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USB OTG power rail schematic
Fedor27 , 04-01-2020, 10:50 PM
Hi all! Hope you are feel good.
Many examples connect net "+5V" from micro USB conector directly to +5V power net, or through the power switch ic (TPS2553 for example).
And, what if main PCB power supply (for example +12V) will turned off? Current from USB connector (I suppose, 1A maximum) will power up whole PCB?
Ok, but what if +5V stepdown converter will powered up from output to input? What if +5V current will flow to +12V net? There are some other loads (much more than 1A), with UVLO less than +5V. Probably I even will see more than +5V on +12V net, cause of inductor in +5V stepdown converter, and dynamic load on +12V net during startup.
So, I want to understand: How can I protect OTG power net?
I want to use OTG for software updating, and for testing.
Many examples connect net "+5V" from micro USB conector directly to +5V power net, or through the power switch ic (TPS2553 for example).
And, what if main PCB power supply (for example +12V) will turned off? Current from USB connector (I suppose, 1A maximum) will power up whole PCB?
Ok, but what if +5V stepdown converter will powered up from output to input? What if +5V current will flow to +12V net? There are some other loads (much more than 1A), with UVLO less than +5V. Probably I even will see more than +5V on +12V net, cause of inductor in +5V stepdown converter, and dynamic load on +12V net during startup.
So, I want to understand: How can I protect OTG power net?
I want to use OTG for software updating, and for testing.
Fedor27 , 04-02-2020, 08:00 AM
So, I read datasheet on TPS2553 again, and find that ic block reverse current, so I don't need another protection for this net.
Also, I add voltage supervisory ic to +12V net, and it block load enabling.
But, I see iMX6 Rex Development Baseboard schematic, and there is no any voltage switch ic on OTG power net (just ferrite bead).
Also, I add voltage supervisory ic to +12V net, and it block load enabling.
But, I see iMX6 Rex Development Baseboard schematic, and there is no any voltage switch ic on OTG power net (just ferrite bead).
robertferanec , 04-06-2020, 01:02 AM
This is what we have on our OpenRex board. See the schematic (Page 28): https://www.imx6rex.com/wp-content/u...Production.pdf
Fedor27 , 04-06-2020, 02:18 AM
Robert, thank you!
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