r5688 - trunk/gta02-core/docs/ecn

rehar at docs.openmoko.org rehar at docs.openmoko.org
Tue Oct 13 06:38:55 CEST 2009

Author: rehar
Date: 2009-10-13 06:38:53 +0200 (Tue, 13 Oct 2009)
New Revision: 5688

- added function of removed components as suggested by Werner
- added missing cap C4114 to the removed components
- added short explaination why R4404 will be removed

- added change of C4128 to 47pF after brief discussion with Joerg

Modified: trunk/gta02-core/docs/ecn/ecn0010.txt
--- trunk/gta02-core/docs/ecn/ecn0010.txt	2009-10-09 02:47:48 UTC (rev 5687)
+++ trunk/gta02-core/docs/ecn/ecn0010.txt	2009-10-13 04:38:53 UTC (rev 5688)
@@ -6,10 +6,11 @@
 gets heavily reconstructed.
 Removing the external amplifier (U4101) as well as the amplifier specific
-components R4115, R4114, R4112, R4109, R4108, R4110, R4113, C4117,and C4115. 
-Also there is no need for the AMP_SHUTDOWN and HP_IN signals anymore,the 
-external speaker and headphone can be fully controlled by the corresponding
-register settings of the codec. (see [1])
+components R4114 (pull-up HP_IN), R4112, R4115 (feedback), R4109 (pull-up 
+AMP_SHUT), R4108 (power supply IO_3V3), R4110, R4113 (input), C4117 (bypass),
+C4114 and C4115 (input decoupling). Also there is no need for the AMP_SHUTDOWN
+and HP_IN signals any more,the external speaker and headphone can be fully 
+controlled by the corresponding register settings of the codec. (see [1])
 The GTA02 earpiece will be connected between OUT3 and LOUT1 of the codec, there
 will be no change of the filter and bypass capacitors.
@@ -20,7 +21,11 @@
 The external headphone will be connected between ROUT1 and LOUT1.
 The common mode choke B4102 will be removed with ECN0032.
+R4404 (MIC_BIAS pull down, NC) does not seem to have any special purpose, 
+therefore it can be removed to free more space in the already crowded area of 
+the hs jack.
 [1] http://www.wolfsonmicro.com/uploads/documents/en/WM8753.pdf

Modified: trunk/gta02-core/docs/ecn/ecn0038.txt
--- trunk/gta02-core/docs/ecn/ecn0038.txt	2009-10-09 02:47:48 UTC (rev 5687)
+++ trunk/gta02-core/docs/ecn/ecn0038.txt	2009-10-13 04:38:53 UTC (rev 5688)
@@ -9,10 +9,10 @@
 earpiece path) so we can remove at least one unique component from the BOM.
 (56 pF would be closer to 39+18 pF, but 47 pF should be good enough.)
-To do:
 I do not see any particular reason why C4128 is 10 pF it's there since GTA01.
-This needs to be clarified because this value is rarely used (vibrator) in
-GTA02 schematics and might be worth replacing it.
+This value is rarely used (vibrator) in GTA02 and a 47 pF capacitor will do
+the job just as good. So C4128 will be replaced by 47 pF.
 Author: Rene Harder <rehar at saweb.de> 

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