FPWM is employed when the FPWM pin is pulled high, or the device is synchronized to an external clock. In this mode, diode emulation is turned off, and the device emains in CCM over the full load range. In FPWM operation, the frequency of operation is constant and fixed unless the minimum tON or tOFF are exceeded, which cause the device to enter foldback mode. In these cases, PWM operation is still maintained, but the frequency of operation is folded back (reduced) to maintain proper regulation. DC accuracy is at a minimum in FPWM mode.