I would like to use LT3094/LT3045-1 for positive and negative power supply. The output voltage is +- 12V but the input may be +-15V or +-18V. We are considering putting a heat sink beneath the LDOs (i.e., on the 4th layer).
But the reference designs of LT3094 and LT3045-1 suggest that a C1 being placed underneath for EMF current flow, which maximize the PSRR performance. Though, this capacitor make placing the heat sink non-feasible.
We would like to known, if we were maintaining the PSRR performance, where should we place this capacitor and why?
The input cap should be placed close to the input pin to bypass the noise. If there is not enough space for C1, it has to be put on the top layer, but you cannot get the best PSRR performance. To get the best PSRR performance, the input and output return path of input current should be exactly overlapped, and the top layer needs to be shielded.
I found that the Rset and OutS must be connected to a Kelvin like Capacitor. I am using LT3045-1/LT3094 dring multiple amplifiers and each power rail is decoupled with a 10uF tantalum capacitor and 0.1uF X7R capacitor, is there any stability issues? Should I connect a small resistor (or an RC filter) at the OUT pins of LT3045-1/LT3094?
Is there a ceramic output cap at each LT3045-1/3094? We recommend to use low ESR and ESL output caps to keep the system stable.
we place these components as those in application manual. A capacitor is placed (4 terminals) at out, outs, gnd, and the gnd terminal of cset. However, 3045 and 3094 drive multiple amplifiers (7 in total) where each one was de coupled by a 10 uF and 0.1 uF capacitors. Is there might be stability issues?
there are multiple 10uF, 0.1uF on the amplifiers powered by AVSS and AVDD
As long as there are low ESR, ESL ceramic caps at LT3045/3094 outputs, there should be no stability issues.