EMC problems with BQ40z60

Karol_Plocha

Other Parts Discussed in Thread: BQ40Z60, BQ24130

Hello,

I have trouble with BQ40z60 with EMC test during radiated emissions. The PCB exceeds allowed levels in many frequencies during charging only.

Did the BQ40z60EVM pass the EMC tests? Do you have any tips, how to handle this issue? Or could you look at the schematic is everything OK?

1326.21.00.1C_scheme.pdf

over 8 years ago

0 ThomasCosby over 8 years ago

TI__Guru 73830 points

Karol
We did not evaluate the bq40z60EVM in an EMI chamber, because the EVM layout contains a lot of options, test points and connectors that would make it difficult to keep emissions low. Here is a video that provides some guidance to reducing EMI in layouts.

training.ti.com/layout-tips-radiated-emi-reduction-your-designs

Tom

0 Karol_Plocha over 8 years ago in reply to ThomasCosby

Intellectual 360 points

Ok, thank you Tom.

0 Simon Stegner over 8 years ago in reply to Karol_Plocha

Prodigy 150 points

Hi Karol,

have you been able to solve your emc problem? What was your solution?

best regards,

Simon

0 Karol_Plocha over 8 years ago in reply to Simon Stegner

Intellectual 360 points

Hello Simon,

Still, I have no luck with my PCB on BQ40z60. I have 4-layer PCB, but the space is very limited. So, now I plan to have separate chargers, to achieve much better layout and to separate noisy part an BMS part.

0 Simon Stegner over 8 years ago in reply to Karol_Plocha

Prodigy 150 points

Hello Karol,

we have a 4-layer PCB too. Does your EMC-problem occur with the standard-charging current of 3-4A? In the TI document SLUSAW3C on page 32-34 are some hardware-design calculations to fit the schematic to other currents.

best,

Simon

0 Karol_Plocha over 8 years ago in reply to Simon Stegner

Intellectual 360 points

Charging current for our battery pack is set to 1.25A and the problem still exist. I check in chamber that the radiation is low when the charging current is <0.5A.

All elements seems to be selected properly - it was checked by few people. I even use common chokes, T - type filter, more capacistors. The results are better but still above allowed level.

0 Simon Stegner over 8 years ago in reply to Karol_Plocha

Prodigy 150 points

With the standard schematic the ripple Current of the L1 (2.2uH) is around about 1.4A. When L1 is replaced, the LC-elements have to be recalculated. You need to replace the capacitors too. Did you do that? Ripple Current should be 20-40% of charging current - e.g. 0,5A

Even addional filter elements didn't help in our layout. Our charing current will be at 300mA.

0 Karol_Plocha over 8 years ago in reply to Simon Stegner

Intellectual 360 points

I use standard L1 2.2uH, which have high saturation current about 8A (2525 case). Capacitors was parallel 22uF, 10uF and 100nF for input and output.

Do you have any EMI charts from EMC tests that you could send. If you want I can send you mine.

0 Simon Stegner over 8 years ago in reply to Karol_Plocha

Prodigy 150 points

We use the standard L1 with 2.2uH. Our emissions are between 100-200 MHz. The emc emissions of the original -TI-EVM-board are comparable.

In the last layout we added some filters between cell, charger, and input without success or influence on emc behaviour.

0 Karol_Plocha over 8 years ago in reply to Simon Stegner

Intellectual 360 points

Simon, My emissions are also between 100 - 200 MHz. I tried three different layouts with filters at the input, output and still no luck with this. Now I decided to use BQ24130. This IC has integrated switching MOSFets and diode and it's much easier to ensure proper layout.

In next week I will have measurements for this latest versions and I will let you know, how it will go.

0 prashanth morkonda over 7 years ago in reply to Karol_Plocha

Prodigy 110 points

I had similar problem, radiated emissions results were 10 db above the margin. Try adding caps on the input of the buck converter, I added a bulk capacitance of 100uF and the peak drops to 1db above the margin. Also, follow the layout guidelines as recommended by TI

FYI, my charging current is 4A max.

Power management

Power management forum

EMC problems with BQ40z60