I am trying to connect the compensation components to TPS65261.
On page 27, under the title "9.2.2.4 Loop Compensation", it gives the formulas to calculate the resistor and capacitor values.
I wrote the following script to do the calculations.
fs = 10^6 * 1 // Switching Frequency : 1 MHz Vo = 5 // Output Voltage : 5 V Co = 10^-6 * 44.1 // Output Capacitance : 44.1 uF Gea = 10^-6 * 300 // Error Amplifier Gain : 300 uS Gps = 7.4 // Power Stage Gain : 7.4 A/V Vref = 0.6 // Reference Voltage : 600 mV Rl_esr = 10^-3 * 19 // ESR of the Inductor : 19 mOhm Rc_esr = 10^-3 * 10 // ESR of the Capacitor : 10 mOhm fc = fs / 10 fp = 1 / (2 * pi * Rl_esr * Co) Rc = (2 * pi * fc * Vo * Co) / (Gea * Vref * Gps) Cc = Rl_esr * Co / Rc Cb = Rc_esr * Co / Rc
The calculated values are:
Rc = 104012 Ohm
Cc = 8.056 pF
Cb = 4.240 pF
However, in the reference design on page 24, values of the Cb capacitors are 3.3nF, 2.2nF, 2.2nF.
On the other hand, I always calculate the Cb capacitors in the range of pico farads. I mean I calculate around 1000 times fewer values.
Why do I calculate the Cb capacitors in pico farads, while the reference design uses nano farad valued capacitors? What am I missing here. Can you find the mistake in my calculation?
Thanks in advance.
