Changeset 5692

Timestamp:

10/14/09 15:59:55 (4 years ago)

Author:

werner

Message:

• reopened ECN0010 (as "Discuss") and added summary of power supply discussion

Location:

trunk/gta02-core/docs/ecn

Files:

• STATUS (modified) (2 diffs)
• ecn0010.txt (modified) (2 diffs)

trunk/gta02-core/docs/ecn/STATUS

@@ -10 +10 @@
 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
@@ -50 +50 @@
 0002    MEMORY, CPU
 0008    GPS
+0010    AUDIO
 0011    USB
 0024    GPS

trunk/gta02-core/docs/ecn/ecn0010.txt

@@ -26 +26 @@
 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
 
 
@@ -34 +50 @@
 Review: Werner Almesberger <werner@openmoko.org>, SVN5675
 Commit: SVN 5689, removed R4404
+Commit: SVN 5692, reopened and added power supply