Dual Output Differential

Speed and Direction Sensor IC

ATS605LSG

8

Allegro MicroSystems, LLC

115 Northeast Cutoff

Worcester, Massachusetts 01615-0036 U.S.A.

1.508.853.5000; www.allegromicro.com

Output

The device provides three outputs (DIRECTION, XOR SPEED,

and SPEED), available in two combinations: Option #1 (-S) is

SPEED (Ch. A) and SPEED (Ch. B), and Option #2 (-F) is XOR

SPEED and DIRECTION. DIRECTION provides the target

rotation direction relative to the device. XOR SPEED provides

an XOR’d output of the two speed channels (Ch. A and Ch. B),

which results in double the speed data rate without requiring

changes to be made to the controller. SPEED will be updated

before DIRECTION and is updated at every transition of both

Channel A and Channel B allowing the use of up-down counters

without the loss of pulses.

Output Polarity

In Figure 4, the top panel, labeled Mechanical Position, repre-

sents the mechanical features of the target gear and orientation

to the device. The bottom panel, labeled Output Option # 1, the

–S variant, displays the square waveforms corresponding to the

digital SPEED output signals for channels A and B for a rotating

gear in the forward rotation direction (gear tooth passing from the

pin 4 side to the pin 1 side, Figure 3). The end result is the sensor

output switching from high state to low state as the leading edge

of a tooth (a rising mechanical edge, as detected by the sensor)

passes the sensor face. If the direction of rotation is reversed so

that the gear rotates from the pin 1 side to the pin 4 side (Figure

3), then the output polarity inverts (i.e., the output signal goes

high when a rising edge is detected, and a tooth is the nearest

feature to the sensor).

The Output Option #2 panel refers to the –F variant, for which

DIRECTION polarity is defined as ON (low) when the target

crosses the sensor face in the forward direction (from the pin

4 side to the pin 1 side), and OFF (high) for the reverse direc-

tion (from the pin 1 side to the pin 4 side). There is an option,

ATS605LSGTN-R-T, that inverts this DIRECTION output signal

polarity (SPEED output polarity is unaffected and remains as

defined above). XOR SPEED polarity is defined as SPEED A

XOR SPEED B.

Table 1: Output Pin Descriptions

Option

Pin 2 / OUTB

Pin 3 / OUTA

Option 1 (“-S”)

SPEED B

SPEED A

Option 2 (“-F”)

XOR SPEED

DIRECTION

Option 2 (“-R”)

XOR SPEED

Inverted DIRECTION

Figure 4: The magnetic profile reflects the geometry of the

target, allowing the ATS605 to present an accurate digital output

response. Please see Figure 5 for more detailed output switching.