r5311 - trunk/gta02-core/docs/ecn

rehar at docs.openmoko.org rehar at docs.openmoko.org
Wed Jul 22 06:38:11 CEST 2009

Author: rehar
Date: 2009-07-22 06:38:10 +0200 (Wed, 22 Jul 2009)
New Revision: 5311

updated ECN0015 and ECN0019

Modified: trunk/gta02-core/docs/ecn/STATUS
--- trunk/gta02-core/docs/ecn/STATUS	2009-07-22 01:31:34 UTC (rev 5310)
+++ trunk/gta02-core/docs/ecn/STATUS	2009-07-22 04:38:10 UTC (rev 5311)
@@ -14,11 +14,11 @@
 0012	Defer	Add fuse to USB_VBUS
 0013	Defer	Increase rated current of B4902
 0014	Defer	Limit non-ESD overvoltage on USB_VBUS
-0015	Edit	Remove Calypso serial interface on headset (U4401)
+0015	Discuss	Remove Calypso serial interface on headset (U4401)
 0016	Edit	Remove upper acceleration sensor (U7801)
 0017	Edit	Move Bluetooth module (U2) to main PCB
 0018	Edit	Add beads/filters to audio signals leaving/entering can
-0019	Edit	Consider applying buzz fix
+0019	Discuss	Consider applying buzz fix
 0020	Discuss	No common mode choke on stereo signals (B4102)
 0021	Defer	Use EMI-hardened microphone (MC4301)
 0022	Discuss	Apply bass fix

Modified: trunk/gta02-core/docs/ecn/ecn0015.txt
--- trunk/gta02-core/docs/ecn/ecn0015.txt	2009-07-22 01:31:34 UTC (rev 5310)
+++ trunk/gta02-core/docs/ecn/ecn0015.txt	2009-07-22 04:38:10 UTC (rev 5311)
@@ -1,5 +1,17 @@
 Remove Calypso serial interface on headset (U4401)
+The Calypso serial interface on the headset port caused many problem. 
+- removed U4401
+- removed R4407 and R4408, these resistors probably keept the input signal from
+  shorting through the amplifier, so there is no need for them anymore.
+- removed TP4405/4406
+- removed R4403, pulldown resistor for U4401 enable lines 
 To do:
-- mixing digital and analog ain't no good
-- we don't really need it - factory could just use test points
+- depending on Calypso replacement we might want to keep/remove R4411 and TP4402/4401 as well
+Author: Rene Harder <rehar at saweb.de>

Modified: trunk/gta02-core/docs/ecn/ecn0019.txt
--- trunk/gta02-core/docs/ecn/ecn0019.txt	2009-07-22 01:31:34 UTC (rev 5310)
+++ trunk/gta02-core/docs/ecn/ecn0019.txt	2009-07-22 04:38:10 UTC (rev 5311)
@@ -1,8 +1,20 @@
 Consider applying buzz fix
+RF feeds into the microphone line of the headset jack JK4401. This RF causes
+ripples on the microphone bias line of the codec which leads to a poor audio
+quality of the microphone.
+One goal of the ECN0018 is to prevent any RF from reaching the wolfson codec,
+therefore this problem would be solved. However in GTA02-A7 this issue was
+taken care of by adding C4306/C4307 to the microphone lines. Those caps are
+still defined as NC but the footprint(1206) is big enough so that a 100uF cap
+can be easily mounted if necessary. Also R4303 is interchangeable with a 2.2k
+resistor as mentioned in the big-C Buzz Fix [1].
-To do:
-- Q: do we still need it after adding beads/filters ? (ECN0018)
-- add 100 uF cap
-- change R4303 from 0R to 2k2
-- reference http://wiki.openmoko.org/wiki/Buzz_Fix
+I'd consider to leave those cap footprints in the circuit if the solution with
+the beads fails and we still get ripple on the mic bias line.
+[1] http://people.openmoko.org/joerg/GSM_EMI_noise/big-C_rework_SOP_rc2.pdf
+Author: Rene Harder <rehar at saweb.de>

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