ALLEGRO ATS643LSH User Manual

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Package SH, 4-pin SIP

1

2

3

4

1. VCC

2. No connection (float or tie to VCC)

3. Test pin (float or tie to GND)

4. GND

ATS643LSH

Self-Calibrating, Zero-Speed Differential

Gear Tooth Sensor with Continuous Update

The ATS643 is an optimized combination of integrated circuit and magnet that
provides a manufacturer-friendly solution for true zero-speed digital gear-tooth
sensing in two-wire applications. The device consists of a single-shot molded
plastic package that includes a samarium cobalt magnet, a pole piece, and a
Hall-effect IC that has been optimized to the magnetic circuit and the automotive
environment. This small package can be easily assembled and used in conjunction
with a wide variety of gear shapes and sizes.

The integrated circuit incorporates a dual element Hall-effect sensor with signal
processing circuitry that switches in response to differential magnetic signals
created by rotating ferrous targets. The device contains a sophisticated compen­sating circuit to eliminate magnet and system offsets immediately at power-on.
Digital tracking of the analog signal is used to achieve true zero-speed operation,
while also setting the device switchpoints. The resulting switchpoints are air gap
independent, greatly improving output and duty cycle accuracy. The device also
uses a continuous update algorithm to fine-tune the switchpoints while in running
mode, maintaining the device specifications even through large changes in air gap
or temperature.

The regulated current output is configured for two-wire operation, offering inher­ent diagnostic information. This device is ideal for obtaining speed and duty cycle
information in gear-tooth based applications such as transmission speed sensing.

AB SO LUTE MAX I MUM RAT INGS

Supply Voltage, VCC..................See Power Derating

Reverse-Supply Voltage, V
Operating Temperature
Ambient, T
Maximum Junction, T
Storage Temperature, T

ATS643-DS, Rev. 1

................................ –40ºC to 150ºC

A

........................–18 V

RCC

........................165ºC

J(max)

.................. –65ºC to 170ºC

S

Features and Benefits

• Fully-optimized differential digital gear
tooth sensor

• Single chip-IC for high reliability

• Internal current regulator for 2-wire
operation

• Small mechanical size (8 mm diameter
x 5.5 mm depth)

• Switchpoints air gap independent

• Digital output representing gear profile

Use the following complete part numbers when ordering:

Part Number Package ICC Typical

ATS643LSH-I1 4-pin plastic SIP 6.0 Low to 14.0 High mA

ATS643LSH-I2 4-pin plastic SIP 7.0 Low to 14.0 High mA

• Precise duty cycle accuracy through­out temperature range

• Large operating air gaps

• <2 ms power-on time

• AGC and reference adjust circuit

• True zero-speed operation

• Undervoltage lockout

• Wide operating voltage range

• Defined power-on state

Allegro MicroSystems, Inc.
115 Northeast Cutoff, Box 15036
Worcester, Massachusetts 01615-0036 [phone]

www.allegromicro.com

ATS643LSH

Self-Calibrating, Zero-Speed Differential GTS with Continuous Update

Functional Block Diagram

VCC (Pin 1)

PDAC

NDAC

Hall AMP

Offset Adjust

ThresholdP

Reference
Generator
and

Updates

ThresholdN

AGC

Internal

Regulator

Threshold

Logic

GND (Pin 4)

ATS643-DS, Rev. 1

Allegro MicroSystems, Inc.
115 Northeast Cutoff, Box 15036
Worcester, Massachusetts 01615-0036 [phone]

www.allegromicro.com

2

ATS643LSH

Self-Calibrating, Zero-Speed Differential GTS with Continuous Update

OPERATING CHARACTERISTICS using reference target 60-0, TA and VCC within specification, unless otherwise noted

Characteristic Symbol Test Conditions Min. Typ. Max. Units

ELECTRICAL CHARACTERISTICS

Supply Voltage V

Undervoltage Lockout V

CC(UV) VCC

Supply Zener Clamp Voltage V

I

CC(Low)

Supply Current

I

CC(High)

I

Supply Current Ratio

CC(High)

I

CC(Low)

POWER-ON CHARACTERISTICS

Power-On State I

Power-On Time

1

CC(PO)

OUTPUT STAGE

Output Slew Rate

2

dI/dt R

Output State V

CC

t

on

OUT

Operating; TJ < 165 °C 4.0 – 24 V

0 → 5 V – 3.5 4.0 V

ICC = 19 mA for ATS643-I1, and 19.8 mA for

Z

ATS643-I2; TA = 25°C

28 – – V

ATS643-I1 4.0 6 8.0 mA

ATS643-I2 5.9 7 8.4 mA

ATS643-I1 12.0 14.0 16.0 mA

ATS643-I2 11.8 14.0 16.8 mA

/

Ratio of high current to low current 1.85 – 3.05 –

t < ton; dI/dt < 5 µs – High – mA

Target gear speed < 100 rpm – 1 2 ms

= 100 Ω, C

LOAD

R

on high side (VCC pin); ICC = I

SENSE

R

on low side (GND pin); ICC = I

SENSE

= 10 pF – 7 – mA/µs

LOAD

CC(High)

CC(High)

– Low – mV

– High – mV

Continued on the next page.

ATS643-DS, Rev. 1

Allegro MicroSystems, Inc.
115 Northeast Cutoff, Box 15036
Worcester, Massachusetts 01615-0036 [phone]

www.allegromicro.com

3

ATS643LSH

Self-Calibrating, Zero-Speed Differential GTS with Continuous Update

OPERATING CHARACTERISTICS (continued) using reference target 60-0, TA and VCC within specification, unless otherwise noted

Characteristic Symbol Test Conditions Min. Typ. Max. Units

SWITCHPOINT CHARACTERISTICS

Rotation Speed S

ROT

Reference Target 60-0 0 – 12,000 rpm

Bandwidth BW Equivalent to f – 3dB 25 40 – kHz

Operate Point B

Release Point B

CALIBRATION

3

Initial Calibration Period C

AGC Calibration Disable C

Start Mode Hysteresis PO

OP

RP

I

f

HYS

% of peak to peak referenced from PDAC to NDAC,
AG < AG

MAX

% of peak to peak referenced from PDAC to NDAC,
AG < AG

MAX

Quantity of rising output (current) edges required for
accurate edge detection

Quantity of rising output (current) edges used for
calibrating AGC

–65– %

–35– %

– – 3 Edge

– – 3 Edge

– 175 – mV

DAC CHARACTERISTICS

Dynamic Offset Cancellation – ±60 – G

Tracking Data Resolution

Quantity of bits available for PDAC/NDAC tracking of
both positive and negative signal peaks

–9–Bit

FUNCTIONAL CHARACTERISTICS

Air Gap Range

Maximum Operable Air Gap AG

4

AG ∆DC within specification 0.5 – 2.5 mm

(opmax)

Output switching (no missed edges); ∆DC not
guaranteed

– – 2.75 mm

Duty Cycle Variation ∆DC Wobble < 0.5 mm, AG within specification – – ±10 %

Input Signal Range Sig ∆DC within specification 40 – 1400 G

Minimum Operable Input Signal Sig

1

Power-On Time includes the time required to complete the internal automatic offset adjust. The DACs are then ready for peak acquisition.

2

dI is the difference between 10% of I

of the bypass capacitor, if one is used.

3

Continuous Update (calibration) functions continuously during Running mode operation.

4

AG is dependent on the available magnetic field. The available field is dependent on target geometry and material, and should be independently

characterized. The field available from the reference target is given in the reference target parameter section of the datasheet.

ATS643-DS, Rev. 1

CC(Low)

(opmin)

and 90% of I

Output switching (no missed edges); ∆DC not
guaranteed

, and dt is time period between those two points. Note: dI/dt is dependent upon the value

CC(High)

30 – – G

Allegro MicroSystems, Inc.
115 Northeast Cutoff, Box 15036
Worcester, Massachusetts 01615-0036 [phone]

www.allegromicro.com

4

ATS643LSH

Reference Gear Magnetic P rofile
Two Tooth-to-Valley Transitions

-700

-600

-500

-400

-300

-200

-100

0

100

200

300

400

500

600

700

0123456789101112

AG (mm)

Self-Calibrating, Zero-Speed Differential GTS with Continuous Update

REFERENCE TARGET, 60-0 (60 Tooth Target)

Characteristics Symbol Test Conditions Typ. Units Symbol Key

Outside Diameter D

Face Width F

Circular Tooth Length t

Circular Valley Length t

Tooth Whole Depth h

Outside diameter of target

o

Breadth of tooth, with respect
to sensor

Length of tooth, with respect
to sensor; measured at D

Length of valley, with respect

v

to sensor; measured at D

t

120 mm

6mm

3mm

o

3mm

o

3mm

Material Low Carbon Steel – –

Peak-to-Peak Differential B* (G)

Reference Gear Magnetic Gradient Amplitude

1800

1600

1400

1200

1000

800

600

400

200

0

0.5 1 1.5 2 2.5

with Reference to Air Gap

Branded Face

of Sensor

Reference Target

60-0

Differential B* (G)

Gear Rotation (°)

*Differential B corresponds to the calculated difference in the magnetic fi eld as

sensed simultaneously at the two Hall elements in the device (B

= BE1 – BE2).

DIFF

ATS643-DS, Rev. 1

2.00 mm AG

0.50 mm AG

AG (mm)

0.50

0.75

1.00

1.25

1.50

1.75

2.00

Allegro MicroSystems, Inc.
115 Northeast Cutoff, Box 15036
Worcester, Massachusetts 01615-0036 [phone]

www.allegromicro.com

5