TLE 4729 G

Data Sheet

25

V1.2, 2008-03-18

Application Hints (cont’d)

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 TLE4729G 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.

To lower EMI a ceramic capacitor of max. 3 nF is advisable from each output to GND.

Thermal Shut Down

To protect the circuit against thermal destruction, thermal shut down has been

implemented.

Error Monitoring

The error outputs signal corresponding to the logic table the errors described below.

Logic Table

Kind of Error

Error Output

Error 1

Error 2

a) No error

H

H

b) Short circuit to GND

H

L

c) Open load

1)

L

H

d) b) and c) simultaneously

H

L

e) Temperature prealarm

L

L

Over-Temperature is implemented as pre-alarm; it appears approximately 20 K before

thermal shut down. To detect an open load, the recirculation of the inductive load is

watched. If there is no recirculation after a phase change-over, an internal error flipflop

is set. Because in most kinds of short circuits there won’t flow any current through the

motor, there will be no recirculation after a phase change-over, and the error flipflop for

open load will be set, too. Additionally an open load error is signaled after a phase

change-over during hold mode.