r5692 - trunk/gta02-core/docs/ecn

[werner at docs.openmoko.org]

Author: werner
Date: 2009-10-14 15:59:55 +0200 (Wed, 14 Oct 2009)
New Revision: 5692

Modified:
   trunk/gta02-core/docs/ecn/STATUS
   trunk/gta02-core/docs/ecn/ecn0010.txt
Log:
- reopened ECN0010 (as "Discuss") and added summary of power supply discussion



Modified: trunk/gta02-core/docs/ecn/STATUS
===================================================================
--- trunk/gta02-core/docs/ecn/STATUS	2009-10-14 13:31:18 UTC (rev 5691)
+++ trunk/gta02-core/docs/ecn/STATUS	2009-10-14 13:59:55 UTC (rev 5692)
@@ -9,7 +9,7 @@
 0007	Done	Remove KEEPACT net and connect PMU.KEEPACT directly to IO_3V3
 0008	Execute	Remove external GPS antenna connector and circuit (CON7602)
 0009	Done	Remove LED transistors (Q1501 and Q1502)
-0010	Done	Remove audio amplifier (U4101)
+0010	Discuss	Remove audio amplifier (U4101)
 0011	Execute	Reduce number of varistors on USB_VBUS (C4902, C4909)
 0012	Defer	Add fuse to USB_VBUS
 0013	Defer	Increase rated current of B4902
@@ -49,6 +49,7 @@
 0001	GLAMO, CPU, LCM
 0002	MEMORY, CPU
 0008	GPS
+0010	AUDIO
 0011	USB
 0024	GPS
 0026	SD-SIM

Modified: trunk/gta02-core/docs/ecn/ecn0010.txt
===================================================================
--- trunk/gta02-core/docs/ecn/ecn0010.txt	2009-10-14 13:31:18 UTC (rev 5691)
+++ trunk/gta02-core/docs/ecn/ecn0010.txt	2009-10-14 13:59:55 UTC (rev 5692)
@@ -25,11 +25,28 @@
 therefore it can be removed to free more space in the already crowded area of 
 the hs jack.
 
+Since HPVDD and SPKRVDD may draw about 150 mA in normal operation,
+CODEC_3V3 needs to be supplied from a more powerful source than LDO2
+(limited to 50 mA). We can use LDO4 (capable of supplying 150 mA) if
+we move BT_3V2 to LDO2. The Bluetooth modules draws only up to 35 mA,
+so the 50 mA of LDO2 are sufficient.
 
+Testing [2] showed that shorting LDO4 will cause it to limit the current
+to about 500 mA, which is still low enough to prevent immediate problems
+for the rest of the system.
+
+Open issue: do we continue feeding LDOs 3 and 4 from Vsys or do we move
+them to IO_3V3 for better efficiency ? (In the latter case, AVDD etc al.
+would have to operate at 3.05 V or less, due to the 250 mV voltage drop
+of the LDO.) [3]
+
 [1] http://www.wolfsonmicro.com/uploads/documents/en/WM8753.pdf
+[2] http://lists.openmoko.org/pipermail/gta02-core/2009-October/000744.html
+[3] http://lists.openmoko.org/pipermail/gta02-core/2009-October/000746.html
 
 
 Author: Rene Harder <rehar at saweb.de>
 Commit: SVN 5118
 Review: Werner Almesberger <werner at openmoko.org>, SVN5675
 Commit: SVN 5689, removed R4404
+Commit: SVN 5692, reopened and added power supply