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L6482H OVER CURRENT

Question asked by engholm.robert on Jul 21, 2015
Latest reply on Aug 27, 2015 by engholm.robert
I need some help on a drive controller that I designed that uses two L6482's. The problem
is sometimes while running, one motor will shut off. Reading the status register shows an over
current condition. The testing current is operating at 3 amps but will go to 5 amps RMS in the end
motor application.
 
I am sure it is a set up problem with the gate charge and rate. I am operating the system in !/4 step
and the maximum motor shaft speed is 7 rev/second. 800 steps for one revolution. The over current
condition is while at 3 rev/second.
 
The output FET's are ST's STP40NF10L with a typical Qg = 46nC, max = 64nC.
  
Setup is as follows:
 
System voltage is 72 volts from a switching power supply.
 
GATE DRIVING:
IGATE = 32mA
TCC = 1750nS
TDT = 500nS
TBLANK = 500nS
BOOST  = DISABLED
VCC = 15 V
UVLO = 11 V
 
PHASE CURRENT CONTROL:
TON MIN = 4uS
TOFF MIN = 21uS
TOFF FAST = 10uS
FAST STEP = 16uS
TSW = 48uS
Predictive current = ENABLED
 
Motor Specs:
R = 0.65 ohms
L = 5.4mH
Rated amps = 5.6A
Torque = 1260 oz-in
Bi-polar parallel winding connection.
 
Two Observations:
 
1) When I increase TCC by one increment, the motor will not run and is in a short circuit condition. I have changed
IGATE to 64mA and TCC to 875nS and the motor will not run. It is in a over current state. Not sure what to do here.
 
2) The 220uF 100V filter caps used for each drive system runs hot. ST did not provide the ESR for the filter caps on the
design information. I installed a United Chemi-Con filter cap with an ESR of 0.023 ohms, 390uF 100V. The filter cap ran
cool but I noticed the over current fault happened more frequent. Any ideas?
 
Please help me as I am not clear what the next step to try.
-------------------------------------
Hello,

Layout for your review. The power comes in on the top right of the board. M1 is on the right side and M2 is on the left side. The output for each motor controller are on the bottom layer and are on the edge of the board. This is a 2 oz copper fab.

I have connected extra power and ground wires from the header to the filter cap of M2. No change in behavior.


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