TLE5250 Datasheet, PDF (6/22 Pages) Siemens Semiconductor Group – 2.5-A High Performance Smart Power Stepper-Motor Driver with Diagnostic Interface

TLE 5250
Nominal-Current Input
The peak current in the motor winding is defined by the voltage on the Nominal input.
This is compared by a fast comparator to the voltage drop on the actual-current sensor.
If the nominal current is exceeded, the sink transistors of the outputs are turned off by
the logic.
RC/Sync Input
The outputs are turned on by the signal applied to the RC input. Synchronization is
possible by TTL signal or chopper mode with an external RC combination.
Chopper Mode
After the supply voltage is applied, capacitor CT is charged with constant current of
1 mA. A regulator limits the maximum voltage on the capacitor to 2.3 V. As a result of the
rising current in the motor winding, the voltage on the actual sensor increases. Once the
value defined by the nominal-current input is exceeded, the fast comparator resets an
RS flipflop. Thus sink transistors T3 and T4 are turned off by the logic. The charge
current is turned off and the parallel RT discharges CT.
The internal logic is designed so that capacitor CT is always charged before the
discharge operation is triggered. This guarantees a constant charge time, even for very
small coil currents (see Figure 7).
Sync Operation
If a sync signal with TTL level is applied to the RC input, the negative edge will set the
RS flipflop - by way of the combined Schmitt trigger and monoflop - if the voltage on the
current sensor is smaller than the nominal value on the nominal-current input. As in
chopper mode, the appropriate output transistors conduct. They are again turned off by
resetting the RS flipflop when the voltage on the current sensor becomes greater than
the nominal value (see Figure 8).
Output-Stage Control
This part of the circuit handles turn-off of the output stages when the output is shorted to
ground. There is separate current monitoring for this purpose in the source transistors.
The temperature of the output stages is also monitored. If this exceeds 175 °C, all output
stages are turned off, and then turned on again when the temperature drops.
Undervoltage also causes turn-off of the transistors in the output stages. These possible
fault states are stored in the diagnostics register.
Semiconductor Group
6
1998-02-01