AN1108 Advanced Linear Devices, AN1108 Datasheet

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AN1108

Manufacturer Part Number
AN1108
Description
Application Note For Electrically Programmable Analog Device Applications
Manufacturer
Advanced Linear Devices
Datasheet
INTRODUCTION
The ALD1108E/ALD1110E are the first members in a grow-
ing family of Electrically Programmable Analog Device
(EPAD) integrated circuits from Advanced Linear Devices.
An EPAD is a new class of analog IC, like the operational
amplifier and the A/D converter.
The ALD 1108E/ALD110E are based on CMOS MOSFET
devices with precision electrically programmable threshold
voltage, which sets their on-resistance characteristics. This
programmed on-resistance is in turn used to set a voltage
or a current level with the use of external, inexpensive fixed
precision resistors.
When used in combination with an inexpensive ALD E100
EPAD Programmer and Adapter Module, the EPAD allows
analog circuit trimming in up to 20,000 discrete steps with
0.1mV increments. In engineering environments, the EPAD
is quickly and easily programmed to fit the needs of a spe-
cific application. In test environments, it can be programmed
in-system, that is, as an integral part of a circuit board as-
sembly — thereby providing precise control over the entire
system. The EPAD technology is designed for use in low
voltage, low power circuits where a precision voltage or cur-
rent trimming function is necessary. In addition, it provides
a simple, inexpensive method for achieving remote trimming
of circuits within user-controlled environments.
The ALD1108E is a quad (4-channel) EPAD device; the
ALD1110E is dual (2-channel) EPAD device. Both EPADs
can be configured to operate in single or dual channel mode,
enabling unlimited variations in functionality. Both EPADs
are supplied as stand-alone, individually programmable de-
vices encased in standard IC packaging. They can be pre-
programmed before being placed into a circuit (application-
specific programming), providing control of standard linear
functions such as operational amplifiers and voltage com-
parators. Alternatively, they can be integrated directly into a
circuit, enabling in-system programming of the entire assem-
bly after it has been built (in-system programming).
NOTICE: Advanced Linear Devices (ALD) reserves the right to make changes and to discontinue any product and or services as identified in this publication without notice. Current specifications for any product and or services
should be verified by customer before placing any orders. ALD warrants its products to current specifications in effect at time of manufacture in accordance to its standard warranty. Unless mandated by government
requirements, ALD performs certain, but not necessarily all, specific testing and procedures as ALD deems necessary to support this warranty.
ALD assumes no liability for any circuitry described herein. Applications for any circuits contained herein is for illustrative purposes only. No representation of continued operation of said circuits under any operating conditions
are implied. Any use of such circuits are the responsibility of the user. No circuit licenses, copyrights or patents of any kind is implied or granted. ALD does not authorize or warrant any of its products or designs for use in life
support applications, and hereby expressly prohibit any such use. All rights reserved.
© 1998 Advanced Linear Devices, Inc. 415 Tasman Drive, Sunnyvale, California 94089 -1706 Tel: (408) 747-1155 Fax: (408) 747-1286 http://www.aldinc.com
ELECTRICALLY PROGRAMMABLE ANALOG DEVICE (EPAD™) APPLICATIONS
A
L
D
INEAR
DVANCED
EVICES,
I
NC.
The ALD1108E/ALD1110E EPADs do not need other active
circuitry to enable functionality. As such, these devices are
extremely versatile as both circuit element and design com-
ponent. EPAD technology presents the user with a wealth
of possible applications, limited only by the imagination of
the user and the many ways an adjustable bias voltage/cur-
rent device can be used as a circuit design element.
The applications listed below outlines in a general way some
of the applications for which EPAD can be used in telecom-
munications, instrumentation, medical devices and indus-
trial process control systems. Note that although automa-
tion can be an important end goal, a primary benefit of EPAD
technology is that it simplifies the manufacturing and control
process, by enabling electrical programming of an analog
circuit transfer function without resorting to difficult and ex-
pensive trim pots or an even more expensive system of
microcontrollers, RAMs, ROMs, EPROMs, data converters
and an entire overhead of system functions. The EPAD is
also an ideal solution for trimming of packaged modules
where trim pot access is no longer readily available.
GENERAL DESCRIPTION
The ALD1108E/ALD1110E devices are based on monolithic
CMOS FETs (Field Effect Transistors) with electrically
programmed threshold voltages that can be precisely con-
trolled via stored, non-volatile charges. Control of these
threshold voltages is enabled through a DOS-based user
interface, an EPAD Programmer and control software sup-
plied by Advanced Linear Devices.
Each channel in the EPAD can be individually programmed
to a different threshold, or bias, voltage. The range of thresh-
old voltage adjustment is 2000mV; programming voltage
resolution is 0.1mV respectively. For a given input voltage,
precisely changing the threshold voltage of a channel
(MOSFET) also changes its drain on-current, resulting in an
on-resistance characteristic that can be precisely con-
trolled and set.
APPLICATION NOTE AN1108

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