DThalhammer
Posts: 2
Joined: Sun Jan 29, 2017 5:35 pm

CMIO Board wrong resistor

Sun Jan 29, 2017 5:54 pm

Hello,
I'm currently designing a custom base board for cm3 modules because the official one does not fit.
My schematics and component choose will be almost identical to the normal one because I only need a very different form factor.
While reading through the official boards power supply section I wondered my self if these values are actually correct.
I wonder about resistors R22, R23, R24 and R25 as well as cap C21 and C22.
In the schematic these are either 0R or have no value.
I can calculate correct values using the chips datasheet:
http://www.mouser.com/ds/2/115/PAM2306-336770.pdf
But it still makes no sense to me why these are not the same as in the official board.
Using the Datasheet I would use these values:
R22=540k
R23=200k
R24=100k
R25=120k
C21=100pF
C22=100pF

Can someone explain the reasons for this to me ?

Sincerly Thalhammer

User avatar
Burngate
Posts: 6313
Joined: Thu Sep 29, 2011 4:34 pm
Location: Berkshire UK Tralfamadore
Contact: Website

Re: CMIO Board wrong resistor

Mon Jan 30, 2017 11:32 am

The CMIO pdf shows the device to be PAM2306AYPKE, and page 13 of its datasheet gives the magic info.
The last two letters indicate fixed voltages of 3v3 and 1v8, without any extra components (my reading of it is that the dividers are internal to the chip, behind the feedback pins)

DThalhammer
Posts: 2
Joined: Sun Jan 29, 2017 5:35 pm

Re: CMIO Board wrong resistor

Mon Jan 30, 2017 8:55 pm

Ahhhh thanks, I didn't see this. :oops:

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