TMC603A Datasheet, PDF (22/44 Pages) TRINAMIC Motion Control GmbH & Co. KG. – Three phase motor driver with BLDC back EMF commutation hallFX™ and current sensing

TMC603A DATA SHEET (V. 1.15 / 2009-Nov-19)
22
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.
Switch Cap filters
Position signal Induction pulse
generation (PSG) supressor (IPS)
U
Low pass LPU
BM1
ULP
E1
H1
V
D
30k
W
BM2
Low pass LPV
VLP
E2
PSG
IPS
H2
D
E1
E2
30k
E3
Low pass LPW
BM3
WLP
E3
H1
H3
D
H2
30k
H3
A
D
ENRS_TEST
SP_SUP
AAA
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
SP_SUP
FILTx_RSx
Hx
SCCLK
Comments
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.
These pins provide the filtered coil voltages when ENRS_TEST is tied to GND. 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.
Emulated hall sensor output signal of hallFX™ block.
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.
Copyright © 2009 TRINAMIC Motion Control GmbH & Co. KG