AND8116 Datasheet, PDF (6/8 Pages) ON Semiconductor – Integrated Relay/Inductive Load Drivers for Industrial and Automotive Applications

AND8116/D
The 73 V waveform shown in the oscilloscope picture
(Figure 9) resulted from the 60 V load dump transient plus
the vehicle’s battery voltage (13 V). In the application field,
the relay driver (NUD3124) is always connected to relays,
therefore if a load dump condition occurs, the current is
limited by the relay’s coil resistance which reduces the
amount of energy that the relay driver (NUD3124) needs to
drain to ground. Figure 10 shows an oscilloscope picture
with the waveforms generated across the NUD3124 device
when it is subjected to a load dump transient. For this case,
the device is controlling an OMRON relay (G8TB−1A−64)
The most stressful and aggressive requirement for
automotive transients is load dump. Therefore if a device is
able to comply with this requirement, it is assured that it will
sustain all the other less aggressive transients such as 240 V
(10 W source impedance), 350 ms time−duration type.
In addition to complying with the load dump transient
requirements and all the other smaller automotive transients,
the NUD3124 device also complies with other automotive
requirements such as reverse battery (−14 V, 1 minute or
more) and dual voltage jump start (24 V "10%).
If a reverse battery condition occurs, it will cause the body
diode of the FET to be forward biased and hence conduct.
During this condition, the current will be limited by the
relay’s coil resistance to a safe level causing the relay be
energized. With the traditional discrete approach, damage
can occur to the control logic circuitry due to a possible
current path from a reverse connected battery through the
driver to the logic’s output. This possibility is eliminated
when the NUD3124 device is used.
If a dual voltage jump start is used (24 V or more), the
NUD3124 device will remain in its off−state and therefore
the relays will too. This is the ideal operation required during
a dual voltage jump start condition, otherwise the relays
would be activated and could create serious operation
problems in the equipment or functions that they are
controlling (windows, seats, etc.).
RELAY MODULE
The benefits of the ON Semiconductor’s relay driver
devices (NUD3105, NUD3112 and NUD3124) are even
more unique and useful if they are integrated inside the relay
body to create relay modules that can be driven directly from
the logic circuitry. The advantages are:
• No need for external driver device
• PC board space reduction
• Reduction for insertion operations.
• Optimized design for lower cost
All the previous advantages will result in costs reduction
for industrial and automotive applications which have the
need for mechanical relays. Figure 10 describes graphically
the design of the relay module. Some relay manufacturers
already integrate a diode connected in parallel with the
relay’s coil to simplify the driver circuitry. Others are
considering to develop the concept of the relay module. The
major goal of the relay’s manufacturers is to offer more
added value to their customers for design optimization and
cost reduction.
Conversion factors:
Ch1 – Direct (Volts)
Ch2 – Max * 20 (Amp)
Ch3 – Direct (Volts)
M1 – Area * 20 (Joules)
Load Dump Transient – 20 V/div
I_D – 100 mA/div
V_DS – 20V/div
P_pk = Ch2 x Ch3
= 73 mJ
Figure 10. Waveforms Generated Across the
NUD3124 Device During a Load Dump Transient
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