The R1225N Series are CMOS-based PWM step-down DC/DC Converter controllers with low
supply current.Each of these ICs consists of an oscillator, a PWM control circuit, a reference voltage unit,
an error amplifier, a soft-start circuit, a latch-type protection circuit, a PWM/VFM alternative circuit, a
chip enable circuit, a phase compensation circuit, and an input voltage detect circuit. Further, protection
circuit delay time adjuster circuit, and resistors for voltage detection are included. A low ripple, high efficiency
step-down DC/DC converter can be easily composed of this IC with some external components, or a power-transistor,
an inductor, a diode and capacitors.
With a PWM/VFM alternative circuit, when the load current is small, the operation is automatically switching
into the VFM oscillator from PWM oscillator, therefore the efficiency at small load current is improved.
The R1225NXXXC/D/K types, which are without a PWM/VFM alternative circuit, are also available.
If the term of maximum duty cycle keeps on a certain time, the embedded protection circuit works. It is
latch-type protection circuit, and it works to latch an external Power MOSFET with keeping it off. To release
the condition of protection, after disable this IC with a chip enable circuit, enable it again, or restart
this IC with power-on. Delay Time for protection circuit is adjustable with an external capacitor. With
a built-in UVLO function, when the input voltage is UVLO threshold or less, this IC keeps standby state,
and saves its consumption current and avoids miss-operation.Further, if the set output voltage is equal
or more than 2.1V, with a built-in start-up function, at the power-on moment, until the input voltage becomes
more than the set output voltage, DC/DC operation is halted and avoids miss-operation.
Wide
Range of Input Voltage 
