TMC246 / TMC246A DATA SHEET (V2.06 / 2011-Aug-10)

10

Copyright © 2005, TRINAMIC Motion Control GmbH & Co KG

Typical winding current values

Current setting

CA3..0 / CB3..0

Percentage of

current

Typical trip voltage of the current sense comparator

(internal reference or analog input voltage of 2V is used)

0000

0%

0 V

(bridge continuously in slow decay condition)

0001

6.7%

23 mV

0010

13.3%

45 mV

...

...

1110

93.3%

317 mV

1111

100%

340 mV

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:

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).

47K

100nF

AGND

INA

INB

ANN

µC-

PWM

using PWM signal

100K

µC-

Port .2

8 level via R2R-DAC

100K

100K

µC-

Port .1

µC-

Port .0

R1

2 level control

µC-

Port

10nF

Controlling the power down mode via the SPI interface

Standard

function

11

MxA

10

CA3

9

CA2

6

PhA

-

0

-

Control

word

function

-

-

Bit

Enable standby mode and

clear error flags

8

CA1

7

CA0

5

MxB

4

CB3

3

CB2

0

PhB

2

CB1

1

CB0

0

0

0

0

0

0

0

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.