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RH5RH301A Datasheet, PDF (2/29 Pages) RICOH electronics devices division – PWM STEP-UP DC/DC CONVERTER | |||
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PWM STEP-UP DC/DC CONVERTER
RH5RH ÃÃ1A/ÃÃ2B/ÃÃ3B SERIES
OUTLINE
The RH5RHÃÃ1A/Ã Ã 2B/Ã Ã 3B Series are PWM Step-up DC/DC converter ICs by CMOS process.
The RH5RHÃ Ã 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 RH5RHÃ Ã1A IC with only three external components, that is, an inductor, a diode and a capacitor.
These RH5RHÃà 1A/à à 2B/ÃÃ3B ICs can achieve ultra-low supply current (no load) âTYP. 15µA âby 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 RH5RHÃÃ1A/ÃÃ2B/ÃÃ3B 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 RH5RHÃÃ2B/ÃÃ3B Series ICs use the same chip as that employed in the RH5RHÃÃ1A 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 RH5RHÃÃ2B/ÃÃ3B Series ICs
are recommendable to the user who need a current as large as several tens mA to several hundreds mA.
The RH5RHÃÃ3B 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 RH5RHÃÃ1A/ÃÃ2B/ÃÃ3B 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 (RH5RHÃÃ1A)
⢠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/ËC
⢠Soft-Start.............................................................MIN. 500µs
⢠Small Packages...................................................SOT-89 (RH5RHÃÃ1A, RH5RHÃÃ2B),
SOT-89-5 (RH5RHÃÃ3B)
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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