T3.6: Tpd3s014

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Frank B

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Just a question:
In the T3.6 is a TPD3S014 which connects VIN with USB-HOST 5V. So that means, if VIN is > 5V, for example 7V, USB -HOST Voltage is 7V, too. Correct ?
The USB-Specs says, USB Voltage is 5.5V max.
 
that would be bad: http://www.ti.com/product/TPD3S014/datasheet/specifications#SLVSCP45501
th_usbmax.PNG
 
Correct, the USB host power comes from VIN. It does go through the PTC fuse and schottky diode, so typically it will be about 0.4 to 0.5 volts less than VIN.
 
Doesn't that mean on T_3.6 using VIN over ~5.5V would harm the TPD chip and perhaps any hosted USB device? Only when USB_host pins are connected completing a circuit through the TPD?
 
Yes, VIN higher than about 5.9 volts (allowing 0.4V for the diode and other stuff) could cause the USB host voltage output to be higher than the 5.5V. Good thing we publish the maximum as 6.0 volts. ;)

With the USBHost_t36 library finally starting to mature and have support for more types of USB devices, soon it'll be time for me to write a page with documentation. This is one of the many details that needs to be covered.
 
Was that in answer to the second question as well? If not using USB_HOST would a full 6V (+) have a chance of harming the TPD? - or is it inert/open when nothing is connected?
 
6V is printed on the cards, so there is no big problem. I'll print "Vin MAX 5.5V" to my 3.6 boards now, since they take 5V from the VIN Pin.
 
If you look at page 4 of the TDP3S014 datasheet, you'll see the absolute max spec is 6V and the recommended max is 5.5V.
Okay - I linked to what I could read of the data sheet above. Is that chip fully connected even when USB_HOST is not used - I suspect it is with both VIN and GND? but my reading of the schematic wouldn't help confirm that.

6V is printed on the cards, so there is no big problem. I'll print "Vin MAX 5.5V" to my 3.6 boards now, since they take 5V from the VIN Pin.

I was just wondering about general use - when not using usb_host, the forum notes the 3.3V regulator chip is good somewhat over 6V { no problem on T_3.2 or T_3.5 } - but would that instantly smoke the T_3.6's TPD at 6.01 to 10V on VIN?
 
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