[Milkymist-devel] M1r4 review: audio (was Re: Ask for reviews on M1R4 draft (was Re: M1R4 draft schematics))
adam at sharism.cc
Tue Mar 6 17:53:41 PST 2012
On Wed, Mar 7, 2012 at 6:39 AM, Werner Almesberger
<werner at almesberger.net>wrote:
> - J1, J2: I found a direct data sheet link that works at least for now:
> Seems that pins 4 and 5 are swapped. In M1rc3, the were connected to
> each other so it didn't matter.
yes, i found that vendor changed their pin assignments number when I
added/checked for insertion/removal, but the footprint/mechanical location
in design files are correct to the same as rc3. If i fix this, means that
we also need to fix footprint library but will uncorresponded to previous
rc3 assignment in schematic.
> - C2, C6: Table 18 on page 33 of the WM9707 data sheet recommends
> C2 (their C20) = 10 uF and C6 (their C18) = 1 uF. We have C2 = 3.3 uF
> and C6 = 2.2 uF.
> While it seems that making C6 bigger is fine, I'd be less sure about
> C2. It appears that, at least at 0805, 10 uF is more common anyway.
(C2/C6) was kept to the same as previous codec lm4550b, since in rc3's
design verification stage we agreed to the performance of audio noise after
dropping wm9707 codec directly. Yes, If we'd like to follow wm9707's
recommended parts (C2 -> 10uF/0805) which is also good to me.
> Also, C2 and C6 are drawn as polarized, which doesn't seem to be
> necessary. Or did you do this to make it easier to tell GND from
> non-GND pins on the PCB ?
(C6 polarized) This can be unpolarized if we follow wm9707.
> - R1: a remnant from the previous codec chip ?
This can be removed directly since it followed with lm4550b codec:
also according to page 14 of http://www.ti.com/lit/an/snoa477c/snoa477c.pdf
10 K ohm pull-up is not needed or recommended for the LM4550B.
Nice catch to all of these.
But it great to know that if Joerg have another idea ?
-------------- next part --------------
An HTML attachment was scrubbed...
More information about the Devel