Looking for 1.8V shift register

[Allan Herriman]

Hi,

I'm looking for a shift register to do some output expansion to drive
LEDs, small relays, etc.

I'd like to use something akin to the 74xx595 which has a serial input
and 8 outputs.

Good so far.

I need to use a shift register with either open drain outputs, or outputs
that can drive at least 3.3V (high or low, I don't mind). The current
will be up to a few tens of mA. I don't mind if I have to parallel a few
outputs to get that.

My problem is that the device that will be controlling the shift register
has 1.8V outputs.
I can't find any shift register devices that can work with 1.8V inputs,
whilst meeting my output requirements.
All the ones I can find seem to have a Vih min of 2.0V, which won't work
reliably when driven with a 1.8V signal.

I could easily design a level converter to go from 1.8V to 3.3, but I was
hoping to find a single device that could do what I want.

Any ideas?

Thanks,
Allan

[Allan Herriman]

I just found the NLSF595 from On Semi. It has open drain outputs, but is
only specified at 50uA output current with a 2.0V supply. At 3.3V its
output drive is fine, but I lose the 1.8V input compatibility.

Allan

[Tim Wescott]

On Thu, 24 Jan 2013 14:49:45 +0000, Allan Herriman wrote:

It's not getting you all the way, but -- surely there are TinyLogic
buffers that'll hear 1.8V and talk 3.3. You'll need what -- three?
Clock, data, and latch or enable? That should be possible in two itty
bitty packages.

--
My liberal friends think I'm a conservative kook.
My conservative friends think I'm a liberal kook.
Why am I not happy that they have found common ground?

Tim Wescott, Communications, Control, Circuits & Software
http://www.wescottdesign.com

[Paul E. Bennett]

You need a level shifter to interface between the controlling device and
your output device. A quick Google on the term "level shifter" should find
plenty of hits.

--
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Paul E. Bennett...............<email://Paul_E....@topmail.co.uk>
Forth based HIDECS Consultancy
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Tel: +44 (0)1235-510979
Going Forth Safely ..... EBA. www.electric-boat-association.org.uk..
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[j.m.gr...@gmail.com]

On Friday, January 25, 2013 3:49:45 AM UTC+13, Allan Herriman wrote:
> Hi,
>
> I'm looking for a shift register to do some output expansion to drive
> LEDs, small relays, etc.

Something like ?
http://www.ti.com/product/tca6408a

Or, there are CPLDs with 3.3V io and 1.8V cores

If you google IO expander they tend to have more level shifting smarts, than shift registers.
-jg