BQ24070: Problem with capacitor between BAT and ISET1

Hello,
The 0.22uF capacitor should be added in your application. It was not added in the EVM because the EVM is configured to charge at 1A which is why it is unpopulated. Try adding the 0.22uF capacitor and let me know if the issue persists.

Hello Raheem,

They added 0.22uF capacitor from start, but the problem is in loud squeak when this capacitor added.
When they remove the capacitor - sound dissapears.

How to solve this problem? Should i ask the customer for additional information?

Ilya.

Raheem,

This is very urgent question for our customer, because they have to ship this devices to their customer in 2 weeks.
And this loud squeak is real problem needed to be solved.

We really hope for your help.

Ilya.

Hello Ilya,
I tried this on my bench and i could't replicate any popping sound. What is the load they have on OUT? Looking at the schematic, they should have 6.04K on ISET1 to get 0.16A.

Hello Raheem,

Thank you for the reply, i provided this information to the customer and got their anwser:
1. Io(out) = V(SET) x K(SET) / Rset = 2.5 *425 / 3300 = 0.320 A (equation 4, page 17). And ISET2 = Low (tied to gnd) => Io(out) = 0.320 / 2 = 0.160 A (The charge level, during IN mode operation only (Mode = High), can be changed by a factor of 2 by setting the ISET2 pin high (full charge) or low (half charge). - page17). So they got 0.16A charge current

2. They tried several tests:
2.1. They removed load from OUT. So only TPS54240 and BQ24070 working.
Sound is still exists but only at the moment of transition from charge mode with constant current to charge mode with constant voltage (Figure 2. Charge Profile of BQ24070).
Also there are strong noise at oscilloscope at this moment.

2.2. They removed C424 = 0.22uF. The sound became much quieter but now it exists in both charging modes. After current becomes 80mA, the sound dissapears completly.

3. What will happen if they remove C424? (Currently they see it as the solution)

BR,
Ilya

Hello Ilya,
Can you please provide scope shots of noise seen on the scope and at what pin this noise was seen. Also is the noise seen when the TPS54240 is not present?

Hello Raheem,

Thank you for the reply!
I will ask the customer.

Could you please give an answer on question 3.
3. What will happen if they remove C424? (Currently they see it as the solution)

BR,
Ilya

Hello Raheem,

Could you please give an answer on question 3.
3. What will happen if they remove C424? (Currently they see it as the solution)

Ilya.

Hello Ilya,
I'm currently in consultation with the design engineers to see the ramifications of removing this capacitor. I'll let you know when i have more details.

Ilya,
Can you post scope shots of VBAT and IBAT with and without the capacitor.

Hello Raheem,

The customer provided scope shots(from VBAT) with acoustic noise(with capacitor) and without.

1 shot without:

3 shots with noise:

Hello Raheem,

Do you need additional information to help to solve customer's problem with noise?

Can they just remove this capacitor?(What is it's function?)

BR,
Ilya

Ilya,
I don't need anymore information from you at this time. I'm currently in some discussion with the design engineers to see the role of this capacitor and if it is ok for it to be removed.