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Looking for 1.8V shift register

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

Reply to
Allan Herriman
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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

Reply to
Allan Herriman

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
Reply to
Tim Wescott

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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Reply to
Paul E. Bennett

Something like ?

formatting link

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

Reply to
j.m.granville

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