BQ24125: Consult for low EMI Li-polymer charge PMIC

Lin Hsian

Part Number: BQ24125
Other Parts Discussed in Thread: BQ24133,

Hi,

I promote BQ24133 for Li-polymer charge PMIC but its higher EMI and customer can’t accept.

Base on E2E, I promote others parts-BQ24125 which is enhanced EMI performance but customer still can’t accept due to EMI over 30dB in 70~100Mhz(EMC rule: 30M~230Mhz need lower than 30dB,230Mhz~1Ghz need lower than 37dB) as below:

Could you please advise TI Li-polymer charge PMIC which EMI meets the EMC rule, thank you.

Thank you.

over 7 years ago

0 Steven Bangdiwala over 7 years ago

TI__Expert 8690 points

Hi Lin,

Can you provide the schematic for the bq24133? There are modifications you can do for the switching chargers in general to make them compliant with EMC standards:
1. RC Snubber at the SW node
2. Series resistor with the BTST cap
3. Overall layout improvement, by placing input caps, and output inductor/caps in optimal locations (follow layout guidelines in the datasheet)

Regards,
Steven

0 Lin Hsian over 7 years ago in reply to Steven Bangdiwala

Expert 1580 points

Hi Steven,
Due to customer circuit confidential, could you please provide your mail to discuss it.
Thank you.

Kevin

0 Lin Hsian over 7 years ago in reply to Lin Hsian

Expert 1580 points

Hi Steven,
1. RC Snubber at the SW node=> what's RC snubber value as you suggest?
2. Series resistor with the BTST cap =>What resistor value as you suggest ?
Thank you.

0 Steven Bangdiwala over 7 years ago in reply to Lin Hsian

TI__Expert 8690 points

Lin,

1. The RC Snubber depends on the switching waveform. You can read more about it here: e2e.ti.com/.../calculate-an-r-c-snubber-in-seven-steps
2. The bq24125 does not use the bootstrap circuit, I was just talking in general terms for all chargers/DC-DC converters. This value is usually around 10 ohms.

Regards,
Steven

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BQ24125: Consult for low EMI Li-polymer charge PMIC