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| 型號(hào)： | AD7864AS-2 |
| 廠商： | ANALOG DEVICES INC |
| 元件分類： | ADC |
| 英文描述： | 4-Channel, Simultaneous Sampling, High Speed, 12-Bit ADC |
| 中文描述： | 4-CH 12-BIT SUCCESSIVE APPROXIMATION ADC, PARALLEL ACCESS, PQFP44 |
| 封裝： | PLASTIC, MO-112-AA, MQFP-44 |
| 文件頁(yè)數(shù)： | 18/19頁(yè) |
| 文件大小： | 214K |
| 代理商： | AD7864AS-2 |
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AD7864
–18–
REV. A
Vector Motor Control
The current drawn by a motor can be split into two compo-
nents: one produces torque and the other produces magnetic
flux. For optimal performance of the motor, these two compo-
nents should be controlled independently. In conventional
methods of controlling a three-phase motor, the current (or
voltage) supplied to the motor and the frequency of the drive are
the basic control variables. However, both the torque and flux
are functions of current (or voltage) and frequency. This cou-
pling effect can reduce the performance of the motor because,
for example, if the torque is increased by increasing the fre-
quency, the flux tends to decrease.
Vector control of an ac motor involves controlling 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 trans-
forms the three phase drive currents into separate torque and
flux components. The AD7864, with its four-channel simulta-
neous sampling capability, is ideally suited for use in vector
motor control applications.
A block diagram of a vector motor control application using the
AD7864 is shown in Figure 23. 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
IN1
and V
IN2
of the
AD7864 are used to digitize this information.
Simultaneous sampling is critical to maintain the relative phase
information between the two channels. A current sensing isola-
tion amplifier, transformer or Hall effect sensor is used between
the motor and the AD7864. Rotor information is obtained by
measuring the voltage from two of the inputs to the motor. V
IN3
and V
IN4
of the AD7864 are used to obtain this 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 informa-
tion fed back by the AD7864.
MULTIPLE AD7864s IN A SYSTEM
Figure 24 shows a system where a number of AD7864s can be
configured to handle multiple input channels. This type of con-
figuration is common in applications such as sonar, radar, etc.
The AD7864 is specified with maximum limits on aperture
delay match. 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. The AD7864 has a maximum aperture delay match-
ing of 4 ns.
All AD7864s use the same external SAR clock (5 MHz). There-
fore, the conversion time for all devices will be the same and so
all devices may be read simultaneously. The example shown in
Figure 24 the data outputs of two AD7864s are enabled onto a
32-bit wide data bus when
EOC
goes low.
EOC
AD7864
V
IN1
V
IN2
V
IN3
V
IN4
ADDRESS
DECODE
V
REF
CLKIN
CS
RD
12
32
AD7864
V
IN1
V
IN2
V
IN3
V
IN4
V
REF
CLKIN
CS
RD
12
ADSP-2106x
RD
REF193
5MHz
Figure 24. Multiple AD7864s in Multichannel System
DAC
TORQUE & FLUX
CONTROL LOOP
CALCULATIONS &
TWO TO THREE
PHASE INFORMATION
DSP MICROPROCESSOR
DAC
DAC
DRIVE
CIRCUITRY
3
PHASE
MOTOR
I
C
I
B
I
A
V
B
V
A
TRANSFORMATION
TO TORQUE &
FLUX CURRENT
COMPONENTS
+
–
+
–
AD7864*
V
IN1
V
IN2
V
IN3
V
IN4
ISOLATION
AMPLIFIERS
VOLTAGE
ATTENUATORS
TORQUE
SETPOINT
FLUX
SETPOINT
*ADDITIONAL PINS OMITTED FOR CLARITY
Figure 23. Vector Motor Control Using the AD7864
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PDF描述 |
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相關(guān)代理商/技術(shù)參數(shù) |
參數(shù)描述 |
|---|---|
| AD7864AS-2REEL | 制造商:Analog Devices 功能描述:ADC Single SAR 520ksps 12-bit Parallel 44-Pin MQFP T/R |
| AD7864AS-2Z | 制造商:Analog Devices 功能描述:ADC 12BIT 4CH 500KSPS 44MQ 制造商:Analog Devices 功能描述:ADC, 12BIT, 4CH, 500KSPS, 44MQFP; Resolution (Bits):12bit; Sampling Rate:520kSPS; Supply Voltage Type:Single; Supply Voltage Min:4.75V; Supply Voltage Max:5.25V; Supply Current:24mA; Digital IC Case Style:MQFP; No. of Pins:44; Input ;RoHS Compliant: Yes |
| AD7864AS-3 | 制造商:Analog Devices 功能描述:ADC Single SAR 520ksps 12-bit Parallel 44-Pin MQFP 制造商:Analog Devices 功能描述:IC 12-BIT ADC |
| AD7864AS-3REEL | 制造商:Analog Devices 功能描述:ADC Single SAR 520ksps 12-bit Parallel 44-Pin MQFP T/R |
| AD7864AS-3Z | 制造商:Analog Devices 功能描述:ADC 12BIT 4CH 500KSPS 44MQ 制造商:Analog Devices 功能描述:ADC, 12BIT, 4CH, 500KSPS, 44MQFP; Resolution (Bits):12bit; Sampling Rate:520kSPS; Supply Voltage Type:Single; Supply Voltage Min:4.75V; Supply Voltage Max:5.25V; Supply Current:24mA; Digital IC Case Style:MQFP; No. of Pins:44; Input ;RoHS Compliant: Yes |
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