TMC262 DATASHEET (Rev. 2.07 / 2013-FEB-14)
41
The short to ground detector is controlled by a mode bit and a parameter:
Mode bit /
Parameter
DISS2G
Description
Setting
Comment
Short to ground detection disable bit.
0/1
0: Short to ground
detection enabled.
1: Short to ground
detection
disabled.
TS2G
This setting controls the short to GND detection 0… 3
delay time. It needs to cover the switching slope
time. A higher setting reduces sensitivity to
capacitive loads.
%00: 3.2µs.
%01: 1.6µs.
%10: 1.2µs.
%11: 0.8µs.
11.2 Open-Load Detection
The open-load detection determines whether a motor coil has an open condition, for example due to
a loose contact. When driving in fullstep mode, the open-load detection will also signal when the
motor current cannot be reached within each step, for example due to a too-high motor velocity in
which the back EMF voltage exceeds the supply voltage. The detection bit is only for information, and
no other action is performed by the chip. Assertion of an open-load condition does not always
indicate that the motor is not working properly. The bit is updated during normal operation whenever
the polarity of the respective coil toggles.
The open-load detection status is indicated by two bits:
Status flag
Description
Range
Comment
OLA
OLB
These bits indicate an open-load condition on 0 / 1
coil A and coil B. The flags become set, if no
chopper event has happened during the last
period with constant coil polarity. The flag is not
updated with too low actual coil current below
1/16 of maximum setting.
0: No open-load
detected
1: Open-load
detected
11.3 Overtemperature Detection
The TMC262 integrates a two-level temperature sensor (100°C warning and 150°C shutdown) for
diagnostics and for protection of the power MOSFETs. The temperature detector can be triggered by
heat accumulation on the board, for example due to missing convection cooling. Most critical
situations, in which the MOSFETs could be overheated, are avoided when using the short to ground
protection. For most applications, the overtemperature warning indicates an abnormal operation
situation and can be used to trigger an alarm or power-reduction measures. If continuous operation
in hot environments is necessary, a more precise mechanism based on temperature measurement
should be used. The thermal shutdown is strictly an emergency measure and temperature rising to
the shutdown level should be prevented by design. The shutdown temperature is above the specified
operating temperature range of the chip.
The high-side P-channel gate drivers have a temperature dependency which can be compensated to
some extent by increasing the gate driver current when the warning temperature threshold is
reached. The chip automatically corrects for the temperature dependency above the warning
temperature when the temperature-compensated modes of SLPH is used. In these modes, the gate
driver current is increased by one step when the temperature warning threshold is reached.
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