TMC236_1 Datasheet, PDF (19/27 Pages) TRINAMIC Motion Control GmbH & Co. KG. – High current, low power dissipation microstep stepper motor driver with protection / diagnostics and SPI Interface

TMC236/A DATA SHEET (V2.06 / 2009-Jul-30)
19
Slope Control Resistor
The output-voltage slope of the full bridge outputs can be controlled to reduce noise on the power
supply and on the motor lines and thus electromagnetic emission of the circuit. It is controlled by an
external resistor at the SLP pin.
Operational range:
0k R_SLP 100k
The SLP-pin can directly be connected to AGND for the fastest output-voltage slope (respectively
maximum output current). In most applications a minimum external resistance of 10 K is
recommended to avoid unnecessary high switching spikes.
Only for non-A-types the slope on the lower transistors is fixed (corresponding to a 5K to 10K slope
control resistor). For applications where electromagnetic emission is very critical, it might be necessary
to add additional LC (or capacitor only) filtering on the motor connections.
For these applications emission is lower, if only slow decay operation is used.
Please remark, that there is a tradeoff between reduced electromagnetic emissions (slow slope) and
high efficiency because of low dynamic losses (fast slope).
The following table and graph depict typical behavior measured from 15% of output voltage to 85% of
output voltage. However, the actual values measured in an application depend on multiple parameters
and may stray in a user application.
Example for slope settings
t_SLP typ.
30ns
60ns
110ns
245ns
460ns
R_SLP
2.2K
10K
22K
51K
100K
500
200
100
50
20
10
0
1
2
5
10
20
R_SLP in KOhm
50
100
Copyright © 2004, TRINAMIC Motion Control GmbH & Co KG