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[FAQ] Production device information

Other Parts Discussed in Thread: MCT8316A, MCF8316A

MCF8316A and MCT8316A are production quality silicon and the errata listed below will have minor impact to the system performance. So, customers can go to production using MCF8316A and MCT8316A. Also, the identified workaround should resolve the issue.  

Errata - MCF8316A

Errata #

Errata

Use case

Functional impact

Workaround

 

 

1

When using PWM signal frequency to control speed, a jitter in speed oscillations might be observed in a corner case only where both PWM frequency and max frequency are set at 32.767kHz.

Applicable to speed control use cases. Setting the motor to maximum speed using PWM frequency method.

 

Speed might oscillate based on the jitter.

 

Set the max operational frequency at any value slightly lower than 32.767 kHz (e.g. 32.5 kHz).

 

2

FG does not output pulses when the device triggers fault.

 

Applicable when FG is used to measure the motor speed after any fault gets triggered.

 

Speed feedback via FG might not be available after the device triggers fault.

 

None

3

MPET measurement is inaccurate when all the three conditions mentioned below are applicable.

•        R > 10 Ω,

•        L > 10 mH

•        Ke > 840 mV/Hz

 

Applicable in motors with R, L and Ke values as mentioned in the errata. 

 

Inaccurate motor parameters might impact motor performance such as maximum speed, rotor angle estimation etc.

 

None, set motor parameters manually for such motors.

 

4

When the device is configured to operate in torque mode, motor does not spin in reverse direction.

Applicable when the device is configured to operate in torque mode.

 

Motor does not spin in reverse direction.

 

None

5

FG output is not cleaner when PWM switching frequencies are set to 35kHz, 65kHz, 70kHz and 75kHz

Applicable when motor speed is measured via FG at the aforementioned PWM frequencies.

 

Speed feedback via FG might not be accurate at the aforementioned PWM frequencies.

 

Set the PWM switching frequency to values other than 35kHz, 65kHz, 70kHz and 75kHz.

6

FG output has a one cycle distortion around 45Hz while ramping up and around 22.5Hz while ramping down at PWM switching frequencies of 10kHz, 15kHz, 20kHz, 25kHz, 30kHz, 40kHz, 45kHz, 50kHz, 55kHz, 60kHz

Applicable when motor speed is measured via FG at the aforementioned PWM frequencies.

 

Speed feedback via FG might not be accurate at the aforementioned PWM frequencies.

 

None

7

Recirculation mode is one of the motor stop options in MCF8316A. This mode is also used as a fault mode option. Recirculation mode does not work in MCF8316A.

Applicable when recirculation mode is chosen as the motor stop or fault mode option.

 

No impact

Alternate motor stop options such as Low side or high side braking can be used.

 

8

Device I2C communication fails when the registers are constantly read during motor operation.

Applicable when registers are read back from the device while spinning the motor.

 

Device stops communicating to the host.

 

Do not read registers from the device during motor operation.

9

Hardware current limit trigger point is inaccurate when the HW current limit threshold is configured above 6A peak. 

Applicable when the HW current limit threshold is configured above 6A.

 

Device triggers hardware current limit at a value lower than the configured threshold. E.g. Device triggers HW current limit fault at 5.3A when the threshold is set to 8A

Set the HW current limit to 6A or below.

 

Errata – MCT8316A (I2C variant)

Errata #

Errata

Use case

Functional impact

Workaround

1

Frequency input case of 32.767kHz(max Freq set at 32.767kHz) results in varying target duty cycle

Set Speed Input mode to PWM frequency mode and set the max operational frequency as 32.767Khz.

For the above setting, setting the input PWM frequency as 32.767Khz results in jitter in the target duty thus speed oscillations

Set the max operational frequency as 32.5Khz when max frequency set as 32.767Khz( still 100% duty cycle operation is possible). Limit the Maximum Frequency setting to 32.5 Khz.

2

CBC report only fault results in occasional PWM chopping.

Set the CBC mode to report only mode and spin the motor at higher loads

Operate the current in motor operational current limit results in occasional chopping in PWM.

Set the CBC iLimit to max value/ Disable CBC.

3

No Motor results in Stall fault for very high deglitch times.

With Motor phase disconnected, when the no motor deglitch window set to very high the motor may indicate Motor stall before the No motor fault.

Latched fault status indicates Motor Stall instead of No motor

Optimally tune the No motor deglitch time to minimum possible value that wouldn’t trigger false no motor at startup.

4

No Stall detect when the motor is vibrating at speeds lesser than Abnormal speeds.

When motor is badly tuned for open Loop acceleration, motor may be set to vibrate in the closed loop resulting in no stall detection/abnormal speed detection

No fault detection even if motor is locked.

Optimally tune open loop and abnormal speed settings. Tune the Degauss Max window and set it to less than default 22 degrees.

5

Notch on the FG during motor stop operation.

Setting the motor stop option to Hi-z state can result in a notch on the FG line during Motor stop

When the motor stops in Hi-Z state, floating current regenerates back to DC supply, during this time a notch is observed on the FG line coming from the BEMF comparator pulled high/low depending on the state of comparator.

Set the motor stop option to Recirculation mode.

6

Delay in FG after Motor Stop

N/A

FG is pulled low for ~1mS after Motor stop.

None

7

Motor starts with Mixed modulation instead of High Side modulation

N/A

Error in open loop modulation mode during startup for the first time when startup brake time is less than 100mS. User may need to retune open loop if motor fails to start only on power up, but spins successfully thereafter.

Setting up startup brake time higher than 100mS or using high side modulation for the normal operation.

8

I2C slave address not configurable.

When multiple slave devices are connected to single I2C bus.

User can communicate with the device using I2C only using the address 0x00.

None

9

Analog based Speed input not functional above 70Khz PWM drive frequency

N/A

User cannot start the motor above 70Khz PWM frequency in Analog based speed Input mode due to ADC bandwidth limitation.

None

10

Incorrect Vm sensing for PWM drive frequency above 70KHz.

N/A

Error in Vm sense reading and incorrect FW based Voltage fault detection during Motor Idle State for PWM frequencies above 70Khz

None

11

Error in Internal Speed reading of ~1% at 3000Hz.

N/A

Difference in the speed monitored on GUI/I2C speed readback of ~ 1% compared to the actual motor speed tracked from FG

None