BQ24261 APPLICATION for EMI Radiation

eiven wu

Prodigy 215 points

Dear ,

I have a question for BQ24261 application for EMI.

I test EMI Radiation and fail on 106MHz and 300MHz.

I put a 0.01uF to ground on SW pin of BQ24261.

Does it have any effect with application?

Thanks.

over 8 years ago

0 Jeff F over 8 years ago

TI__Guru**** 166246 points

Hello Eiven,

All switching converters produce EMI. Adding only a large capacitor from SW to ground will reduce EMI but also reduce the switcher's efficiency to impractical levels. I wrote an application note for boost converter on sizing an Resistive-Capacitance snubber. http://www.ti.com/lit/an/slva255/slva255.pdf. The same procedure applies except you likely will be looking at the ringing on the SW waveform failing edge not rising.

0 eiven wu over 8 years ago in reply to Jeff F

Prodigy 215 points

Dear Jeff

I understood it.But i must to make sure the application of Cap connect SW pin to ground,is't ok?
I used the method better than snubber circuit.

0 Jeff F over 8 years ago in reply to eiven wu

TI__Guru**** 166246 points

Eiven,

I have not tested and therefore cannot recommend such a large capacitor from SW to ground. I know that the efficiency will be very bad due to slow rise and fall times of the SW node. Such slow rise and fall times may cause shoot through current as well. I urge you to change to an optimized RC snubber from SW node to ground.

0 eiven wu over 8 years ago in reply to Jeff F

Prodigy 215 points

Dear Jeff

Thanks.
I think to increase the Coss of hi side and low side MOSFET.
If i put a 0.01uF Cap on IN pin to SW pin and SW pin to grond,can it avoid the shoot through ?

0 Jeff F over 8 years ago in reply to eiven wu

TI__Guru**** 166246 points

Eiven,

Placing such a large capacitor from IN to SW will allow large current spikes to bypass the internal blocking FET from IN to PMID.

0 eiven wu over 8 years ago in reply to Jeff F

Prodigy 215 points

Dear Jeff

I check my SW PIN waveform. it have jitter on falling .Do you have any comment to reduce the jitter?

Thanks.

Power management

Power management forum

BQ24261 APPLICATION for EMI Radiation