AN555

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Figure 2. Motor driver protection with discrete components

The NPN transistors supplied via D1 are protected in the classical fashion already described. The PNP

devices are connected directly to the car supply network and are protected as follows:

– Positive surges : overvoltage is clamped by T2 with D1 forward- biased.

– Negative surges : These are clamped by T1 with T2 forward - biased.

Three components are thus required per motor driver, representing significant component and area cost.

DISTRIBUTED PROTECTION WITH THE RBOXX FAMILY

The RBOxx devices integrate all the protection functions required by car electronic modules: (see Figure

3).

Figure 3. Schematic diagram of an RBO device

D1

T2

T1

PROTECTION

COMPOMENTS

MOTOR

MOTOR

CONTROL

BATTERY

FILTER

1

3

2

D1

T1

T2