TPS61197: Calculation of compensation values

I think I've answered my initial question inasmuch as I now understand that D stands for Duty cycle. The problem I now have is that we operate this device in the full range of 0 - 100% duty cycle. At 100%, the compensation resistor is infinite (the right hand plane zero frequency is 0Hz), assuming tht 1-D = 0 at 100%. What value of duty cycle should be used when calculating the compensation R and C values? Should I assume a mean value of 50%?

Hi Julian,

The duty cycle can't be 100% due to real components parasitic.

BTW, may I know what is your LED configuration like the amount of LEDs and LED current? TPS61197 is not recommended for new design so maybe I can give you another candidate.

BR

Patrick

Hi Patrick, thanks for replying. Yes, I subsequently saw that the upper limit is 98%, so I used that as the value of D, since most clients use the panel backlight at maximum. The backlight is running 6 LED strings with a total current of 420mA at 38V and we’re having to modify the compensation filter because this new panel’s backlight is quite different from the other models in our range. We’re aware that we will have to replace the 61197 soon, so I’d be interested to hear your suggestions for a replacement.

best regards

Julian Hiorns

Hi Julian,

You can refer to TPS92365x.

TPS923652 data sheet, product information and support | TI.com

BR

Patrick