TMC603 DATA SHEET (V. 1.06 / 26. Mar. 2009)
21
5.4 hallFX sensorless commutation
hallFX provides emulated hall sensor signals. The emulated hall sensor signals are available without a
phase shift and there is no error-prone PLL necessary, like with many other systems, nor is the
knowledge of special motor parameters required. Since it is based on the motors’ back-EMF, a
minimum motor velocity is required to get a valid signal. Therefore, the motor needs to be started
without feedback, until the velocity is high enough to generate a reliable hallFX signal.
Position signal
generation (PSG)
Induction pulse
supressor (IPS)
Switch Cap filters
U
V
Low pass LPU
ULP
E1
E2
E3
BM1
BM2
BM3
H1
H2
H3
D
30k
W
Low pass LPV
E1
E2
E3
VLP
D
PSG
IPS
30k
Low pass LPW
H1
H2
H3
WLP
D
30k
A
D
A
A
A
SP_SUP
CSUP
figure 16: hallFX block diagram and timing
A switched capacitor filter for each coil supplies the measured effective coil voltages. Its filter
frequency can be adapted to the chopper frequency and the desired maximum motor velocity. An
induction pulse suppressor unit gates the commutation spikes which result from the inductive behavior
of the motor coils after switching off the current. The gating time can be adapted by an external
capacitor to fit the motor inductivity and its (maximum) velocity.
Pin
Comments
SP_SUP
A capacitor attached to this pin sets the spike suppression time. This pin charges the
capacitor via an internal current source. If more exact timing is required, an external
47k pull-up resistor to VCC can be used in parallel to the internal current source. The
capacitor becomes discharged upon each valid commutation. The capacitor can
optionally be left away, and the suppression can be done in software.
FILTx
These pins provide the filtered coil voltages. For most applications this will be of no
use, except when an external back-EMF commutation is realized, e.g. using a
microcontroller with ADC inputs. Because of the high output resistance and low
current capability of these pins, it is advised to add an external capacitor of a few
hundred picofarad up to a few nanofarad to GND, if the signals are to be used. This
prevents noise caused by capacitance to adjacent signal traces to disturb the signal.
Hx
Emulated hall sensor output signal of hallFX block.
SCCLK
An external clock controls the corner frequency of the switched capacitor filter. A 1.25
MHz clock gives a filter bandwidth of 3kHz. A lower clock frequency may be better for
lower motor velocities.
5.4.1 Adjusting the hallFX spike suppression time
hallFX needs two minimum motor- and application-specific adjustments: The switched capacitor clock
frequency and the spike suppression time should be adapted. Both can easily be deducted from basic
application parameters and are not very critical. The SCCLK frequency should be matched to the
chopper frequency of the system and the maximum motor velocity. The spike suppression time needs
to be adapted to the desired maximum motor velocity.
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TRINAMIC [ TRINAMIC MOTION CONTROL GMBH & CO. KG. ]
