Re: USB 2.0 hub chip
- From: Paul Carpenter <paul@xxxxxxxxxxxxxxxxxxxxxxxxxxx>
- Date: Fri, 31 Jul 2009 13:14:21 +0100
In article <Xni*cvlNs@xxxxxxxxxxxxxxxxxxxxxxxxxxx>,
theom+news@xxxxxxxxxxxxxxxxxxxxxx says...
I want to modify a laptop to fit an internal USB flash drive. While there's
USB available inside all the ports are used, so I need to insert a two port
hub in between one of them so I can break out another connector.
The trouble is space is /extremely/ tight. That means everything will have
to be uncased, hardwired in, with no USB connectors. And the amount of area
I have to fit in a PCB isn't large (constrained in thickness and in area by
various pillars etc)
I've been looking around for a USB hub I can abuse in this way, but the
problem is that the type A sockets used are hugely bigger than the chip used
so there's no reason for the board layout to be compact. I found something
like this:
http://www.dealextreme.com/details.dx/sku.15664
The sockets are mounted on a bar which could easily be trimmed off, and I'd
hope the area under the label containing the chips would be small enough.
But according to the comments this hub gets hot, which is always a concern
in a laptop.
If USB A sockets are large to you and space constraints what are you
going to do about preferable USB designs that have large cap on 5V to
each USB port.
So I wondered if it was easier to make it myself with a chip I could get
data for, rather than wandering around the shops peering through the
packaging trying to work out which chipset is used. Only I can't seem to
find anyone (I'm in the UK) selling USB 2.0 hub chips. Plenty of 1.1
though. Digikey has some 2.0, but the delivery is very expensive.
Well I bought a small batch of NXP1520 four port USB hub chips in UK, if
stuck I can probably sort out a small quantity for you.
I realise layout of a USB 2.0 board is a bit more tricky than 1.1 due to the
higher speeds. But I'm only using it for very short distances, and every
piece of Chinese tat seems to manage it with the cheapest construction
available. And in theory I'd only need a chip with power, ground, 2 crystal
pins, 2 USB pins in and N*2 USB pins out, not a TQFP64 or something.
What I configured the four port to actually be a three port hub on a
stripboard and schmart board lash up, worked perfectly well with 5m
cables.
see http://www.pcserviceselectronics.co.uk/images/breadboardusb.jpg
Also has a USB device chip talking to a PLD and then other logic not
shown.
So is there a sensible source of USB 2.0 hub chips in 1-off quantities that
won't cost me a fortune? For example, someone like Maxim with a samples
programme (Maxim don't make hubs) or someone who ships small orders? Or is
my best bet still to wander around the shops looking at translucent hubs
until I find one with a suitable chip and desolder it?
Thanks
Theo
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- References:
- USB 2.0 hub chip
- From: Theo Markettos
- USB 2.0 hub chip
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