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.
FEATURES
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Small Number of External Components
Only an inductor, a diode and a capacitor (RH5RH 1A)
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Low Supply Current
Low Ripple and Low Noise
Low Start-up Voltage (when the output current is 1mA)
TYP. 15µA (RH5RH301A)
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MAX. 0.9V
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High Output Voltage Accuracy
±2.5%
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High Efficiency
TYP. 85%
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Low Temperature-Drift Coefficient of Output Voltage
TYP. ±50 ppm/˚C
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Soft-Start
MIN. 500µs
×× ××
SOT-89 (RH5RH 1A, RH5RH 2B),
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Small Packages
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SOT-89-5 (RH5RH
3B)
APPLICATIONS
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Power source for battery-powered equipment.
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Power source for cameras, camcorders, VCRs, PDAs, electronic data banks,and hand-held communication
equipment.
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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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RICOH [ RICOH ELECTRONICS DEVICES DIVISION ]
