LM5122: maximum off-time?

Hi

That is 'Forced off-time' during PWM operation. In the bypass mode, LM5122 is capable of 100% duty cycle.

Regards,

EL 

I still do not understand how I could use the information about the "forced off-time" ..I set the maximum frequency in relation to the minimum on-time in this way:
my specs are Vin_min=5V , Vin_max=8.4V and Vout=9V. As a consequence of that, I have a Duty_min=1-(Vin_max/Vout)=0.066 that leads to a Fsw_max=Duty_min/Ton_min=220Khz. Am I wrong?

Hello

I think you are confusing between buck and boost, high-side switch on-time and low-side switch on-time.
In bypass mode & boost topology, low-side switch duty cycle is 0% and high-side switch duty cycle is 100%. Boost converter duty cycle is the same as the low-side switch duty cycle.
In bypass mode & buck topology, low-side switch duty cycle is 0% and high-side switch duty cycle is 100%. Buck converter duty cycle is the same as the high-side switch duty cycle.
'forced off-time' in the LM5122 datasheet is low-side switch off-time.
'100%' on the first page of LM5122 datasheet is '100% duty cycle for the high-side synchronous switch'
Please refer section 7.3.12 of LM5122 datasheet.

Regards,
EL

thanks for the reply, I've read the recommended section. So, the maximum forced off-time is referring to the case when high duty cycle occurs..
In my situation,with D_min=0.066 and D_max=0.44 , that constraint should not treat me..Is it right?I mean..
I must only ensure that the selected fsw is such that the converter does not go beyond the minimum on-time that is 300ns.Correct?

Thank you, now I'm more serene..I'm at the end of the design process, and I was worried about having to redo the calculations