Micropower Dual Comparator
PDF, 230 Kb, File published: Sep 1, 1985
This note covers the considerations for designing precision linear circuits which must operate from a single 5V supply. Applications include various transducer signal conditioners, instrumentation amplifiers, controllers and isolated data converters.
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Application Note 11
September 1985
Designing Linear Circuits for 5V Single Supply Operation
Jim Williams
In predominantly digital systems it is often necessary
to include linear circuit functions. Traditionally, separate
power supplies have been used to run the linear components (see Box, “Linear Power Supplies—Past, Present,
and Future”).
Recently, there has been increasing interest in powering
linear circuits directly from the 5V logic rail. The logic
rail is a difficult place for analog components to function.
The high amplitude broadband current and voltage noise
generated by logic clocking makes analog circuit operation difficult. (See Box, “Using Logic Supplies for Linear
Functions”.)
Generally speaking, analog circuitry which must achieve
very high performance levels should be driven from dedicated supplies. The difficulties encountered in maintaining
the lowest possible levels of noise and drift in an analog
system are challenging enough without contending with
a digitally corrupted power supply.
Many analog applications, however, can be successfully
implemented using the logic supply. Combining components intended to provide high performance from the 167Ω Q1 –
+ 2M L, LT, LTC, LTM, Linear Technology and the Linear logo are registered trademarks of Linear
Technology Corporation. All other trademarks are the property of their respective owners. RATIOMETRIC …
PDF, 195 Kb, File published: Nov 1, 1985
1.5V powered circuits for complex linear functions are detailed. Designs include a V/F converter, a 10-bit A/D, sample-hold amplifiers, a switching regulator and other circuits. Also included is a section of component considerations for 1.5V powered linear circuits.
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Application Note 15
November 1985
Circuitry for Single Cell Operation
Jim Williams
Portable, battery-powered operation of electronic apparatus has become increasingly desirable. Medical, remote
data acquisition, power monitoring and other applications
are good candidates for battery operation. In some circumstances, due to space, power or reliability considerations,
it is preferable to operate the circuitry from a single 1.5V
cell. Unfortunately, a 1.5V supply eliminates almost all
linear ICs as design candidates. In fact, the LM10 op
amp-reference and the LTВ®1017/LT1018 comparators are
the only IC gain blocks fully specified for 1.5V operation.
Further complications are presented by the 600mV drop
of silicon transistors and diodes. This limitation consumes
a substantial portion of available supply range, making
circuit design difficult. Additionally, any circuit designed
for 1.5V operation must function at end-of-life battery
voltage, typically 1.3V. (See Box Section, “Components
for 1.5V Operation.”)
500k
10kHz
TRIM
EIN …
PDF, 2.5 Mb, File published: Mar 1, 1986
This note presents output state circuits which provide power gain for monolithic amplifiers. The circuits feature voltage gain, current gain, or both. Eleven designs are shown, and performance is summarized. A generalized method for frequency compensation appears in a separate section.
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Application Note 18
March 1986
Power Gain Stages for Monolithic Amplifiers
Jim Williams
Most monolithic amplifiers cannot supply more than a few
hundred milliwatts of output power. Standard IC processing
techniques set device supply levels at 36V, limiting available output swing. Additionally, supplying currents beyond
tens of milliamperes requires large output transistors and
causes undesirable IC power dissipation.
Many applications, however, require greater output power
than most monolithic amplifiers will deliver. When voltage
or current gain (or both) is needed, a separate output
stage is necessary. The power gain stage, sometimes
called a “booster”, is usually placed within the monolithic
amplifier’s feedback loop, preserving the IC’s low drift and
stable gain characteristics. 150mA Output Stage
Figure 1a shows the LTВ®1010 monolithic 150mA current
booster placed within the feedback loop of a fast FET
amplifier. At lower frequencies, the buffer is within the
feedback loop so that its offset voltage and gain errors
are negligible. At higher frequencies, feedback is through
Cf, so that phase shift from the load capacitance acting
against the buffer output resistance does not cause loop …
PDF, 975 Kb, File published: Aug 2, 1984
This application note describes a number of enhancement circuit techniques used with existing 3-terminal regulators which extend current capability, limit power dissipation, provide high voltage output, operate from 110VAC or 220VAC without the need to switch transformer windings, and many other usefu application ideas.
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Application Note 2
August 1984
Performance Enhancement Techniques for
Three-Terminal Regulators
Jim Williams
Three terminal regulators provide a simple, effective solution to voltage regulation requirements. In many situations
the regulator can be used with no special considerations.
Some applications, however, require special techniques
to enhance the performance of the device.
Probably the most common modification involves extending the output current of regulators. Conceptually, the
simplest way to do this is by paralleling devices. In practice,
the voltage output tolerance of the regulators can cause
problems. Figure 1 shows a way to use two regulators to
achieve an output current equal to their sum. This circuit
capitalizes on the 1% output tolerance of the specified
regulators to achieve a simple paralleled configuration.
Both regulators sense from the same divider string and
the small value resistors provide ballast to account for the
slightly differing output voltages. This added impedance
degrades total circuit regulation to about 1%. Figure 2 shows another way to extend current capability
in a regulator. Although this circuit is more complex than
Figure 1, it eliminates the ballasting resistor’s effects
and has a fast-acting logic-controlled shutdown feature. …
PDF, 3.3 Mb, File published: Sep 1, 1987
AN22 details the theoretical and application aspects of the LT1088 thermal RMS/DC converter. The basic theory behind thermal RMS/DC conversion is discussed and design details of the LT1088 are presented. Circuitry for RMS/DC converters, wideband input buffers and heater protection is shown.
PDF, 2.2 Mb, File published: Apr 1, 1987
Low power operation of electronic apparatus has become increasingly desirable. AN23 describes a variety of low power circuits for transducer signal conditioning. Also included are designs for data converters and switching regulators. Three appended sections discuss guidelines for micropower design, strobed power operation and effects of test equipment on micropower circuits.
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Application Note 23
April 1987
Micropower Circuits for Signal Conditioning
Jim Williams
Low power operation of electronic apparatus has become
increasingly desirable. Medical, remote data acquisition,
power monitoring and other applications are good candidates for battery driven, low power operation. Micropower
analog circuits for transducer-based signal conditioning
present a special class of problems. Although micropower
ICs are available, the interconnection of these devices to
form a functioning micropower circuit requires care. (See
Box Sections, “Some Guidelines for Micropower Design
and an Example” and “Parasitic Effects of Test Equipment
on Micropower Circuits.”) In particular, trade-offs between
signal levels and power dissipation become painful when
performance in the 10-bit to 12-bit area is desirable. Additionally, many transducers and analog signals produce +V inherently small outputs, making micropower requirements complicate an already difficult situation. Despite the
problems, design of such circuits is possible by combining
high performance micropower ICs with appropriate circuit
techniques.
Platinum RTD Signal Conditioner
Figure 1 shows a simple circuit for signal conditioning
a platinum RTD. Correction for the platinum sensor’s
nonlinear response is included. Accuracy is 0.25В°C over …
PDF, 1.2 Mb, File published: Oct 1, 1988
This note examines a wide range of DC/DC converter applications. Single inductor, transformer, and switched-capacitor converter designs are shown. Special topics like low noise, high efficiency, low quiescent current, high voltage, and wide-input voltage range converters are covered. Appended sections explain some fundamental properties of different types of converters.
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Application Note 29
October 1988
Some Thoughts on DC/DC Converters
Jim Williams and Brian Huffman
INTRODUCTION
Many systems require that the primary source of DC power
be converted to other voltages. Battery driven circuitry is
an obvious candidate. The 6V or 12V cell in a laptop computer must be converted to different potentials needed for
memory, disc drives, display and operating logic. In theory,
AC line powered systems should not need DC/DC converters
because the implied power transformer can be equipped
with multiple secondaries. In practice, economics, noise
requirements, supply bus distribution problems and other
constraints often make DC/DC conversion preferable. A
common example is logic dominated, 5V powered systems
utilizing В±15V driven analog components.
The range of applications for DC/DC converters is large,
with many variations. Interest in converters is commensurately quite high. Increased use of single supply powered
systems, stiffening performance requirements and battery
operation have increased converter usage.
Historically, efficiency and size have received heavy emphasis. In fact, these parameters can be significant, but
often are of secondary importance. A possible reason
behind the continued and overwhelming attention to size …
PDF, 606 Kb, File published: Feb 1, 1989
Switching regulators are of universal interest. Linear Technology has made a major effort to address this topic. A catalog of circuits has been compiled so that a design engineer can swiftly determine which converter type is best. This catalog serves as a visual index to be browsed through for a specific or general interest.
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Application Note 30
February 1989
Switching Regulator Circuit Collection
John Seago
Switching regulators are of universal interest. Linear
Technology has made a major effort to address this topic.
A catalog of circuits has been compiled so that a design
engineer can swiftly determine which converter type is
best. This catalog serves as a visual index to be browsed
through for a specific or general interest. The catalog is organized so that converter topologies can
be easily found. There are 12 basic circuit categories:
Battery, Boost, Buck, Buck-Boost, Flyback, Forward, High
Voltage, Multioutput, Off Line, Preregulator, Switched
Capacitor and Telecom. Additional circuit information can
be located in the references listed in the index. The
reference works as follows, i.e., AN8, Page 2 = Application
Note 8, Page 2; LTC1044 DS = LTC1044 data sheet;
DN17 = Design Note 17. DRAWING INDEX
FIGURE TITLE FIGURE # PAGE REFERENCE/SOURCE Battery
2A Converter with 150ВµA Quiescent Current (6V to 12V)
200mA Output Converter (1.5V to 5V)
Up Converter (6V to 15V)
Regulated Up Converter (5V to 10V) …
PDF, 1.5 Mb, File published: Feb 2, 1989
Subtitled "Some Affable Analogs for Digital Devotees," discusses a number of analog circuits useful in predominantly digital systems. VPP generators for flash memories receive extensive treatment. Other examples include a current loop transmitter, dropout detectors, power management circuits, and clocks.
PDF, 688 Kb, File published: Aug 1, 1993
This publication details several LCD backlight circuits which feature 92% efficiency. Other benefits include low voltage operation, synchronizing capability, higher output power for color displays, and extended dimming range. Extensive coverage of practical issues includes layout problems, multi-lamp displays, safety and reliability concerns and efficiency and photometric measurements. Also included is a review of circuits which did not work along with appropriate commentary.
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Application Note 55
August 1993
Techniques for 92% Efficient LCD Illumination
Waste Not, Want Not .
Jim Williams
INTRODUCTION
In August of 1992 LTC published Application Note 49,
“Illumination Circuitry for Liquid Crystal Displays.” One
notable aspect of this event is that it generated more
response than all previous LTC application notes combined. This level of interest, along with significant performance advances since AN-49’s appearance, justifies
further discussion of LCD backlighting circuitry.
This publication includes pertinent information from the
previous effort in addition to updated sections and a large
body of new material. The partial repetition is a small
penalty compared to the benefits of text flow, completeness and time efficient communication. The most noteworthy performance advance is achievement of 92%
efficiency for the backlight power supply. Additional new
benefits include low voltage operation, synchronizing capability, higher output power for color displays, and extended dimming range.
A practical 92% efficient LCD backlight design is a classic
study of compromise in a transduced electronic system.
Every aspect of the design is interrelated, and the physical
embodiment is an integral part of the electrical circuit. The
choice and location of the lamp, wires, display housing
and other items has a major effect on electrical characteristics. The greatest care in every detail is required to …
