LM25088：LM25088 CYCLE BY CYCLE CURRENT LIMIT

Hi 

I use LM25088-2, I use the RES function now.

There is a new problem.

I find the DFC would change the frequency three steps. 

At the three steps boundary, the PWM would be very unstable.

In my opinion, that is the root cause.

How could I do to make DFC very smooth?

Thanks.

Hi

I set the R-Shunt to 0.1ohm.

In the stead state 28V/06A, the RES pin raised itself. 

I set the  R-Shunt to 0.022ohm, I try to add the load to 28V/2.5A, the RES pin keep 0V

I think the reason is DCM. 

Is that right?

Hi

3. Externally Controlled Hiccup: The RES pin can also be used as an input. By externally driving the pin to a
level greater than the 1.2-V hiccup threshold, the controller is forced into the delayed restart sequence. For
example, the external trigger for a delayed restart sequence can come from an overtemperature protection
or an output overvoltage sensor.

I try this function, give a extenal singal from current mirror voltage level, and the LM25088 was broken now.

Ripple, Iin & RES

UPDATE

Change the Cramp, the IC works in order.

Hi

It looks like not a nice DFC function.

Fisrt, once DD works into CCM, the Vout would dropout voltage lower related Iout.

Second, if 28V/2A works all DCM, the DFC in the two boundary (1/3 & 2/3 load) would shake.

Hello Andy 

Unfortunately this device doesn't provide a smooth transition. Please check recently released device (LM5148) which should be able to provide smoother waveform when VIN is close to the VOUT.  

-EL 

Hello Andy 

 I will close this thread. Please let me know if you have an additional question.

-EL