Ricoh RH5RH12B Instructions for use

ELECTRONIC DEVICES DIVISION
PWM STEP-UP DC/DC CONVERTER
RH5RH××1A/××2B/××3B SERIES
APPLICATION MANUAL
NO.EA-023-9803

NOTICE
1. The products and the product specifications described in this application manual are subject to change or dis-
continuation of production without notice for reasons such as improvement. Therefore, before deciding to use
the products, please refer to Ricoh sales representatives for the latest information thereon.
2. This application manual may not be copied or otherwise reproduced in whole or in part without prior written con-
sent of Ricoh.
3. Please be sure to take any necessary formalities under relevant laws or regulations before exporting or other-
wise taking out of your country the products or the technical information described herein.
4. The technical information described in this application manual shows typical characteristics of and example
application circuits for the products. The release of such information is not to be construed as a warranty of or a
grant of license under Ricoh's or any third party's intellectual property rights or any other rights.
5. The products listed in this document are intended and designed for use as general electronic components in
standard applications (office equipment, computer equipment, measuring instruments, consumer electronic
products, amusement equipment etc.). Those customers intending to use a product in an application requiring
extreme quality and reliability, for example, in a highly specific application where the failure or misoperation of
the product could result in human injury or death (aircraft, spacevehicle, nuclear reactor control system, traffic
control system, automotive and transportation equipment, combustion equipment, safety devices, life support
system etc.) should first contact us.
6. We are making our continuous effort to improve the quality and reliability of our products, but semiconductor
products are likely to fail with certain probability. In order prevent any injury to persons or damages to property
resulting from such failure, customers should be careful enough to incorporate safety measures in their design,
such as redundancy feature, fire-containment feature and fail-safe feature. We do not assume any liability or
responsibility for any loss or damage arising from misuse or inappropriate use of the products.
7. Anti-radiation design is not implemented in the products described in this application manual.
8. Please contact Ricoh sales representatives should you have any questions or comments concerning the prod-
ucts or the technical information.
June 1995

OUTLINE
......................................................................................................1
FEATURES
....................................................................................................1
APPLICATIONS
.............................................................................................1
BLOCK DIAGRAM
.........................................................................................2
SELECTION GUIDE
.......................................................................................2
PIN CONFIGURATION
...................................................................................3
PIN DESCRIPTION
........................................................................................3
ABSOLUTE MAXIMUM RATINGS
...................................................................4
ELECTRICAL CHARACTERITICS
...................................................................5
OPERATION OF STEP-UP DC/DC CONVERTER
...........................................10
TYPICAL CHARACTERISTICS
......................................................................13
1) Output Voltage vs. Output Current .......................................................................13
2) Efficiency vs. Output Current.............................................................................14
3) Supply Current (No Load) vs. Input Voltage..............................................................15
4) Output Current vs. Ripple Voltage........................................................................15
5) Start-up/Hold-on Voltage vs. Output Current (Topt=25˚C) ...............................................16
6) Output Voltage vs. Temperature .........................................................................17
7) Start-up Voltage vs. Temperature ........................................................................18
8) Hold-on Voltage vs. Temperature ........................................................................18
9) Supply Current 1 vs. Temperature .......................................................................18
10) Supply Current 2 vs. Temperature .......................................................................18
11) Lx Switching Current vs. Temperature ...................................................................18
12) Lx Leakage Current vs. Temperature ....................................................................18
13) Oscillator Frequency vs. Temperature....................................................................19
14) Oscillator Duty Cycle vs. Temperature ...................................................................19
15) Vlx Voltage Limit vs. Temperature........................................................................20
16) EXT “H” Output Current vs. Temperature ................................................................20
17) EXT “L” Output Current vs. Temperature.................................................................20
18) Load Transient Response................................................................................21
19) Distribution of Output Voltage ............................................................................22
20) Distribution of Oscillator Frequency ......................................................................22
RH5RH SERIES
APPLICATION MANUAL
CONTENTS

TYPICAL APPLICATIONS
............................................................................23
• RH5RH××1A .................................................................................................23
• RH5RH××2B..................................................................................................23
• RH5RH××3B..................................................................................................24
• CE pin Drive Circuit............................................................................................22
APPLICATION CIRCUITS
.............................................................................26
• 12V Step-up Circuit............................................................................................26
• Step-down Circuit..............................................................................................26
• Step-up/Step-down Circuit with Flyback .......................................................................27
PACKAGE DIMENSIONS
..............................................................................28
TAPING SPECIFICATIONS
...........................................................................28

PWM STEP-UP DC/DC CONVERTER
1
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.