Data sheet help - TI REF5025 decoupling

[juz_ad]

The first image is taken from the data sheet for a TI 8x DAC evaluation board. it shows C11 at the REF5025 output with a 1R5 Resistor to GND.

When I checked the data sheet for the REF5025 it doesn't show this R to GND (second image) - it quotes "A 1-μF to 50-μF, low-ESR output capacitor (CL) must be connected from VOUT to GND. The ESR value should be less than or equal to 1.5 Ω."

So - these two sheets seem to contradict each other. The original data sheet says a Cap with an ESR ≤1R5 and the DAC eval data sheet shows a Cap with an R of 1R5.

Any comments on what one might be right or wrong?

Thanks

 

[dick_freebird]

Whichever one works for you is right. If this is a bipolar shunt
reference then you must beware transient saturation in the
output device which can set up a relaxation oscillation (not
small signal and missed by any analysis which does not induce
said saturation). A too-large cap or one with too-low ESR
can do this on supply or load steps.

Check high temperature as a worst case condition. Try a
matrix of capacitor values, ESR (by part number) and
series resistor (which can also help HF stability if a zero
around 15MHz is what you need) and pick a combo that
puts you well away from all of the various forms of
unpleasantness.

Datasheets and app notes are the beginning of wisdom,
not the end.

 

[David_]

Maybe they put in the resistor just in case, if not needed just jumper it with a 0ohm resistor.
Then you would have a larger number of possible capacitors that could be made to work.