BQ24725A: PEC capable alternative?

Adam Shrey

Part Number: BQ24725A
Other Parts Discussed in Thread: BQ20Z65-R1, BQ20Z65, BQ20Z60-R1, BQ24765, BQ25708

I am using a bq20z65-r1 based battery that has PEC enabled for the charge current/voltage broadcasts. Unfortunately this is not compatible with the bq24725A charge controller I currently have design into my system. The battery manufacturer is unwilling to disable PEC for us (why this option is buried in a private key protected area of the flash instead of exposed to the end user is beyond me), and I would like to use the broadcast feature to enable charging without processor intervention. The leaves my only option as replacing the bq24725A with another part.

Which part is the most similar to the bq24725A (in terms of application), but that also supports PEC?

Thanks

over 6 years ago

0 Wang5577 over 6 years ago

TI__Guru 56650 points

All our chargers don't support PEC. The PEC could add cost to customers and most customers don't use it.

bq20z65 can disable PEC.

0 Adam Shrey over 6 years ago in reply to Wang5577

Intellectual 290 points

That's surprising. Let me phrase the question a different way - does TI have any chargers that will ignore the PEC byte entirely? The issue with the bq24725A is that if it sees a broadcast with PEC, it treats it as invalid and immediately stops charging.

Is it possible to disable PEC on the bq20z65 without having access to the unseal key needed to access the dataflash? I am not the OEM for the battery, and do not have access to the sealed portions of the dataflash.

0 Wang5577 over 6 years ago in reply to Adam Shrey

TI__Guru 56650 points

So far, all TI charger SMBus follows the same protocol. If bq24725A immediately stops charging, I would think other SMBus chargers have same behave.
I am familiar with bq20z65. Would you start a new e2e thread on gauge forum?

0 Adam Shrey over 6 years ago in reply to Wang5577

Intellectual 290 points

Sure - e2e.ti.com/.../664625

0 Adam Shrey over 6 years ago in reply to Adam Shrey

Intellectual 290 points

I created the thread as requested a week ago, could you please reply to it?

0 Wang5577 over 6 years ago in reply to Adam Shrey

TI__Guru 56650 points

I saw that post was signed to Bryan. Can you create a new post in the gauge forum to get the support of BQ20Z65-R1?

0 Bryan Kahler over 6 years ago in reply to Wang5577

TI__Mastermind 25955 points

Hi Adam,

For the bq20z65-r1, please refer to Section 2.5.1, Section 2.11.2, Section 2.11.4 and Section C.7.1.2 of the Technical Reference Manual found here: www.ti.com/.../sluu386.pdf

The bq20z65-r1 can send/receive data with or without PEC. If the host does not support PEC, the HPE bit should be set to 0 (default).

The bq20z60-R1/bq20z65-R1 can broadcast messages to the smart battery charger and smart battery host. This can be enabled with the [BCAST] bit.

The PEC byte for alarm transmissions to the charger in master mode can be enabled with the [CPE] bit.

The PEC byte for alarm transmissions in master mode to the smart battery host and the PEC byte for receiving communications from all sources in slave mode can be enabled with the [HPE] bit.

Sincerely,
Bryan Kahler

0 Adam Shrey over 6 years ago in reply to Wang5577

Intellectual 290 points

No, he verified what I already thought - That there is no way to disable the PEC byte unless you have access to the dataflash. Sine I am not the OEM, I do not have access, and the battery using the BQ20Z65-R1 (which has PEC enabled) can not be used with the BQ24725A unless all broadcasts are turned off.

0 Bryan Kahler over 6 years ago in reply to Adam Shrey

TI__Mastermind 25955 points

Hi Adam,

You will have to get that key from the OEM, or ask them to ship you the device with your own key or in an unsealed state where you seal the device on your production line with your own key. This isn't a private variable, but one that is modifiable by the customer. In this case, that seems to be the OEM.

You can try using the default UnSealKey (0x3412 and 0x7856) as described in section B.16 of the TRM. Perhaps the OEM has left the device in a default state for your production line?

Sincerely,
Bryan Kahler

0 Adam Shrey over 6 years ago in reply to Adam Shrey

Intellectual 290 points

Could we please re-visit my rephrased question?

Which chargers, while not supporting PEC, are capable of ignoring that byte?

I know you replied that you assumed they would all behave the same, but the OEM of the battery has stated that they tested their battery with a bq24765 EVM after a customer reported it as working, and were able to confirm that it did in fact deal with the PEC byte.

This particular charger isn't something I can use in my design, but I am interested in the newer bq25708, and wonder if it behaves similarly.

Is there a way to have someone test it or otherwise confirm one way or another if some modules are PEC tolerant?

Thanks

0 Wang5577 over 6 years ago in reply to Adam Shrey

TI__Guru 56650 points

Can you send your battery pack (broadcast mode with PEC) to me? I can verify it with bq25708.
Or, you can order an bq25700AEVM and verify it on your side?