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© Semiconductor Components Industries, LLC, 2015
May, 2015 − Rev. 2
1 Publication Order Number:
AND8116/D
AND8116/D
Integrated Relay/Inductive
Load Drivers for Industrial
and Automotive
Applications
Abstract
Most PC board mounted relays are driven by
microprocessors or other sensitive electronic devices.
A successful coil drive circuit requires isolation between the
relay and the microprocessor circuitry. Effective drive
circuits must account for drive current and voltage
requirements as well as effective suppression of L di/dt
transients which can destroy microprocessor circuits. While
it is easy to over-design an effective drive circuit, today’s
designs must be cost competitive. Integrating a monolithic
IC driver device into the relay will provide significant value
to the system designer.
This paper describes the operation of
ON Semiconductor’s integrated relay driver products to
interface sensitive electronic devices with mechanical
relays to accomplish different control/power functions.
Important benefits such as PC board space savings and
components count reduction are also explained.
Introduction
Although the advances in the electronics industry are
increasing day by day, mechanical relays are still
extensively used in industrial and automotive applications to
control high current loads. Their low cost and excellent fault
tolerance make relays to be an useful and reliable solution
in industrial and automotive applications environments.
The integrated relay driver devices NUD3105, NUD3112
and NUD3124 offered by ON Semiconductor are
considered to be the ideal device solution to control
mechanical relays used in industrial and automotive
applications. Their integrated design allows significant
simplification and cost reductions when replacing
traditional discrete solutions such as bipolar transistors plus
free-wheeling diodes.
Industrial and Automotive Application Requirements
The device requirements for industrial and automotive
applications are different and must be addressed in different
manner. While the requirements for automotive applications
are the most difficult to comply with, industrial
requirements traditionally allow more latitudes. Relay coil
currents vary considerably depending on the applications.
The largest class of industrial and automotive relays have
coils with current consumption between 50 and 150 mA.
Selection of a suitable relay driver requires many
constraints to be evaluated. For automotive applications, it
is necessary to put special attention in the following
requirements:
• Load Dump (80 V, 300 ms)
• Dual Voltage Jump Start (24 V or More)
• Reverse Battery (−14 V, 1 Minute or More)
• ESD Immunity (according AEC−Q100 Specification)
• Operating Ambient Temperature (−40°C to 85°C)
Meeting these automotive requirements usually results in
specifying an oversized and non-cost effective relay driver,
or one requiring many protection components.
Industrial applications on the other hand do not have many
requirements different than the standard ones such as ESD
immunity (usually 2.0 kV HBM), and a given range of
operating ambient temperature (usually between 0°C to
85°C). However, some applications also call for protection
devices against transient voltage conditions, which creates
the need for extra protection components too.
APPLICATION NOTE
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