>I am powering my TS-7260 using an unregulated 12V 2A power supply as
...
>Of course, this is where the problem might lie, as the 12V is regulated
>down to 3.3V, whence charge pump circuitry is used to create the 5V
>rail. It is quite likely that this latter circuitry hasn't got the
>necessary "oomph" to handle the initial current spike which the USB
>hard drive requires.
You could test this theory with a hefty external 5 volt supply. JP7
shorts the input supply directly to the on-board 5 volt bus, bypassing
the on-board 5 V regulator. In this configuration, you are depending
on the capability of the external supply, not the on-board regulator.
See section 5.11 of the TS-7260 manual.
>Anyhoo, since my drive can be powered externally, I will follow
>Markus's suggestion and buy a cheap 5V power supply.
>
>However, this leaves me with a new problem :-(
>
>By default, the USB ports are enabled to receive the internally
>generated 5V supply - which I neither need nor indeed want. This can
>of course, be turned off by setting the appropriate bit in register
>0x1200_0000 using the poke8 command. The only problem is that this
>will be done late in the boot cycle, whereas I need it to be in effect at
>power up - otherwise the power supply electronics will get their
>knickers in a twist!
I expect that the answer is "do nothing". If you provide the drive with
external power, I would expect that it would not draw a lot of power
from the USB port. Otherwise, why would the drive have an external
power input? Or have I missed something?
Mark S.
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