BQ34Z100: Battery line

PAN-M

Part Number: BQ34Z100

Dear all.

Our customer is going to insert ferrite beads in the line of the battery.
The resistance level of this FB is 7mΩ, so total is 14mΩ(+/-).
What kind of impact will it have?

Regards,
PAN-M

over 6 years ago

0 Bryan Kahler over 6 years ago

TI__Mastermind 25955 points

Hi PAN-M,

This really depends on the purpose of the ferrite bead. Cost will be increased. Any element that changes resistance due to external factors may introduce error in the voltage measurement. Please ensure that the reason for adding the ferrite bead is an appropriate tradeoff.

Sincerely,
Bryan Kahler

0 PAN-M over 6 years ago in reply to Bryan Kahler

Mastermind 8375 points

Thank you Bryan.
When battery is NiMH and discharge current is 1A, an error range of 14mV occurs, do it produce 7% of errors with the voltage to change from 1V to 1.2V?
I want to know the error range.
Thanks and Regards,
PAN-M

0 Bryan Kahler over 6 years ago in reply to PAN-M

TI__Mastermind 25955 points

Hi PAN-M,

Please refer to the ferrite bead part datasheet for information on how to derate and calculate the error this will cause to the input of the system.

Sincerely,
Bryan Kahler

0 PAN-M over 6 years ago in reply to Bryan Kahler

Mastermind 8375 points

The ferrite bead DC impedance is 7mΩ, so it totals 14m Ω with both + and - line.
Is this makes the error of 7% of gass gauging?
Best Regards,
PAN-M

0 Bryan Kahler over 6 years ago in reply to PAN-M

TI__Mastermind 25955 points

Hi PAN-M,

Please share a schematic showing the placement of this component. By in line of battery, I assumed high side in series with the battery.

Sincerely,
Bryan Kahler

0 PAN-M over 6 years ago in reply to Bryan Kahler

Mastermind 8375 points

Thank you for support.
This is customer's schematic.
Please send me e-mail to my e-mail address in the profile.
I will attach schematic in reply.

0 Bryan Kahler over 6 years ago in reply to PAN-M

TI__Mastermind 25955 points

Hi PAN-M,

If the schematic cannot be sent publicly, please click on my profile and send me a private message. We can share the file privately through this feature.

I have sent you a +Connect request (friend request).

Sincerely,
Bryan Kahler

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

TI__Mastermind 25955 points

Hi PAN-M,

Thank you for the schematic. I will provide an update on Wednesday.

Sincerely,
Bryan Kahler

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

TI__Mastermind 25955 points

Hi PAN-M,

The Ferrite beads are located on all pins going off board. Is this out of an abundance of caution? Are there issues with EMI and noise in this design? What is the intended purpose of the ferrite bead on the ground (BATT -)? The effect on the circuit may not be intended. If after testing it is determined that they are not required, replace with a 0 ohm resistor.

Sincerely,
Bryan Kahler

0 PAN-M over 6 years ago in reply to Bryan Kahler

Mastermind 8375 points

Thank you.
Do you think that there is what percentage error when it exist?

0 Bryan Kahler over 6 years ago in reply to PAN-M

TI__Mastermind 25955 points

Hi PAN-M,

Since the ferrite bead will have a dynamic effect on the system, comparing SOC accuracy with 0 ohm populated vs ferrite bead populated of a test board would seem prudent.

Sincerely,
Bryan Kahler

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BQ34Z100: Battery line