AD7863ARZ-2 Analog Devices Inc, AD7863ARZ-2 Datasheet - Page 19

• Manufacturer Part Number: AD7863ARZ-2
• Description: IC,Data Acquisition System,2-CHANNEL,14-BIT,SOP,28PIN,PLASTIC
• Manufacturer: Analog Devices Inc

Specifications of AD7863ARZ-2

• Number Of Bits: 14
• Sampling Rate (per Second): 175k
• Data Interface: Parallel
• Number Of Converters: 2
• Power Dissipation (max): 94.5mW
• Voltage Supply Source: Analog and Digital
• Operating Temperature: -40°C ~ 85°C
• Mounting Type: Surface Mount
• Package / Case: 28-SOIC (0.300", 7.50mm Width)
• Lead Free Status / RoHS Status: Lead free / RoHS Compliant

Vector control of an ac motor involves controlling the phase in
addition to drive and current frequency. Controlling the phase
of the motor requires feedback information on the position of
the rotor relative to the rotating magnetic field in the motor.
Using this information, a vector controller mathematically
transforms the three phase drive currents into separate torque
and flux components. The AD7863 is ideally suited for use in
vector motor control applications.
A block diagram of a vector motor control application using the
AD7863 is shown in Figure 24. The position of the field is
derived by determining the current in each phase of the motor.
Only two phase currents need to be measured because the third
can be calculated if two phases are known. V
AD7863 are used to digitize this information.
Simultaneous sampling is critical to maintaining the relative
phase information between the two channels. A current sensing
isolation amplifier, transformer, or Hall effect sensor is used
between the motor and the AD7863. Rotor information is
obtained by measuring the voltage from two of the inputs to the
motor. V
information. Once again the relative phase of the two channels
is important. A DSP microprocessor is used to perform the
mathematical transformations and control loop calculations on
the information fed back by the AD7863.
SETPOINT
SETPOINT
TORQUE
FLUX
B1
*ADDITIONAL PINS
OMITTED FOR CLARITY.
and V
Figure 24. Vector Motor Control Using the AD7863
CALCULATIONS AND
MICROPROCESSOR
TRANSFORMATION
TORQUE AND FLUX
TO TORQUE AND
CONTROL LOOP
FLUX CURRENT
TWO TO THREE
COMPONENTS
INFORMATION
PHASE
B2
DSP
of the AD7863 are used to obtain this
AD7863*
DAC
DAC
DAC
V
V
V
V
A1
A2
B1
B2
CIRCUITRY
AMPLIFIERS
ISOLATION
DRIVE
ATTENUATORS
VOLTAGE
A1
and V
I
I
I
C
B
A
A2
V
V
B
of the
A
MOTOR
THREE
PHASE
Rev. B | Page 19 of 24
MULTIPLE AD7863S
Figure 25 shows a system where a number of AD7863s can be
configured to handle multiple input channels. This type of
configuration is common in applications such as sonar and
radar. The AD7863 is specified with typical limits on aperture
delay. This means that the user knows the difference in the
sampling instant between all channels. This allows the user to
maintain relative phase information between the different
channels.
A common read signal from the microprocessor drives the RD
input of all AD7863s. Each AD7863 is designated a unique
address selected by the address decoder. The reference output of
AD7863 Number 1 is used to drive the reference input of all
other AD7863s in the circuit shown in Figure 25. One V
be used to provide the reference to several other AD7863s.
Alternatively, an external or system reference can be used to
drive all V
scale tracking between all channels.
V
V
V
V
V
V
V
V
V
V
V
V
A1
B1
A2
B2
A1
B1
A2
B2
A1
B1
A2
B2
Figure 25. Multiple AD7863s in Multichannel System
REF
inputs. A common reference ensures good full-
V
V
V
REF
REF
REF
AD7863
AD7863
AD7863
(1)
(2)
(n)
RD
CS
RD
CS
RD
CS
ADDRESS
DECODE
RD
ADDRESS
AD7863
REF
can