The A4403 is a buck converter that uses valley current-mode
control. This control scheme allows very short switch on-times
to be achieved, making it ideal for applications that require
high switching frequencies combined with high input voltages
and low output voltages.
Low cost is accomplished through high switching frequencies
of up to 2 MHz, allowing smaller and lower value inductors
and capacitors. In addition, minimal external components are
required through high levels of integration. Optimal drive
circuits are utilized to minimize switching losses.
The switching frequency is maintained constant, as the on-time
is modulated by the input voltage. This feed-forward control
ensures excellent line correction. The on-time is set by an
external resistor pulled-up to the input supply.