[time-nuts] ULN regulator with more current capability than LT3042?

[John Ackermann N8UR]

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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