R1224N SERIES
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 consist s of an oscillator, a PWM control circuit, a reference volt age unit, an e rror amplifier, a
phase compensatio n circuit, a soft-start circuit, a protection circuit, a PWM/VFM alternative circuit, a chip enable
circuit, resistors for output volt age detect, and input voltage detect circuit. A low ripple, high efficiency step-down
DC/DC conve rter can be ea sily compose d of this IC with onl y several external compone nts, o r a power-transistor,
an inductor, a diode and capacitors. Output Voltage is fixed or can be adjusted with external resistors (Adjust able
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 cycl e condition is released. When the ca use of large load current or som ething
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 sta ndby and suppresses the consumption current and av oid an unstab le operation.
FEATURES
• Supply Current................................................................Typ. 20µA (R1224Nxx2E/F/M/L, R1224N102M)
Ty p. 30µA (R1224Nxx2G, R12 24N102G)
Ty p. 40µA (R1224Nxx2H, R1224N102H)
• Standby Current..............................................................Typ. 0µA
• Input Voltage Range .......................................................2.3V~18.5V
• Output Voltage Range.....................................................1.2V to 6.0V (R1224Nxx2x)
1.0V to VIN (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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