R1245x Series

1.2A, 30V Step Down DC/DC converter

Data Sheet / Flyer
Data Sheet * Flyer
(2.03 MB)    

The R1245x series are CMOS-based Step-down DC/DC converter with internal N-channel high side Tr. The ON resistance of the built-in high-side transistor is 0.35Ω and the R1245 can provide the maximum 1.2A output current. Each of the ICs consists of an oscillator, a PWM control circuit, a voltage reference unit, an error amplifier, a phase compensation circuit, a slope compensation circuit, a soft-start circuit, protection circuits, an internal voltage regulator, and a switch for bootstrap circuit. The ICs can make up a step-down DC/DC converter with an inductor, resistors, a diode, and capacitors.

The R1245x series are current mode operating type DC/DC converters without an external current sense resistor, and realizes fast response and high efficiency. As an output capacitor, a ceramic type capacitor can be used with the R1245X series. The options of the internal oscillator frequency are preset at 330kHz for version A and B, 500kHz for version C and D, 1000kHz for version E and F, 2400kHz for version G and H.

As for protection, an Lx peak current limit circuit cycle by cycle, a thermal shutdown function and an under voltage lockout (UVLO) function are built in. Furthermore, there are two types for short protection, for A/C/E/G version, a latch protection function which makes the output latch off if the output voltage keeps lower than the set output voltage for a certain time after detecting current limit is built in, for B/D/F/H version, a fold-back protection function which changes the oscillator frequency slower after detecting short circuit or equivalent.

As for the packages of the R1245 series, HSOP-8E, DFN(PLP)2020-8, SOT23-6W are available.

Operating Voltage 4.5 V to 30 V
Internal N-channel MOSFET Driver Typ. RON = 0.35 Ω
Adjustable Output Voltage with External Resistor 0.8 V or more
Feedback Voltage and Tolerance 0.8 V±1.0%
Peak Current Limit Typ. 2.0 A
UVLO Function Released Voltage Typ. 4.0 V
Operating Frequency 330 kHz (Ver. A/B), 500 kHz (Ver. C/D),
1000 kHz (Ver. E/F), 2400 kHz (Ver. G/H)
Fold-back Protected Frequency 170 kHz (Ver. B/D), 250 kHz (Ver. F), 400 kHz (Ver. H)
Latch Protection Delay Time Typ. 4 ms (Ver. A/C/E/G)
Ceramic Capacitors Recommended for Input and Output.
Stand-by Current Typ. 0 µA
Packages SOT-23-6W, DFN(PLP)2020-8, HSOP-8E
  • Digital Home Appliances: Digital TVs, DVD Players
  • Office Equipment: Printers, Faxes
  • 5V PSU or 2-cell or more Li-ion Battery Powered Communication Equipment, Cameras, VCRs, Camcorders
  • High Voltage Battery-powered Equipment

Data Sheet Flyer Package Mark Info. Quality Assurance Data
R1245x Series(2.03 MB) R1245x Series DFN(PLP) 2020-8 R1245K Reliability
SOT-23-6W R1245N Reliability
HSOP-8E R1245S Reliability

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