Datasheet

TMC2300 DATASHEET (Rev. 1.02 / 2019-NOV-06) 55
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14 Driver Diagnostic Flags
The TMC2300 drivers supply a complete set of diagnostic and protection capabilities, like short to GND
protection, short to VS 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.
14.1 Temperature Measurement
The driver integrates a two-level temperature sensor (pre-warning and thermal shutdown) for
diagnostics and for protection of the IC against excess heat. Heat is mainly generated by the motor
driver stages. Most critical situations, where the driver MOSFETs could be overheated, are avoided by
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.
TEMPERATURE THRESHOLDS
Temperature
Level
Comment
150°C
This value is relatively safe to switch off the driver stage before the IC can be
destroyed by overheating. On a large PCB, the power MOSFETs reach roughly
150°C peak temperature when the temperature detector is triggered with this
setting.
120°C
Temperature level for pre-warning. In most applications, reaching this level is a
sign for abnormal heat accumulation. The overtemperature pre-warning threshold
of 120°C gives lots of headroom to react to high driver temperature, e.g. by
reducing motor current, or increasing waiting-time in between of two motions.
Attention
Overtemperature protection cannot in all cases avoid thermal destruction of the IC. In case the rated
motor current is exceed, e.g. by operating a motor in StealthChop with wrong parameters, or with
automatic tuning parameters not fitting the operating conditions, excess heat generation can quickly
heat up the driver before the overtemperature sensor can react. This is due to a delay in heat
conduction over the IC die.
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.
14.2 Short Protection
The TMC2300 power stages are protected against a short circuit condition by an additional measure-
ment of the current flowing through each of the power stage 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 both driver bridges become switched off, and the s2ga
or s2gb flag, respectively s2vsa or s2vsb becomes set. In order to restart the motor, disable and re-
enable the driver. Note, that short 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.