TMC246/A ETC2 [List of Unclassifed Manufacturers], TMC246/A Datasheet - Page 24

• 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)
Application Note: Extending the Microstep Resolution
For some applications it might be desired to have a higher microstep resolution, while keeping the
advantages of control via the serial interface. The following schematic shows a solution, which adds
two LSBs by selectively pulling up the SRA / SRB pin by a small voltage difference. Please remark,
that the lower two bits are inverted in the depicted circuit. A full scale sense voltage of 340mV is
assumed. The circuit still takes advantage of completely switching off of the coils when the internal
DAC bits are set to “0000”. This results in the following comparator trip voltages:
Current setting
(MSB first)
SPI bit
i
Copyright © 2005, TRINAMIC Motion Control GmbH & Co KG
DAC bit
DAC bit
SPI is a trademark of Motorola
SPI bit
SDO
SCK
SDI
/CS
000111
000110
000101
000100
111101
111100
0000xx
1/2 74HC74
...
Q
C
/B1
100K
D
A2
15
7
SDO
CSN
SCK
+V
SDI
CC
Trip voltage
0 V
5.8 mV
11.5 mV
17.3 mV
23 mV
334.2 mV
340 mV
PHA
/B0
14
6
/OE
C2
/MR
C1
DS1D
TMC236 /
74HC595
Vcc = 5V
TMC239
MDB
/A1
13
5
Q7'
Q0
Q1
Q2
Q3
Q4
Q5
Q6
Q7
/DACA.0
/DACA.1
/DACB.0
/DACB.1
Free for
second
TMC239
/A0
B5
12
4
SRA
Note: Use a 74HC4094
instead of the HC595 to get
rid of the HC74 and inverter
4.7nF
opt.
MDA
B4
11
3
47K
47K
47K
A5
B3
10
2
110R
A4
B2
9
1
R
S
PHB
A3
8
0
24