LM35 / SOT23?

What do you mean by "supply voltage compliance"?

John

The '35 and '45 are (I think) the same chip, with the LM35 having a higher max voltage rating based on self-heating effects.

But be warned: both have a lot of personality. Small spikes can make either latch up, especially if the supply voltage is above 5. And the datasheet suggests you can pull the output below ground to measure negative temps, but that can make it latch, too. And they oscillate with capacitive loads.

Bob Pease promised me he'd fix it, 10 years ago or so.

One remaining advantage of the Fahrenheit temp scale is that you can get LM34's, which output zero volts at zero F!

John

Microchip MCP9700 except 0°C is 500mV. It works down to 2.3V w/output

Best regards, Spehro Pefhany

They look more to me like they were designed to be similar. Check out the turn-on response curve and noise voltage graph, for example. More relevant to Fred's application would be the abs max supply voltage limit, unfortunately.

Hmmm.. the 1994, 1999 and 2000 data sheets all have the -1V abs max output voltage limit (which is potentially exceeded by a circuit in their 1986 application note).

Do you have an earlier datasheet? I think it came out in '83 (and it's not in my 1982 NS databook).

Being voltage-output devices..

Maybe they just 'fixed' the datasheet. ;-)

What's the point of a circuit that will only work down to a couple degrees C above freezing anyway?

Best regards, Spehro Pefhany

There is apparently a substrate diode to Vout. Or more precisely, a substrate SCR.

What's especially nasty is if you do the pulldown thing before you apply Vcc. A tiny amount of substrate current can then make it latch up when the main power is applied.

If you use the F part, the LM34, you can measure down to ... computes furiously ... -17.8 C without doing the dangerous negative pulldown thing.

After all, it never gets colder than 0F anywhere in the civilized world.

John

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and

Thanks Spehro.

I've already spotted those and also the TC4017, but neither will do.

Unfortunately I realise I wasn't clear enough about the voltage compliance: they have to be mounted inside a constant current supplied 2 wires sensor that settles its average bias point from 6V to maybe 16-17V on the whole temperature range. And the 0degreeC->0V is mandatory too, since we have to align on competition, which is a defacto standard.

The LM35 is the ideal device, except the packaging. I was hoping of maybe a SOT23 packaged second source.

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and

It has to accept a supply voltage range from 5-6V up to at least 20V.

Buy the chips, mount them on the board, and wire bond to the traces. Slightly smaller than the package...