TMC5130A DATASHEET (Rev. 1.14 / 2017-MAY-15)
68
When I_scale_analog is enabled for analog scaling of VFS, the resulting voltage VFS‘ is calculated by:
푉
퐴ꢌ푁
푉′ = 푉
∗
퐹ꢒ
퐹ꢒ
ꢀ.5푉
with VAIN the voltage on pin AIN_IREF in the range 0V to V5VOUT/2
The sense resistor needs to be able to conduct the peak motor coil current in motor standstill
conditions, unless standby power is reduced. Under normal conditions, the sense resistor conducts
less than the coil RMS current, because no current flows through the sense resistor during the slow
decay phases.
CALCULATION OF PEAK SENSE RESISTOR POWER DISSIPATION
2
푃ꢠꢒ푀퐴푋 = 퐼ꢋ푂ꢌ퐿 ∗ 푅ꢒꢓ푁ꢒꢓ
Hint
For best precision of current setting, it is advised to measure and fine tune the current in the
application.
Attention
Be sure to use a symmetrical sense resistor layout and short and straight sense resistor traces of
identical length. Well matching sense resistors ensure best performance.
A compact layout with massive ground plane is best to avoid parasitic resistance effects.
Parameter
Description
Setting Comment
IRUN
Current scale when motor is running. Scales coil 0 … 31
current values as taken from the internal sine
wave table. For high precision motor operation,
work with a current scaling factor in the range 16
to 31, because scaling down the current values
reduces the effective microstep resolution by
making microsteps coarser. This setting also
controls the maximum current value set by
coolStep.
scaling factor
1/32, 2/32, … 32/32
IHOLD
IHOLD
DELAY
Identical to IRUN, but for motor in stand still.
Allows smooth current reduction from run current 0
instant IHOLD
1*218 … 15*218
clocks per current
decrement
to hold current. IHOLDDELAY controls the number
of clock cycles for motor power down after
TZEROWAIT in increments of 2^18 clocks: 0=instant
power down, 1..15: Current reduction delay per
current step in multiple of 2^18 clocks.
1 …15
Example: When using IRUN=31 and IHOLD=16, 15
current steps are required for hold current
reduction. A IHOLDDELAY setting of 4 thus results
in a power down time of 4*15*2^18 clock cycles,
i.e. roughly one second at 16MHz.
vsense
Allows control of the sense resistor voltage range 0
VFS = 0.32V
VFS = 0.18V
for full scale current.
1
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TRINAMIC [ TRINAMIC MOTION CONTROL GMBH & CO. KG. ]
