I have three prototype custom PCBs which each have a TPS65988DHRSHR chip. On each board, I have the ADCIN2 voltage divider setup like so:
On two of my three boards, the chip correctly responds to an I2C scan on I2C1 for the addresses 0x23 and 0x27. However, on the third board, it answers to 0x20 and 0x24.
I probed the ADCIN2 pin on each board, and they all show a voltage around 3.2 V. What else could cause this one chip to respond to the wrong address?
Best regards,
Cory
LDO_3V3 is decoupled with a 10 µF capacitor per the datasheet:
If the ADC input does require a circuit that can sink current, that could explain the issue I'm facing. I'm using just a 100 kΩ pull-up with no pull down. I got that value directly from section 1.3.1 of the Hardware Design Guideline for TPS65987 and TPS65988 USB Power Delivery Controllers app note, so TI may want to update that if it is indeed the issue.
Best regards,
Cory
Hi Taylor,
Per Table 1.2:
Recommends R1 = 100k, no recommendation for R2 (no-pop). Also says short ADCIN2 to LDO_3V3 which isn't really true since it's "shorted" through a 100k pull-up but that does infer a 0/100 divider which is implemented with only a pull-up resistor (R1), and no R2.
