ALLEGRO ATS645LSH User Manual

True Zero Speed

a Hall effect IC that has been optimized to the magnetic circuit.

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ATS645LSH

Preliminary – Subject to Change

PRELIMINARY DATASHEET

(subject to change without notice)

Pin 1: Supply Pin 2: No connection Pin 3: Test pin Pin 4: Ground

Miniature Gear Tooth Sensor

The ATS645LSH is an optimized Hall effect sensing integrated circuit and magnet combination that provides a user-friendly solution for true zero-speed digital gear-tooth sensing in two-wire applications. The sensor consists of a single-shot molded plastic package that includes a samarium cobalt magnet, a pole piece, and

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 and signal processing that switches in response to differential magnetic signals created by ferrous gear teeth. The circuitry contains a sophisticated digital circuit to eliminate magnet and system offsets and to achieve true zero speed operation (ref U.S. Patent 5,917,320). A-D and D-A converters are used to adjust the device gain at power up and to allow air gap independent switching.

The regulated current output is configured for two wire applications and the sensor is ideally suited for obtaining speed and duty cycle in ABS and transmission application gear-tooth-based configurations.

ABSOLUTE MAXIMUM RATINGS

Supply Voltage,

VCC . . . . . . . . . . . . . . . . . . . . . . . . . 26.5 V*

Reverse Supply Voltage,

VR . . . . . . . . . . . . . . . . . . . . . . . . . . . . –18 V

Operating Temperature Range,

TA . . . . . . . . . . . . . . . . . –40 °C to 150 °C*

Storage Temperature,

TS . . . . . . . . . . . . . . . . . . . . . . . . . . . 170 °C

Package Power Rating,

ϑJA . . . . . . . . . . . . . . . . . . . . . . . . 126 °C/W

Maximum Junction Temperature, T

* Operation at increased supply voltages with external

circuitry is described in the Applications Information.

. . . . . . . . . . . . . . . . . . . . . 165 °C

Jmax

FEATURES

s Fully optimized differential digital gear tooth sensor s Single chip sensing IC for high reliability s Internal current regulator for 2 wire operation s Small mechanical size (8 mm dia x 5.5 mm length) s Air gap independent switch points s Digital output representing gear profile s Precise duty cycle signal with temperature s Large operating air gaps s Automatic Gain Control (AGC) s Automatic Offset Adjustment circuit s True zero speed operation s Under-voltage lockout s Wide operating voltage range s Defined power-on state

ATS645LSH – Preliminary – Allegro Confidential

TRUE ZERO SPEED DIFFERENTIAL PEAK DETECTOR

CHARACTERISTICS

Valid over operating temperature range and Supply Voltage within specification unless otherwise noted.

Limits

Characteristics Symbol Test Conditions

Min. Typ. Max. Units

ELECTRICAL CHARACTERISTICS

Supply Voltage VCC Operating, TJ < 165°C 4.0 24 V Under Voltage Lockout V

Supply Zener Clamp Voltage VZ IZT = 1 mA 28 32 - V

VCC 0 → 5 V - - <Vcc

CC(UV)

Min

Max Zener Pulse Current IZ t=20mS Pulse Mode - - 50 mA Supply Zener Resistance RZ - 50 - Ω

Supply Current ATS645LSH – I1

Supply Current ATS645LSH – I2

ICC

Low Current State: Icc

High Current State: Icc

Low Current State: Icc

ICC

High Current State: Icc

4.0 6 8.0 mA

Low

12.0 14.0 16.0 mA

High

5.9 7 8.4 mA

Low

11.8 14.0 16.8 mA

High

POWER-ON STATE CHARACTERISTICS

Power-On State SPO VCC 0 → 5 V - Icc

Power-On Time t

Gear speed < 100 rpm - 1 2 ms

- -

High

OUTPUT STAGE

Icc

Output Current Slew Rate IR

à Icc

High

RS = 100 Ω, CS = 10 pF, 10 to 90%

Low

, Icc

Low

à Icc

High

mA/µs

The zener is tested using a pulse method and is designed for transient protection, continuous operation may destroy the device.

Power On Time is the time required to complete internal offset adjust. It does not include automatic gain control, which requires

three tooth valley transitions to complete and is therefore RPM dependent.

Revision 1.2; MHN; 07.Aug.02

Page 2 of 12

ATS645LSH – Preliminary – Allegro Confidential

TRUE ZERO SPEED DIFFERENTIAL PEAK DETECTOR

Operating Characteristics: Valid with Reference Target unless otherwise specified

Characteristics Symbol Test Conditions

Min. Typ. Max. Units

SWITCH POINT CHARACTERISTICS

Rotation Speed S

max

Using Reference Target over Operating Air Gap Range

Analog Signal Bandwidth f-3db -3dB Point 20 40 KHz

Operate Point Bop

Release Point Brp

Icc

High

à Icc

Low

Positive Peak referenced, AG < AG Icc

Low

à Icc

High

Negative Peak referenced, AG < AG

max

Calibration

Initial Calibration CI

Number of Rising Mechanical Edges for

Accurate Edge Detection

DAC Characteristics Allowable User Induced

Differential Offset

Output switching only; may not meet data sheet specifications

-60 60 G

Limits

0 8K RPM

- 100 150 mV

3 Edges

SWITCH POINT DETAIL

Bop

Input

Differential

Signal

Device Output

Current

Pin 3 Differential Signal (not magnetic signal)

Bop and Brp should be adjustable with metal mask changes, limits max air gap but improves vibration immunity.

Revision 1.2; MHN; 07.Aug.02

Page 3 of 12

Brp

ATS645LSH – Preliminary – Allegro Confidential

TRUE ZERO SPEED DIFFERENTIAL PEAK DETECTOR

Operating Characteristics: Valid only if magnetic offset is within the Dynamic Offset Compensation DAC Range as specified above

Characteristics Symbol Test Conditions

Min. Typ. Max. Units

OPERATING CHARACTERISTICS: Using Reference Target and Valid Over Operating Temperature Range

Operational Air Gap Range Op

Switching Air Gap Range Op

MaxAG

Duty cycle within specification 0.5 2.75 mm

Output Switching: Duty cycle Not in Specification Wobble < 0.5mm

Duty Cycle Variation DC

Typical value at 1.5mm air gap

37 53 57 %

Valid over operating air gap range

Operating Signal Range Sig

Minimum Operating Signal

Sig

Duty cycle within Specification Wobble < 0.5mm Output Switching: Duty Cycle Not in

Min

Specification

30 - 1000 G 20 - - G

Limits

3 - - mm

Operating air gap is dependent on the available magnetic field. The available field is target geometry and materiel dependent and should be independently characterized. The field available from the reference target is given in the reference gear parameter section of the datasheet

In order to remain in specification the magnetic signal must be larger than the minimum value specified, this includes the effect of target wobble.

Duty cycle is not guaranteed to be in specification. Reference the Duty Cycle vs. Air Gap Over Temperature graph in the typical operating characteristics section of this document.

Revision 1.2; MHN; 07.Aug.02

Page 4 of 12

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