TMC4330A Datasheet | Document Revision 1.01 • 2017-JAN-12
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Internal Ramp Generator Units
This section provides information about the arithmetical units of the ramp parameters.
All parameter units are real arithmetical units.
Clock Frequency
Therefore, it is necessary to set the CLK_FREQ register 0x31 to proper [Hz] value,
which is defined by the external clock frequency fCLK. Any value between
fCLK = 4.2 MHz and 32 MHz can be selected.
Default configuration is 16 MHz.
Velocity values are always defined as pulses per second [pps].
Velocity Value
Units
VACTUAL is given as a 32-bit signed value with no decimal places. The unsigned
velocity values VSTART, VSTOP, and VBREAK consist of 23 digits and 8 decimal places.
VMAX is a signed value with 24 digits and 8 decimal places.
The maximum velocity VMAX is restricted as follows:
Velocity mode:
|VMAX| ≤ ½ pulse · fCLK
Positioning mode: |VMAX| ≤ ¼ pulse · fCLK
NOTE:
In case VACTUAL exceeds this limit INCORRECT step pulses at STPOUT output
occur and/or positioning is not executed properly.
Furthermore, VMAX have to be the highest nominal value of all velocity values:
|VMAX| > max(VSTART;VSTOP;VBREAK)
The unsigned values AMAX, DMAX, ASTART, DFINAL, and DSTOP consist of 22 digits
and 2 decimal places.
AACTUAL shows a 32-bit nondecimal signed value. Acceleration and deceleration units
Acceleration
Value Units
are defined per default as pulses per second² [pps²].
If higher acceleration/deceleration values are required for short and steep
ramps, do as follows:
Action:
Set direct_acc_val_en =1 (GENERAL_CONF register 0x00).
Result:
The parameters are defined as velocity value change per clock cycle with 24-bit
unsigned decimal places (MSB =2-14). The values are calculated as follows:
2
AMAX [pps2] = AMAX / 237 · fCLK
2
DMAX [pps2] = DMAX / 237 · fCLK
2
ASTART [pps2] = ASTART / 237 · fCLK
2
DFINAL [pps2] = DFINAL / 237 · fCLK
2
DSTOP [pps2] = DSTOP / 237 · fCLK
The maximum acceleration or deceleration values are as follows:
max(AMAX;DMAX;ASTART;DFINAL;DSTOP) [pps²] ≤ VMAX · fCLK / 1024
In case direct_acc_val_en = 1, the maximum value is also limited to:
max(AMAX;DMAX;ASTART;DFINAL;DSTOP) ≤ 220
Continued on next page.
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