Cypress Perform

 Example: Let the current through an LED string be 300mA with a ripple of 40%.

 So I_avg = 300 mA.

 Hence I_peak = 1.2 x I_avg = 360 mA and I_valley = 0.8 x I_avg = 240 mA

 Let the,

sense resistance value R_sense = 0.22 W

gain of CSA be 20 and,

the 8-bit DAC be set at a resolution of 2.6V/10mV.

 Current sense voltage V_peak = I_peak x R_sense = 360 x 0.22 = 79.2 mV.

 Similarly V_valley= I_valley x R_sense = 240 x 0.22 = 52.8 mV.

 Corresponding to V_peak and V_valley, the output of CSA would be the gain multiplied by the voltage.

 Hence,

                        V’_peak = V_peak x 20 = 1.584 V and

                        V’_valley= V_valley x 20 = 1.056 V.

Now, the peak or upper limit DAC reference is calculated as,

REF_upper = (V’_peak/2.6) x 256 = 156

Similarly, valley or lower DAC reference is,

REF_lower = (V’_valley/2.6) x 256 = 104