adressable leds

[4LEKS1]

Hey! I'm working on project that uses around 200 SK6812 RGBWW leds. The boards are custom is shape, and because the design as overhead lightning I'm running around 24V to each light. So I made custom stepdowm powersupply to handle the conversion to 5V. I used ti's webench powerdesigner page to help me to get right configuration for the voltage controller that I'm using. The controller is LM25145RGYT and the schematics and picture are in the attachments below.(the R4 is actually 20K ohms for setting the frequency to around 500khz) So the output is 5.02V and it keeps it there even when draving 12A with resistive load. but as soon as I drive the leds with it, after just 1A the controller goes crazy, with the frequency bouning here and there, and the voltage getting spikes between 3V and 9V with destructive impacts on the leds. the leds all have 100nF caps close to them, and the "branches" have 8x 4.7uF capasitors on them. So I'm assuming that the leds are generating so much noice, that it messes up with the feedback. what should I do to midigate this problem?



-Aleksi

[Refrigerator]

Maybe try pulling SYNCIN low.

A continuous logic low
state at the SYNCIN pin enables diode emulation to prevent reverse current flow in the inductor. Diode
emulation results in DCM operation at light loads, which improves efficiency. A logic high state at the
SYNCIN pin disables diode emulation producing forced-PWM (FPWM) operation. During soft-start when
SYNCIN is high or a clock signal is present, the LM25145 operates in diode emulation mode until the
output is in regulation, then gradually increases the SW zero-cross threshold, resulting in a gradual
transition from DCM to FPWM.

Also SMPS's don't like big remote capacitances and can go a little unstable.

the leds all have 100nF caps close to them, and the "branches" have 8x 4.7uF capasitors on them.

I don't see anything obviously bad with the schematic. Perhaps there could be a problem with your PCB design?

[Refrigerator]

Also there's no need to connect PGOOD to anything, it's an open drain output. You use it to indicate to some other device that the power is good.

Power Good indicator. This pin is an open-drain output. A high state indicates that the voltage at the FB pin
is within a specified tolerance window centered at 0.8 V.

[Smokey]

Did you ever sort this out?