[time-nuts] ULN regulator with more current capability than LT3042?
John Ackermann N8UR
jra at febo.com
Mon Mar 19 14:11:13 UTC 2018
Thanks, all. I think I'll end up using the 3042 with pass transistor,
partly for reasons of cost. I have no idea whether paralleling two
3042s would result in lower noise from the device, and there are already
three or four fairly pricey chips on the board.
I appreciate all the info!
John
----
On 03/18/2018 06:43 PM, Charles Steinmetz wrote:
> Tom wrote:
>
>> Run two in parallel for twice the current and less noise?
>
> This is actually a better solution than using an LT3045, for two
> reasons. First, as Tom noted, by paralleling two devices, the noise is
> reduced by sqrt 2 = ~1.4:
>
> "Designed as a precision current reference followed by a high
> performance voltage buffer, the LT3042 is easily paralleled to increase
> output current, spread heat on the PCB and further reduce noise --
> output noise decreases by the square-root of the number of devices in
> parallel." [LT Journal of Analog Innovation, v25 n1 Apr 2015].
> <http://www.linear.com/docs/46398>
>
> Second, it reduces the dissipation of each regulator, so they run
> cooler. And as LT says, it allows spreading the heat on the board (but
> it is not advisable to put them too far apart).
>
> The primary disadvantage is that two 3042s cost about half again more
> than one 3045. Also, board space may be a factor in some applications.
>
> So, unless you are extremely tight on board space or the ~1.5x cost
> increase is prohibitive, two 3042s in parallel are a better solution
> than one 3045 if you are seeking the lowest noise possible.
>
> Best regards,
>
> Charles
>
>
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