ULN2803 ok to be driven by 3.3V logic?
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From: Joerg on 8 Jan 2010 14:16 Spehro Pefhany wrote: > On Fri, 08 Jan 2010 18:46:42 GMT, nico(a)puntnl.niks (Nico Coesel) > wrote: > >> Joerg <invalid(a)invalid.invalid> wrote: >> >>> Gents, >>> >>> Have to drive a bucket full of 12V relays but the uC is only 3.3V. The >>> ULN2803 is touted as a driver for 5V TTL logic by most companies (like >>> TI) but datasheets hint that it can happily live down to around 3V drive >>> level. Is that kosher? >> I never had problems driving it with 3.3V. Its a darlington array >> after all. Not mosfets. > > 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. > Under 100mA in my case and we can live with the 1V or so of drop because it's driving 12V relays. > 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). > 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. -- Regards, Joerg http://www.analogconsultants.com/ "gmail" domain blocked because of excessive spam. Use another domain or send PM.
From: Nico Coesel on 8 Jan 2010 16:07 Joerg <invalid(a)invalid.invalid> wrote: >Spehro Pefhany wrote: >> On Fri, 08 Jan 2010 18:46:42 GMT, nico(a)puntnl.niks (Nico Coesel) >> wrote: >> >>> Joerg <invalid(a)invalid.invalid> wrote: >>> >>>> Gents, >>>> >>>> Have to drive a bucket full of 12V relays but the uC is only 3.3V. The >>>> ULN2803 is touted as a driver for 5V TTL logic by most companies (like >>>> TI) but datasheets hint that it can happily live down to around 3V drive >>>> level. Is that kosher? >>> I never had problems driving it with 3.3V. Its a darlington array >>> after all. Not mosfets. >> >> 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. >> > >Under 100mA in my case and we can live with the 1V or so of drop because >it's driving 12V relays. > > >> 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). >> > >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. 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 :-) -- Failure does not prove something is impossible, failure simply indicates you are not using the right tools... nico(a)nctdevpuntnl (punt=.) --------------------------------------------------------------
From: Nico Coesel on 8 Jan 2010 16:14 Joerg <invalid(a)invalid.invalid> wrote: >John Larkin wrote: >> On Thu, 07 Jan 2010 14:27:59 -0800, Joerg <invalid(a)invalid.invalid> >> wrote: >> >>> Jim Thompson wrote: >>>> On Thu, 07 Jan 2010 13:20:52 -0800, Joerg <invalid(a)invalid.invalid> >>>> wrote: >>>> >>>>> Gents, >>>>> >>>>> Have to drive a bucket full of 12V relays but the uC is only 3.3V. The >>>>> ULN2803 is touted as a driver for 5V TTL logic by most companies (like >>>>> TI) but datasheets hint that it can happily live down to around 3V drive >>>>> level. Is that kosher? >>>>> >>>>> http://focus.ti.com/lit/ds/symlink/uln2803a.pdf >>>>> http://www.toshiba.com/taec/components2/Datasheet_Sync//393/22738.pdf >>>>> >>>>> App note SLAA148 suggests it is kosher but ... I figure I'd better ask >>>>> the famous gurus in this here group :-) >>>> Should work just fine. >>>> >>>>> http://focus.ti.com/lit/an/slaa148/slaa148.pdf >>>>> >>>>> A FET version would be nice as it gets the outputs lower but that's only >>>>> available from the more boutiquish suppliers. Demasiados Dolares, as usual. >>>> I'm quite surprised there isn't a MOS version. >>>> >>> 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: >>> >>> http://www.allegromicro.com/en/Products/Part_Numbers/6259/6259.pdf >>> >>> >>>> I don't keep track of off-the-shelf stuff. Have you looked at >>>> open-drain buffers/inverters? >>>> >>> 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. >> >> 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. >> > >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: > >http://focus.ti.com/lit/ds/symlink/tpic6595.pdf 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. -- Failure does not prove something is impossible, failure simply indicates you are not using the right tools... nico(a)nctdevpuntnl (punt=.) --------------------------------------------------------------
From: Joerg on 8 Jan 2010 16:40 Nico Coesel wrote: > Joerg <invalid(a)invalid.invalid> wrote: > >> John Larkin wrote: >>> On Thu, 07 Jan 2010 14:27:59 -0800, Joerg <invalid(a)invalid.invalid> >>> wrote: >>> >>>> Jim Thompson wrote: >>>>> On Thu, 07 Jan 2010 13:20:52 -0800, Joerg <invalid(a)invalid.invalid> >>>>> wrote: >>>>> >>>>>> Gents, >>>>>> >>>>>> Have to drive a bucket full of 12V relays but the uC is only 3.3V. The >>>>>> ULN2803 is touted as a driver for 5V TTL logic by most companies (like >>>>>> TI) but datasheets hint that it can happily live down to around 3V drive >>>>>> level. Is that kosher? >>>>>> >>>>>> http://focus.ti.com/lit/ds/symlink/uln2803a.pdf >>>>>> http://www.toshiba.com/taec/components2/Datasheet_Sync//393/22738.pdf >>>>>> >>>>>> App note SLAA148 suggests it is kosher but ... I figure I'd better ask >>>>>> the famous gurus in this here group :-) >>>>> Should work just fine. >>>>> >>>>>> http://focus.ti.com/lit/an/slaa148/slaa148.pdf >>>>>> >>>>>> A FET version would be nice as it gets the outputs lower but that's only >>>>>> available from the more boutiquish suppliers. Demasiados Dolares, as usual. >>>>> I'm quite surprised there isn't a MOS version. >>>>> >>>> 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: >>>> >>>> http://www.allegromicro.com/en/Products/Part_Numbers/6259/6259.pdf >>>> >>>> >>>>> I don't keep track of off-the-shelf stuff. Have you looked at >>>>> open-drain buffers/inverters? >>>>> >>>> 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. >>> 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. >>> >> 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: >> >> http://focus.ti.com/lit/ds/symlink/tpic6595.pdf > > 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. > But for that they would have to be << 50 cents :-) -- Regards, Joerg http://www.analogconsultants.com/ "gmail" domain blocked because of excessive spam. Use another domain or send PM.
From: Jim Thompson on 8 Jan 2010 17:22
On Fri, 08 Jan 2010 13:40:56 -0800, Joerg <invalid(a)invalid.invalid> wrote: >Nico Coesel wrote: >> Joerg <invalid(a)invalid.invalid> wrote: >> >>> John Larkin wrote: >>>> On Thu, 07 Jan 2010 14:27:59 -0800, Joerg <invalid(a)invalid.invalid> >>>> wrote: >>>> >>>>> Jim Thompson wrote: >>>>>> On Thu, 07 Jan 2010 13:20:52 -0800, Joerg <invalid(a)invalid.invalid> >>>>>> wrote: >>>>>> >>>>>>> Gents, >>>>>>> >>>>>>> Have to drive a bucket full of 12V relays but the uC is only 3.3V. The >>>>>>> ULN2803 is touted as a driver for 5V TTL logic by most companies (like >>>>>>> TI) but datasheets hint that it can happily live down to around 3V drive >>>>>>> level. Is that kosher? >>>>>>> >>>>>>> http://focus.ti.com/lit/ds/symlink/uln2803a.pdf >>>>>>> http://www.toshiba.com/taec/components2/Datasheet_Sync//393/22738.pdf >>>>>>> >>>>>>> App note SLAA148 suggests it is kosher but ... I figure I'd better ask >>>>>>> the famous gurus in this here group :-) >>>>>> Should work just fine. >>>>>> >>>>>>> http://focus.ti.com/lit/an/slaa148/slaa148.pdf >>>>>>> >>>>>>> A FET version would be nice as it gets the outputs lower but that's only >>>>>>> available from the more boutiquish suppliers. Demasiados Dolares, as usual. >>>>>> I'm quite surprised there isn't a MOS version. >>>>>> >>>>> 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: >>>>> >>>>> http://www.allegromicro.com/en/Products/Part_Numbers/6259/6259.pdf >>>>> >>>>> >>>>>> I don't keep track of off-the-shelf stuff. Have you looked at >>>>>> open-drain buffers/inverters? >>>>>> >>>>> 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. >>>> 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. >>>> >>> 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: >>> >>> http://focus.ti.com/lit/ds/symlink/tpic6595.pdf >> >> 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. >> > >But for that they would have to be << 50 cents :-) Cheapskate ;-) ...Jim Thompson -- | James E.Thompson, CTO | mens | | Analog Innovations, Inc. | et | | Analog/Mixed-Signal ASIC's and Discrete Systems | manus | | Phoenix, Arizona 85048 Skype: Contacts Only | | | Voice:(480)460-2350 Fax: Available upon request | Brass Rat | | E-mail Icon at http://www.analog-innovations.com | 1962 | I love to cook with wine. Sometimes I even put it in the food. |