BQ76952: BQ7695204 Problem with ADCIN functionality on multipurpose pins

Hello Federico,

Do you mind sharing your schematic showing the connections at those pins? I see you have them configured for ADCIN functionality. Do you have any of your own pull-ups you are using for your thermistors?

Best Regards,
Alexis

Hello Alexis,

Thanks for replying! Here is a schematic of the connections at those pins:

The thermistors would be connected at CONN_TEMP_X

Hi Federico,

What voltage is being applied to the pins? The recommended range for ADCIN mode is between 0~1.8V:

If you have an EV2400 available, I suggest connecting it to the board to see if there is an issue with the readout.

Regards,

Max Verboncoeur

Hello Max,

Thanks for your reply. The voltage being applied to the pins is within the range you mentioned. I am using the same thermistors connected in the same manner to TS1, TS3, DCHG and DDSG. Only TS1 reads correctly the voltage, all the other ones are measuring 0 as ADCIN. If I measure with a multimeter, I can see around 1,6 V on those pins.

Unfortunately, I do not have an EV2400 available.

Hello Federico,

From what you have shared, it seems there is a chance the configuration you set didn’t apply/isn’t applying. Can you check the configuration settings for those pins again to see if they are properly set to ‘0xB3’?

Best Regards,
Alexis

Hello Alexis,

Sorry for the delay. I have checked and the configuration settings for those pins is correct. I read the same value I programmed: 0xB3.

Here is a summary of the current situation:

- TS1, TS3, DDSG and DCHG are all configured as ADCIN, with value 0xB3. I've checked after setting the configuration and the values are properly set in the memory.

- Voltage in REG18 is 1.83 [V]

- Connected to CONN_TEMP_X (see schematic in previous message) I have the same thermistors for each pin.

- Measuring with a multimeter, I can see all pins have the same reading, around 1.7 [V].

TS1 measures correctly the voltage in ADCIN functionality, but the other three pins measure 0 [V].

Best regards,

Federico

Hello Federico,

Thank you for double checking the configuration settings and summarizing the situation.

Are you reading the ADCIN voltages through the 0x70, 0x74, 0x78, and 0x7A commands as well or are you using different commands?

Do you mind sending a logic analyzer file of you sending the commands to read the voltages for TS1, TS3, DCHG, and DDSG?

Do you also have an EVM you are using?

Best Regards,
Alexis

Hello Alexis,

Yes, I am using the 0x70, 0x74, 0x78, and 0x7A commands to read the ADCIN voltages. I've also tried to read the DASTATUS 6 and 7 to get the raw counts, but they show the same issue: TS1 reports some counts but the other 3 show 0.

I've used a Digital Analyzer to monitor the SPI communication during these commands. Here is what I got for each of them:

(in case you are not familiar with WaveForms, each line represents an SPI transaction (CS high->low). Within it, each byte transaction is displayed in a pair ( x | y ), where x is the byte in the MOSI and y is the corresponding byte in the MISO)

0x70 (TS1, the one that measures correctly)

for example, here there are three pairs of bytes. The first pair is the command (0x70), the second one is the data (0xFF means I don't care since I am reading data in this case), and the third pair is the CRC.

0x74

0x78

0x7A

Unfortunately, I do not have an EVM available. I am using the BQ76952 in a customized board.

Best regards,

Federico

Hello Federico,

Do you mind sharing your entire schematic? If you would like to keep it private, you can DM it to me instead as well.

Best Regards,
Alexis

Hello Federico,

Thanks for sharing your schematic. Please give me some time to review it.

Do you mind sending me a logic analyzer file of you configuring TS3, DDSG, and DCHG as an ADCIN as well and then reading the RAM registers of the configurations? Are you also going into CONFIG_UPDATE mode to make these changes? 

Best Regards,
Alexis 

Hello Alexis,

Somehow, I was able to briefly read those pins correctly. I say briefly because the behavior seems to be erratic. The same code I use to program the registers does not yield the same results every time. So, seems that the problem here is a software one (which is some relief). Can you give me some advice on what is the correct procedure to put the device into config mode and write the ram registers with my desired configuration? Should I add delays between each ram register write operation? Is there a prefered order I should configure the registers? 

Have you noticed anything in the schematic that could be causing issues?

Best regards,

Federico

What drives the MISO pin? I've noticed that when I power up the system, the MISO line is always low and there is no voltage in REG1. I then send a reset subcommand to the device and after that, the SPI starts working fine and there is voltage in REG1. I then go into config mode, start writing the ram registers, but after I send the subcommand to exit config mode, the MISO is again kept low during SPI communications and there is no voltage in REG1.