SLOSE98A December 2022 – September 2023 DRV8461
PRODUCTION DATA
Open-load fault is detected -
When the motor is running -
If coil current drops below the open-load current threshold (IOL)
When the motor is in a holding condition -
If coil current drops below the ITRIP level set by the indexer
If either of the above conditions persists for more than the open-load detection time (tOL)
When the device is operating with SPI interface, the EN_OL bit must be 1b to enable open-load detection.
The open-load detection time (tOL) is set as shown in Table 7-27 -
Interface | OL_T | Maximum tOL (ms) |
---|---|---|
H/W interface | NA | 60 |
SPI interface | 00b | 30 |
01b (default) | 60 | |
10b | 120 |
Once the open-load fault is detected -
nFAULT is pulled low.
If the device is operating with SPI interface -
OL and FAULT bits are latched 1b
If the OL_A bit is 1b, it indicates an open load fault in winding A, between AOUT1 and AOUT2.
An open load fault between BOUT1 and BOUT2 causes the OL_B bit to become 1b.
When the open-load condition is removed, the behavior depends on whether the device is configured with H/W interface or SPI interface.
When the device is configured with H/W interface and open-load condition is removed:
If the ENABLE pin is logic HIGH, nFAULT is released immediately.
If the ENABLE pin is Hi-Z, nFAULT is released after a nSLEEP reset pulse has been applied.
When the device is configured with SPI interface and open-load condition is removed:
If the OL_MODE bit is 1b, nFAULT is released immediately. OL bit in FAULT register and OL_X bits in DIAG2 register are cleared only after a clear faults command is issued either via the CLR_FLT bit or an nSLEEP reset pulse.
If the OL_MODE bit is 0b, nFAULT and the fault bits are released after a clear faults command is issued either via the CLR_FLT bit or an nSLEEP reset pulse.
The open-load fault also clears when the device is power cycled or comes out of sleep mode.
Figure 7-44 and Figure 7-45 show open-load detection in cases where coil A and coil B were opened respectively. The open load detection time was selected to be 60 ms maximum, and the OL_MODE bit was 0b.
In silent step decay mode, open-load fault detection works only if the motor is in motion. If the motor is in standstill, open-load detection is not supported.
When open-load fault is detected -
If ENABLE pin is changed from logic HIGH to Hi-Z on-the-fly, apply a nSLEEP reset pulse once the open-load condition is removed.
If OL_MODE is changed from 1b to 0b or EN_OL is changed from 1b to 0b, apply a clear faults command once the open-load condition is removed.
When the device is operating with auto-torque enabled, if open-load fault is detected, the coil current goes to a value corresponding to TRQ_DAC.