IMX8MM EVK: Purpose of using FET in DCDC (5V) MP8759GD

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IMX8MM EVK: Purpose of using FET in DCDC (5V) MP8759GD

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haryanl
Contributor III

Hi Everyone!


In the reference Schematic of IMX8M Mini, can anyone show me the purpose of using FET Q903 (NX3008NBKW, 115)?

How does it affect the Enable of DCDC MP8759?

In the datasheet of NX3008NBKW, VGS (th) = 0.6 0.9 1.1V (~ Min Type Max)
By default VBUS_IN = 5V, Q903, VGS = 0.36V (<VGSth) means that Q903 will be off. So, what function does Q903 have?
And, in case I want to use VBUS_IN = 12V, how does it affect the Enable of DCDC MP8759?

pastedImage_1.png

(Page 12 of Schematic)

Best Regards,

Yah

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haryanl
Contributor III

I'm sorry

I have understood the principle of operation

MP8759 Datasheet(Page14):

[set the EN voltage above the EN rising threshold(1.35V) and below the 4.5V absolute maximum rating.
The rising threshold should be set to provide enough hysteresis to allow for any input supply variations.]

So it is necessary to use FET

View solution in original post

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haryanl
Contributor III

I'm sorry

I have understood the principle of operation

MP8759 Datasheet(Page14):

[set the EN voltage above the EN rising threshold(1.35V) and below the 4.5V absolute maximum rating.
The rising threshold should be set to provide enough hysteresis to allow for any input supply variations.]

So it is necessary to use FET

View solution in original post

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