AD7862
–15–
REV. 0
VOLTAGE
ATTENUATORS
DAC
DAC
DAC
TORQUE
SETPOINT
A1
V
V
B2
V
B1
V
A2
*ADDITIONAL PINS OMITTED FOR CLARITY
TORQUE & FLUX
CONTROL LOOP
CALCULATIONS &
TWO TO THREE
PHASE
INFORMATION
TRANSFORMATION
TO TORQUE &
FLUX CURRENT
COMPONENTS
FLUX
SETPOINT
DRIVE
CIRCUITRY
ISOLATION
AMPLIFIERS
AD7862*
DSP
MICROPROCESSOR
I
C
I
B
I
A
V
B
V
A
3
PHASE
MOTOR
Figure 19. Vector Motor Control Using the AD7862
MULTIPLE AD7862S
Figure 20 shows a system where a number of AD7862s can be
configured to handle multiple input channels. This type of
configuration is common in applications such as sonar, radar,
etc. The AD7862 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 AD7862s. Each AD7862 is designated a unique
address selected by the address decoder. The reference output
of AD7862 number 1 is used to drive the reference input of all
other AD7862s in the circuit shown in Figure 20. One VREF
pin can drive several AD7862 REF IN pins. Alternatively, an
external or system reference can be used to drive all VREF
inputs. A common reference ensures good full-scale tracking
between all channels.
AD7862(1)
AD7862(2)
AD7862(n)
CS
RD
CS
RD
CS
RD
RD
ADDRESS
VREF
REF IN
REF IN
ADDRESS
DECODE
V
A1
V
B1
V
A2
V
B2
V
A1
V
B1
V
A2
V
B2
V
A1
V
B1
V
A2
V
B2
Figure 20. Multiple AD7862s in Multichannel System
