AND8116 Datasheet, PDF (3/8 Pages) ON Semiconductor – Integrated Relay/Inductive Load Drivers for Industrial and Automotive Applications

AND8116/D
The 40 V N−channel FET is designed to switch the relay’s
coil for currents up to 500 mA. The clamping protection
Zener diodes (14 V) provides a clamp function to suppress
the voltage spike generated by the relay’s coil during the
turn−off interactions (V = Ldi/dt). The ESD protection
Zener diodes protects the gate−source silicon junction
against ESD conditions possibly induced by persons during
the handling or assembly of the device. And the bias resistor
provides the drive control signals to the FET.
Figure 3 illustrates the typical connection diagram of the
NUD3105 / NUD3112 devices:
+12 V/5.0 V
NUD3105, NUD3112
+5 V/3.3 V
LOGIC
ESD
Zener
14 V
ESD
Zener
14 V
1.0 k
300 k
RELAY
Clamp Zener
7 V or 14 V
Clamp Zener
7 V or 14 V
0
Figure 3. Typical Connection Diagram
(NUD3105 5.0 V Relay’s Coils and NUD3112 for 12 V)
When positive logic voltage is applied to the gate of the
device (5.0 V/3.3 V), the FET is turned−on which activates
the relay. When the FET is turned−off, the relay’s coil is
deactivated which causes it to kickback and generates a high
voltage spike, this voltage spike is suppressed by the clamp
Zener diodes placed across the FET. This operation
sequence is repeated for all the on and off operations of the
relay driver. Figure 4 shows the voltage and current
waveforms generated across the NUD3112 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 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.
V_SUPPLY – 10 V/div
V_GS – 10 V/div
V_DS – 10 V/div
Inductor
kick back
I_D – 50 mA/div
Figure 4. Traces Generated Across NUD3112 Device
when Driving OMRON Relay G8TB−1A−64
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