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Question about UCC27322 Vcc and Power dissipation

Satoshi
Guru 19585 points
Other Parts Discussed in Thread: UCC27322, LM5085

Please let me know two points below about the drive of UCC27322.

[Background]

・Circuit configuration LM5085 ⇒ UCC27322 ⇒ SQM40P10-40L

・Vin:16～24V, Vout:16V, 30W (1.875A)

------------------------------------------------

[Question]

・Since Qgs of SQM40P10-40L is large(134nC), it is due to drive by UCC27322.

Is this composition right?

And, is electric supply right below?

　・LM5085・・・Vin:16～24V

　・UCC273232・・・VDD,IN:16V

・About calculation of power dissipation

　When connecting UCC27323, which calculation does power dissipation use the following?

　・Datasheet 　　 P14 (14)

　　Pdiss=Vin × ((Qg × Fs) + Iin)

　・The formula currently examined 　　

　　Pdiss=Vcc(reg) × Qg × Fs + Vin × Iin 　　

　　　　　※Vcc(reg)_max:8.5V

　　～For example～ 　

　　Vin=24V, Iin =1.8 mA, Qg=134nC (SQM40P-40L), Vcc(reg) =8.5V 　　

　　・Datasheet

　　　1.01W = 24 × ((134/1000000000 × 300 × 1000) + 1.8/1000) 　　

　　・Examination 　

　　　 0.385W = 8.5 × ((134/1000000000 × 300 × 1000) + 24 × 1.8/1000

------------------------------------------------

 

Best regards,

Satoshi

  • 0
    Guru 19585 points

    The request of the reminder came from the customer.

    How about the situation of content which questioned the other day?

    Please teach if there are spec and information necessary to confirm.

    I will confirm it.

    Best regards,

    Satoshi