Changeset 5311

Timestamp:

07/22/09 06:38:10 (4 years ago)

Author:

rehar

Message:

updated ECN0015 and ECN0019

Location:

trunk/gta02-core/docs/ecn

Files:

• STATUS (modified) (1 diff)
• ecn0015.txt (modified) (1 diff)
• ecn0019.txt (modified) (1 diff)

trunk/gta02-core/docs/ecn/STATUS

@@ -15 +15 @@
 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)

trunk/gta02-core/docs/ecn/ecn0015.txt

@@ -1 +1 @@
 Remove Calypso serial interface on headset (U4401)
 
+
+The Calypso serial interface on the headset port caused many problem. 
+
+Changes:
+- 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@saweb.de>

trunk/gta02-core/docs/ecn/ecn0019.txt

@@ -1 +1 @@
 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@saweb.de>