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L6480 Abnormal over current detection behaviour

Question asked by Phlip Cornelissen on Apr 10, 2017
Latest reply on Jul 13, 2017 by Phlip Cornelissen


Abnormal over current detection behaviour on stepper motor controller L6480. After initialization a hard stop command is given to hold the stepper motor, which seems to work just fine, all the expected waveforms appear on the gates of the transistors. When a move command of 128 micro-steps are given the bridge disengaged with no errors in the status register. After a hard HiZ command and another hard stop command the status register shows an over current fault and phase loss A and B faults! How do I proceed to overcome this situation?


Register setup:

CONFIG = 0x3880 (PWM div fact=2, PWM mul fact=1.75, VCCVAL=7.5,UVLOVAL=6.3,Bridge shut down on over current detection)

GATECFG1 = 0x04FD (WD_EN disabled, TBOOST=375ns, IGate=96mA, TCC=3750ns)

GATECFG2 = 0xE2 (TBLANK = 1000ns, TDT=375ns)

STEP_MODE = 0x07 (128 microsteps)

OCD_TH = 0x1F (1V, the maximum)

KVAL_HOLD = 0x25 (0.15xVs where Vs=13V)

KVAL_RUN =0x52 (0.33xVs where Vs=13V)

KVAL_ACC  = 0x64 (0.4xVs where Vs=13V)

KVAL_DEC = 0x32 (0.2xVs where Vs=13V)

MAX_SPEED = 0x34 (800 steps/s)

MIN_SPEED = 0x00 (0 steps/s)

ACC = 0x89 (2000 steps/s^2)

DEC = 0x89 (2000 steps/s^2)

FS_SPD = 0xA0 (2449 steps/s)


The transistors used are all IRF520N (100V, 9.7A, RDSon = 0.2 ohm, Qg total gate charge = 25nC max).Choice of transistors focused on the low gate charge. STB35NF10 were also used with less success due to the higher total gate charge of 55nC typical, although the RDSon is a mere 0.035 ohm.


Any advise welcome.

Best regards