pin is always high, which rules out any hardware physical layer issues in the 981-928 link. We conducted the following verifications: 

1. The local MCU can read the address of the 928 device.

2. Comparing the configurations of 981 and 928 for normal and faulty parts, our software engineer replied that the printed configurations of both the normal and faulty parts are the same.

3. After removing the I2C series resistor between the MCU and 928, the host cannot read the 928 device via I2C. 

4. No abnormalities in power-on sequence.

5. Take the defective parts to the SMT factory for AOI and X-RAY inspection, all are OK. 

Thanks a lot! 

Andy