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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