We are a US based Automotive company working on Electric Vehicle Chargers and Heaters.
- While testing boards with TI ADCs (ADS7142QDQCRQ1) at -20 Degree C or below, we find the I2C data from Channel 1 (AIN1) is the same on Channel 0 (AIN1).
- The I2C Data on the two channels are different and work fine above -20 Degree C.
- Channel 0 has High Voltage analog input data (HV_IN_Sense) as shown in the schematic below and he Channel 1 has the High Voltage Current analog input (HV_I_Sense).
- The High Voltage is connected by unit is not enabled therefore should not have any current showing. The current meter does not indicate any current but the CAN interface data shows current draw.
- With the unit is the cold chamber around -20 Degree C, we probed a number of input and output pins on components up to pin 4 of U15 and it shows 300mV indicating zero current flow as per the component datasheet. The VCC levels on these ICs were within the normal range. The HV_I_Sense signal measured around 300mV with the element disabled indicating the current is 0A. When the High Voltage line was increased, the HV_I_Sense current values in the CAN interface showed increase in this value. The measured value pin 4 of U15 ADC stayed within 300mV. The schematic below shows points tested. Table 1 below shows data collected.
- We targeted U15 and sprayed with cold spray and were able to duplicate the problem.