PMP7819: LM5119 reference design , 2DB1694-7

Ryuji

Guru 20090 points

Part Number: PMP7819

Hello,

In the LM5119 reference design PMP7819, there are four 2DB1694-7 as Q9~Q12.
Could you please let me know the role of these transistors?
I think that the transistor was making faster falling speed of Low Side FET for efficiency improvement.

Best Regards,
Ryuji

over 6 years ago

0 Qian Chen over 6 years ago

TI__Mastermind 24075 points

Hi Ryuji,

The the Q9-Q12 helps to turn off low side FETs quickly, hence to reduce the conduction loss on bode diode.

Thanks
Qian

0 Ryuji over 6 years ago in reply to Qian Chen

Guru 20090 points

Hello Qian san,

Thank you for the reply.
Are there any notes on selection of these transistors?

Best Regards,
Ryuji

0 Qian Chen over 6 years ago in reply to Ryuji

TI__Mastermind 24075 points

Hi Ryuji,

Current rating and appropriate package size are two things to select these transistors.

Thanks

Qian

0 Xinyu Dai over 6 years ago in reply to Qian Chen

TI__Intellectual 925 points

Hi Ryuji,

These PNP transistors are there to hold the low side FETs off when the high side FETs turn on to prevent re triggering.

Best regards,
Max

0 Ryuji over 6 years ago in reply to Xinyu Dai

Guru 20090 points

Hello Max san,

Thank you for your reply.
In selecting this transistor to prevent simultaneous ON, which parameter should we pay attention to?
Same with current ratings and package size?

Best Regards,
Ryuji

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PMP7819: LM5119 reference design , 2DB1694-7