Am Mi 29. Oktober 2008 schrieb silver62: > > Hi, > why there is a requirement for VCHGR_UNDSHT < 4V? If the voltage of charger > fall below 4V when the charger is connected for 2 ms is this a big issue? > > Regards, > > Silvestro
I didn't write this spec ;-), but I guess it's to avoid possible oscillation caused by device detecting USB-removal due to Vusb < 4V and switching off USB power path. Also note this is a USB2.0 complying spec, and USB2/USB-OTG uses Vusb modulation to signal certain status changes between host and device. cheers jOERG > > > Joerg Reisenweber wrote: > > > > FYI: > > > > From http://www.usb.org/developers/devclass_docs/batt_charging_1_0.zip > > > > ----- > > Battery Charging > > Specification > > Revision 1.0 > > Mar 8, 2007 > > > > p.19: > > If the current drawn from a USB charger changes suddenly within the range > > of > > 0mA to 500mA, then the > > transient voltage from a USB charger shall not go below VCHGR_UNDSHT. > > Under no > > circumstances shall the > > transient voltage of a USB charger exceed VCHGR_OVRSHT. > > > > p.23: > > Charger Overshoot Voltage VCHGR_OVRSHT 6.0 V max. > > ----- > > > > Though we couldn't even attach a USB-charger compliant to this spec, as it > > has > > to be equipped with micro-USB plug, we should expect to see voltages on > > USB-receptacle of up to 6.0V AT LEAST. > > > > I think it's a strong argument for additional OVP extending our actual > > abs.max.rating of 5.5V to limits safely beyond 6.0V, like we are actually > > about to do for GTA03. > > > > cheers > > jOERG > > > > > > _______________________________________________ > > hardware mailing list > > hardware@lists.openmoko.org > > http://lists.openmoko.org/mailman/listinfo/hardware > > > > > > -- > View this message in context: http://n2.nabble.com/USB-OVP-tp790003p1394138.html > Sent from the Openmoko Hardware mailing list archive at Nabble.com. > > > _______________________________________________ > hardware mailing list > hardware@lists.openmoko.org > http://lists.openmoko.org/mailman/listinfo/hardware >
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