TLE 8444SL

Block Description

Data Sheet

14

Rev. 1.1, 2009-07-07

5.2

Input / Output Stages

Input Circuit

The control inputs consist of TTL/CMOS-compatible schmitt-triggers with hysteresis. Inputs IN1 and IN3 have

internal pull down circuits whereas IN2 and IN4 have internal pull up circuits. If no signal is applied to the inputs

and INH=HIGH, then the drivers will by default be placed in Brake LL mode. In sleep mode, the outputs are

switched OFF (tristate or HIgh-Z). For optimized bipolar stepper motor control applications, the IN2 and IN4 inputs

have internal inverting structures. This concept allows IN1+IN2 and IN3+IN4 to be tied together, which ultimately

reduces µC output pins and provides a ‘2-phase’ type of control to the device (refer to Figure 19 and Figure 21).

Output stages

The output stages consist of a total of 4 DMOS Half-bridges. Integrated circuits protect the outputs against

overcurrent and overtemperature. Positive and negative voltage spikes, which occur during switching of inductive

loads, are supressed through integrated free-wheeling diodes.

The Truth Table below shows the output behavior of OUT1 and OUT2 for DC-motor applications. The same table

is also applied to OUT 3 and OUT4.

Note: Half-Bridges 1 and 2 form a full bridge

The Truth Table below shows the output behavior of OUT1 and OUT2 for bipolar Stepper-motor applications. The

same table is also applied to OUT 3 and OUT4.

Note: Half-Bridges 1 and 2 form a full bridge

Table 1

Functional Truth Table of Half-bridge 1 and 2 for DC-Motor Application

INH

IN1

IN2

OUT1

OUT2

Mode

0

1

X

open

X

open

|Z|

L

|Z|

L

Sleep Mode (Low current consumption mode)

Brake LL (both low side transistors turned-ON)

1

1

1

1

0

0

1

1

0

1

0

1

L

L

H

H

H

L

H

L

DC-Motor turns counterclockwise (CCW)

Brake LL (both low side transistors turned-ON)

Brake HH (both high side transistors turned-ON)

DC-Motor turns clockwise (CW)

Table 2

Functional Truth Table of Half-bridge 1 and 2 for Bipolar Stepper Motor Application

INH

IN1

IN2

OUT1

OUT2

Mode

0

1

X

open

X

open

|Z|

L

|Z|

L

Sleep Mode (Low current consumption mode)

no current (both low side transistors turned-ON)

1

1

1

1

0

0

1

1

0

1

0

1

L

L

H

H

H

L

H

L

negative phase current

no current (both low side transistors turned-ON)

no current (both high side transistors turned-ON)

positive phase current