AMIS-30622_13 Datasheet, PDF (14/50 Pages) ON Semiconductor – I2C Micro-Stepping Motor Driver

AMIS−30622
Position Ranges
A position is coded by using the binary two’s complement format. According to the positioning commands used and to the
chosen stepping mode, the position range will be as shown in the following table.
Table 11. POSITION RANGE
Command
Stepping Mode
Half−stepping
SetPosition
1/4^th micro−stepping
1/8^th micro−stepping
1/16^th micro−stepping
Position Range
−4096 to +4095
−8192 to +8191
−16384 to +16383
−32768 to +32767
Full Range Excursion
8192 half−steps
16384 micro−steps
32768 micro−steps
65536 micro−steps
Number of Bits
13
14
15
16
When using the command SetPosition, although
coded on 16 bits, the position word will have to be shifted to
the left by a certain number of bits, according to the stepping
mode.
Secure Position
A secure position can be programmed. It is coded in
11−bits, thus having a lower resolution than normal
positions, as shown in the following table. See also
command GotoSecurePosition.
Table 12. SECURE POSITION
Stepping Mode
Secure Position Resolution
Half−stepping
1/4^th micro−stepping
1/8^th micro−stepping
4 half−steps
8 micro−steps (1/4^th)
16 micro−steps (1/8^th)
1/16^th micro−stepping
32 micro−steps (1/16^th)
Important
NOTES: The secure position is disabled in case the programmed value is the reserved code “10000000000” (0x400 or most negative
position).
The resolution of the secure position is limited to 9 bit at start−up. The OTP register is copied in RAM as illustrated below. The
RAM bits SecPos1 and SecPos0 are set to 0.
SecPos10
SecPos9
SecPos8
SecPos2
SecPos1
SecPos0
RAM
SecPos10 SecPos9
SecPos8
SecPos2
OTP
Shaft
A shaft bit, which can be programmed in OTP or with
command SetMotorParam, defines whether a positive
motion is a clockwise (CW) or counter−clockwise rotation
(CCW) (an outer or an inner motion for linear actuators):
• Shaft = 0 ⇒ MOTXP is used as positive pin of the X
coil, while MOTXN is the negative one.
• Shaft = 1 ⇒ opposite situation
STRUCTURAL DESCRIPTION
See also the Block Diagram in Figure 1.
Stepper Motordriver
The Motordriver receives the control signals from the
control logic. The main features are:
• Two H−bridges, designed to drive a stepper motor with
two separated coils. Each coil (X and Y) is driven by
one H−bridge, and the driver controls the currents
flowing through the coils. The rotational position of the
rotor, in unloaded condition, is defined by the ratio of
current flowing in X and Y. The torque of the stepper
motor when unloaded is controlled by the magnitude of
the currents in X and Y.
• The control block for the H−bridges, including the
PWM control, the synchronous rectification and the
internal current sensing circuitry.
• The charge pump to allow driving of the H−bridges’
high side transistors.
• Two pre−scale 4−bit DAC’s to set the maximum
magnitude of the current through X and Y.
• Two DAC’s to set the correct current ratio through X
and Y.
Battery voltage monitoring is also performed by this
block, which provides the required information to the
control logic part. The same applies for detection and
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