TMC246 DATA SHEET (V2.01 / Sep. 14th, 2005)
17
Copyright © 2005, TRINAMIC Motion Control GmbH & Co KG
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
Ω ≤ R
SLP ≤ 100kΩ
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
Ω 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
Ω to 10KΩ
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 trade off 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
tSLP typ.
RSLP
30ns
2.2K
Ω
60ns
10K
Ω
110ns
22K
Ω
245ns
51K
Ω
460ns
100K
Ω
10
100
R
SLP in KOhm
10
5
2
0
20
50
100
20
50
200
500
1
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