TLE4727 Datasheet, PDF (20/22 Pages) Siemens Semiconductor Group – 2-Phase Stepper-Motor Driver

TLE 4727
Application Hints
The TLE 4727 is intended to drive both phases of a stepper motor. Special care has
been taken to provide high efficiency, robustness and to minimize external components.
Power Supply
The TLE 4727 will work with supply voltages ranging from 5 V to 16 V at pin V_S. Surges
exceeding 16 V at V_S won’t harm the circuit up to 45 V, but whole function is not
guaranteed. As soon as the voltage drops below approximately 16 V the TLE 4727 works
promptly again.
As the circuit operates with chopper regulation of the current, interference generation
problems can arise in some applications. Therefore the power supply should be
decoupled by a 0.1 µF ceramic capacitor located near the package. Unstabilized
supplies may even afford higher capacities.
Current Sensing
The current in the windings of the stepper motor is sensed by the voltage drop across
R_sense. Depending on the selected current internal comparators will turn off the sink
transistor as soon as the voltage drop reaches certain thresholds (typical 0 V, 0.07 V,
0.50 V and 0.70 V ). These thresholds are not affected by variations of V_S. Consequently
unstabilized supplies will not affect the performance of the regulation. For precise current
level it must be considered, that internal bonding wire (typ. 60 mΩ) is a part of R_sense.
Due to chopper control fast current rises (up to 10A/µs) will occur at the sensing
resistors. To prevent malfunction of the current sensing mechanism R_sense should be
pure ohmic. The resistors should be wired to GND as directly as possible. Capacitive
loads such as long cables (with high wire to wire capacity) to the motor should be
avoided for the same reason.
Synchronizing Several Choppers
In some applications synchronous chopping of several stepper motor drivers may be
desirable to reduce acoustic interference. This can be done by forcing the oscillator of
the TLE 4727 by a pulse generator overdriving the oscillator loading currents
(approximately ± 120 µA). In these applications low level should be between 0 V and
0.8 V while high level should be between 3 V and 5 V.
Semiconductor Group
20
1998-12-16