Description
The ATS657 includes an optimized Hall-effect sensing
integrated circuit (IC) and rare earth pellet to create a user-
friendly solution for direction detection and true zero-speed,
digital gear tooth sensing in two-wire applications. The small
package can be easily assembled and used in conjunction with
a wide variety of gear tooth sensing applications.
The IC employs patented algorithms for the special operational
requirements of automotive transmission applications.
The speed and direction of the target are communicated by
this two-wire device through a variable pulse width output
protocol. The advanced vibration detection algorithm
systematically calibrates the IC on the initial teeth of a true
rotation signal and not on vibration, always guaranteeing
an accurate signal in running mode. Even the high angular
vibration caused by engine cranking is completely rejected
by the device.
Patented running mode algorithms also protect against air
gap changes whether or not the target is in motion. Advanced
signal processing and innovative algorithms make the ATS657
an ideal solution for a wide range of speed and direction
sensing needs.
The device package is lead (Pb) free, with 100% matte tin
leadframe plating.
ATS657-DS, Rev. 3
Features and Benefits
▪ Rotational direction detection
▪ High start-up and running mode vibration immunity
▪ Single-chip sensing IC for high reliability
▪ Internal current regulator for two-wire operation
▪ Variable pulse width output protocol
▪ Automatic Gain Control (AGC) and offset adjust circuit
▪ True zero-speed operation
▪ Wide operating voltage range
▪ Undervoltage lockout
▪ ESD and reverse polarity protection
Dynamic, Self-Calibrating, Threshold-Detecting, Dif ferential
Speed and Direction Hall-Ef fect Gear Tooth Sensor IC
Package: 4-pin SIP (suffix SH)
Functional Block Diagram
Not to scale
ATS657
Internal
Regulator
VCC
Offset
Adjust
PDAC
NDAC
THRESHP
Reference
Generator
and Update
THRESHN
Offset
Adjust
PDAC
NDAC
THRESHP
Reference
Generator
THRESHN
AGC
AGC
＋
–
＋
Threshold
Logic
＋
＋
Threshold
Logic
Speed and
Direction
Logic
Peak
Detection
Logic
Output
Protocol
Control
and Update
–
–
–
GND
Dynamic, Self-Calibrating, Threshold-Detecting, Dif ferential
Speed and Direction Hall-Ef fect Gear Tooth Sensor IC
ATS657
2
Allegro MicroSystems, Inc.
115 Northeast Cutoff
Worcester, Massachusetts 01615-0036 U.S.A.
1.508.853.5000; www.allegromicro.com
Pin-out Diagram
Absolute Maximum Ratings
Characteristic Symbol Notes Rating Unit
Supply Voltage VSUPPLY
See Power Derating curve; proper operation
at VSUPPLY = 24 V requires circuit configuration
with a series 100 Ω load resistor. Please refer
to figure 7. Voltage between pins 1 and 4 of
greater than 22 V may partially turn on the ESD
protection Zener diode in the IC.
24 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
Terminal List
Number Name Function
1 VCC Connects power supply to chip
2 NC No connection
3 NC Float or tie to GND
4 GND Ground terminal
Selection Guide
Part Number Packing*
ATS657LSHTN-T 800 pieces per 13-in. reel
*Contact Allegro® for additional packing options
2431
Dynamic, Self-Calibrating, Threshold-Detecting, Dif ferential
Speed and Direction Hall-Ef fect Gear Tooth Sensor IC
ATS657
3
Allegro MicroSystems, Inc.
115 Northeast Cutoff
Worcester, Massachusetts 01615-0036 U.S.A.
1.508.853.5000; www.allegromicro.com
ELECTRICAL CHARACTERISTICS Valid over operating voltage and temperature ranges, unless otherwise noted
Characteristics Symbol Test Conditions Min. Typ.1Max. Unit2
Supply Voltage VCC Operating, TJ < TJ(max) 4.0 – 18 V
Undervoltage Lockout VCC(UV) VCC = 0 → >4 V, or >4 → 0 V – 3.5 4.0 V
Reverse Supply Current IRCC VCC = –18 V – – –10 mA
Supply Zener Clamp Voltage VZ(SUPPLY) ICC = ICC(max) + 3 mA, TA = 25°C 24.0 – – V
Supply Zener Resistance RZ–<5– Ω
Supply Current
I
CC(LOW) Low-current state (Running mode) 5.0 6.5 8.0 mA
ICC(HIGH) High-current state (Running mode) 12 14.0 16 mA
ICC(SU)(LOW) Startup current level and Power-On mode 5.0 7.0 8.5 mA
I
CC(SU)(HIGH)
High-current state (Calibration) 12 14.5 16.5 mA
Current Level Difference ∆ICC ICC(HIGH) – ICC(LOW) 5––mA
Power-On Characteristics3
Power-On Time ton Speed < 200 Hz – – 2.0 ms
Initial Calibration
First Output Pulse with Direction4NDIR Speed < 200 Hz, constant rotation direction – – 6 Edge
First Output Pulse5NNONDIR Speed < 200 Hz, constant rotation direction – – 2 Edge
AGC Disable NfSpeed < 200 Hz, constant rotation direction – – 5 Edge
Vibration Check NVIBCHECK Speed < 200 Hz, after AGC disable – 3 – Edge
Time Until Correct Direction Output on
High-Speed Startup tHIGHSU 10 kHz startup, B = 300 Gpk-pk –5–ms
Running Mode Calibration6
Non-Direction Pulse Output on Direction
Change NNONDIR_DC Running mode, direction change – 1 2 Pulse
First Direction Pulse Output on Direction
Change NDC Running mode, direction change – 2 3 Pulse
DAC Characteristics
Allowable User-Induced Differential
Offset7BDIFFEXT Both differential channels – ±60 – G
Output Stage
Output Slew Rate SROUT
RL = 100 Ω, CL = 10 pF; ICC(HIGH) → ICC(LOW) ,
ICC(LOW) → ICC(HIGH) , 10% to 90% points 7 16.0 – mA/μs
1Typical data is at VCC = 8 V and TA = +25°C, unless otherwise noted. Performance may vary for individual units, within the specified maximum and
minimum limits.
21 G (gauss) = 0.1 mT (millitesla).
3Power-On Time is the time required to complete the initial internal automatic offset adjust; the DACs are then ready for peak acquisition.
4Direction of the first output pulse on the 6th edge may not be correct when undergoing vibration.
5Non-direction pulse output only. See figure 3 for more details.
6Direction pulse will typically occur on the 2nd output pulse after a direction change. This will hold true unless an offset change at zero speed results in
an offset correction event. Note that no output blanking occurs after a direction change.
7The device will compensate for magnetic and installation offsets up to ±60 G. Offsets greater than ±60 G may cause inaccuracies in the output.
Dynamic, Self-Calibrating, Threshold-Detecting, Dif ferential
Speed and Direction Hall-Ef fect Gear Tooth Sensor IC
ATS657
4
Allegro MicroSystems, Inc.
115 Northeast Cutoff
Worcester, Massachusetts 01615-0036 U.S.A.
1.508.853.5000; www.allegromicro.com
OPERATING CHARACTERISTICS: Switchpoint Characteristics Valid over operating voltage and temperature ranges,
unless otherwise noted (refer to figure below)
Characteristics Symbol Test Conditions Min. Typ. Max. Unit
Target Frequency, Forward Rotation fFWD – – 12 kHz
Target Frequency, Reverse Rotation fREV – – 6 kHz
Target Frequency, Non-Direction Pulses*fND – – 4 kHz
Bandwidth f-3dB Cutoff frequency for low-pass filter 15 20 – kHz
Operate Point BOP
% of peak-to-peak VPROC referenced from
PDAC to NDAC, AG < AGmax
–70– %
Release Point BRP
% of peak-to-peak VPROC referenced from
PDAC to NDAC, AG < AGmax –30– %
*At power-on, rotational speed or vibration leading to a target frequency greater than 4 kHz may result in a constant high output state until true
direction is detected.
OPERATING CHARACTERISTICS: Output Pulse Characteristics* Valid over operating temperature range, unless otherwise noted
Characteristics Symbol Test Conditions Min. Typ. Max. Unit
Pulse Width, Forward Rotation tw(FWD) RL = 500 Ω, CL = 10 pF 38 45 52 μs
Pulse Width, Reverse Rotation tw(REV) RL = 500 Ω, CL = 10 pF 76 90 104 μs
Pulse Width, Non-Direction tw(ND) RL = 500 Ω, CL = 10 pF 153 180 207 μs
*Measured at a threshold of ( ICC(HIGH) + ICC(LOW)
) / 2.
Differential Magnetic
Flux Density, B
DIFF
(G)
ValleyTooth
Forward
Reverse
+B
–B
Differential Processed
Signal, V
Proc
(V)
+V
–V
t
B
OP(FWD)
b
V
PROC(BOP)
V
PROC(BRP)
B
RP(FWD)
B
OP
%B
RP
%
100 %
B
OP(REV)
b
B
RP(REV)
Sensed Edgea
aSensed Edge: leading (rising) mechanical edge in forward rotation, trailing (falling) mechanical edge in reverse rotation
b
B
OP(FWD)
triggers the output transition during forward rotation, and B
OP(REV)
triggers the output transition during reverse rotation
Dynamic, Self-Calibrating, Threshold-Detecting, Dif ferential
Speed and Direction Hall-Ef fect Gear Tooth Sensor IC
ATS657
5
Allegro MicroSystems, Inc.
115 Northeast Cutoff
Worcester, Massachusetts 01615-0036 U.S.A.
1.508.853.5000; www.allegromicro.com
Tooth
Valley
Definition of Terms for Input Characteristics
VPROC(BOP)
VPROC(BRP)
VSP
[BOP]
[BRP]
VPROC(pk-pk)
TVPROC
VPROC = the processed analog signal of the sinusoidal magnetic input (per channel)
Ttooth = period of 2 successive sensed target edges
VSP
TTOOTH
VSP(sep) = VSP
VPROC(pk-pk)
OPERATING CHARACTERISTICS: Input Characteristics Valid over operating temperature range and using Reference
Target 60-0, unless otherwise noted
Characteristics Symbol Test Conditions Min. Typ. Max. Unit
Operating Input Range1BDIFF
Differential magnetic signal; correct direction
output on 6th edge 60 – 1200 Gpk-pk
Maximum Operation Air Gap1AGmax Correct direction output on 6th edge – – 2.2 mm
Vibration Immunity (Startup) ErrVIB(SU)
Allowed rotation detected due to vibration;
TTOOTH = period between 2 successive sensed
edges, sinusoidal signal; ΔTA<10°C; BDIFF(AG) = 0
TTOOTH –– –
Vibration Immunity (Running mode)2ErrVIB
Allowed rotation detected due to vibration;
TTOOTH = period between 2 successive sensed
edges, sinusoidal signal; ΔTA<10°C; BDIFF(AG) = 0
TTOOTH
× 0.5 –– –
Maximum Sudden Air Gap Change
Induced Signal Reduction3,4 ΔBDIFF(AG)
Differential magnetic signal reduction due to
instantaneous air gap change; symmetrical
signal reduction, target frequency < 500 Hz
– – 40 %pk-pk
Axial / Radial Runout / Wobble Induced
Signal Reduction5,6 ΔBDIFF(RO)
Differential magnetic signal reduction due to
instantaneous runout per edge; symmetrical
signal reduction, multiple edges
––5%
pk-pk
Relative Repeatability7TθE
Differential magnetic signal, BDIFF = 100 Gpk-pk ,
ideal sinusoidal signal, TA = 150°C, Reference
Target rotational speed = 1000 rpm (f = 1000 Hz)
– 0.12 – deg.
Switchpoint Separation VSP(sep)
Minimum separation between channels as
a percentage of VPROC amplitude at each
switchpoint (see figure below)
20 – – %
1Under certain extreme conditions, especially for smaller differential magnetic signals, the device may require more than 6 edges to output correct
direction on startup. Please contact the Allegro factory for assistance when using this device.
2Small amplitude vibration while in Running mode may result in one additional direction pulse, prior to non-direction pulse. See section Running Small
Amplitude Vibration Detection for details.
3If the minimum VSP(sep) is not maintained after a sudden air gap change, output may be blanked or non-direction pulses may occur.
4Sudden air gap change during startup may increase the quantity of edges required to get correct direction pulses.
5If the minimum VSP(sep) is not maintained, output may be blanked or non-direction pulses may occur.
6Minimum VPROC(pk-pk) signal of 200 mV and minimum VSP(sep) must be maintained
7The repeatability specification is based on statistical evaluation of a sample population, evaluated at 1000 Hz.
Dynamic, Self-Calibrating, Threshold-Detecting, Dif ferential
Speed and Direction Hall-Ef fect Gear Tooth Sensor IC
ATS657
6
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
Angular Tooth Thickness t Length of tooth, with respect
to branded face 3 deg.
Angular Valley Thickness tv
Length of valley, with respect
to branded face 3 deg.
Tooth Whole Depth ht3mm
Material Low Carbon Steel – –
Doht
F
Air Gap
Branded Face of Package
t
tv
Reference Target
60-0
of Package
Branded Face
Dynamic, Self-Calibrating, Threshold-Detecting, Dif ferential
Speed and Direction Hall-Ef fect Gear Tooth Sensor IC
ATS657
7
Allegro MicroSystems, Inc.
115 Northeast Cutoff
Worcester, Massachusetts 01615-0036 U.S.A.
1.508.853.5000; www.allegromicro.com
Functional Description
Data Protocol Description
When a target passes in front of the branded face of the pack-
age, each tooth of the target generates a pulse at the output of the
IC. Each pulse provides target speed and direction data: speed
is provided by the pulse rate, while direction of target rotation is
provided by the pulse width.
The ATS657 can sense target movement in both the forward and
reverse directions. The maximum allowable target rotational
speed is limited by the width of the output pulse and the shortest
low-state duration the system controller can resolve.
Forward Rotation (see panel A in figure 1) When the target is
rotating such that a tooth near the package passes from pin 4 to
pin 1, this is referred to as forward rotation. Forward rotation is
indicated on the output by a tw(FWD) (45 μs typical) pulse width.
Reverse Rotation (see panel B in figure 1) When the target is
rotating such that a tooth passes from pin 1 to pin 4, it is referred
to as reverse rotation. Reverse rotation is indicated on the output
by a tw(REV) (90 μs typical) pulse width, twice as long as the pulse
generated by forward rotation.
Non-Direction Output In situations where the IC is not able to
discern direction of target rotation, as occurs during initial cali-
bration or during target vibration, the output pulse width is tw(ND).
Timing As shown in figure 2, the pulse appears at the output
slightly before the sensed magnetic edge traverses the branded
face. For targets in forward rotation, this shift, Δfwd, results in
the pulse corresponding to the valley with the sensed mechanical
edge, and for targets in reverse rotation, the shift, Δrev, results in
the pulse corresponding to the tooth with the sensed edge. The
sensed mechanical edge that stimulates output pulses is kept the
same for both forward and reverse rotation by using only channel
1 for switching.
The overall range between the forward and reverse pulse occur-
rences is determined by the 1.5 mm spacing between the Hall
elements of the corresponding differential channel. In either
direction, the pulses appear close to the sensed mechanical edge.
The size of the target features, however, can slightly bias the
occurrence of the pulses.
(A) Forward Rotation
(B) Reverse Rotation
Rotating Target Branded Face
of Package
Pin 1
Pin 4
Pin 1
Pin 4
Rotating Target Branded Face
of Package
Figure 1. Target rotation Figure 2. Output pulse timing
∆rev
tw(REV) 90 μs
Reverse Rotation
Forward Rotation
Output Pulse
(Forward Rotation)
Output Pulse
(Reverse Rotation)
ToothValley
∆fwd
tw(FWD) 45 μs
t
t
Dynamic, Self-Calibrating, Threshold-Detecting, Dif ferential
Speed and Direction Hall-Ef fect Gear Tooth Sensor IC
ATS657
8
Allegro MicroSystems, Inc.
115 Northeast Cutoff
Worcester, Massachusetts 01615-0036 U.S.A.
1.508.853.5000; www.allegromicro.com
After the power-on time is complete, the ATS657 internally
detects the profile of the target. The output becomes active at the
first detected switchpoint. Figure 3 shows where the first output
pulse occurs for various starting target phases. After calibration is
complete, direction information is available and this information
is communicated through the output pulse width.
Figure 3. Start-up position effect on first device output switching
t
IC Output
Power-on
opposite valley
Power-on opposite
rising edge
Power-on opposite
falling edge
Power-on
opposite tooth
Target Differential
Magnetic Profile
Forward Target Rotation (Target passes from pin 4 to pin 1)
Device Location at Power-On
tw(ND)
tw(ND)
tw(ND)
ToothValley
Start-Up Detection
Dynamic, Self-Calibrating, Threshold-Detecting, Dif ferential
Speed and Direction Hall-Ef fect Gear Tooth Sensor IC
ATS657
9
Allegro MicroSystems, Inc.
115 Northeast Cutoff
Worcester, Massachusetts 01615-0036 U.S.A.
1.508.853.5000; www.allegromicro.com
The processed differential internal analog signal, VPROC
, of each
of the two channels is used to determine switchpoints, at which
the device determines direction information and changes to out-
put signal polarity. Because the value of VPROC is directly propor-
tional to the differential magnetic flux density, BDIFF, induced by
the target and sensed by the Hall elements, the switchpoints occur
at threshold levels that correspond to certain levels of BDIFF.
The operate point, BOP , occurs when VPROC rises through a cer-
tain limit, VPROC(BOP) . When BOP occurs, the channel internally
switches from low to high. When VPROC falls below VPROC(BOP)
through a certain limit, VPROC(BRP) , the release point, BRP
,
occurs and the channel state switches from high to low.
As shown in panel C of figure 4, the threshold levels for the
ATS657 switchpoints are established as a function of the two
previous signal peaks detected. The ATS657 incorporates an
algorithm that continuously monitors VPROC and then updates the
switching thresholds to correspond to any amplitude reduction.
For any given target edge transition, the change in threshold level
is limited. Each channel operates in this manner, independent of
each other, so independent switchpoint thresholds are calculated
for each channel.
Continuous Update of Switchpoints
(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)
VPROC (V)
V+
Larger
TEAG
Smaller
TEAG
IC
Target
Larger
TEAG
Target
IC
Smaller
TEAG
Smaller
TEAG
Pk
(#4)
Pk
(#5)
Pk
(#7)
Pk
(#9)
Pk
(#2)
Pk
(#3)
Pk
(#1)
Pk
(#6)
Pk
(#8)
V
PROC
(V)
B
HYS(#4)
B
HYS(#3)
V+
B
RP(#1)
B
OP(#1)
B
RP(#2)
B
RP(#3)
B
OP(#3)
B
RP(#4)
B
OP(#4)
B
OP(#2)
V
PROC(BOP)
(#1)
V
PROC(BOP)
(#2)
V
PROC(BOP)
(#3)
V
PROC(BOP)
(#4)
V
PROC(BRP)
(#1)
V
PROC(BRP)
(#2)
V
PROC(BRP)
(#3)
V
PROC(BRP)
(#4)
B
HYS(#1)
B
HYS(#2)
Figure 4. The Continuous Update algorithm allows the Allegro IC to immediately interpret and adapt to variances in the magnetic field generated 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). Not detailed in the figure are the boundaries for peak capture DAC movement which
intentionally limit the amount of internal signal variation the IC is able to react to over a single transition. The algorithm is used to dynamically establish
and subsequently update the device switchpoint levels (VPROC(BOP) and VPROC(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 switchpoint
levels 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)
4
BOP(#4) Pk(#7), Pk(#8)
BRP(#4) Pk(#8), Pk(#9)
(C) Referencing the internal analog signal, VPROC, to continuously update device response
Dynamic, Self-Calibrating, Threshold-Detecting, Dif ferential
Speed and Direction Hall-Ef fect Gear Tooth Sensor IC
ATS657
10
Allegro MicroSystems, Inc.
115 Northeast Cutoff
Worcester, Massachusetts 01615-0036 U.S.A.
1.508.853.5000; www.allegromicro.com
During normal running mode, vibration can interfere with the
direction detection functions. In that case, during the vibration the
device may continue to output speed data with non-directional
pulses.
If the vibration that occurs has a large enough amplitude such
that the peaks of the VPROC signals continue to pass through both
switchpoints, non-direction pulses will be outputted during the
vibration, as shown in figure 5.
If the vibration has a low enough amplitude such that its posi-
tive peak is less than VPROC(BOP)
, no pulses are outputted and
no switchpoint updating occurs until the vibration becomes large
enough that VPROC exceeds VPROC(BOP) . If its negative peak is
greater than VPROC(BRP), then there is no output or update until
VPROC falls below VPROC(BRP) . As shown in figure 6, when that
does occur, a single direction pulse may be outputted, however,
regardless of whether or not that single pulse occurs, non-direction
pulses are outputted throughout the remainder of the vibration.
Figure 6. Small amplitude vibration during Running mode operation
Figure 5. Large amplitude vibration during Running mode operation
Operation During Running Mode Vibration
+V
Switchpoint
Hysteresis
t
w(FWD)
or t
w(REV)
t
w(ND)
+t
+t
Normal Rotation Vibration
}
V
PROC
V
PROC(BOP)
V
PROC(BRP)
+I
I
OUT
+V
Switchpoint
Hysteresis
t
w(FWD)
or t
w(REV)
t
w(FWD)
or t
w(REV)
t
w(ND)
V
PROC
+t
+t
Normal Rotation Vibration
}
V
PROC
> V
PROC(BOP)
V
PROC(BOP)
V
PROC(BRP)
+I
I
OUT
Dynamic, Self-Calibrating, Threshold-Detecting, Dif ferential
Speed and Direction Hall-Ef fect Gear Tooth Sensor IC
ATS657
11
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 volt-
age, VCC(UV), ICC goes to the Power-On state and remains regard-
less of the state of the magnetic gradient from the target. This
lockout feature prevents false signals, caused by undervoltage
conditions, from propagating to the output of the IC. ICC levels
may not meet datasheet limits when VCC < VCC(min).
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 unregu-
lated power supply, transient protection must be added externally.
For applications using a regulated line, EMI/RFI protection may
still be required. Contact Allegro for information on the circuitry
needed for compliance with various EMC specifications. Refer to
figure 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 speci-
fication). 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 automatically adjusted. Figure 8 illustrates the effect
of this feature. The two differential channels have their gain set
independent of each other, so both channels may or may not have
the same gain setting.
Automatic Offset Adjust (AOA)
The AOA circuitry, when combined with AGC, automatically
compensates for the effects of chip, magnet, and installation
offsets. (For capability, see Allowable User Induced Differential
Offset, in the Electrical Characteristics table.) This circuitry is
continuously active, including both during Power-On mode and
Running mode, compensating for offset drift. Continuous opera-
tion also allows it to compensate for offsets induced by tempera-
ture variations over time. Similar to AGC, the AOA is set inde-
pendently for each channel, so the offset adjust is set per channel,
based on the offset characteristics of that specific channel.
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, as shown in the lowest panel.
Figure 7. Typical application circuit
Mechanical Profile
AGSmall
AGLarge
AGSmall
AGLarge
Internal Differential Signal
Response, without AGC
Internal Differential Signal
Response, with AGC
Ferrous Target
V+
V+
2ATS657
1
3
4
0.01 MF (optional)
100 7
RLCL
CBYPASS
VCC
Dynamic, Self-Calibrating, Threshold-Detecting, Dif ferential
Speed and Direction Hall-Ef fect Gear Tooth Sensor IC
ATS657
12
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 Power Derating section
Characteristic Symbol Test Conditions* Value Unit
Package Thermal Resistance RθJA
Single layer PCB, with copper limited to solder pads 126 ºC/W
Single layer PCB, with limited to solder pads and 3.57 in.2 (23.03 cm2)
copper area each side 84 ºC/W
*Additional thermal information available on the Allegro website
6
7
8
9
2
3
4
5
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
20 40 60 80 100 120 140 160 180
Temperature (ºC)
Maximum Allowable V
CC
(V)
Power Derating Curve
R
QJA
= 126 ºC/W
R
QJA
= 84 ºC/W
VCC(min)
VCC(absmax)
0
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
D
(mW)
Power Dissipation versus Ambient Temperature
RQJA = 126 ºC/W
RQJA = 84 ºC/W
Dynamic, Self-Calibrating, Threshold-Detecting, Dif ferential
Speed and Direction Hall-Ef fect Gear Tooth Sensor IC
ATS657
13
Allegro MicroSystems, Inc.
115 Northeast Cutoff
Worcester, Massachusetts 01615-0036 U.S.A.
1.508.853.5000; www.allegromicro.com
The device must be operated below the maximum junction tem-
perature of the device, TJ(max). Under certain combinations of
peak conditions, reliable operation may require derating supplied
power or improving the heat dissipation properties of the appli-
cation. 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, RJA, 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, RJC, is
a relatively small component of RJA. 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 × RJA (2)
TJ = TA + ΔT (3)
For example, given common conditions such as: TA= 25°C,
VCC = 12 V, ICC = 6.5 mA, and RJA = 126 °C/W, then:
P
D = VCC × ICC = 12 V × 6.5 mA = 78 mW
T = PD × RJA = 78 mW × 126 °C/W = 9.8°C
T
J = TA + T = 25°C + 9.8°C = 34.8°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 RJA and TA.
Example: Reliability for VCC at TA =
150°C, package SH, using
single layer PCB.
Observe the worst-case ratings for the device, specifically:
RJA
=
126°C/W, TJ(max) =
165°C, VCC(absmax)
=
24
V, and
ICC = 13
mA (Note: At maximum target frequency, ICC(LOW) =
8 mA, ICC(HIGH) = 16 mA, and maximum pulse widths, the result
is a duty cycle of 62.4% and a worst case mean ICC of 13 mA.)
Calculate the maximum allowable power level, PD(max). First,
invert equation 3:
T(max) = 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) = T(max) ÷ RJA = 15°C ÷ 126 °C/W = 119 mW
Finally, invert equation 1 with respect to voltage:
VCC(est) = PD(max) ÷ ICC = 119 mW ÷ 13 mA = 9.2 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
RJA. If VCC(est) ≥ VCC(max), then operation between VCC(est) and
VCC(max) is reliable under these conditions.
Power Derating
Dynamic, Self-Calibrating, Threshold-Detecting, Dif ferential
Speed and Direction Hall-Ef fect Gear Tooth Sensor IC
ATS657
14
Allegro MicroSystems, Inc.
115 Northeast Cutoff
Worcester, Massachusetts 01615-0036 U.S.A.
1.508.853.5000; 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
1A
A
B
D
For Reference Only, not for tooling use (reference DWG-9003)
Dimensions in millimeters
A
B
C
C
D
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
F
E
F
FE
1.50
E2 E3
E1
1.50
Hall elements (E1, E2, E3); not to scale
Package SH 4-Pin SIP
Dynamic, Self-Calibrating, Threshold-Detecting, Dif ferential
Speed and Direction Hall-Ef fect Gear Tooth Sensor IC
ATS657
15
Allegro MicroSystems, Inc.
115 Northeast Cutoff
Worcester, Massachusetts 01615-0036 U.S.A.
1.508.853.5000; www.allegromicro.com
For the latest version of this document, visit our website:
www.allegromicro.com
Copyright ©2009, Allegro MicroSystems, Inc.
The products described herein are manufactured under one or more of the following U.S. patents: 5,264,783; 5,389,889; 5,442,283; 5,517,112;
5,581,179; 5,619,137; 5,621,319; 5,650,719; 5,686,894; 5,694,038; 5,729,130; 5,917,320; 6,091,239; 6,100,680; 6,232,768; 6,242,908; 6,265,865;
6,297,627; 6,525,531; 6,690,155; 6,693,419; 6,919,720; 7,046,000; 7,053,674; 7,138,793; 7,199,579; 7,253,614; 7,365,530; 7,368,904; or other
patents pending.
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.
