Datasheet

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Application guidelines

Suppressor circuits

Note for soldering

When switching inductive loads such as relays, DC motors, and

DC solenoids, it is always important to absorb surges (e.

g. with a

diode) to protect the contacts. When these inductive loads are

switched off, a counter emf can severely damage switch contacts

and greatly shorten lifetime.

Fig. 1 shows an inductive load with a free-wheeling diode connec

ted in parallel. This free-wheeling diode provides a path for the

inductor current to ow when the current is interrupted by the

switch. Without this free-wheeling diode, the voltage across the

coil will be limited only by dielectric breakdown voltages of the

circuit or parasitic elements of the coil. This voltage can be kilo

Process parameter for wave soldering

Basic specication for wave soldering J-STD 75 W4C.

Maximum temperature on the component side (Temp 2):

(Temperature must not exceed during the entire processing)

Preheating phase (t1 … t2):

Ramp up:

Ramp up to maximum temperature (t2 … t3):

Maximum temperature on the soldering side (Temp 3):

Maximum time of soldering process (t3 … t4):

Ramp down at 170

°C:

120 °C

70 … 120 sec

typ.+ 1 °C / sec

not dened

250 °C

3 sec

typ. – 2 °C/sec

volts in amplitude even when nominal circuit voltages are low (e. g.

12 VDC) see Fig. 2.

The free-wheeling diode should be chosen so that the reverse

breakdown voltage is greater than the voltage driving the induc tive

load. The DC blocking voltage (VR) of the free-wheeling diode can

be found in the datasheet of a diode. The forward current should

be equal or greater than the maximum current owing through the

load.

To get an efﬁcient protection, the free-wheeling diode must be connected as

close as possible to the inductive load!

Several hundred

to several

thousend volts

ON OFF

e = L

Switch

Free-wheeling

diode

Inductive

load

Counter EMF

over load without free-wheeling diode

Fig. 2

Switching with inductive load

Fig. 1

01/2019 § eao.com

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