TLE 5250

Semiconductor Group

5

1998-02-01

Application

Two TLE 5250 drivers are required to operate a bipolar stepping motor. To implement

full-step operation, a squarewave voltage with the required stepping frequency is applied

to the phase input of the upper driver, and the same squarewave voltage, but offset in

phase by 90

°el, to the phase input of the lower driver. Motor-current limiting is produced

by a DC signal that is applied to both nominal-current inputs. In microstep operation the

nominal current tracks sinusoidally and synchronously with the required stepping

frequency. This produces a sinusoidal current in the motor windings to ensure very

smooth running and a high stepping frequency. If an instantaneous nominal value (sine

or cosine) is held on the second driver, it is possible to set a certain angle of rotation while

the motor is stationary. The motor current produced by this depends on nominal voltage

and sense resistance (normally 0.5

Ω), i.e.

The actual voltage should be thoroughly filtered for precise current regulation, especially

in microstep operation. So the actual input is accessible, and an RC element is

necessary between the Sense output and Actual input. The resistance R

correspond to the internal resistance of the nominal-current input-voltage source to

prevent additional voltage offset on the nominal/actual comparator.

Circuit Description

Outputs

Outputs Q1 and Q2 are fed by push-pull output stages. Four integrated free-wheeling

diodes referred to ground or the supply voltage protect the integrated circuit against

reverse voltages from an inductive load.

Enable and Phase

Outputs Q1 and Q2 can be disabled by a voltage V

sink transistors are enabled by V

The voltage on the Phase input determines the phase of the output current. Output Q1

acts as a sink for V

For output Q2 this is reversed: sink for V

The sink transistors are chopped. Low signal on the Enable pin plus a clock signal on the

Phase pin enable readout of the multiplexer.

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