NSD-2101_07 Datasheet, PDF (17/23 Pages) ams AG – Piezo Motor Driver ASIC for SQL-RV Series Reduced Voltage SQUIGGLE RV and UTAF Motors

NSD-2101
Datasheet - Application Information
Directing the NSD-2101.
The basic command that is sent to the NSD-2101 is the pulse count (with direction). When a non-zero value is written to registers 02 and 03 by
the host microprocessor, the NSD-2101 begins generating pulses on the output pins at the interval defined by the period register (01). For each
pulse, the specified pulse count is decremented. Pulse generation continues until the pulse count reaches zero or the host writes a zero to
registers 02 and 03. See Register Map (page 10) and Pulse Counter (page 12).
Since the pulse counter is limited to 2047 (11 bits), the maximum duration of motion is the 2047 x period. If the period were 5.8 µsec (172.4 kHz),
then the duration would be ~11.8 msec. Therefore to produce continuous motion, the pulse count must be reloaded by the host before the
previous pulse count expires (in this case - at least every 11.7 msec - but every 10 msec would provide more margin allowing for variations in
motor frequency and overhead in the host processer handling I²C traffic).
lid ^{Given the nominal 25MHz power-up frequency of the VCO within the NSD-2101, the motor period is specified in units of 40 nsec. Therefore the}
period value necessary to generate a frequency of 172.4 kHz is 145 (or 91 hexadecimal).
As indicated in the previous section, to generate motion, the pulse period must be very near the interval of the mechanical resonant frequency of
the motor. However, for a given motor type, manufacturing tolerances, ambient temperature and mounting have an affect on this resonant
a _{frequency. To cancel out these affects, the NSD-2101 supports a frequency tuning (or calibration) feature.}
v _{Therefore on power-up, it is recommended that after an appropriate default period count for the given motor type is loaded, a frequency sweep}
calibration is performed followed by an incremental calibration. See Frequency Tracking (page 9). The sweep needs to be performed only once
ill ^{(for a given power cycle); After that, the incremental calibration will keep the motor in tune.}
Note: While performing the frequency calibration, the NSD-2101 is adjusting the trimming of its internal VCO to maximize the performance of
t ^{the motor (not the period count itself).}
Furthermore, it is recommended that frequency calibration be performed in a direction that is against the load (typically forward). The reason is
G _{s that, depending on the mass being moved (i.e. the inertia), there may be chatter (intermittent contact between the load and the screw) when}
moving with the load. This chatter can affect the calibration.
A ^t _{Starting a frequency sweep calibration (assuming an SQL-RV-1.8 motor):}
s ⁿ _Reg
Value (hex) Comment
e ₀₀
6B
Enables sweep calibration using both motor phases
m ^t ₀₁
91
172.4 kHz
a ⁿ ₀₂
77
Fwd, DT=11*, Upper 3 bits of pulse count set
o ₀₃
FF
Lower 8 bits of pulse count set
c _{Actual data stream: A8006B9177FF (the host should wait at least 10 msec after start)}
l _{Starting a frequency incremental calibration:}
a _Reg
Value (hex) Comment
ic ⁰⁰
67
Enables inc. calibration using both motor phases
01
91
172.4 kHz
n ₀₂
77
Fwd, DT=11*, Upper 3 bits of pulse count set
h ₀₃
FF
Lower 8 bits of pulse count set
Tec ^{Actual data stream: A800679177FF (the host should wait at least 10 msec after start)}
www.austriamicrosystems.com/NSD-2101
Revision 0.6
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