R1225N Series

PWM/VFM step-down DC/DC controller

Data Sheet / Flyer
Data Sheet * Flyer

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 2.3V~18.5V
Built-in Soft-start Function and Latch-type Protection Function
Three options of Oscillator Frequency 180kHz, 300kHz, 500kHz
High Efficiency Typ. 90%
Output Voltage Stepwise Setting with a step of 0.1V in the range of 1.2V ~ 6.0V
Standby Current Typ. 0.0μA
High Accuracy Output Voltage ±2.0%
Low Temperature-Drift Coefficient of Output Voltage Typ. ±100ppm/°C

  • Power source for hand-held communication equipment, cameras, video instruments such as VCRs, camcorders.
  • Power source for battery-powered equipment.
  • Power source for household electrical appliances.

Data Sheet Flyer Package Info. Mark Info. Quality Assurance Data
R1225N Series R1225N Series SOT-23-6W R1225N Reliability

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