r5450 - in trunk/gta02-core/docs/ecn: . ecn0014
werner at docs.openmoko.org
werner at docs.openmoko.org
Sat Aug 15 12:16:23 CEST 2009
Author: werner
Date: 2009-08-15 12:16:23 +0200 (Sat, 15 Aug 2009)
New Revision: 5450
Added:
trunk/gta02-core/docs/ecn/ecn0014/
trunk/gta02-core/docs/ecn/ecn0014/U4905-circuit.png
Modified:
trunk/gta02-core/docs/ecn/STATUS
trunk/gta02-core/docs/ecn/ecn0014.txt
Log:
- ECN0014: added motivation and replacement part number
- ECN0014: added Joerg's BQ24314DSG design
Modified: trunk/gta02-core/docs/ecn/STATUS
===================================================================
--- trunk/gta02-core/docs/ecn/STATUS 2009-08-14 23:34:25 UTC (rev 5449)
+++ trunk/gta02-core/docs/ecn/STATUS 2009-08-15 10:16:23 UTC (rev 5450)
@@ -13,7 +13,7 @@
0011 Edit Reduce number of varistors on USB_VBUS (C4902, C4909)
0012 Defer Add fuse to USB_VBUS
0013 Defer Increase rated current of B4902
-0014 Defer Limit non-ESD overvoltage on USB_VBUS
+0014 Defer Limit non-ESD overvoltage on USB_VBUS (U4905)
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
Added: trunk/gta02-core/docs/ecn/ecn0014/U4905-circuit.png
===================================================================
(Binary files differ)
Property changes on: trunk/gta02-core/docs/ecn/ecn0014/U4905-circuit.png
___________________________________________________________________
Name: svn:mime-type
+ application/octet-stream
Modified: trunk/gta02-core/docs/ecn/ecn0014.txt
===================================================================
--- trunk/gta02-core/docs/ecn/ecn0014.txt 2009-08-14 23:34:25 UTC (rev 5449)
+++ trunk/gta02-core/docs/ecn/ecn0014.txt 2009-08-15 10:16:23 UTC (rev 5450)
@@ -1,7 +1,20 @@
-Limit non-ESD overvoltage on USB_VBUS
+Limit non-ESD overvoltage on USB_VBUS (U4905)
-To do:
-- issue: broken power supply and such, PMU not very tolerant
-- change U4905 to better part
-- defer since it's not an emergency
+The issue: the highest USB voltage the PMU is specied for is 5.5 V,
+which makes it not very tolerant to USB overvoltage. Excessive USB
+voltage may come from defective power supplies and supplies with
+loose design tolerances, such as car chargers.
+
+The RT9711 only provides overcurrent protection but no overvoltage
+protection. A better choice would be the TI BQ24314DSG:
+http://focus.ti.com/lit/ds/symlink/bq24314.pdf
+
+Joerg Reisenweber has designed a circuit using the BQ24314DSG:
+ecn0014/U4905-circuit.png
+
+Defer this to post-gta02-core since it requires a new part and it's
+not an emergency.
+
+
+Author: Werner Almesberger <werner at openmoko.org>
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