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Powering Circuit Q's

Hello,

I am have some questions regarding the Schematics of the BF548 ezkit (attached). Specifically

the powering sections.

Firstly, a basic questions, what is the difference between the filled square and hollow

circle schematic symbol for the power buses? The page Power Page 1, for example,

on the bottom right shows the circuitry for the VDDEXT and 3.3V, shown as filled square

and hollow circle respectively. They are both 3.3V so what is the difference?

Looking now at Power Page 2, I don't really understand the power supply for VDDDR and

5V. What does the adp1823 chip setup do? I looked briefly at its datasheet but didn't

understand how it relates to the regulation of VDDDR and 5V (again the symbols are different?).

On the bottom left of this page there are two outputs for 5V_USB? Why?

Also, on the bottom right there are these symbols (MH4, MH5, etc) but they aren't connected

to anything? What are they for?

It's pretty evident there are lots of things that I'm confused with - the power circuitry has been

a bit of a hurdle. Is there an easier design for the power supply? Would really appreciate

any reference designs that have a simpler powering system.

Thanks to anyone who can be bothered to try and help. I know it is not exactly 'fun', but it

will be much appreciated.

Cheers...

A0206-2006_CUST.pdf
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  • Hello,

    To elaborate further in what BobK mentions:

    The BF548 schematics currently does not show a 150uF cap that is needed when the BF548 is a USB Host. (Meaning when EZ-KIT supplies the 5V_USB).

    This needs to be added on the side of U39.7 (next to C279).

    When the BF548 is a device this FET (U39) is off and the cap is not seen on the 5V_USB line.

    It only sees the 4.7uF cap (C198).

    We will be adding this 150uF when we update the BF548 schematics.

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  • Hello,

    To elaborate further in what BobK mentions:

    The BF548 schematics currently does not show a 150uF cap that is needed when the BF548 is a USB Host. (Meaning when EZ-KIT supplies the 5V_USB).

    This needs to be added on the side of U39.7 (next to C279).

    When the BF548 is a device this FET (U39) is off and the cap is not seen on the 5V_USB line.

    It only sees the 4.7uF cap (C198).

    We will be adding this 150uF when we update the BF548 schematics.

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