Hi,
Any recommendations about selecting the bottom feedback resistor?
In the datasheet a use case of 115K ohm is shown, but it fits for 3.3V.
I need to produce output voltages of 12V up to 33V.
Thanks,
Kobi
Hi,
Any recommendations about selecting the bottom feedback resistor?
In the datasheet a use case of 115K ohm is shown, but it fits for 3.3V.
I need to produce output voltages of 12V up to 33V.
Thanks,
Kobi
Hi Kobi,
The 115K ohm for bottom resistor is still fits for the 12V and 33V VOUT.
It has a good balance in terms of power dissipation (VOUT^2/Rfb_total) and error (cause by Ifb * Rtop).
Example:
For 33V use case,
Rbottom = 115 K ohm (std value)
Rtop = 4.64M ohm (std value)
VOUT = 33.078V
Power dissipation across FB resistors = 230uW
Error (Ifb * Rtop) = 0.1uA * 4.64M ohm = +464mV (max)
% Error_total_max = {[(33.078V + 0.464V) - 33V]/33}*100% = 1.64% (max)
Thus, for 12V up to 33V operation (I assume you'll be using adjustable resistor for Rtop - can you confirm? or perhaps give us some insight in your application), Rtop range = 1.61 M ohm to 4.64 M ohm.
Thanks and regards,
Jefferson
Hi Jefferson,
In my design, a single ADP2360 is used, to support different VCOs, each has a different maximal Vtune.
It is a one time configuration for each physical board, so I use a fixed resistor Rtop.
Your answer is very helpful,
Thanks,
Kobi