When a travel charger (2- wire charger) is used, the power switch is turned ON and OFF by the PWM input when the PWM rate is 1Hz. When PWM is HIGH, the switch is ON and the output current lout = charger current - CHAPS supply current. When PWM is LOW, the switch is OFF and the output current lout = 0. To prevent the switching transients inducing noise in audio circuitry of the phone soft switching is used.
The performance travel charger (3- wire charger) is controlled with PWM at a frequency of 32Hz. When the PWM rate is 32Hz CHAPS keeps the power switch continuously in the ON state.
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