TMC4671 Datasheet • IC Version V1.00 | Document Revision V1.04 • 2018-Dec-11
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Application
RP U RP D RLN
CP
5 V Encoder signal 4K7
n.c. 100R 100pF
Table 27: Reference Values for circuitry components
The raw signal (ENC_A_RAW) is divided by a voltage divider and filtered by a lowpass filter. A pull up resistor
is applied for open collector encoder output signals. Diodes protect the input pin (ENC_A) against over-
and undervoltage. The cutoff-frequency of the lowpass is:
1
fc =
(39)
2 π RP DCP
10.4 Analog Frontend
Analog Encoders are encoding the motor position into sinusoidal signals. These signals need to be
digitalized by the TMC4671 in order to determine the rotor position. The input voltage range depends on
V5 input, which is usually 5V and GNDA (usually 0V). Due to nonlinearity issues of the ADC near input limits,
an ADC input value from 1V to 4V is recommended. For a single ended application, the sample circuit from
fig. 36 can be used. All single ended analog input pins (AGPI_A, AGPI_B and ADC_VM) have their negative
input value tied to GNDA internally, so this sample circuit can also be used for them.
Figure 36: Sample Circuit for Interfacing of a single ended analog signal
If the power stage and the TMC4671 share a common ground, the ADC_VM input signal can be generated
by a voltage divider to scale the voltage down to the needed range.
If the analog encoder has differential output signals, these can be used without signal conditioning (no OP
AMPs), when voltage range matches. Differential analog inputs can be used to digitize differential analog
input signals with high common mode voltage error suppression.
10.5 Phase Current Measurement
The TMC4671 requires two phase currents of a 2 or 3 phase motor to be measured. For a DC Motor only
one current in the phase needs to be measured (see Fig. 38). In the ADC engine mapping of current signals
to motor phases can be changed. Default setting is I0 to be the current running into the motor in phase U
for a 3 phase motor. Respectively the current running into the motor from half-bridge X1 of a 2 phase
motor. Figs. 37 and 38 illustrates the currents to be measured and their positive direction.
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