LM22675: Do you have any load transient response waveform of LM22675?

HI  

what is the input and output conidition? and what is customer inductor and output capacitor?

you can also use webench for transient simulation 

Thanks

Hi Daniel,

Thank you very much for your reply.

The customer condition is the follows.

Vin=24V, Vo=5V, L=33uH, Co=200uF.

And I can't LM22675 Webench simulation because the transient simulation is not available.

Thank you again and best regards,

Kazuya.

HI 

let me see whether we can simulated from pspice and send you result later.

Thanks

HI

pls see below simulation result , using TINA model. the transient using 0.1A/us current slew rate , Vomin is 4.99V, Vomax is 5.03V

schematic as below

Hi Daniel,

Thank you very much for your strong supports.

The output voltage waveform is similar with the customer one.

The customer wants to reduce the total ripple voltage.

Is there any way to reduce the ripple voltage?

I think that the output capacitor (200uF) might be large a little to take a good phase margin of LM22675.

Is the output ripple voltage reduced when the output capacitor value is reduced (For example, 200uF -> 100uF)?

Could you please give me your reply?

Thank you again and best regards,

Kazuya.    

HI 

customer more care the Vo overshoot when load change from 80mA to 2mA, or they more care the ripple when load is 2mA?

Thanks

Hi Daniel,

The customer cares the Vo overshoot when load change from 80mA to 2mA.

Also the customer cares the Vo undershoot when load change from 2mA to 80mA.

Thank you and best regards,

Kazuya. 

HI Nakai:

I don't see very effective way to improve the transient, maybe customer can try below way:

1. adding some dummy load like 10mA-15mA

2. add a feedforward cap 470pF-1nF

3. add more capacitor 

Thanks

Hi Daniel,

Thank you very much for your strong supports.
I understood that any very effective way was not found.
I will tell those countermeasure to the customer except No.2 because they use 5V fixed version
which does not have FB terminal connected to the internal error amp directly.

Could you please give me your comment if you have any idea about the following question?

Q. The ripple voltage (undershoot + overshoot) is reduced from about 50mV to about 30mV when they replace 33uH inductor
     with 270uH one. Do you know why?

Thank you again and best regards,

Kazuya. 

Hi Nakai:
from simulation result, when you increase the inductor, the ripple on the output will be reduce. so it may helpful to also reduce the total overshoot voltage.

below is 220uH inductor, you can compare to original 33uH value waveform in previous simulation