OUTLINE

The R1221N Series are PWM step-down DC/DC Converter controllers embedded with a voltage detector, with low supply current by CMOS process.

Each step-down DC/DC converter in these ICs consists of an oscillator, a PWM control circuit, a reference voltage unit, an error amplifier, a soft-start circuit, a protection circuit, a PWM/VFM alternative circuit, a chip enable circuit, and resistors for voltage detection. A low ripple, high efficiency step-down DC/DC converter can be composed of this IC with only four external components, or a power-transistor, an inductor, a diode and a capacitor.

The output voltage of DC/DC converter can be supervised by the built-in voltage detector.

With a PWM/VFM alternative circuit, when the load current is small, the operation turns into the VFM oscillator from PWM oscillator automatically, therefore the efficiency at small load current is improved.

FEATURES

● Wide Range of Input Voltage · · · · · · · · · · · · · 2.3V to 13.2V

● Built-in Soft-start Function and two choices of Protection Function(Latch-type or Reset-type)

● Two choices of Oscillator Frequency · · · · · · · · · · 300kHz, 500kHz

● High Efficiency · · · · · · · · · · · · · · · · · · · · · · TYP. 90

● Standby Current · · · · · · · · · · · · · · · · · · · · · TYP. 0µA

● Setting Output Voltage · · · · · · · · · · · · · · · · · Stepwise setting with a step of 0.1V in the range of 1.5V to 5.0V

● High Accuracy Output Voltage · · · · · · · · · · · · · · ±2.0

● Setting Detector Threshold Voltage · · · · · · · · · · · Stepwise setting with a step of 0.1V in the range of 1.2V to 4.5V

● High Accuracy Detector Threshold Voltage· · · · · · · ±2.0

● Low Temperature-Drift Coefficient of Output Voltage · TYP. ±100ppm/°C

APPLICATIONS

● 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.