L6221AD datasheet(9/15 Pages) STMICROELECTRONICS

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Figure 19 : Driver for Solenoids up to 3A.

Some care must be taken to ensure that the collec-

tors are placed close together to avoid different cur-

rent partitioning at turn-off.

We suggest to put in parallel channel 1 and 4 and

channel 2 and 3 as shown in figure 19 for the similar

electrical characteristics of the logic section (turn-on

and turn-off delay time) and the power stages (col-

lector saturation voltage, free-wheeling diode for-

ward voltage).

APPLICATION INFORMATION

When inductive loads are driven by L6221A/N, 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 (fig. 18).

For reliability it is suggested that the zener is chosen

so that Vp + Vz < 35 V.

The reasons for this are two fold :

1) The zener voltage changes in temperature and

current.

2) The instantaneous power must be limited to avoid

the reverse second breakdown.

Figure 18.

L6221AS - L6221AD - L6221N

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L6221AD Datasheet(PDF) 9 Page - STMicroelectronics