RICOH Manuals

The RP505K Series is a 1A*1 step-down DC/DC converter with synchronous rectifier. The supply current is low and the ICs use CMOS process and DFN(PLP)2020-8 package. With the ICs, it is easy to make a low ripple, high efficiency synchronous rectifier step-down DC/DC converter with only an inductor and capacitors

RP505K series are low supply current CMOS-based PWM/VFM step-down DC/DC converters with synchronous rectifier. RP505K can be selected from two control types by input signal to the MODE pin - forced PWM control or PWM/VFM auto switching control in which mode automatically switches to high-efficiency VFM mode in low output current. The xx1A/B version with an internally fixed output voltage type and the 001C version with an externally adjustable output voltage type are available. RP505K includes a soft start circuit, an under-voltage lockout circuit (UVLO), thermal shutdown circuit and a latch protection circuit. By simply using an inductor, (resistors) and capacitors as external components, a high-efficiency step-down DC/DC converter can be easily configured. The small inductor (2.2μH) and output capacitor (10μF) can be used by the switching of 2.25MHz. A 2mm square compact DFN(PLP)2020-8 package is available.

RP550K001A is a CMOS-based 1A* dual step-down DC/DC converter with synchronous rectifier. Internally, each converter consists of oscillators, reference voltage units, error amplifiers, switching control circuits, soft-start circuit, latch type protection circuit, an under voltage lockout (UVLO) circuit, a thermal shutdown circuit and switching transistors. By adopting a synchronous rectifier with built-in switching transistors, a low ripple high efficiency synchronous rectifier step-down DC/DC converter can be easily configured with simply using two inductors, resistors and capacitors as the external components. RP550K001A is available in DFN(PLP)2730-12 package which achieves high-density mounting on boards. Output voltage is adjustable with external divider resistors. Latch type protection circuit latches the built-in driver to the OFF state during high load or if the output is short-circuited for a specified time (protection delay time). The latch type protection circuit can be released by once setting the converter into the standby mode with the CE pin and then setting it back to the active mode, or, by turning the power off and back on. Setting the supply voltage lower than the UVLO detector threshold can also release the latch type protection circuit. Thermal shutdown circuit detects overheating of the converter and stops the converter operation to protect it from damage.

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 stopped.

The R1224N Series are low supply current CMOS-based PWM/VFM step-down DC/DC controller with an external output transistor. By simply using a power transistor, an inductor, a diode, and a capacitor as external components, a high-efficiency step-down DC/DC converter can be easily configured. The PWM/VFM alternative circuit automatically switches to VFM control in the smaller output current range and provides high efficiency even in the smaller output current range. The version with fixed PWM control and adjustable output voltage with an external resistor is also available. The reset type protection circuit embedded into the device limits output current by repeatedly triggering the soft start circuit when the oscillator maximum duty cycle continues for a predetermined period of time. When the oscillator maximum duty cycle ends, normal operation is resumed automatically. R1224N also includes an under-voltage lockout circuit (UVLO) that stops DC/DC operation and prevents malfunction when the supply voltage falls below the UVLO detect voltage and reduces supply current.

The R1225N 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 soft-start circuit, a latch-type protection circuit, a PWM/VFM alternative circuit, a chip enable circuit, a phase compensation circuit, and an input voltage detect circuit. Further, protection circuit delay time adjuster circuit, and resistors for voltage detection are included. A low ripple, high efficiency step-down DC/DC converter can be easily composed of this IC with some external components, or a power-transistor, an inductor, a diode and capacitors.

R1225N Series 18.5V Input PWM/VFM Step-down DC/DC Controller

R1245x series 1.2A, 30V step down DC/DC converter

The R1245x series is a 30V input CMOS-based PWM step-down DC/DC converter with 1.2A* output current. R1245x includes a soft start circuit and latch or fold-back protection circuit. By simply using an inductor, resistors, a diode, and capacitors as external components, a high-efficiency step-down DC/DC converter can be easily configured. Due to current mode PWM control, the R1245x provides a fast response and high efficiency. Ceramic output capacitors can be used. Compared with R1240x, R1245x has a lot of variation of oscillator frequency and can select 330kHz. In case of 330kHz, R1245x can set VOUT lower than R1240x. The oscillator maximum duty cycle (Min.) of R1245x is larger than R1240x, so it is suitable for low dropout voltage situation. The noise characteristic has been improved rather than R1240x, and voltage accuracy is also improved. In addition to HSOP-8E package can be selected, so R1245S is suitable for high power dissipation case.

The R1243x series is a CMOS-based Step-Down DC/DC Converter with internal Nch high side Tr. (0.175Ω), which can provide the maximum 2A output current. The IC consists of an Oscillator, a PWM control circuit, a Reference Voltage unit, an Error amplifier, phase compensation circuits, a slope circuit, a soft start circuit, protection circuits, internal voltage regulators, and a switch for bootstrap circuit. The R1243x Series can make up a Step-Down DC/DC Converter with the following external components: an inductor, resistors, a diode, and capacitors. The R1243x series are current mode operating type DC/DC converter which does not require external current sense resistor, and it works high speed response time, high efficiency and compatible with ceramic capacitors. There are two types for the oscillator frequency. A/B version's frequency is fixed 1000kHz, and C/D version's frequency is fixed 330kHz.As a protection function, it has cycle by cycle peak current limit function, short protection function, thermal shutdown function and UVLO. There are two types for short protection, A/C version has latch protection function with 2ms delay time, and B/D version has fold back protection function that keep operating at short condition with lower operating frequency and limiting the Lx current. The R1243 Series has the built-in soft start time (Typ. 0.4ms). In addition to this, the soft start time is adjustable by controller's I/O port.

The R1243x Series is a 30V input, CMOS-based PWM step-down DC/DC converter with 2A∗ output current. R1243x includes a soft start circuit and a latch or fold-back protection circuit. A high-efficiency step-down DC/DC converter can be easily configured by using an inductor, resistors, a diode, and capacitors as external components. The R1243x provides a fast response and high efficiency due to current mode PWM control. Ceramic output capacitors can be used.

The R1242S Series are CMOS-based 30V Input, 3A, Synchronous Rectified Step-down DC/DC Converters with built-in Highside Switch.

The R1242S Series are 30V input, CMOS-based PWM step-down DC/DC converters featuring 3A∗ output current. R1242S includes a soft start circuit and a latch or fold-back protection circuit. By simply using an inductor, resistors, a low side switch (FET), and capacitors as external components, a high-efficiency step-down DC/DC converter can be easily configured. Due to current mode PWM control, the R1242S provides a fast response and high efficiency. Ceramic output capacitors can be used.