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BQ24773EVM-540: Power-up and initial checks & 'Device ACK error' with EV2400 and BQstudio

Ved Soni
Intellectual 530 points
Part Number: BQ24773EVM-540
Other Parts Discussed in Thread: BQ24773, BQSTUDIO, EV2400

I'm setting up a BQ24773EVM-540 as indicated in its datasheet. The charger power supply is at 19.5V, I2C power supply is at 3.3V and the I2C wires are connected properly to port2 of EV2400. Also, TP11 port on the BQ24773 EVM is connected to ground for 1 cell. However, I'm getting incorrect readings of voltage for the checks which are mentioned in the datasheet. Following are the readings:

Measurement between Expected Value Actual Value
TP11 and GND <0.3V <0.3V
TP7 and GND 2.6V -0.452V
D5 LED LIT LIT
TP15 and GND 5.5V -0.024V
BAT and GND 1V(+-1.1V) -0.27V
SYS and GND 4.4V -0.344V

I checked the power supply voltages on EVM terminals with a DMM, and they are what I had set them to earlier as specified in the datasheet.

Also, upon running BQstudio and trying to read registers, it is showing a 'Device ACK error'. I had done this process yesterday, but it had given me all the correct voltages and 'Device ACK OK' status on BQstudio. What might be the problem now?

Eventually, I'll be using this EVM and read its registers using LabVIEW with a NI USB-8451, which is an I2C interface. I tried using that interface instead of the EV2400 and I'm getting a similar error of 'device acknowledgement failed' in LabVIEW.

  • 0
    TI__Expert 5330 points
    Hello,

    Test Point 15 is the REGN LDO output of the device. If this is not generating a valid voltage (5.0-6.0V) then the device is not being powered. We need to determine why REGN LDO is inactive before attempting to communicate over I2C.

    Test Point 7 is the ACDET. It must be above 0.6V for REGN LDO to be active. The ACDET input is a resistor-divider from VIN. I would not expect it to be negative (-0.45V) unless VIN is negative. Can you double-check that the power supply at J1 is attached correctly? With 20V applied at VIN, the TP7 should be ~2.6V.

    Regards,
    Steve
  • 0 in reply to Steve Preissig
    Intellectual 530 points
    Thanks for the reply! I checked the input screw terminals and the frayed wires seemed to be the problem. I replaced them and now its working fine! Thanks!