TMC5031 DATASHEET (Rev. 1.11 / 2016-APR-28)
41
8 Driver Diagnostic Flags
The TMC5031 drivers supply a complete set of diagnostic and protection capabilities, like short to GND
protection and undervoltage detection. A detection of an open load condition allows testing if a
motor coil connection is interrupted. See the DRV_STATUS table for details.
8.1 Temperature Measurement
The driver integrates a two level temperature sensor (120°C pre-warning and 150°C thermal shutdown)
for diagnostics and for protection of the IC against excess heat. Heat is mainly generated by the
motor driver stages, and, at increased voltage, by the internal voltage regulator. Most critical
situations, where the driver MOSFETs could be overheated, are avoided when enabling the short to
GND protection. For many applications, the overtemperature pre-warning will indicate an abnormal
operation situation and can be used to initiate user warning or power reduction measures like motor
current reduction. The thermal shutdown is just an emergency measure and temperature rising to the
shutdown level should be prevented by design.
After triggering the overtemperature sensor (ot flag), the driver remains switched off until the system
temperature falls below the pre-warning level (otpw) to avoid continuous heating to the shutdown
level.
8.2 Short to GND Protection
The TMC5031 power stages are protected against a short circuit condition by an additional measure-
ment of the current flowing through the high-side MOSFETs. This is important, as most short circuit
conditions result from a motor cable insulation defect, e.g. when touching the conducting parts
connected to the system ground. The short detection is protected against spurious triggering, e.g. by
ESD discharges, by retrying three times before switching off the motor.
Once a short condition is safely detected, the corresponding driver bridge becomes switched off, and
the s2ga or s2gb flag becomes set. In order to restart the motor, the user must intervene by disabling
and re-enabling the driver. It should be noted, that the short to GND protection cannot protect the
system and the power stages for all possible short events, as a short event is rather undefined and a
complex network of external components may be involved. Therefore, short circuits should basically
be avoided.
8.3 Open Load Diagnostics
Interrupted cables are a common cause for systems failing, e.g. when connectors are not firmly
plugged. The TMC5031 detects open load conditions by checking, if it can reach the desired motor coil
current. This way, also undervoltage conditions, high motor velocity settings or short and
overtemperature conditions may cause triggering of the open load flag, and inform the user, that
motor torque may suffer. In motor stand still, open load cannot be measured, as the coils might
eventually have zero current.
In order to safely detect an interrupted coil connection, read out the open load flags at low or
nominal motor velocity operation, only. However, the ola and olb flags have just informative
character and do not cause any action of the driver.
www.trinamic.com
TRINAMIC [ TRINAMIC MOTION CONTROL GMBH & CO. KG. ]
