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PDF AND8116 Data sheet ( Hoja de datos )
| Número de pieza | AND8116 | |
| Descripción | Integrated Relay/Inductive Load Drivers for Industrial and Automotive Applications | |
| Fabricantes | ON Semiconductor | |
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AND8116/D
Integrated Relay/Inductive
Load Drivers for Industrial
and Automotive
Applications
Prepared by: Alejandro Lara
ON Semiconductor
http://onsemi.com
APPLICATION NOTE
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 msec)
• Dual voltage jump start (24 V or more)
• Reverse battery (−14 V, 1minute 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.
© Semiconductor Components Industries, LLC, 2003
September, 2003 − Rev. 1
1
Publication Order Number:
AND8116/D
1 page  
AND8116/D
Figure 7 shows the voltage and current waveforms
generated across the NUD3124 relay driver when it is
controlling an OMRON relay (G8TB−1A−64). This relay
has the following coil characteristics: L = 46 mH, Rdc =
100 W. The current that the OMRON relay takes for 12 V of
supply voltage is 120 mA. The integrated FET has a typical
on−resistance of 1.0 W, therefore the power dissipation
generated in the FET is around 15 mW (P=I2R) at 25°C of
ambient temperature. It results in an on−voltage drop of only
125 mV at 120 mA of current.
VSUPPLY – 10 V/div
VGS – 10 V/div
Inductor
kick back
VDS – 10 V/div
ID – 50 mA/div
Figure 7. Waveforms Generated Across the
NUD3124 when Driving OMRON Relay
G8TB−1A−64
Unlike the NUD3105 and NUD3112 devices (industrial
version), the unique design of the NUD3124 device
(automotive version) provides the active clamp feature that
allows higher reverse avalanche energy capability by
activating the FET anytime transient voltage conditions
exceed the breakdown voltage of the clamp Zener diodes
(28 V). The energy capability of the NUD3124 device is
350 mJ typically. Figure 8 shows an oscilloscope picture of
a surge test applied to the device when it was characterized
to find its maximum reverse avalanche energy capability.
The high reverse avalanche energy capability of this
device (350 mJ) allows to control most of the relays used in
automotive applications since they usually have coils
between 50 mA and 150 mA with inductance values lower
than 1 Henry. These type of coils do not transfer high levels
of energy to the NUD3124 device (E = ½ L I2), and therefore
each of them can be controlled with the same device
(NUD3124). Big advantages are obtained when a common
relay driver product is used to control the majority of the
relays used in a particular application circuit. PC board
space is saved and the circuit design is optimized. In
addition, components count purchasing operations are also
simplified.
The active clamp characteristic of the NUD3124 device
also allows it to comply with automotive requirements of
load dump and other voltage transients required by the
automotive specifications. Load dump transients are
generated by the vehicle’s alternator when the battery
connection fails during heavy charging. These type of
transients could occur when the relay is on or off. Although
automotive requirements for load dump vary between
suppliers, it has been learned that most of the load dump
requirements can be covered by devices which can sustain
a load dump transient of 60 V with 350 msec of duration.
Figure 9 shows a load dump transient of 60 V and 350 msec
of duration.
VGS – 10 V/div
ID – 100 mA/div
Ppk = Ch2 x Ch3
Conversion Factors:
Ch2 – Max * 100
Ch3 – Max * 10
M1 – Area * 1000
= 351 mJ
Figure 8. Waveforms Generated Across the
NUD3124 Device During Surge Test
Figure 9. Load Dump Transient Waveform
(60 V, 350 msec).
http://onsemi.com
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| PDF Descargar | [ Datasheet AND8116.PDF ] | |
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