PWM DC Motor Regulator – Data Sheet

AS8410

Rev. 1.0, December 2000

For all detected failures an adequate failure handling procedure is integrated to fully protect the

motor regulator module. This failure procedures works without interaction of the controlling

µP

and so the AS8410 can also be used to develop regulator modules without

µP. Nevertheless

the most important failures are reported in operating mode 1 (OM1) by pull down the set value

input pin IN with a current source (3 mA … 10 mA).

4.1.8.1

Motor Failures

The principle of the load circuit (motor and power FET) failure detection and handling procedures

is the following:

a) Motor failure detection principle: The motor current at the high side of the motor and the

average value of the motor voltage is permanently measured. In this way the actual

motor working point is monitored and permanently compared with the normal motor

characteristic. This comparison delivers then the different motor or power FET failures.

b) Failure handling procedures: After the detection of any motor or power FET failure, the

control of the motor is taken by internal settings (no longer by the input set value IN) to

protect the whole system.

After a predefined time the AS8410 restarts the control by the input set value again and

monitors the motor and power FET.

This procedure is repeated up the failure disappears (or the controlling

µP is executing

a protection reaction by itself).

The main internal setting values and reactions of the different load circuit failures in OM1 are

listed here below:

1. Over current or short circuit of the motor

Handling:

a) switch off the motor immediately (delay < 1

µs)

b) report of the failure at the pin IN

c) check the failure condition again after a waiting time

d) reuse the input set value, if the over current condition is over

2. No load of the motor

Handling:

a) report of the failure at the pin IN

b) internal setting of the set value to 75 %

c) reuse the input set value, if the no load condition is over

3. Open wire (motor or power FET line)

Handling:

a) report of the failure at the pin IN

b) internal setting of the set value to 75 %

c) reuse the input set value, if the open wire condition is over

4. Short-circuited power switch (power FET)

Handling:

a) report of the failure at the pin IN

b) internal setting of the set value to 75 %

c) reuse the input set value, if the short-circuit condition is over

5. Mechanically blocked motor

Handling:

a) report of the failure at the pin IN

b) pull down the motor

c) check the failure condition again after a waiting time

d) reuse the input set value, if the blocked motor condition is over