AMC1210_14 Datasheet, PDF (38/54 Pages) Texas Instruments – Quad Digital Filter for 2nd-Order Delta-Sigma Modulator

AMC1210
SBAS372D – APRIL 2006 – REVISED MAY 2009.............................................................................................................................................................. www.ti.com
APPLICATION INFORMATION
The AMC1210 is designed for use in motor control systems utilizing delta-sigma modulators, particularly the
ADS120x family of modulators.
Resolver Applications
Resolvers are used in motor control to determine the angular position and speed of the motor. The resolver
consists of three coils, one connected to the rotor and the other two situated orthogonally on the stator. By
supplying a sine wave carrier signal to the rotor coil, a voltage is magnetically coupled onto the stator coils, of
which the amplitude of the signal is directly proportional to the position of the rotor. By digitizing the stator
signals, the exact position of the rotor can be mathematically calculated.
Figure 23 shows a block diagram of a standard resolver application.
3
Sinc
OSR = 128
Digital, 12-bit
AMC1210
Demodulation
(including phase
adjustment)
Integrator
OSR = 8
Carrier cancellation
Digital, 14-bit
Parallel Interface
(including configuration
registers)
PWM
ADS1205
IN1P
CLK
IN1N
DATA
IN2P
DATA
IN2N
Analog
Sine
Cosine
Resolver
Figure 23. Typical Resolver Application with AMC1210
The AMC1210, along with the ADS120x family of modulators, provides a high-resolution resolver-to-digital
converter. The user can program a carrier signal that is synchronous with the data rate of the modulator. The
modulators digitize the resulting sine and cosine signals from the resolver. The AMC1210 then filters the
modulator data with the sinc filter. The resulting data can then be passed to the integrator, where demodulation
occurs.
The demodulated signal first gets multiplied by the polarity of the carrier signal. If the integrator is programmed
with the correct OSR, it sums a clock cycle of the rectified signal. The resulting signal is the baseband signal of
the sine or cosine wave. These values can then be processed by a microcontroller to obtain the actual digital
representation of the motor position.
Several factors need to be considered for a high-performance resolver design. The first item of importance is to
establish the timing of the motor control loop. This timing is the rate at which the microcontroller updates the
motor driving circuitry. A typical application synchronizes the frequency of the carrier signal to the motor control
loop frequency. With a known motor control frequency and a system clock frequency, the user can determine
how to set up the AMC1210 for optimal performance. Example 2 shows how the AMC1210 would be set up with
a carrier frequency of 8kHz and a system clock frequency of 32MHz.
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