The DSP can be directly connected at the output of two
channels of the optocoupler, C28x or C24x. In this configu-
ration, the signals arriving at C28x or C24x are standard
delta-sigma modulator signals and are connected directly to
the SPICLK and SPISIMO pins. Being a delta-sigma con-
verter, there is no need to have word synch on the serial
data, so SPI is ideal for connection. McBSP would work as
well in SPI mode.
APPLICATIONS
Mode 0 operation in a typical application is shown in Figure
10. Measurement of the motor phase current is done via the
shunt resistor. For better performance, both signals are
filtered. R2 and C2 filter noise on the noninverting input
signal, R3 and C3 filter noise on the inverting input signal, and
C4 in combination with R2 and R3 filter the common-mode
input noise. In this configuration, the shunt resistor is con-
nected via three wires with the ADS1202.
When component reduction is necessary, the ADS1202 can
operate in mode 2, as shown in Figure 11. M1 is HIGH and
M0 is LOW. Only the noninverting input signal is filtered.
R2 and C2 filter noise on the input signal. The inverting input
is directly connected to the GND pin, which is simultaneously
connected to the shunt resistor.
The power supply is taken from the upper gate driver power
supply. A decoupling capacitor of 0.1µF is recommended for
filtering the power supply. If better filtering is required, an
additional 1µF to 10µF capacitor can be added.
The control lines M0 and M1 are both LOW while the part is
operating in mode 0. Two output signals, MCLK and MDAT,
are connected directly to the optocoupler. The optocoupler
can be connected to transfer a direct or inverse signal
because the output stage has the capacity to source and sink
the same current. The discharge resistor is not needed in
parallel with optocoupler diodes because the output driver
has the capacity to keep the LED diode out of the charge.
The output signal from the ADS1202 is Manchester coded. In
this case, only one signal is transmitted. For that reason, one
optocoupler channel is used instead of two channels, as in
the previous example of Figure 10. Another advantage of this
configuration is that the DSP will use only one line per
channel instead of two. That permits the use of smaller DSP
packages in the application.
Floating
Power Supply
HV+
Gated
Drive Circuit
R1
C28x
or
C24x
R5
Optocoupler
D1
5.1V
C1
0.1µF
ADS1202
M0 VDD
R4
C4
10nF
R2
27Ω
SPICLK
VIN
VIN
M1
+
MCLK
MDAT
GND
–
SPISIMO
RSENSE
R3
27Ω
C2
0.1µF
C3
0.1µF
Power
Supply
Gated
Drive Circuit
HV–
FIGURE 10. Application Diagram in Mode 0.
ADS1202
16
SBAS275
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