ULN2803 or equivalent in SMD package? TI's???

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I'm having difficulty finding a surface-mount replacement for the
venerable ULN2803 (octal Darlington driver, 50V max, 500mA per driver,
clamp diodes included). The application is low-speed stepper motor
driving.

I found the Texas Instruments ULN2803ADWR, but the documentation for
it has me thoroughly confused. Digi-Key says it's an 18 SOIC but has
no drawing or datasheet. The datasheet from TI shows a DIP package in
both the pinout and mech drawings, but the description table shows
"SOIC (DW)". Going to TI's packaging info page at
<http://www.ti.com/sc/docs/psheets/mechanic/D.htm> shows they don't
even have an 18-SOIC package!

Can anyone clarify the actual dimensions of TI's part? I don't want to
make boards with the wrong land pattern.. been there, done that.

Or can someone suggest a replacement? I'm actually only switching
about 110mA of load but the extra is nice to have; I don't want to go
below 250mA per channel capability.

Re: ULN2803 or equivalent in SMD package? TI's???
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I'd be glad to order you some samples and
let you know what they look like when they
come in (:



Re: ULN2803 or equivalent in SMD package? TI's???
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Possibly you're looking for a narrow (150 mils) body, and the 18 pin is
a wide (300 mils) body?



Also, Toshiba has a surface mount version of the ULN2803. I don't have
the part number though...


Tony

Re: ULN2803 or equivalent in SMD package? TI's???
Hi,

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Either one will save me a boatload of space and a little money. More
importantly, this is the last through-hole part in this particular
design. I just finished changing all the electros over to SMD, now if I
can get rid of that pesky Darlington driver, I will have a significantly
cheaper PCB.

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ULN2803AFW, 300 mil package, but it's more expensive than the TI part. I
guess I should lay out for the Toshiba part and assume that TI's is
identical. Actually now I come to think of it, that's very likely to be
true. I think I need sleep.



Re: ULN2803 or equivalent in SMD package? TI's???
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You could always do both a 150 and 300mil patterns. I have not seen
std SO packages not on 50mil pitch, but there are offerings in both
150 and 300 mils width - mainly for thermal reasons.

You could also look at SMD MOSFETS, they are lower loss than
darlingtons, and so can give a smaller thermal layout ?
-jg


Re: ULN2803 or equivalent in SMD package? TI's???
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The only thing that worries me is pinouts. I don't feel comfortable
assuming things. Chip mfrs do weird things for no apparent reason.

This is also a "mature" design that is just being respun for lower
production cost, so I don't want to change it any more than necessary.
I'm going to take a chance on rework and order a 250-piece run of
boards. This component is the single item I'm not happy about;
everything else, I have checked datasheets for all important
characteristics, and I've physically checked components on a 1:1
printout of the artwork.

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I don't really have a thermal problem though. The package does not
become noticeably warmer than ambient during normal operation of the
appliance. I'm actually using paired channels to drive four outputs,
each output only needs to sink 120mA continuous at most (more typically,
60mA), and the switching speeds are low. There *are* some transient
current spikes that can get up pretty high, which is why I want plenty
of margin. But they are rare and don't significantly contribute to chip
heating.


The other part I'm going to be looking for soon is an H-bridge IC
equivalent to the LMD18200 or 18201 (the next thing I'm costing-down is
the DC motor controller). That should be fun. I bet it will be some odd
package with big heatsink tabs. OBTW, these are submarine modules in
case you didn't guess :)



Re: ULN2803 or equivalent in SMD package? TI's???

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The 'W' almost universally means wide body, which is 300 mils.
I see someone mentioned Allegro is dropping the ULN2803, (and TI
is only doing the SMD one now ) - it could be devices like TPIC6B273 /
595 etc (which have 3 current grades) have replaced it ?

See
http://focus.ti.com/docs/search/paramsearch.jhtml?tfsection=param_table&templateId52%55&showAssociated=false&familyId35%6
-jg



Re: ULN2803 or equivalent in SMD package? TI's???


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Thanks, but I would like to order PCBs this weekend if I can :)


Re: ULN2803 or equivalent in SMD package? TI's???

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  Alegro has taken them of the market (almost)
  http://www.allegromicro.com/sf/2801 /

Re: ULN2803 or equivalent in SMD package? TI's???
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Right... However TI and Toshiba (and I think ST?) list them as current
production without caveats.

The problem is finding a replacement with similar characteristics. I
think that the target applications for these devices are being filled by
ASSP microcontrollers with high-current drivers built in.

It's simple enough to build something out of discrete components, but
it's easier to use an off-the-shelf part like the ULN28xx.


Re: ULN2803 or equivalent in SMD package? TI's???

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ULN2803 - like all darlingtons - drop around 1V. This can make them
marginal in 5V systems, let alone lower voltages.

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"Digital" transistors are very easy indeed.

--
Mike Page BEng(Hons) MIEE           www.eclectic-web.co.uk
Quiet! Tony's battling the forces of conservatism, whoever we are.

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