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 reference 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 newly 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 oscillator 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 provided 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 supply 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.

FEATURES

• 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)

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MAX. 0.9V

• High Output Voltage Accuracy

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±2.5%

 

 

 

• High Efficiency

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TYP. 85%

 

• Low Temperature-Drift Coefficient of Output Voltage

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TYP. ±50 ppm/˚C

• Soft-Start

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MIN. 500µs

 

• Small Packages

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SOT-89 (RH5RH⋅⋅1A, RH5RH⋅⋅2B),

 

 

SOT-89-5 (RH5RH⋅⋅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 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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