AD73360 datasheet(27/35 Pages) AD

27 / 35 page

REV. A

AD73360

–27–

DSP SPORT Interrupts

If SPORT interrupts are enabled, it is important to note that the

active signals on the frame sync pins do not necessarily corre-

spond with the positions in time of where SPORT interrupts are

generated.

On ADSP-21xx processors, it is necessary to enable SPORT

interrupts and use Interrupt Service Routines (ISRs) to handle

Tx/Rx activity, while on the TMS320C5x processors it is pos-

sible to poll the status of the Rx and Tx registers, which means

that Rx/Tx activity can be monitored using a single ISR that

would ideally be the Tx ISR as the Tx interrupt will typically

occur before the Rx ISR.

APPLICATIONS EXAMPLES

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 AD73360, with its six-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

AD73360 is shown in Figure 30. The position of the field is

derived by determining the current in each phase of the motor.

VIN1, VIN2 and VIN3 of the AD73360 are used to digitize this

information.

Simultaneous sampling is critical to maintain the relative phase

information between the channels. A current-sensing isolation

amplifier, transformer or Hall-effect sensor is used between the

motor and the AD73360. Rotor information is obtained by

measuring the voltage from the three inputs to the motor. VIN4,

VIN5 and VIN6 of the AD73360 are used to obtain this informa-

tion. A DSP microprocessor is used to perform the mathematical

transformations and control loop calculations on the informa-

tion fed back by the AD73360.

DAC

DRIVE

CIRCUITRY

TORQUE

SETPOINT

FLUX

SETPOINT

THREE-

PHASE

MOTOR

ISOLATION

AMPLIFIERS

VOLTAGE

ATTENUATORS

DSP

MICROPROCESSOR

TORQUE & FLUX

CONTROL LOOP

CALCULATIONS

DAC

AD73360

VIN1

VIN2

VIN3

VIN4

VIN6

VIN5

TRANSFORMATION

TO TORQUE &

FLUX

CURRENT

COMPONENTS

Figure 30. Vector Motor Control Using the AD73360

Industrial Power Metering

The AD73360 can be used to measure the voltage and current

in all three phases of a three-phase supply. The simultaneous

sampling architecture of the AD73360 is ideal for this applica-

tion where simultaneous sampling is critical to maintaining the

relative phase information between the three voltage and three

current phases. Figure 31 shows a block diagram of a three-

phase metering system. The VIN1, VIN2 and VIN3 channels are

used to measure the voltages in each phase (via voltage attenua-

tors). The current flowing in each phase can be detected by the

use of current-sensing isolation amplifiers, transformers or

Hall-effect sensors. VIN4, VIN5 and VIN6 are used to digitize

this information. A DSP microprocessor is used to perform

the mathematical calculations on the information provided by

the AD73360.

DSP

MICROPROCESSOR

ISOLATION

AMPLIFIERS

VOLTAGE

ATTENUATORS

THREE-

PHASE

SUPPLY

AD73360

VIN1

VIN2

VIN3

VIN4

VIN6

VIN5

Figure 31. Three-Phase Power Metering

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