BQ27750: The ON resistance of the open drain output circuit of I2C

user4522287

Part Number: BQ27750

Please tell me about the following items to estimate the margin of I2C communication in my system.

①The ON resistance of the open drain output circuit (transistor) of I2C
　* Iol=3mA

②The variation of the ON resistance
　* For example (± xx%).

③The variation of I2C VOL

　* Iol=3mA

By the way, what is the condition of Vreg> 2.0V?
Is Vreg a voltage other than 1.8V?
* VOL section of “6.25 I2C Interface I / O” on page 11 of the Data sheet.

I look forward to your reply.

over 5 years ago

0 Onyx Ahiakwo over 5 years ago

TI__Guru* 76230 points

unfortunately, the values in the data sheet are the only values that were captured during IC characterization. However, let me pull in the device expert that might have more information. If he does, expect a response within two days.

thanks

Onyx

0 user4522287 over 5 years ago in reply to Onyx Ahiakwo

Prodigy 180 points

Hello,

Thank you for your reply.

I look forward to hearing from you for more information.

What does VREG> 2.0 in VOL test condition mean?
Isn't VREG 1.8V?

Best regards,

0 user4522287 over 5 years ago in reply to Onyx Ahiakwo

Prodigy 180 points

Hello,

I will tell you just in case,

Please tell me the worst values of ON resistance and VOL,

including temperature(0~45℃).

Best regards,

0 Onyx Ahiakwo over 5 years ago in reply to user4522287

TI__Guru* 76230 points

I checked with the test team and the values we have in the data sheet are all that was tested. We don't have any more data we can share.

thanks

Onyx

0 user4522287 over 5 years ago in reply to Onyx Ahiakwo

Prodigy 180 points

Hello,

Thank you for your reply.

When we evaluated bq27750, VOL was more than 0.5V.
※(Pull up resistor = 1kΩ。IOL = about 3mA)

This means that the internal resistance of bq27750 is about 200Ω.
Is it too big?

I think that the driving power of bq27750 is insufficient.

Best regards

0 Vos over 5 years ago in reply to user4522287

TI__Genius 10370 points

Hello,

Following back up on this. the bq27750 has a mac pulldown IOL of 1mA.

Thanks,

Eric Vos

0 user4522287 over 5 years ago in reply to Vos

Prodigy 180 points

Hello,

Mr. Onyx Ahiakwo answered below that there is no problem with 3mA.

[https://e2e.ti.com/support/power-management/f/196/t/826899?tisearch=e2e-sitesearch&keymatch=BQ27750]

[https://e2e.ti.com/support/power-management/f/196/t/828909?tisearch=e2e-sitesearch&keymatch=BQ27750]

[https://e2e.ti.com/support/power-management/f/196/t/828685?tisearch=e2e-sitesearch&keymatch=BQ27750]

There is also a description of Iol = 3mA in the data sheet.
I made many inquiries and TI responded “No problem at Iol=3mA”.
Mr. Ming Yu (sector manager at TI and is responsible for all gauge products.) said the same thing.

Please tell me the truth.
Is there a chip defect?
Customers using bq27750 recognize that Iol=3mA is no problem.
Does TI need to revise the datasheet and notify each company using bq27750?

I want a sincere response.

Best regards,

0 Vos over 5 years ago in reply to user4522287

TI__Genius 10370 points

Hello,

There is an issue with our datasheet i am working to get resolved.

The bq27750 device has a max sink current of 1mA, all testing and validation on the device was done at this 1mA threshold. I did test on our EVM using a 1K (3mA sink) pull-up and was successful in communicating, but i expect this communication to be marginal and not consistent.

Thanks,

Eric Vos

0 user4522287 over 5 years ago in reply to Vos

Prodigy 180 points

Hello,

That is a critical problem for us.

There are many products on the market that use a 1kΩ pull-up.
Why did TI ever say that 3mA is no problem?

I would like you to consider the solution as soon as possible.

Best regards,

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BQ27750: The ON resistance of the open drain output circuit of I2C