RH5RH552B-T1 datasheet(2/29 Pages) RICOH

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PWM STEP-UP DC/DC CONVERTER

RH5RH

××1A/××2B/××3B SERIES

OUTLINE

The RH5RH

××1A/××2B/××3B Series are PWM Step-up DC/DC converter ICs by CMOS process.

The RH5RH

××1A IC consists of an oscillator, a PWM control circuit, a driver transistor (Lx switch), a refer-

ence voltage unit, an error amplifier, a phase compensation circuit, resistors for voltage detection, a soft-start cir-

cuit, and an Lx switch protection circuit. A low ripple, high efficiency step-up DC/DC converter can be constructed

of this RH5RH

××1A IC with only three external components, that is, an inductor, a diode and a capacitor.

These RH5RH

××1A/××2B/××3B ICs can achieve ultra-low supply current (no load) –TYP. 15µA –by a new-

ly developed PWM control circuit, equivalent to the low supply current of a VFM (chopper) Step-up DC/DC con-

verter.

Furthermore, these ICs can hold down the supply current to TYP. 2µA by stopping the operation of the oscil-

lator when the input voltage > (the output voltage set value + the dropout voltage by the diode and the inductor).

These RH5RH

××1A/××2B/××3B Series ICs are recommendable to the user who desires a low ripple PWM

DC/DC converter, but cannot adopt a conventional PWM DC/DC converter because of its too large supply current.

The RH5RH

××2B/××3B Series ICs use the same chip as that employed in the RH5RH××1A IC and are pro-

vided with a drive pin (EXT) for an external transistor. Because of the use of the drive pin (EXT), an external

transistor with a low saturation voltage can be used so that a large current can be caused to flow through the

inductor and accordingly a large output current can be obtained. Therefore, these RH5RH

××2B/××3B Series ICs

are recommendable to the user who need a current as large as several tens mA to several hundreds mA.

The RH5RH

××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 RH5RH

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

and low supply current.

•

Small Number of External Components ..........Only an inductor, a diode and a capacitor (RH5RH

××1A)

•

Low Supply Current...........................................TYP. 15µA (RH5RH301A)

•

Low Ripple and Low Noise

•

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

•

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

•

High Efficiency ...................................................TYP. 85%

•

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

•

Soft-Start.............................................................MIN. 500µs

•

Small Packages...................................................SOT-89 (RH5RH

××1A, RH5RH××2B),

SOT-89-5 (RH5RH

××3B)

FEATURES

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 instruments which require low noise and low supply current, such as hand-held audio equip-

ment.

•

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

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