Application information

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Application information

When inductive loads are driven by the L6221, a Zener diode in series with the integral free-

wheeling diodes increases the voltage across which energy stored in the load is discharged

and therefore speeds the current decay (

Figure 19).

For reliability it is suggested that the Zener is chosen so that

There are two reasons for this:

●

The Zener voltage changes in temperature and current.

●

The instantaneous power must be limited to avoid the reverse second breakdown.

Figure 19.

Free-wheeling diode connection when driving inductive loads

Care must be taken to ensure that the collectors are placed close together to avoid different

current partitioning at turn-off.

It is suggested to put in parallel channel 1 and 4 and channel 2 and 3 as shown in

Figure 20

for the similar electrical characteristics of the logic section (turn-on and turn-off delay time)

and the power stages (collector saturation voltage, free-wheeling diode forward voltage).

Vp Vz 35 V

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