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L6219R

3

Functional Description

The circuit is intended to drive both windings of a bipolar stepper motor.

The peak current control is generated through switch mode regulation.There is a choice of three different current

The current can also be switched off completely

The current level in the motor winding is selected with these inputs. (See fig. 5)

If any of the logic inputs is left open, the circuit will treat it has a high level input.

Table 6.

3.2 Phase

This input determines the direction of current flow in the windings, depending on the motor connections. The

signal is fed through a Schmidt-trigger for noise immunity, and through a time delay in order to guarantee that

no short-circuit occurs in the output stage during phase-shift.High level on the PHASE input causes the motor

current flow from Out A through the winding to Out B

3.3 Current Sensor

comparator is active at a time. It is activated by the input logic according to the current level chosen with signals

voltage across RS becomes higher than the reference voltage on the other comparator input, the comparator

goes high, which triggers the pulse generator.

The max peak current Imax can be defined by:

3.4 Single-pulse Generator

The pulse generator is a monostable triggered on the positive going edge of the comparator output.The

monostable output is high during the pulse time, toff , which is determined by the time components Rt and Ct.

The single pulse switches off the power feed to the motor winding, causing the winding current to decrease dur-

ing toff.If a new trigger signal should occur during toff, it is ignored.

3.5 Output Stage

The output stage contains four Darlington transistors (source drivers) four saturated transistors (sink drivers)

and eight diodes, connected in two H bridge.

Current Level

H

H

No Current

L

H

H

L

L

L

I

max

V

ref

10R

s

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