LM2576HV-5 switching regulator

Hello Michael, 

The regulator should work fine at light load. It will be operating in discontinuous conduction mode (DCM). You may see slightly larger output voltage ripple at light load. 

I can look into the component values you mentioned, but please provide the input voltage range. 

Regards, 
Denislav 

Denislav,

Our input is a fairly well regulated 24V + 5%.

thks

Hi Michael, 

I am looking at page 12 of the datasheet. Here is a link to it: http://www.ti.com/lit/ds/symlink/lm2576hv.pdf

It looks like the 470uF cap you chose should be acceptable. 

Looking at page 13, figure 24, for 24V input and 5V 1A output the recommended inductor is 330uH. Your inductor is undersized and you will see larger output ripple voltage. You should check if that is acceptable for your design.

Also, the choice of inductor and output capacitor will affect the stability of the regulator. If the larger ripple is acceptable, you should still check if the regulator is stable. You can perform a load transient and see how well the regulator responds to it.

Regards, 
Denislav 

To add some more to the previous post, if you are observing unstable operation and cannot change the inductor, try increasing the output capacitance and see if the regulation improves. 

Regards, 

Denislav

Denislav,

Thanks,  how fast is the on/off pin response on this device?  Can it be reliably be used for protection?  The tolerance is quite wide to disable the output so

I guess it shouldn't be used directly as a voltage off sense, correct?

thks

Hi Michael, 

I am not sure about the on/off response time, but I would guess it is in a few microseconds range. I don't have a board handy to check this, but I will see if I can find one later today or tomorrow.

In terms of the threshold it is a logic level input so the guaranteed ON/OFF points are spread out. 

Regards, 
Denislav 

Denislav,

Thanks again for the info.

Regards,

Michael  aka Bruce