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RH5RI251B

VFM STEP-UP DC/DC CONVERTER

RICOH Co.,Ltd. 

VFM STEP-UP DC/DC CONVERTER

RH5RI ××1B/××2B/××3B SERIES

OUTLINE

The RH5RI××1B/××2B/××3B Series are VFM (Chopper) Step-up DC/DC converter ICs with ultra low supply

current by CMOS process.

The RH5RI××1B IC consists of an oscillator, a VFM control circuit, a driver transistor (Lx switch), a reference

voltage unit, an error amplifier, resistors for voltage detection, and an Lx switch protection circuit. A low ripple,

high efficiency step-up DC/DC converter can be constructed of this RH5RI××1B IC with only three external com-

ponents, that is, an inductor, a diode and a capacitor.

The RH5RI××2B IC uses the same chip as that employed in the RH5RI××1B IC and is provided with a drive

pin (EXT) for an external transistor instead of an Lx pin, so that a power transistor with a low saturation voltage

can be externally provided, whereby a large current can be caused to flow through the inductor and accordingly a

large current can be obtained. Therefore, the RH5RI××2B IC is recommendable to the user who need a current

as large as several tens mA toseveral hundreds mA.

The RH5RI××3B IC also includes an internal chip enable circuit so that it is possible to set the standby sup-

ply current at MAX. 0.5µA.

These RH5RI××1B/××2B/××3B ICs are suitable for use with battery-powered instruments with low noise

and ultra low supply current.

FEATURES

• Small Number of External Components ..........Only an inductor, a diode and a capacitor (RH5RI××1B)

• Ultra Low Input Current ...................................TYP. 4µA (RH5RI301B/303B at no load,with 1.5V input)

• High Output Voltage Accuracy .........................±2.5%

• Low Ripple and Low Noise

• Low Start-up Voltage (When the output current is 1mA)......................MAX. 0.9V

• High Efficiency ...................................................TYP.80%

• Low Temperature-Drift Coefficient of Output Voltage ..........................TYP. ±50 ppm/˚C

• Small Packages...................................................SOT-89 (RH5RI××1B, RH5RI××2B)

SOT-89-5 (RH5RI××3B)

APPLICATIONS

• Power source for battery-powered equipment.

• Power source for cameras, camcorders, VCRs, PDAs, electronic data banks,and hand-held communication

equipment.

• Power source for appliances which require higher cell voltage than that of batteries used in the appliances.

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