About MCIMX8M-EVKB design

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About MCIMX8M-EVKB design

278 Views
nadira
Contributor I

1) As Per schematics file on page no 12, there are Four capacitors C929, C930, C931 and C932 (High lighted in below image) added on VSYS 12V power rail: My question here is the total some of capacitance is 100uf only but why these four caps added in schematics? what is the purpose?

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2)  As per same schematics why the USB J903 connector VBUS current is limited to 2.1A, any specific use case? (Refer below image)

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3) In WiFi/BT section, U1301B as per LBEH5IL1CX datasheet: VBAT should be up before or at the same time as VIO. VIO should NOT be present first or be held high before VBAT is high

In Schematics power sequence: VDD_3V3 (VIO) rails is power up first than DCDC_5V(VBAT) rail will going to up (U706, DCDC 5V module is Enable from VDD_3V3 rail), this will leads to wrong power up sequence can you just clarify on this?

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6 Replies

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weidong_sun
NXP TechSupport
NXP TechSupport

Hi Yaseen,

   See below, please!

1. When two capacitors of the same capacity are connected in series, their rating voltage will double, but the capacitance will be reduced by half. So the purpose of this connection is to improve rating voltage.

2. The rating current of USB connectors should not exceed 2.1A

3. According to the LBEH5IL1CX data sheet, what you said is correct. However, after EVK verification, EVK's LBEH5IL1CX power-on sequence is not a problem, so there is no need to worry about this problem.

Hope above information is helpful for you!

Have a nice day!

Best regards,

Weidong

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105 Views
nadira
Contributor I

Hi Weidong,

1 and 2 query i understood Thanks for reply,

However for 2nd Query: USB 3.0 Host Max port current is 900mA only, here my question is any specific reason to set here current limit for 2.1A, any USB 3.0 Host device consume up to 2.1A current?

Regards,

Yaseen

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105 Views
nadira
Contributor I

Hi Weidong,

Any updates for previous query.

Regards,

Yaseen

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105 Views
weidong_sun
NXP TechSupport
NXP TechSupport

VBUS's source is from  DCDC_5V,  which means that DCDC_5V cannot provide more than 2.1A of current to USB devices, otherwise, 5V of the internal circuit may not be enough. If you want to limit VBUS to the maximum 1A current in your circuit, you can.

I hope this explanation will help you.

Have a nice day!

BR,

Weidong

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105 Views
weidong_sun
NXP TechSupport
NXP TechSupport

Hi Yaseen,

    The current is determined by the USB connector you select.

Have a nice day!

BR,

Weidong

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105 Views
nadira
Contributor I

As per standard any host device USB 3.0 max current consumption is 0.9A only.

As per schematics any specific reason to set here 2.1A even though such host device will not get connect here

Regards,

Yaseen

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