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

Discussion in 'General Electronics' started by Lewin A.R.W. Edwards, Jul 23, 2004.

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  1. 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

    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
    <> 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.
  2. Jim Stewart

    Jim Stewart Guest

    I'd be glad to order you some samples and
    let you know what they look like when they
    come in :)
  3. The6502man

    The6502man Guest

    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...

  4. Thanks, but I would like to order PCBs this weekend if I can :)
  5. Hi,
    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.
    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.
  6. 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 ?
  7. You could always do both a 150 and 300mil patterns. I have not seen
    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.
    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

    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 :)
  8. Ryan Wheeler

    Ryan Wheeler Guest

    Alegro has taken them of the market (almost)
  9. 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 ?

  10. I'm having difficulty finding a surface-mount replacement for the
    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.
  11. Mike Page

    Mike Page Guest

    ULN2803 - like all darlingtons - drop around 1V. This can make them
    marginal in 5V systems, let alone lower voltages.
    "Digital" transistors are very easy indeed.
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