Dear peeps!

I am working on a design that decodes DMX over Artnet and outputs WS2813 digital strip signals.

The board should be able to take in 5–12 V so it can run on the same PSU as different types of LED strips. To achieve this, I used an LM5175 buck-boost controller. However, on my first prototype the buck-boost stage fails to provide the correct Vout for the rest of the board.

Here are the test results I have so far:

With Load (Teensy attatched)
In (v): Out (v):
5.4 2.4
7 3.4
9 3.7
12 3.9
24 3.9

Without Load
5.4 3.7
7 4.8
9 5.5
12 5.5
24 5.5

​

BOOT1 – SW1 (no load): 1.8 V
BOOT1 – SW1 (under load): ~3 V noise
BOOT2 – SW2 (no load): 2.0 V
BOOT2 – SW2 (under load): ~3.5 V

Has anyone worked with the LM5175 in this kind of setup and can point me in the right direction?
Any insights would be highly appreciated — thanks in advance!

Best,
Jeppe

 

No knowledge of that particular IC, so only commenting on what the datasheet suggests. The voltage on VBIAS is shown as recommended minimum 7.5V, so it may be worth disconnecting it from the 5V output. Some forums suggest lower values for RSENSE and others suggest there are some fake ICs out there.

 

Have you done a sanity check of your component values using https://www.ti.com/tool/LM5175QUICKSTART-CALC ?

 

Thanks for your replies. I still don't see any obvious errors in the design. However, I have recalculated every component and found a few to change. Also, I will be more careful with the layout.