BQ28Z620: The setting of FD/TD, FC/TC and COV delay time

Kailun Liu

Part Number: BQ28Z620

Hi expert,

Could you help to explain the difference of FD and TD, FC and TC?

From my understanding, the FD and FC act as an indicator of battery status, gauge will set flag base on FD and FC. While TD and TC is the ultimate symbol that will force gauge turn off MOSFET, right?

However,

In the description in TRM, only TC could turn off CFET. Can TD turn off DFET?
Besides, I notice that the default setting in BQZ file, the TD value is higher than FD, any consideration about this?

Finally,

Our customer set the COV delay =0s, and find that the actual delay change from 500ms to 1s, could you help to check the minimum time and max time when set delay time=0s? Thanks!

over 1 year ago

0 Kailun Liu over 1 year ago

TI__Expert 3113 points

Also, when the charging process is terminated by gauge, will it broadcast to charger IC and let it stop enable charging?

0 Jonny over 1 year ago in reply to Kailun Liu

TI__Mastermind 24931 points

Hello Kailun,

Please refer to this E2E post for the difference between FC FD and TC TD. For the delay time of the COV protection, please refer to this E2E post.

In regards to your last question, if the FET Options[CHGFET] = 1 and the GaugingStatus()[TC] = 1, then the CHG FET will turn off, and this would suspend charging, please see the image below.

Regards,

Jonny.

0 Kailun Liu over 1 year ago in reply to Jonny

TI__Expert 3113 points

Thanks Jonny!

Last question: Will [TD]=1 make DSG FET turns off or any other condition will terminate discharging?

0 Jonny over 1 year ago in reply to Kailun Liu

TI__Mastermind 24931 points

Hello Kailun,

There are other conditions that will cause the DSG FET to turn off. I recommend referring to the device TRM as this document states the scenarios that would turn off the DSG FET.

Regards,

Jonny.

0 Kailun Liu over 1 year ago in reply to Jonny

TI__Expert 3113 points

Hi Jonny,

Sorry I mislead the question. I want to confirm if the DSG FET will turn off when TD is triggered since I did not find the description about it in TRM.

0 Jonny over 1 year ago in reply to Kailun Liu

TI__Mastermind 24931 points

Hello Kailun,

Not necessarily, The [TD] is just a flag that gets triggered based on the threshold you have programmed.

Regards,

Jonny.

0 Kailun Liu over 1 year ago in reply to Jonny

TI__Expert 3113 points

Thanks Jonny,

[TD] is just a flag when discharge threshold is met. So when the cell voltage is approaching term voltage. Will gauge turn off DSG FET automatically?

0 Jonny over 1 year ago in reply to Kailun Liu

TI__Mastermind 24931 points

Hello Kailun,

This is just a flag and does not directly control the FET. It is up to the host to configure when you want to have the FD and TD flags triggered during discharge. Then it is up to the host to determine what occurs after these flags are set. So to answer your question, the TD flag getting set does not automatically turn off the DSG FET.

Regards,

Jonny.

0 Kailun Liu over 1 year ago in reply to Jonny

TI__Expert 3113 points

Thanks Jonny!

One last question:)

Could you share why the default value of TD is larger than FD? Any consideration about this design?

0 Jonny over 1 year ago in reply to Kailun Liu

TI__Mastermind 24931 points

Hello Kailun,

The reason for this is explained in this E2E thread.

Regards,

Jonny.

0 Kailun Liu over 1 year ago in reply to Jonny

TI__Expert 3113 points

Thanks Jonny,

As this E2E thread explain: TD should lower than FD.

However, I notice that in BQ28Z620TRM, the default value of TD is higher than FD.

0 Jonny over 1 year ago in reply to Kailun Liu

TI__Mastermind 24931 points

Hello Kailun,

These are just flags, so you can configure them for your application. You are correct though, the E2E post shows the reverse from what is stated in the TRM, please refer to this E2E post instead. Again though, how these flags are configured is determined by how your system plans on using them.

Regards,

Jonny.

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BQ28Z620: The setting of FD/TD, FC/TC and COV delay time