BQ76942: OTP of the BQ76942 using the EV2400

Hello Jim,

Can you measure at the BAT pin to make sure the device is seeing a voltage between 10 to 12V? Also, is the device in FULLACCESS Mode? We usually recommend users to follow this guide for OTP programming: BQ769x2 Calibration and OTP Programming Guide.

Best Regards,
Alexis

Alexis, the BAT pin had a voltage of 11.54 volts and the VC10 was at 12.04 volts.  I set the Security Settings to 0x00.  This should be FULL ACCESS, no?

Jim

Alexis, I followed section 3.1.  When it came to step 6, most of the registers came back highlighted in Red.  Any help would be appreciated.

Jim

Hello Jim,

Can you check the SEC0/SEC1 bits to see if the device is in FULL ACCESS? This is shown in Table 6-2. 0x12 Battery Status() Bit Definitions (continued) in the BQ76942 Technical Reference Manual. A picture is shown below as well. The security settings do not really inform us if the part is in FULL ACCESS mode or not. 


Another factor that could affect OTP, is if the device is in the right temperature range. Your battery thermistor started reading -273.2. Is this because it’s floating? If so, you might want to pull it down with a 10k resistor.

When you said you followed up to Step 6 and ‘most of the registers came back highlighted in red’, could you share a picture of what you meant?

Best Regards,
Alexis

Hi Alexis,  

When I have the battery connected, and all the cell inputs have their proper voltages, SEC1, SEC0 = 0,1.

 When I replace the battery with a power supply at +12 volts for the stack, I get the same SEC1, SEC0 = 0,1   For this test I did shut down BQStudio and restarted it after the 12 volts was applied.  

As I noted above when the battery is connected the thermocouples are operating correctly.  When the +12-volt power supply is connected the Thermocouples give the -273.2 reading.  There is no reason I can see why the thermocouples stopped working.

I ran through the OTP programming (section 3.1) again.  When I have the battery connected, I get to step 8 when I see the OTPB pin is high.  This makes sense since we have BAT at too high a voltage.

Then I ran through the OTP programming using the +12-volt power supply to replace the battery.  This time I made it to step 5 where I was supposed to exit the Config_Update mode.  When pressing the EXIT_CFGUPDATE button, no command was sent (from the Transaction Log) and all the Registers (after pressing the register tab) were grayed out.  So, it looks like I am losing communication with the BQ76942.  This doesn't happen when I have the battery connected.

Note that I am using the latest versions of BQStudio and the EV2400 Firmware.  So, all software is up to date.

Any suggestions?

Thanks,

Jim

Hello Jim,

Thank you for going more in detail regarding your steps there. When you say thermocouples, do you mean TS1? I agree that it is weird that the thermistor suddenly reads -273.2, however, because the OTPB bit indicates whether or not voltage and temperature conditions are valid for OTP programming, and your voltage looks correct, we want to make sure the temperature condition is not the issue.

Can you still communicate normally with the device and EV2400? Also, can you share oscilloscope waveforms of your thermistor and share your .gg file or a picture of bqStudio if any further errors pop up?

Best Regards,
Alexis

Hi Alexis,

We are using 10Kohm Thermistors (sorry I mistakenly typed thermocouples in my previous post).  We use 4 Thermistors for cell monitoring.  We have the BQ76943 configured to read these thermistors on these pins:

TS1, TS3, DCHG, & CFETOFF

For this testing I just have the thermistors hanging in the air, so they are reading room temp.

Below are screen shots of BQStudio registers.  The first one is using the battery voltage and writing the gg file values into the IC and running a scan.  This operates correctly.

The one to the right (grayed out values) is when I connected a 12-volt supply to the stack and wrote the gg file values into the IC and ran a scan.  It stops communicating.  Note the program seemed to be operating correctly until I issued the write command.

The last one is the 12-volt supply connection before loading the gg file and running a scan to show proper operation.

So, it looks like the program is crashing at the lower voltage (12-volt) when trying to update the registers......   It seems to be running correctly before that.

Let me know if you can view these images or if I need to send them in another way.

Jim

Hello Jim,

Thanks for sharing those images and explaining it further in detail. Can you share your .gg file for what you’re OTPing? There might be something being configured to SHUTDOWN the device after you write to it. Also do you mind checking the voltage of REG18 pin and restarting bqStudio after the 2^nd image?

Best Regards,
Alexis

Hi Alexis,

I restarted BQStudio after the registers went gray (2nd image above) and got the following:

BQStudio failed to communicate with the BQ76942.

When using the battery voltage setup REG18 always had 1.8 volts at its output.  This setup worked correctly (no communication issues).

When using the +12-volt bench supply, the 1.8 volts was at the output of REG18 until I wrote the gg file to the BQ76942.  At the end of the write cycle the 1.8 volts dropped down to 0 volts.  I'm not sure why it is doing this.  Starting a scan after this turned the register values gray.

Below is a copy of the gg file I used.

  Bq 2024-10-24.gg.csv

Thanks,

Jim