TLE 4726

Data Sheet

21

1999-09-15

Application Hints

The TLE 4726 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 4726 will work with supply voltages ranging from 5 V to 50 V at pin

V

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

0.22

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

1

and

R

transistor as soon as the voltage drop reaches certain thresholds (typical 0 V, 0.25 V,

0.5 V and 0.75 V); (

R

of

V

Due to chopper control fast current rises (up to 10 A/

µs) will occur at the sensing

resistors

R

R

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 synchrone chopping of several stepper motor drivers may be

desireable to reduce acoustic interference. This can be done by forcing the oscillator of

the TLE 4726 by a pulse generator overdriving the oscillator loading currents

(approximately

± 100 µA). In these applications low level should be between 0 V and 1 V

while high level should be between 2.6 V and

V

Optimizing Noise Immunity

Unused inputs should always be wired to proper voltage levels in order to obtain highest

possible noise immunity.

To prevent crossconduction of the output stages the TLE 4726 uses a special break

before make timing of the power transistors. This timing circuit can be triggered by short

glitches (some hundred nanoseconds) at the Phase inputs causing the output stage to

become high resistive during some microseconds. This will lead to a fast current decay

during that time. To achieve maximum current accuracy such glitches at the Phase

inputs should be avoided by proper control signals.