TMC236_1 TRINAMIC [TRINAMIC Motion Control GmbH & Co. KG.], TMC236_1 Datasheet - Page 16

• Manufacturer Part Number: TMC236_1
• Description: High current, low power dissipation microstep stepper motor driver with protection / diagnostics and SPI Interface
• Manufacturer: TRINAMIC [TRINAMIC Motion Control GmbH & Co. KG.]

TMC236/A DATA SHEET (V2.06 / 2009-Jul-30)
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 sine step mode, multiply this value by 1.41 for the maximum current
(I
In a typical application:
Examples for sense resistor settings
R
0.47
0.43
0.39
0.33
0.27
0.22
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 10
100
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
can be used for VT. This might also be desired to limit the peak short to GND current, as
max
max
TRIP
S
S
S
SH
SH
SH
:
= V
= 0.34V / I
:
:
:
= 0.1V / (1.41
= 0.1V / (2
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
I
max
I
)
max
)
S
) to set the desired motor current. The maximum motor
SH
SH
traces.
16
to