ATS643LSHTN-I1-T - Allegro MicroSystems, LLC

NOTE: For detailed information on purchasing options, contact your

local Allegro field applications engineer or sales representative.

Allegro MicroSystems, Inc. reserves the right to make, from time to time, revisions to the anticipated product life cycle plan

for a product to accommodate changes in production capabilities, alternative product availabilities, or market demand. The

information included herein is believed to be accurate and reliable. However, Allegro MicroSystems, Inc. assumes no respon-

sibility for its use; nor for any infringements of patents or other rights of third parties which may result from its use.

Recommended Substitutions:

Self-Calibrating, Zero-Speed Differential

Gear Tooth Sensor IC with Continuous Update

ATS643LSH

For existing customer transition, and for new customers or new appli-

cations, refer to the ATS685.

Date of status change: May 2, 2011

Deadline for receipt of LAST TIME BUY orders: October 31, 2011

This part is in production but has been determined to be

LAST TIME BUY. This classification indicates that the product is

obsolete and notice has been given. Sale of this device is currently

restricted to existing customer applications. The device should not be

purchased for new design applications because of obsolescence in the

near future. Samples are no longer available.

Last Time Buy

Description

The ATS643 is an optimized combination of integrated circuit

and rare-earth pellet 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 pellet, 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

IC with signal processing circuitry that switches in response to

differential magnetic signals created by rotating ferromagnetic

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

ATS643-DS, Rev. 6

Features and Benefits

▪ Fully-optimized differential digital gear tooth sensor IC

▪ 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

▪ Precise duty cycle accuracy throughout temperature range

▪ Large operating air gaps

▪ <2 ms power-on time

▪ AGC and reference adjust circuit

Self-Calibrating, Zero-Speed Dif ferential

Gear Tooth Sensor IC with Continuous Update

Continued on the next page…

Functional Block Diagram

Not to scale

Packages: 4 pin SIP (suffix SH)

ATS643LSH

Hall AMP AGC

Threshold

Logic

ThresholdP

ThresholdN

PDAC

Internal

Regulator

VCC (Pin 1)

NDAC

GND (Pin 4)

Reference

Generator

and Updates

Offset Adjust

Continued on the next page…

Self-Calibrating, Zero-Speed Dif ferential

Gear Tooth Sensor IC with Continuous Update

ATS643LSH

Allegro MicroSystems, Inc.

115 Northeast Cutoff

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

1.508.853.5000; www.allegromicro.com

Part Number Packing*ICC Typical

ATS643LSHTN-I1-T Tape and Reel 13-in. 800 pcs./reel 6.0 Low to 14.0 High mA

ATS643LSHTN-I2-T Tape and Reel 13-in. 800 pcs./reel 7.0 Low to 14.0 High mA

*Contact Allegro for additional packing options. Some restrictions may apply to certain types of sales. Contact

Allegro for details.

▪ True zero-speed operation

▪ Undervoltage lockout

▪ Wide operating voltage range

▪ Defined power-on state

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.

Features and Benefits (continued) Description (continued)

Terminal List

Name Description Number

VCC Connects power supply to chip 1

NC No connection. Float or tie to VCC 2

TEST For Allegro use, float or tie to GND 3

GND Ground terminal 4

2431

Pin-out Diagram

Absolute Maximum Ratings

Characteristic Symbol Notes Rating Units

Supply Voltage VCC See Power Derating section – V

Reverse-Supply Voltage VRCC –18 V

Operating Ambient Temperature TARange L –40 to 150 ºC

Maximum Junction Temperature TJ(max) 165 ºC

Storage Temperature Tstg –65 to 170 ºC

Self-Calibrating, Zero-Speed Dif ferential

Gear Tooth Sensor IC with Continuous Update

ATS643LSH

Allegro MicroSystems, Inc.

115 Northeast Cutoff

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

1.508.853.5000; www.allegromicro.com

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 VCC Operating; TJ < 165 °C 4.0 – 24 V

Undervoltage Lockout VCC(UV) VCC 0  5 V – 3.5 4.0 V

Supply Zener Clamp Voltage VZ

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

ATS643-I2; TA = 25°C 28 – – V

Supply Current

ICC(Low)

ATS643-I1 4.0 6 8.0 mA

ATS643-I2 5.9 7 8.4 mA

ICC(High)

ATS643-I1 12.0 14.0 16.0 mA

ATS643-I2 11.8 14.0 16.8 mA

Supply Current Ratio ICC(High)/

ICC(Low)

Ratio of high current to low current 1.85 – 3.05 –

POWER-ON CHARACTERISTICS

Power-On State ICC(PO) t < ton; dI/dt < 5 s – High – mA

Power-On Time1ton Target gear speed < 100 rpm – 1 2 ms

OUTPUT STAGE

Output Slew Rate2dI/dt RLOAD = 100 , CLOAD = 10 pF – 7 – mA/s

Output State VOUT

RSENSE on high side (VCC pin); ICC = ICC(High) – Low – mV

RSENSE on low side (GND pin); ICC = ICC(High) – High – mV

Continued on the next page.

Self-Calibrating, Zero-Speed Dif ferential

Gear Tooth Sensor IC with Continuous Update

ATS643LSH

Allegro MicroSystems, Inc.

115 Northeast Cutoff

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

1.508.853.5000; www.allegromicro.com

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 SROT Reference Target 60-0 0 – 12,000 rpm

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

Operate Point BOP

% of peak to peak referenced from PDAC to NDAC,

AG < AGMAX

–65– %

Release Point BRP

% of peak to peak referenced from PDAC to NDAC,

AG < AGMAX

–35– %

CALIBRATION3

Initial Calibration Period CI

Quantity of rising output (current) edges required for

accurate edge detection – – 3 Edge

AGC Calibration Disable Cf

Quantity of rising output (current) edges used for

calibrating AGC – – 3 Edge

Start Mode Hysteresis POHYS – 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 Range4AG DC within specification 0.5 – 2.5 mm

Maximum Operable Air Gap AG(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(opmin)

Output switching (no missed edges); DC not

guaranteed 30 – – G

1Power-On Time includes the time required to complete the internal automatic offset adjust. The DACs are then ready for peak acquisition.

2dI is the difference between 10% of ICC(Low) and 90% of ICC(High) , and dt is time period between those two points. Note: dI/dt is dependent upon the value

of the bypass capacitor, if one is used.

3Continuous Update (calibration) functions continuously during Running mode operation.

4AG 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.

Self-Calibrating, Zero-Speed Dif ferential

Gear Tooth Sensor IC with Continuous Update

ATS643LSH

Allegro MicroSystems, Inc.

115 Northeast Cutoff

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

1.508.853.5000; www.allegromicro.com

REFERENCE TARGET, 60-0 (60 Tooth Target)

Characteristics Symbol Test Conditions Typ. Units Symbol Key

Outside Diameter DoOutside diameter of target 120 mm

Face Width F Breadth of tooth, with respect to

branded face 6mm

Circular Tooth Length t Length of tooth, with respect to

branded face; measured at Do

3mm

Circular Valley Length tv

Length of valley, with respect to

branded face; measured at Do

3mm

Tooth Whole Depth ht3mm

Material Low Carbon Steel – –

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

sensed simultaneously at the two Hall elements in the device (BDIFF = BE1 – BE2).

of Package

Reference Target

60-0

of Package

Branded Face

Reference Gear Magnetic Gradient Amplitude

with Reference to Air Gap

200

400

600

800

1000

1200

1400

1600

1800

AG (mm)

Peak-to-Peak Differential B* (G)

0.5 1 1.5 2 2.5

Reference Gear Magnetic Profile

Tw o Toot h -t o- Val ley Tr ansit i ons

-700

-600

-500

-400

-300

-200

-100

100

200

300

400

500

600

700

0123456789101112

Gear Rotation (°)

Differential B* (G)

0.50 mm AG

2.00 mm AG

0.50

0.75

1.00

1.25

1.50

1.75

2.00

AG (mm)

Self-Calibrating, Zero-Speed Dif ferential

Gear Tooth Sensor IC with Continuous Update

ATS643LSH

Allegro MicroSystems, Inc.

115 Northeast Cutoff

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

1.508.853.5000; www.allegromicro.com

Characteristic Data

Data taken from 3 lots, 30 pieces/lot; I1 trim

Reference Target 60-0

Duty Cycle at 1000 RPM

–50 0 50 100 150 200

(°C)

Duty Cycle (%)

Duty Cycle at 1000 RPM

0 0.5 1 1.5 2 2.5 3 3.5

AG (mm)

Duty Cycle (%)

-40

150

Duty Cycle (25°C)

0 500 1000 1500 2000 2500

RPM

Duty Cycle (%)

TA (ºC)

3.0

2.75

2.5

2.25

2.0

1.5

1.0

0.5

AG (mm)

3.0

2.75

2.5

2.25

2.0

1.5

1.0

0.5

AG (mm)

Continued on the next page.

Self-Calibrating, Zero-Speed Dif ferential

Gear Tooth Sensor IC with Continuous Update

ATS643LSH

Allegro MicroSystems, Inc.

115 Northeast Cutoff

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

1.508.853.5000; www.allegromicro.com

Characteristic Data (continued)

Data taken from 3 lots, 30 pieces/lot; I1 trim

CC (Low)

–50 0 50 100 150 200

Icc (mA)

ICC(Low)

0 5 10 15 20 25 30

Vcc (V)

Icc (mA)

CC(High)

–50 0 50 100 150 200

(°C)

Icc (mA)

26.5V

20V

12V

CC(High)

0 5 10 15 20 25 30

Vcc (V)

Icc (mA)

(°C)

26.5

20.0

12.0

4.0

26.5

20.0

12.0

4.0

150

–40

TA (ºC)

150

–40

TA (ºC)

BOP

BRP

BHYS

ICC(High)

ICC

ICC(Low)

Switch to High

Switch to Low

B+

I+

Hysteresis of ΔIICC

Switching Due to ΔB

Output current in relation to sensed mag-

netic flux density. Transition through BOP

must precede by transition through BRP

Self-Calibrating, Zero-Speed Dif ferential

Gear Tooth Sensor IC with Continuous Update

ATS643LSH

Allegro MicroSystems, Inc.

115 Northeast Cutoff

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

1.508.853.5000; www.allegromicro.com

THERMAL CHARACTERISTICS may require derating at maximum conditions, see application information

Characteristic Symbol Test Conditions Min. Typ. Max Units

Package Thermal Resistance RθJA

Minimum-K PCB (single-sided with copper limited to

solder pads) 126 – – ºC/W

Low-K PCB (single-sided with copper limited to solder

pads and 3.57 in.2 (23.03 cm2) of copper area) 84 – – ºC/W

20 40 60 80 100 120 140 160 180

Maximum Allowable V

(V)

TJ(max) = 165ºC; ICC = ICC(max)

Power Derating Curve

θJA

= 126 ºC/W)

Minimum-K PCB

θJA

= 84 ºC/W)

Low-K PCB

VCC(min)

VCC(max)

100

200

300

400

500

600

700

800

900

1000

1100

1200

1300

1400

1500

1600

1700

1800

1900

20 40 60 80 100 120 140 160 180

Temperature (°C)

Power Dissipation, P

(mW)

TJ(max) = 165ºC; VCC = VCC(max); ICC = ICC(max)

Maximum Power Dissipation, PD(max)

θJA

= 126 ºC/W)

Minimum-K PCB

(RθJA = 84 ºC/W)

Low-K PCB

Self-Calibrating, Zero-Speed Dif ferential

Gear Tooth Sensor IC with Continuous Update

ATS643LSH

Allegro MicroSystems, Inc.

115 Northeast Cutoff

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

1.508.853.5000; www.allegromicro.com

Hall Technology. The ATS643 contains a single-chip differ-

ential Hall effect sensor IC, a samarium cobalt pellet, and a flat

ferrous pole piece (concentrator). As shown in figure 1, the Hall

IC supports two Hall elements, which sense the magnetic profile

of the ferrous gear target simultaneously, but at different points

(spaced at a 2.2 mm pitch), generating a differential internal

analog voltage (VPROC) that is processed for precise switching of

the digital output signal.

The Hall IC is self-calibrating and also possesses a tempera-

ture compensated amplifier and offset cancellation circuitry. Its

voltage regulator provides supply noise rejection throughout the

operating voltage range. Changes in temperature do not greatly

affect this device due to the stable amplifier design and the offset

rejection circuitry. The Hall transducers and signal processing

electronics are integrated on the same silicon substrate, using a

proprietary BiCMOS process.

Target Profiling During Operation. When proper power is

applied to the IC, it is capable of providing digital information

that is representative of the mechanical features of a rotating

gear. The waveform diagram in figure 3 presents the automatic

translation of the mechanical profile, through the magnetic

profile that it induces, to the digital output signal of the ATS643.

No additional optimization is needed and minimal processing

circuitry is required. This ease of use reduces design time and

Functional Description

Target (Gear)

Back-biasing

Rare-earth Pellet

South Pole

North Pole Case

(Pin 1 Side)(Pin n >1 Side)

Hall IC

Pole Piece

Element Pitch

(Concentrator)

Dual-Element

Hall Effect Device

Hall Element 1

Hall Element 2

of Package

Rotating Target Branded Face

incremental assembly costs for most applications.

Determining Output Signal Polarity. In figure 3, the top

panel, labeled Mechanical Position, represents the mechanical

features of the target gear and orientation to the device. The bot-

tom panel, labeled IC Output Signal, displays the square wave-

form corresponding to the digital output signal that results from

a rotating gear configured as shown in figure 2. That direction of

rotation (of the gear side adjacent to the package face) is: perpen-

dicular to the leads, across the face of the device, from the pin 1

side to the pin 4 side. This results in the IC output switching from

low, ICC(Low), to high, ICC(High), as the leading edge of a tooth (a

rising mechanical edge, as detected by the IC) passes the package

face. In this configuration, the device output current switches to

its high polarity when a tooth is the target feature nearest to the

package. If the direction of rotation is reversed, so that the gear

rotates from the pin 4 side to the pin 1 side, then the output polar-

ity inverts. That is, the output signal goes high when a falling

edge is detected, and a valley is the nearest to the package. Note,

however, that the polarity of IOUT depends on the position of the

sense resistor, RSENSE (see Operating Characteristics table).

Continuous Update of Switchpoints. Switchpoints are the

threshold levels of the differential internal analog signal, VPROC,

at which the device changes output signal polarity. The value of

VPROC is directly proportional to the magnetic flux density, B,

Figure 1. Relative motion of the target is detected by the dual Hall ele-

ments mounted on the Hall IC.

Figure 2. This left-to-right (pin 1 to pin 4) direction of target rotation

results in a high output signal when a tooth of the target gear is nearest

the face of the package (see figure 3). A right-to-left (pin 4 to pin 1) rota-

tion inverts the output signal polarity.

Figure 3. The magnetic profile reflects the geometry of the target, allow-

ing the ATS643 to present an accurate digital output response.

OP(#1)

RP(#1)

OP(#2)

On OffOff On

IC Internal Switch State

Package Orientation to Target

IC Internal Differential Analog Signal, V

PROC

Mechanical Position (Target movement pin 1 to pin 4)

IC Output Signal, I

OUT

Target

(Gear)

Package

Package Branded Face

Pin 1

Side

Pin 4

Side

Target Magnetic Profile

This tooth

sensed

earlier

This tooth

sensed

later

Self-Calibrating, Zero-Speed Dif ferential

Gear Tooth Sensor IC with Continuous Update

ATS643LSH

Allegro MicroSystems, Inc.

115 Northeast Cutoff

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

1.508.853.5000; www.allegromicro.com

induced by the target and sensed by the Hall elements. When

VPROC transitions through a switchpoint from the appropriate

higher or lower level, it triggers IC switch turn-on and turn-off.

As shown in figure 3, when the switch is in the off state, as

VPROC rises through a certain limit, referred to as the operate

point, BOP

, the switch toggles from off to on. When the switch is

in the on state, as VPROC falls below BOP to a certain limit, the

release point, BRP

, the switch toggles from on to off.

HYS(#1)

(#4)

(#5)

(#7)

(#9)

(#2)

(#3)

(#1)

(#6)

(#8)

VPROC (V)

RP(#1)

OP(#1)

RP(#2)

RP(#3)

OP(#3)

RP(#4)

OP(#4)

HYS(#4)

HYS(#3)

HYS(#2)

V+

OP(#2)

(A) TEAG varying; cases such as

eccentric mount, out-of-round region,

normal operation position shift

(B) Internal analog signal, V

PROC

typically resulting in the IC

0360

Target Rotation (°)

Hysteresis Band

(Delimited by switchpoints)

PROC

(V)

V+

Larger

TEAG

Smaller

TEAG

Target

Larger

TEAG

Target

Smaller

TEAG

Smaller

TEAG

As shown in panel C of figure 4, threshold levels for the ATS643

switchpoints are established dynamically as function of the

peak input signal levels. The ATS643 incorporates an algorithm

that continuously monitors the system and updates the switch-

ing thresholds accordingly. The switchpoint for each edge is

determined by the detection of the previous two edges. In this

manner, variations are tracked in real time.

Figure 4. The Continuous Update algorithm allows the Allegro IC to immediately interpret and adapt to significant variances in the magnetic field gener-

ated by the target as a result of eccentric mounting of the target, out-of-round target shape, elevation due to lubricant build-up in journal gears, and

similar dynamic application problems that affect the TEAG (Total Effective Air Gap). The algorithm is used to dynamically establish and subsequently

update the device switchpoints (BOP and BRP). The hysteresis, BHYS(#x), at each target feature configuration results from this recalibration, ensuring that

it remains properly proportioned and centered within the peak-to-peak range of the internal analog signal, VPROC.

As shown in panel A, the variance in the target position results in a change in the TEAG. This affects the IC as a varying magnetic field, which results in

proportional changes in the internal analog signal, VPROC, shown in panel B. The Continuous Update algorithm is used to establish accurate switchpoints

based on the fluctuation of VPROC, as shown in panel C.

BHYS Switchpoint Determinant

Peak Values

1BOP(#1) Pk(#1), Pk(#2)

BRP(#1) Pk(#2), Pk(#3)

2BOP(#2) Pk(#3), Pk(#4)

BRP(#2) Pk(#4), Pk(#5)

3BOP(#3) Pk(#5), Pk(#6)

BRP(#3) Pk(#6), Pk(#7)

BOP(#4) Pk(#7), Pk(#8)

BRP(#4) Pk(#8), Pk(#9)

Self-Calibrating, Zero-Speed Dif ferential

Gear Tooth Sensor IC with Continuous Update

ATS643LSH

Allegro MicroSystems, Inc.

115 Northeast Cutoff

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

1.508.853.5000; www.allegromicro.com

Power-On State Operation. The ATS643 is guaranteed to

power-on in the high current state, ICC(High).

Initial Edge Detection. The device self-calibrates using the

initial teeth sensed, and then enters Running mode. This results

in reduced accuracy for a brief period (less than four teeth),

however, it allows the device to optimize for continuous update

yielding adaptive sensing during Running mode. As shown in

figure 5, the first three high peak signals are used to calibrate

AGC. However, there is a slight variance in the duration of

initialization, depending on what target feature is nearest the

package when power-on occurs.

Figure 5. Power-on initial edge detection. This figure demonstrates four typical power-on scenarios. All of these examples assume that the target is

moving relative to the package in the direction indicated. The length of time required to overcome Start Mode Hysteresis, as well as the combined effect

of whether it is overcome in a positive or negative direction plus whether the next edge is in that same or opposite polarity, affect the point in time when

AGC calibration begins. Three high peaks are always required for AGC calibration.

Target

(Gear)

Output

VPROC

Output

Power-on

over valley

Power-on

at rising edge

Power-on

over tooth

Power-on

at falling edge

AGC Calibration Running Mode

Package Position

1 3 42

Start Mode

Hysteresis

Overcome

Start Mode

Hysteresis

Overcome

Start Mode

Hysteresis

Overcome

Start Mode

Hysteresis

Overcome

Self-Calibrating, Zero-Speed Dif ferential

Gear Tooth Sensor IC with Continuous Update

ATS643LSH

Allegro MicroSystems, Inc.

115 Northeast Cutoff

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

1.508.853.5000; www.allegromicro.com

Start Mode Hysteresis. This feature helps to ensure optimal

self-calibration by rejecting electrical noise and low-amplitude

target vibration during initialization. This prevents AGC from

calibrating the IC on such spurious signals. Calibration can be

performed using the actual target features.

A typical scenario is shown in figure 6. The hysteresis, POHYS,

is a minimum level of the peak-to-peak amplitude of the internal

analog electrical signal, VPROC, that must be exceeded before the

ATS643 starts to compute switchpoints.

Figure 6. Operation of Start Mode Hysteresis

Position 1. At power-on, the ATS643 begins sampling VPROC.

Position 2. At the point where the Start Mode Hysteresis is exceeded, the device begins to establish switching thresholds (BOP and BRP) using the Con-

tinuous Update algorithm. After this point, Start Mode Hysteresis is no longer a consideration. Note that a valid VPROC value exceeding the Start Mode

Hysteresis can be generated either by a legitimate target feature or by excessive vibration.

Position 3. In this example, the first switchpoint transition is through BOP

. and the output transitions from high to low.

If the first switchpoint transition had been through BRP (such as position 4), no output transition would occur because IOUT already would be in the high

polarity. The first transition would occur at position 5 (BOP).

RP(#1)

OP(#1)

OP(#2)

345

1 2

Start Mode Hysteresis, PO

HYS

Output Signal, I

OUT

Package Position Relative to Target

Target Magnetic Profile

Differential Signal, V

PROC

Target, Gear

Self-Calibrating, Zero-Speed Dif ferential

Gear Tooth Sensor IC with Continuous Update

ATS643LSH

Allegro MicroSystems, Inc.

115 Northeast Cutoff

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

1.508.853.5000; www.allegromicro.com

Undervoltage Lockout. When the supply voltage falls

below the minimum operating voltage, VCC(UV), ICC goes high

and remains high regardless of the state of the magnetic gradi-

ent from the target. This lockout feature prevents false signals,

caused by undervoltage conditions, from propagating to the

output of the IC.

Power Supply Protection. The device contains an on-chip

regulator and can operate over a wide VCC range. For devices

that need to operate from an unregulated power supply, transient

protection must be added externally. For applications using a

regulated line, EMI/RFI protection may still be required. Contact

Allegro Microsystems for information on the circuitry needed

for compliance with various EMC specifications. Refer to fig-

ure 7 for an example of a basic application circuit.

Automatic Gain Control (AGC). This feature allows the

device to operate with an optimal internal electrical signal,

regardless of the air gap (within the AG specification). At power-

on, the device determines the peak-to-peak amplitude of the

signal generated by the target. The gain of the IC is then auto-

matically adjusted. Figure 8 illustrates the effect of this feature.

Automatic Offset Adjust (AOA). The AOA is patented cir-

cuitry that automatically cancels the effects of chip, magnet, and

installation offsets. (For capability, see Dynamic Offset Cancel-

lation, in the Operating Characteristics table.) This circuitry is

continuously active, including both during power-on mode and

running mode, compensating for any offset drift. Continuous

operation also allows it to compensate for offsets induced by

temperature variations over time.

Assembly Description. The ATS643 is integrally molded

into a plastic body that has been optimized for size, ease of

assembly, and manufacturability. High operating temperature

materials are used in all aspects of construction.

2ATS643

VCC

0.01 μF

100 Ω

(Optional)

Figure 7. Typical basic circuit for proper device operation.

Mechanical Profile

Small

Large

Small

Large

Internal Differential

Analog Signal

Response, with AGC

Internal Differential

Analog Signal

Response, without AGC

Ferrous Target

V+

Figure 8. Automatic Gain Control (AGC). The AGC function corrects for

variances in the air gap. Differences in the air gap cause differences in

the magnetic field at the device, but AGC prevents that from affecting

device performance, a shown in the lowest panel.

Self-Calibrating, Zero-Speed Dif ferential

Gear Tooth Sensor IC with Continuous Update

ATS643LSH

Allegro MicroSystems, Inc.

115 Northeast Cutoff

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

1.508.853.5000; www.allegromicro.com

Power Derating

The device must be operated below the maximum junction

temperature of the device, TJ(max). Under certain combinations of

peak conditions, reliable operation may require derating sup-

plied power or improving the heat dissipation properties of the

application. This section presents a procedure for correlating

factors affecting operating TJ. (Thermal data is also available on

the Allegro MicroSystems Web site.)

The Package Thermal Resistance, RJA, is a figure of merit sum-

marizing the ability of the application and the device to dissipate

heat from the junction (die), through all paths to the ambient air.

Its primary component is the Effective Thermal Conductivity,

K, of the printed circuit board, including adjacent devices and

traces. Radiation from the die through the device case, RJC, is

relatively small component of RJA. Ambient air temperature,

TA, and air motion are significant external factors, damped by

overmolding.

The effect of varying power levels (Power Dissipation, PD), can

be estimated. The following formulas represent the fundamental

relationships used to estimate TJ, at PD.

PD = VIN × IIN (1)

 T = PD × RJA (2)

TJ = TA + ΔT (3)

For example, given common conditions such as: TA= 25°C,

VCC = 12 V, ICC = 4 mA, and RJA = 140 °C/W, then:

D = VCC × ICC = 12 V × 4 mA = 48 mW

T = PD × RJA = 48 mW × 140 °C/W = 7°C

J = TA + T = 25°C + 7°C = 32°C

A worst-case estimate, PD(max), represents the maximum allow-

able power level (VCC(max), ICC(max)), without exceeding TJ(max),

at a selected RJA and TA.

Example: Reliability for VCC at TA =

150°C, package L-I1, using

minimum-K PCB

Observe the worst-case ratings for the device, specifically:

RJA

126°C/W, TJ(max) =

165°C, VCC(max)

V, and

ICC(max) = 16

mA.

Calculate the maximum allowable power level, PD(max). First,

invert equation 3:

Tmax = TJ(max) – TA = 165

°C

–

150

°C = 15

°C

This provides the allowable increase to TJ resulting from internal

power dissipation. Then, invert equation 2:

PD(max) = Tmax ÷ RJA = 15°C ÷ 126 °C/W = 119 mW

Finally, invert equation 1 with respect to voltage:

VCC(est) = PD(max) ÷ ICC(max) = 119 mW ÷ 16 mA = 7 V

The result indicates that, at TA, the application and device can

dissipate adequate amounts of heat at voltages ≤VCC(est).

Compare VCC(est) to VCC(max). If VCC(est) ≤ VCC(max), then reli-

able operation between VCC(est) and VCC(max) requires enhanced

RJA. If VCC(est) ≥ VCC(max), then operation between VCC(est) and

VCC(max) is reliable under these conditions.

Self-Calibrating, Zero-Speed Dif ferential

Gear Tooth Sensor IC with Continuous Update

ATS643LSH

Allegro MicroSystems, Inc.

115 Northeast Cutoff

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

1.508.853.5000; www.allegromicro.com

Package SH, 4-pin SIP

For the latest version of this document, visit our website:

www.allegromicro.com

0.71±0.05

5.00±0.10 4.00±0.10

1.00±0.10

0.60±0.10

24.65±0.10

13.10±0.10

1.0 REF

0.71±0.10 0.71±0.10

1.60±0.10

1.27±0.10

5.50±0.10

5.50±0.05

8.00±0.05

5.80±0.05

1.70±0.10

243

For Reference Only, not for tooling use (reference DWG-9003)

Dimensions in millimeters

Dambar removal protrusion (16X)

Metallic protrusion, electrically connected to pin 4 and substrate (both sides)

Thermoplastic Molded Lead Bar for alignment during shipment

Active Area Depth 0.43 mm REF

Branded

Face

Standard Branding Reference View

= Supplier emblem

L = Lot identifier

N = Last three numbers of device part number

Y = Last two digits of year of manufacture

W = Week of manufacture

LLLLLLL

YYWW

NNN

Branding scale and appearance at supplier discretion

0.38 +0.06

–0.04 E

E2E1

1.10

Hall elements (E1, E2); not to scale

Allegro MicroSystems, Inc. reserves the right to make, from time to time, such de par tures from the detail spec i fi ca tions as may be required to per-

mit improvements in the per for mance, reliability, or manufacturability of its products. Before placing an order, the user is cautioned to verify that the

information being relied upon is current.

Allegro’s products are not to be used in life support devices or systems, if a failure of an Allegro product can reasonably be expected to cause the

failure of that life support device or system, or to affect the safety or effectiveness of that device or system.

The in for ma tion in clud ed herein is believed to be ac cu rate and reliable. How ev er, Allegro MicroSystems, Inc. assumes no re spon si bil i ty for its use;

nor for any in fringe ment of patents or other rights of third parties which may result from its use.