TMC262 DATASHEET (Rev. 2.07 / 2013-FEB-14)
40
11 Diagnostics and Protection
11.1 Short to GND Detection
The short to ground detection prevents the high-side power MOSFETs from being damaged by
accidentally shorting the motor outputs to ground. It disables the MOSFETs only if a short condition
persists. A temporary event like an ESD event could look like a short, but these events are filtered out
by requiring the event to persist.
When a short is detected, the bridge is switched off immediately, the chopper cycle on the affected
coil is terminated, and the short counter is incremented. The counter is decremented for each phase
polarity change. The MOSFETs are shut off when the counter reaches 3 and remain shut off until the
short condition is cleared by disabling the driver and re-enabling it.
The short to ground detection status is indicated by two bits:
Status
Description
Range
Comment
S2GA
S2GB
These bits identify a short to GND condition on 0 / 1
coil A and coil B persisting for multiple chopper
cycles. The bits are cleared when the MOSFETs
are disabled.
0: No short
condition
detected.
1: Short condition
detected.
An overload condition on the high-side MOSFET (“short to GND”) is detected by monitoring the coil
voltage during the high-side on phase. Under normal conditions, the high-side power MOSFET reaches
the bridge supply voltage minus a small voltage drop during the on phase. If the bridge is
overloaded, the voltage cannot rise to the detection level within the time defined by the internal
detection delay setting. When an overload is detected, the bridge is switched off. The short to GND
detection delay needs to be adjusted for the slope time, because it must be longer than slope, but
should not be unnecessarily long.
Hxy
0V
VVS
VVS-
VBMS2G
Short to GND
detected
Valid area
BMxy
Short
detection
0V
0V
Driver off
Driver
enabled
tS2G
tS2G
Short to GND
monitor phase
BM voltage
monitored
inactive delay
inactive
delay
Short detected
Figure 11.1 Short to GND detection timing
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