Thank you for your answer. i understand 10mV to 30mV on FB is appropriate ripple voltage. When I look at the datasheet page-21, equiation (13) is the ripple injection equatio and equation (14 ) is the output ripple voltage VINJ(OUT). Although equation (15) presented VFB ripple voltage, VINJ(OUT) must be multiplied by R2/(R1+R2) of feed back resistors as shown in below.
VINJ(total) = VINJ(SW) + VINJ(OUT) x R1 / (R1+R2)
Please correct me if my understanding is incorrect.
