[gta02-core] Fwd: Re: [gta03] GTA03 sch review

Werner Almesberger werner at openmoko.org
Fri Aug 14 15:31:17 CEST 2009

Joerg Reisenweber wrote:
> The requested "mega-ECN".

Thanks a lot ! I've tried to "diff" it and break it down by subsystem:


- different component for JK4401 (not applicable to gta02-core)
- add ESD protection to all signals from audio jack
- add EMI filters to all signals from audio jack
- remove all the 22 pF caps (C4403, C4404, C4405)
- remove DL_GSM circuit (we did that in gta02-core)
- capless, GND becomes VGND (you recommend not doing this part)
- route JACK_INSERT to codec, not CPU. Remove pull-up R4406.
- remove the nHOLD network 
- remove the 33 Ohm resistors R4405 and R4407 (we've changed them to 0R)
- eliminate common-mode choke B4102 from the jack path (Q: is the idea
  that the EMI filters take its role ?)

Front speaker:

- add ESD protection to the front speaker 

Rear speaker:

- use codec-internal amplifier and remove amplifier LM4853 (we have that)
- remove 18 pF caps (C4120, C4121)
- swap location of common-mode choke and capacitor network: choke goes
  next to speaker and ESD, caps go next to the codec


- different microphone component with different circuit
- removed R4305 (2k2 series on MICBIAS)
- increase mic out cap from 100 nF to 1 uF 

gta02-core has Openmoko's GTA02 microphone circuit. We still need to
weed out some junk there. Also, what do we do with the buzz-fix issue ?
Add EMI filters besides the common-mode choke, add MICBAS buffer cap, 
both, or will it be okay if we remove all the digital junk from the 
analog nets ?


- remove absentee MICBIAS buffering cap C3020 (yeah, we should do that
- increase caps on RXP/RXN (modem to codec) and MONO1/MONO2 (codec to 
  modem) from 100 nF to 1 uF
- route LOUT1/ROUT1 back to LINE1/LINE2 (neat :-)
- route GP1 (CODEC_IRQ) to the CPU

Does that sounds about right ?

> > o- Has separate power HPVDD/SPKRVDD(4V5 AMR, 3V6 recommended) for
> > HP-/SPK-AMPs, I suggest direct Vsys(???) or lowdrop Reg 3V3 at 250mA. Speaker
> > shall be = 8 Ohm.

BTW, the front speaker has 32 Ohm and the rear speaker 8 Ohm.

- Werner

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