ULN2803 ok to be driven by 3.3V logic?

Should work just fine.

I'm quite surprised there isn't a MOS version.

I don't keep track of off-the-shelf stuff. Have you looked at open-drain buffers/inverters? ...Jim Thompson

So am I. There are some but with boutique pricing. Not surprisingly many of them didn't make it in the marketplace because guys like me wouldn't use them. Here is a decoder type which can be used in "memory mode", and it also went to lalaland:

Yeah, they are either too wimpy or way more expensive than two dozen discrete parts. This time I need to drive relays with up to 60mA coil current each.

A devious loaded question... What would you consider a reasonable price for such a device? Max output voltage? Max output load current?

I'm working with an entrepreneur... sold his last company and is looking at new ventures, new parts.

We just spun a specialty part aimed at surveillance camera controls.

We'll take a look at the relay/low-side/high-side market and see what looks realistic.

Don't be surprised if you get a call from Kiwi Semiconductors ;-) ...Jim Thompson

Oooh, big brother ... Should be a good market in the UK, they seem to have every single pine cone under 24/7 surveillance.

Anytime. But I am usually more into fast stuff when it comes to power drivers. Injectors, transducers, pulsers et cetera.

P.S.: If you guys are eyeing the automotive and aerospace markets as well it needs to be at least 60V. I prefer 100V parts there, but you know automotive quite well. Avoids having to place a surge cutter. And don't forget them thar catch diodes.

TPIC6595 is cool, serial in and eight fet drains out, but it needs 5 volts. We're using them to drive a lot of relays.

John

A buck fifty wouldn't fly in this case, serial would work well though. However, I have (almost) been burned by TPIC parts in the past, by part obsolescence. Somehow I had a hunch and chickened out. Now I am glad I did. But this one is cool if you have the budget and it's been around for almost two decades. If anyone is interested:

Infineon SPIDER Driver IC's - Multi channel SPI Driver?

See here

Parallel and Serial Isolated ISOFACE Driver?

Joe

Thanks. However, it costs almost two bucks in qties and Digikey has no stock (which is always a red flag for me). Yikes. That's almost ten times the cost of the ULN parts, not a chance. What were they thinking?

Those are very nice indeed when you need isolation (I often do). But also non-stock and they'd have to compete with the usual optocoupler plus driver solution. Considering that they want $6 for them that'll be a tall order for their sales guys.

I wish Infineon would come off their key account thinking and stuff the channels, such as Digikey. And adjust their pricing. Their R&D develops top notch products but I often shun them because of past purchasing problems.

I never had problems driving it with 3.3V. Its a darlington array after all. Not mosfets.

The first thing Infineon needs to do is learn how to write datasheets. Back in my design-stuff-for-telecom days I noticed Zarlink (formerly Mitel) could explain the same in 20 pages where Infineon needed 200 pages to explain nothing at all. Guess what made it to the PCB.

Those also work at 3.3V. There is an appnote from TI. I don't know about the second source version from (IIRC) ST though.

It should be fine-- "5V" TTL has output voltage in the 3.3V range when sourcing current, but I'd get nervous if driving a lot of output current and the nominal supply is less than 3.3V.

I have not been able to use them in some cases because the output voltage drop is too high (Darlington). A CMOS version with low Rds(on) would be nice, but it has to be really cheap (the bipolar 7-output ULN2003A is under a dime).

Thanks. I was just wondering about resistor tolerances in there, can be quite high in chips. But the datasheet sez ok and you plus others also said it, so that gives me the warm and fuzzy about it.

Under 100mA in my case and we can live with the 1V or so of drop because it's driving 12V relays.

The drop also causes it to warm up. Hey, an anti-icing feature :-)

Wish I could use the 2003 but it's eight relays. Darn. I never understood why nobody came out with a CMOS equivalent. It would be ok if it had only 30V or so, since 2.7V logic level FETs are difficult on a cheap process if you want higher voltages.

So, get some ULN-2805A. Or ULN-2801 and pick your own input resistors. ;-)

A graph of Iin vs. Vin for the '03, in the 22 year old Sprague datasheet, shows the normal operating range is expected to be about 2 1/3 and about 3 2/3 volts. Giving an input current of .5 to 1.25 mA.

TTL Voh was pretty limp, so CMOS at 3.3 can't be much worse.

Mark Zenier snipped-for-privacy@eskimo.com Googleproofaddress(account:mzenier provider:eskimo domain:com)

IIRC we use the TSM2302 N channel MOSFET a lot for small relays. Dirt cheap but only up to 20V though. And beware there is also a P channel datasheet which is wrong :-)

ST has some equivalents so thats not bad. IMHO this series of chips have become an industry standard like the NE555, ULN2003 and the 8051.

usual.

But for that they would have to be