E-TEA3718DP Datasheet, PDF (14/26 Pages) STMicroelectronics – Stepper motor driver

Functional blocks
4.1
Alarm output (TEA3718SP, TEA3718DP and TEA3718SDP)
The ALARM output pin becomes low when the junction temperature reaches T ° C. When an
alarm condition occurs, parts of the supply voltage (dividing bridge R - R_C) is fed to the
comparator input pin (Figure 16). Depending on the R_C value the behavior of the circuit on
an alarm condition is as follows:
● RC > 80 ohms, the output stage is switched off
● RC > 60 ohms, the current in the motor windings is reduced according to the
approximate formula: (see also Figure 18 and Figure 19)
Im
=
-^V----^T---^H--
RS
–
----^V-----^C---^C------
R + RC
•
R_-----C_--
RS
with V_TH = threshold of the comparator (VCH, VCM, VCL) R = 700 ohms (typical).
For several Multiwatt packages a common detection can be obtained as in Figure 17.
Figure 16. Alarm detection for power DIP package
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