
R1224N S ERIES  
PWM/VFM step-down DC/DC Converter 
NO.EA-096-061102 
OUTLINE 
The R1224N 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 
phase compensation circuit, a soft-start circuit, a protection circuit, a PWM/VFM alternative circuit, a chip enable 
circuit, resistors for output voltage detect, and input voltage detect circuit. A low ripple, high efficiency step-down 
DC/DC converter can be easily composed of this IC with only several external components, or a power-transistor, 
an inductor, a diode and capacitors. Output Voltage is fixed or can be adjusted with external resistors (Adjustable 
types are without PWM/VFM alternative circuit). 
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. Several 
types of the R1224Nxxx, 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. The 
protection circuit is Reset-type protection circuit, and it works to restart the operation with soft-start and repeat 
this operation until maximum duty cycle condition is released. When the cause of large load current or something 
else is removed, the operation is automatically released and returns to normal operation. 
Further, built-in UVLO function works when the input voltage is equal or less than UVLO threshold, it makes 
this IC be standby and suppresses the consumption current and avoid an unstable operation. 
FEATURES 
 
Supply Current................................................................Typ. 20
μ
A (R1224Nxx2E/F/M/L, R1224N102M)  
Typ. 30
μ
A (R1224Nxx2G, R1224N102G) 
Typ. 40
μ
A (R1224Nxx2H, R1224N102H) 
 
Standby Current..............................................................Typ. 0
μ
A 
 
Input Voltage Range .......................................................2.3V~18.5V 
 
Output Voltage Range.....................................................1.2V to 6.0V (R1224Nxx2x) 
1.0V to V
IN
 (R1224N102x) 
 
Output Voltage Accuracy.................................................
±
2.0% 
 
Oscillator Frequency.......................................................Typ. 180kHz (R1224Nxx2M, R1224N102M) 
Typ. 300kHz (R1224Nxx2E/G, R1224N102G) 
Typ. 500kHz (R1224Nxx2F/H, R1224N102H) 
 
Efficiency.........................................................................Typ. 90% 
 
Low Temperature-Drift Coefficient of Output Voltage......Typ. 
±
100ppm/°C 
 
Package.......................................................................... SOT-23-5 
 
Built-in Soft-start Function............................................... Typ. 10ms 
 
Built-in Current Limit Circuit 
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. 
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