Andy Green schrieb: > | o- I suggest PTC-fuse&crowbar USB OVP like attached sketch. Component > values > | and exact types to be decided upon by Allen/hw team - just suggestion > in my > | sketch. > > I don't know that we really need this protection, or it is a reaction to > the unknown "switch burnings" that are seen. If it is a goal to survive > large overvoltage events for long periods on USB, this circuit will be > good, maybe it will help also with the switch burnings, but is it a goal?
Well it's just a consideration of mine about AbsMaxRating of our device, that I would like to see to be more robust. A connector that's desgned for receiving nominal 5V, and goes up in smoke at ~6V, is broken by design in my opinion, so that's my suggestion to fix a "bug" in hw. > > | o- detect USB charger: should we try to detect D+/D- short? Can we detect > | 47kR-ID-Pin with 6400 or do we need additional hw to handle this? > > This short is meant to be seen by the "USB OTG" PHY I believe... if 6400 > supports it I didn't look yet. > > | o- what do we need additional hw for 6400 USB-OTG (charge pump, OVP, > | ESD-prot...)? > > Now we chose pcf50633 we either need some OTG-specific management chip > that does this, or to re-use the GTA02 parts. Well for the charge pump (plus possibly additional circuitry) I had a long visit at 6400-UM, USB-OTG chapter, and at http://www.usb.org/developers/docs/USB_OTG_1-3.pdf especially 5.1.3, 5.3.4. It seems there are quite a few very specific requirements for the Vbus voltage, current, impedance etc pp. Though 6400 shuld do a lot of the weird signaling of OTG by itself (that's what I *think*, didn't find decent data on it) there isn't a pin called USB-OTG_capacitor or sth like that. And Vusb has to be created by some external component that's not quite clear for it's specs. I really like to see some application notes on USB-OTG with 6400 from Samsung!!! Someone who may ask them whether they got soemthing useful? BTW: this whole USB-OTG pretty much collides with our "externally powered hostmode", and I really like to use dedicated powerconnector and use the second power rail of 50633 to have this sorted out. More on this in a separate mail later on. /jOERG
