TMC246/A ETC2 [List of Unclassifed Manufacturers], TMC246/A Datasheet - Page 8

• Manufacturer Part Number: TMC246/A
• Description: High Current Microstep Stepper Motor Driver with sensorless stall detection, protection / diagnosis and SPI Interface
• Manufacturer: ETC2 [List of Unclassifed Manufacturers]

TMC246 DATA SHEET (V2.01 / Sep. 14th, 2005)
Typical winding current values
Current setting
CA3..0 / CB3..0
The current values correspond to a standard 4 Bit DAC, where 100%=15/16. The contents of all
registers is cleared to “0” on power-on reset or disable via the ENN pin, bringing the chip to a low
power standby mode. All SPI inputs have Schmitt-Trigger function.
Base current control via INA and INB in SPI mode
In SPI mode, the IC can use an external reference voltage for each DAC. This allows the adaptation to
different motors. This mode is enabled by tying pin ANN to GND. A 2.0V input voltage gives full scale
current of 100%. In this case, the typical trip voltage of the current sense comparator is determined by
the input voltage and the DAC current setting (see table above) as follows:
A maximum of 3.0V V
to get the overall coil current. It is advised to operate at a high base current setting, to reduce the
effects of noise voltages. This feature allows a high resolution setting of the required motor current
using an external DAC or PWM-DAC (see schematic for examples).
Controlling the power down mode via the SPI interface
Programming current value “0000” for both coils at a time clears the overcurrent flags and switches
the TMC246 into a low current standby mode with coils switched off.
Copyright © 2005, TRINAMIC Motion Control GmbH & Co KG
Standard
INA
INB
AGND
ANN
function
function
Control
0000
0001
0010
1110
1111
word
V
V
...
TRIP,A
TRIP,B
Bit
MxA
= 0.17 V
= 0.17 V
11
-
using PWM signal
CA3
Percentage of
current
0%
6.7%
13.3%
...
93.3%
100%
10
47K
100nF
0
INA
INB
IN
CA2
9
0
is possible. Multiply the percentage of base current setting and the DAC table
× “percentage SPI current setting A”
× “percentage SPI current setting B”
µC-
PWM
CA1
8
0
CA0
7
0
10nF
Typical trip voltage of the current sense comparator
(internal reference or analog input voltage of 2V is used)
0 V
23 mV
45 mV
317 mV
340 mV
PhA
8 level via R2R-DAC
6
-
100K
100K
100K
MxB
5
-
(bridge continuously in slow decay condition)
CB3
4
0
µC-
Port .2
µC-
Port .1
µC-
Port .0
CB2
3
0
CB1
2
0
CB0
2 level control
1
0
µC-
Port
R1
PhB
0
-
Enable standby mode and clear
error flags
8