參數(shù)資料
型號(hào)： AD7865
廠商： Analog Devices, Inc.
英文描述： Simultaneous Sampling, Fast, 14-Bit ADC(四通道,同時(shí)采樣,高速,14位A/D轉(zhuǎn)換器)
中文描述： 同步采樣，快速，14位ADC（四通道，同時(shí)采樣，高速，14位的A / D轉(zhuǎn)換器）
文件頁(yè)數(shù)： 19/21頁(yè)
文件大小： 375K
代理商： AD7865
AD7865
Rev. PrC
–19–
Preliminary Technical Data
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 AD7865,
with its four-channel simultaneous sampling capability, is
ideally suited for use in vector motor control applications.
A block diagram of a vector motor control application
using the AD7865 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
and V
of the AD7865 are used to
digitize this information.
Simultaneous sampling is critical to maintain 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 AD7865. Rotor
information is obtained by measuring the voltage from two
of the inputs to the motor. V
and V
of the AD7865 are
used to obtain this information. Once again the relative
phase of the two channels is important. A DSP micropro-
cessor is used to perform the mathematical transforma-
tions and control loop calculations on the information fed
back by the AD7865.
TECHNCAL
CS
RD
CONVST
DB0-DB13
AD7865
V
IN1
V
IN2
V
IN3
V
IN4
DTACK
AS
D0-D13
A0-A15
MC68000
ADDRESS
DECODE
CLOCK
R/W
Figure 22. AD7865–MC68000 Interface
Vector Motor Control
The current drawn by a motor can be split into two
components: one produces torque and the other produces
magnetic flux. For optimal performance of the motor,
these two components 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 coupling effect can
reduce the performance of the motor because, for ex-
ample, 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
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
+
-
+
-
AD7865*
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 AD7865.
MULTIPLE AD7865s IN A SYSTEM
Figure 24 shows a system where a number of AD7865s
can be configured to handle multiple input channels. This
type of configuration is common in applications such as
sonar, radar, etc. The AD7865 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 AD7865
has a maximum Aperture Delay Matching of ±4ns.
All AD7865's use the same external SAR clock (5MHz).
Therefore the conversion time for all devices will be the
same and so all devices may be read simulateously. The
the example shown in Figure 24 the data outputs of two
AD7865's are enabled onto a 32 bit wide data bus when
EOC
goes low.
相關(guān)PDF資料
PDF描述
AD7868 Complete 12-bit I/O System Containing a DAC And an ADC(完備的12位I\O系統(tǒng)（包含一個(gè)A/D轉(zhuǎn)換器和一個(gè)D/A轉(zhuǎn)換器）)
AD7869 Complete 14-bit I/O System Containing a DAC and a ADC(完備的14位I/O系統(tǒng)（包含一個(gè)A/D轉(zhuǎn)換器和一個(gè)D/A轉(zhuǎn)換器）)
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相關(guān)代理商/技術(shù)參數(shù)
參數(shù)描述
AD7865AS-1 制造商:Rochester Electronics LLC 功能描述:4 CH. SIMULTANEOUS BIPOLAR,14-B ADC I.C. - Bulk 制造商:Analog Devices 功能描述:Analog-Digital Converter IC Number of Bi
AD7865AS-1REEL 制造商:Analog Devices 功能描述:ADC Single SAR 350ksps 14-bit Parallel 44-Pin MQFP T/R 制造商:Rochester Electronics LLC 功能描述:4 CH. SIMULTANEOUS BIPOLAR,14-B ADC I.C. - Tape and Reel
AD7865AS2 制造商:AD 功能描述:*
AD7865AS-2 制造商:Analog Devices 功能描述:ADC Single SAR 350ksps 14-bit Parallel 44-Pin MQFP 制造商:Analog Devices 功能描述:IC 14-BIT ADC
AD7865AS-2REEL 制造商:Analog Devices 功能描述:ADC Single SAR 350ksps 14-bit Parallel 44-Pin MQFP T/R 制造商:Analog Devices 功能描述:ADC SGL SAR 350KSPS 14BIT PARALLEL 44MQFP - Tape and Reel
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