datasheetbank_Logo
Integrated circuits, Transistor, Semiconductors Search and Datasheet PDF Download Site

AD2S1210WDSTZ View Datasheet(PDF) - Analog Devices

Part Name
Description
View to exact match
AD2S1210WDSTZ Datasheet PDF : 36 Pages
First Prev 11 12 13 14 15 16 17 18 19 20 Next Last
AD2S1210
THEORY OF OPERATION
RESOLVER TO DIGITAL CONVERSION
The AD2S1210 operates on a Type II tracking closed-loop
principle. The output continually tracks the position of the
resolver without the need for external conversion and wait
states. As the resolver moves through a position equivalent
to the least significant bit weighting, the output is updated by
one LSB.
The converter tracks the shaft angle θ by producing an output
angle ϕ that is fed back and compared to the input angle θ, and
the resulting error between the two is driven towards 0 when
the converter is correctly tracking the input angle. To measure
the error, S3 − S1 is multiplied by cosϕ and S2 − S4 is multiplied by
sinϕ to give
E0 sin ωt × sinθ cos φ (for S3 − S1)
E0 sin ωt × cosθ sinφ (for S2 − S4)
The difference is taken, giving
E0 sinωt ×(sinθ cos φ cosθ sinφ)
(2)
This signal is demodulated using the internally generated
synthetic reference, yielding
E0 (sinθ cos φ cosθ sinφ)
(3)
Equation 3 is equivalent to E0sin(θ − ϕ), which is approximately
equal to E0(θ − ϕ) for small values of θ − ϕ, where θ − ϕ =
angular error.
The value E0 ϕ) is the difference between the angular error
of the rotor and the digital angle output of the converter.
A phase-sensitive demodulator, some integrators, and a compensa-
tion filter form a closed-loop system that seeks to null the error
signal. When this is accomplished, ϕ equals the Resolver Angle θ
within the rated accuracy of the converter. A Type II tracking
loop is used so that constant velocity inputs can be tracked
without inherent error.
FAULT DETECTION CIRCUIT
The AD2S1210 fault detection circuit can sense loss of resolver
signals, out-of-range input signals, input signal mismatch, or
loss of position tracking; however, in the event of a fault, the
position indicated by the AD2S1210 may differ significantly
from the actual shaft position of the resolver.
Monitor Signal
The AD2S1210 generates a monitor signal by comparing the
angle in the position register to the incoming sine and cosine
signals from the resolver. The monitor signal is created in a
similar fashion to the error signal described in the Resolver to
Digital Conversion section. The incoming signals, sinθ and
cosθ, are multiplied by the sin and cos of the output angle,
respectively, and then added together.
Monitor = A1× sinθ × sinφ + A2× cosθ × cos φ
(4)
where:
A1 is the amplitude of the incoming sine signal (A1 × sinθ).
A2 is the amplitude of the incoming cosine signal (A2 × cosθ).
θ is the resolver angle.
ϕ is the angle stored in the position register.
Note that Equation 4 is shown after demodulation, with the
Carrier Signal sinωt removed. Also, note that for matched input
signal (that is, a no fault condition), A1 = A2.
When A1 = A2 and the converter is tracking (θ = ϕ), the
monitor signal output has a constant magnitude of A1 (Monitor
= A1 × (sin2 θ + cos2 θ) = A1), which is independent of shaft
angle. When A1 ≠ A2, the monitor signal magnitude varies
between A1 and A2 at twice the rate of shaft rotation. The
monitor signal is used as described in the following sections to
detect degradation or loss of input signals.
Loss of Signal Detection
The AD2S1210 indicates that a loss of signal (LOS) has
occurred for four separate conditions.
When either resolver input (sine or cosine) falls below the
specified LOS sine/cosine threshold. This threshold is
defined by the user and is set by writing to the internal
register, Address 0x88 (see the Register Map section).
When any of the resolver input pins (SIN, SINLO, COS, or
COSLO) are disconnected from the sensor.
When any of the resolver input pins (SIN, SINLO, COS, or
COSLO) are clipping the power rail or ground rail of the
AD2S1210. Refer to the Sine/Cosine Input Clipping section.
When a configuration parity error has occurred. Refer to
the Configuration Parity Error section.
A loss of signal is caused if either of the stator windings of the
resolver (sine or cosine) are open circuit or have a number of
shorted turns. LOS is indicated by both the DOS and LOT pins
latching as logic low outputs. The DOS and LOT pins are reset
to a no fault state when the user enters configuration mode and
reads the fault register. The LOS condition has priority over
both the DOS and LOT conditions, as shown in Table 6. To
determine the cause of the LOS fault detection, the user must
read the fault register, Address 0xFF (see the Register Map
section).
When a loss of signal is detected due to the resolver inputs (sine
or cosine) falling below the specified LOS sine/cosine threshold,
the electrical angle through which the resolver may rotate before
the LOS can be detected by the AD2S1210 is referred to as the
LOS angular latency. This is defined by the specified LOS sine/
cosine threshold set by the user and the maximum amplitude of
the input signals being applied to the AD2S1210. The worst-case
angular latency can be calculated as follows:
Rev. 0 | Page 16 of 36
 

Share Link: 

datasheetbank.com [ Privacy Policy ] [ Request Datasheet ] [ Contact Us ]