Rainbow-electronics ATA6824 Manuel d'utilisateur télécharger pdf (Page 12)

4931C–AUTO–09/06

ATA6824 [Preliminary]

Figure 5-4. Timing of the Drivers

The delays t

HxLH

and t

LxLH

include the cross conduction time t

5.10 Short Circuit Detection

To detect a short in H-bridge circuitry, internal comparators detect the voltage difference

between source and drain of the external power NMOS. If the transistors are switched ON and

the source-drain voltage difference is higher than the value V

(4V with tolerances) for a time

(typically 10 µs) the signal SC (short circuit) will be set and the drivers will be switched off

immediately. The diagnostic pin DG1 will be set to “H”. With the next transition on pin PWM, the

bit will be cleared and the corresponding drivers, depending on the DIR pin, will be switched on

again.

There is a PBAT supervision block implemented to detect the possible voltage drop on PBAT

during a short circuit. If the voltage at PBAT falls under V

SCPB

(5.6V with tolerances) for a time

the drivers will be switched off immediately and DG1 will be set to “H”. It will be cleared as

above.

LxLH

Lxr

HxLH

Hxr

HxHL

Hxf

LxHL

Lxf

PWM or

DIR

80%

50%

20%

80%

20%

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Rainbow-electronics ATA6824 Manuel d'utilisateur Page 12