TMC236/A ETC2 [List of Unclassifed Manufacturers], TMC236/A Datasheet - Page 15

• Manufacturer Part Number: TMC236/A
• Description: High Current Microstep Stepper Motor Driver with protection / diagnosis and SPI Interface
• Manufacturer: ETC2 [List of Unclassifed Manufacturers]

TMC236/A DATA SHEET (V2.04 / Nov. 6th, 2006)
Calculation of the external components
Sense Resistor
Choose an appropriate sense resistor (R
current is reached, when the coil current setting is programmed to “1111”. This results in a current
sense trip voltage of 0.34V when the internal reference or a reference voltage of 2V is used.
When operating your motor in fullstep mode, the maximum motor current is as specified by the
manufacturer. When operating in sinestep mode, multiply this value by 1.41 for the maximum current
(I
In a typical application:
Examples for sense resistor settings
R
0.47Ω
0.43Ω
0.39Ω
0.33Ω
0.27Ω
0.22Ω
High side overcurrent detection resistor R
The TMC236 detects an overcurrent to ground, when the voltage between VS and VT exceeds
150mV. The high side overcurrent detection resistor should be chosen in a way that 100mV voltage
drop are not exceeded between VS and VT, when both coils draw the maximum current. In a sinestep
application, this is when sine and cosine wave have their highest sum, i.e. at 45 degrees,
corresponding to 1.41 times the maximum current setting for one coil. In a fullstep application this is
the double coil current.
In a microstep application:
In a fullstep application:
However, if the user desires to use higher resistance values, a voltage divider in the range of 10Ω to
100Ω can be used for VT. This might also be desired to limit the peak short to GND current, as
described in the following chapter.
Attention: A careful PCB layout is required for the sense resistor traces and for the R
Copyright © 2004, TRINAMIC Motion Control GmbH & Co KG
max
S
).
R
R
R
V
I
R
R
R
I
max
max
TRIP
S
S
S
SH
SH
SH
:
= V
= 0.34V / I
:
:
:
= 0.1V / (1.41 × I
= 0.1V / (2 × I
I
723mA
790mA
870mA
1030mA
1259mA
1545mA
:
max
TRIP
Current sense resistor of bridge A, B
Programmed trip voltage of the current sense comparators
Desired maximum coil current
High side overcurrent detection resistor
Maximum coil current
/ I
max
max
max
)
max
)
S
) to set the desired motor current. The maximum motor
SH
SH
traces.
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