Nisshinbo Micro Devices Inc. R1245K003C-TR

The R1245x is a CMOS-based step-down DC/DC converter with a built-in N-channel high-side transistor. The on-resistance of the built-in high-side transistor is 0.35 Ω, with a maximum output current of 1.2 A. This IC includes an oscillator, PWM control circuit, voltage reference unit, error amplifier, phase compensation circuit, slope compensation circuit, soft-start circuit, protection circuit, internal regulator, and a switch for the bootstrap circuit. It can form a step-down DC/DC converter using an inductor, resistors, diode, and capacitors.

The R1245x operates in current mode without an external current sense resistor, providing fast response and high efficiency. Ceramic capacitors can be used as output capacitors. The internal oscillator frequency is preset to 330 kHz for versions A and B, 500 kHz for versions C and D, 1000 kHz for versions E and F, and 2400 kHz for versions G and H.

For protection, the R1245x incorporates a cycle-by-cycle Lx peak current limiting circuit, thermal shutdown, and undervoltage lockout (UVLO). Two types of short-circuit protection are available: for versions A/C/E/G, if the output voltage remains below the set output voltage for a period of time after current limiting is detected, a latch protection function is triggered to shut down the output; for versions B/D/F/H, foldback protection is implemented by slowing down the oscillator frequency when a short circuit or equivalent condition is detected. The R1245x is available in HSOP-8E, DFN(PLP)2020-8, and SOT23-6W packages.