AD2S105

REV. 0

–7–

Output Analog Signals

There are two sets of analog output from the AD2S105.

Sin/Cos orthogonal output signals are derived from the Clark/

three-to-two-phase conversion before the Park angle rotation.

These signals are available on Pin 25 (Cos ) and Pin 26 (Sin

), and occur before Park angle rotation.

Two-Phase (Sin ( +

), Cos ( + )) Signals

These represent the output of the coordinate transformation.

These signals are available on Pin 6 (PH/OP4, Sin ( +

)) and

Pin 7 (PH/OP1, Cos ( +

)).

HOMOPOLAR OUTPUT

HOMOPOLAR Reference

In a three-phase ac system, the sum of the three inputs to the

converter can be used to indicate whether or not the phases are

balanced.

Cos ( + 120

°) + Cos ( + 240°)] = 0. Any imbalances in the

≠ 0. The AD2S105 homopolar

level at which the HPOP indicates an imbalance is determined

±0.5 V dc

(

±0.1 V dc). The HPOP goes high when

(Cos

θ+ Cos(θ+ 120° ) + Cos(θ+ 240° ))

3

×V

where V is the nominal input voltage.

±1.5 V dc in

order for HPOP to indicate an imbalance. The sensitivity of the

threshold can be reduced by connecting an external resistor be-

tween HPOP and ground in Figure 5 where

20k

Ω

25

µA

HOMOPOLAR

REFERENCE

EXTERNAL

RESISTOR

TO TRIGGER

Figure 5. The Equivalent Homopolar Reference Input

Circuitry

Example: From the equivalent circuit, it can be seen that the in-

clusion of a 20 k

Ω resistor will reduce V

±0.25 V dc. This

corresponds to an imbalance of

±0.75 V dc in the inputs.

Homopolar Filtering

≠ 0. There are conditions,

however, when an actual imbalance will occur and the condi-

phase was open circuit when

= 90

° or 270°, the first phase is

In order to detect an imbalance

has to move away from 90

° or

270

°, i.e., when on a balanced line Cos ≠ 0.

Line imbalance is detected as a function of HPREF, either set

by the user or internally set at

±0.5 V dc. This corresponds to a

dead zone when

= 90

° or 270° ± 30°, i.e., V

therefore, no indicated imbalance. If an external 20 k

Ω resistor

±15°. Note this

example only applies if the first phase is detached.

In order to prevent this false triggering an external capacitor

needs to be placed from HPFILT to ground, as shown in Figure

5. This averages out the perceived imbalance over a complete

cycle and will prevent the HPOP from alternatively indicating

balance and imbalance over

= 0

° to 360°.

For

d

θ

dt

= 1000 rpm C

d

θ

dt

= 100 rpm C

Note: The slower the input rotational speed, the larger the time

constant required over which to average the HPOP output. Use

of the homopolar output at slow rotational speeds becomes im-

AD2S105

TOP VIEW

1

23

12

34

HPREF

HPOP

HPFILT

220nF

DGND

HPOP

GND

HPREF

Figure 6. AD2S105 Homopolar Output Connections