ATS657 Datasheet

ATS657
Dynamic, Self-Calibrating, Threshold-Detecting, Differential
Speed and Direction Hall-Effect Gear Tooth Sensor IC
Discontinued Product
These parts are no longer in production The device should not be
purchased for new design applications. Samples are no longer available.
Date of status change: December 1, 2015
Recommended Substitutions:
For existing customer transition, and for new customers or new applications, refer to the ATS692.
NOTE: For detailed information on purchasing options, contact your
local Allegro field applications engineer or sales representative.
Allegro MicroSystems, LLC 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, LLC assumes no responsibility for its use; nor for any infringements of patents or other rights of third parties which may result from its use.
ATS657
Dynamic, Self-Calibrating, Threshold-Detecting, Differential
Speed and Direction Hall-Effect Gear Tooth Sensor IC
Features and Benefits
Description
▪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
The ATS657 includes an optimized Hall-effect sensing
integrated circuit (IC) and rare earth pellet to create a userfriendly 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.
Package: 4-pin SIP (suffix SH)
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.
Not to scale
Functional Block Diagram
VCC
PDAC
NDAC
PDAC
NDAC
Offset
Adjust
AGC
Offset
Adjust
AGC
THRESHP
Reference
Generator
and Update
THRESHN
THRESHP
Reference
Generator
and Update
THRESHN
Internal
Regulator
Peak
Detection
Logic
＋
–
Threshold
Logic
–
＋
＋
–
Speed and
Direction
Logic
Threshold
Logic
–
＋
GND
ATS657-DS, Rev. 5
Output
Protocol
Control
ATS657
Selection Guide
Part Number
Dynamic, Self-Calibrating, Threshold-Detecting, Differential
Speed and Direction Hall-Effect Gear Tooth Sensor IC
Packing*
ATS657LSHTN-T
800 pieces per 13-in. reel
*Contact Allegro™ for additional packing options
Absolute Maximum Ratings
Characteristic
Supply Voltage
Symbol
Notes
Rating
Unit
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
–40 to 150
ºC
TJ(max)
165
ºC
Tstg
–65 to 170
ºC
Operating Ambient Temperature
TA
Maximum Junction Temperature
Storage Temperature
Range L
Pin-out Diagram
Terminal List
1 2 3 4
Number
Name
Function
1
VCC
Connects power supply to chip
2
TEST
Test pin: float
3
TEST
Test pin: float
4
GND
Ground terminal
Allegro MicroSystems, LLC
115 Northeast Cutoff
Worcester, Massachusetts 01615-0036 U.S.A.
1.508.853.5000; www.allegromicro.com
2
ATS657
Dynamic, Self-Calibrating, Threshold-Detecting, Differential
Speed and Direction Hall-Effect Gear Tooth Sensor IC
ELECTRICAL CHARACTERISTICS Valid over operating voltage and temperature ranges, unless otherwise noted
Characteristics
Supply Voltage
Undervoltage Lockout
Reverse Supply Current
Supply Zener Clamp Voltage
Supply Zener Resistance
Supply Current
Min.
Typ.1
Max.
Unit2
4.0
–
18
V
VCC = 0 → >4 V, or >4 → 0 V
–
3.5
4.0
V
VCC = –18 V
–
–
–10
mA
Symbol
VCC
VCC(UV)
IRCC
Test Conditions
Operating, TJ < TJ(max)
VZ(SUPPLY) ICC = ICC(max) + 3 mA, TA = 25°C
RZ
24.0
–
–
V
–
<5
–
Ω
ICC(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
ICC(SU)(HIGH) High-current state (Calibration)
12
14.5
16.5
mA
ICC(HIGH) – ICC(LOW)
5
–
–
mA
Speed < 200 Hz
–
–
2.0
ms
NDIR
Speed < 200 Hz, constant rotation direction
–
–
6
Edge
NNONDIR
Speed < 200 Hz, constant rotation direction
–
–
2
Edge
Nf
Speed < 200 Hz, constant rotation direction
–
–
5
Edge
–
3
–
Edge
–
5
–
ms
Non-Direction Pulse Output on Direction
NNONDIR_DC Running mode, direction change
Change
–
1
2
Pulse
First Direction Pulse Output on Direction
Change
Running mode, direction change
–
2
3
Pulse
Both differential channels
–
±60
–
G
RL = 100 Ω, CL = 10 pF; ICC(HIGH) → ICC(LOW) ,
ICC(LOW) → ICC(HIGH) , 10% to 90% points
7
16.0
–
mA/µs
Current Level Difference
∆ICC
Power-On Characteristics3
Power-On Time
ton
Initial Calibration
First Output Pulse with Direction4
First Output
Pulse5
AGC Disable
Vibration Check
Time Until Correct Direction Output on
High-Speed Startup
NVIBCHECK Speed < 200 Hz, after AGC disable
tHIGHSU
10 kHz startup, B = 300 Gpk-pk
Running Mode Calibration6
NDC
DAC Characteristics
Allowable User-Induced Differential
Offset7
BDIFFEXT
Output Stage
Output Slew Rate
SROUT
1Typical data is at V
CC = 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.
Allegro MicroSystems, LLC
115 Northeast Cutoff
Worcester, Massachusetts 01615-0036 U.S.A.
1.508.853.5000; www.allegromicro.com
3
Dynamic, Self-Calibrating, Threshold-Detecting, Differential
Speed and Direction Hall-Effect Gear Tooth Sensor IC
ATS657
OPERATING CHARACTERISTICS: Switchpoint Characteristics Valid over operating voltage and temperature ranges,
unless otherwise noted (refer to figure below)
Min.
Typ.
Max.
Unit
Target Frequency, Forward Rotation
Characteristics
Symbol
fFWD
Test Conditions
–
–
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.
Sensed Edgea
Differential Processed
Signal, VProc (V)
Differential Magnetic
Flux Density, BDIFF (G)
Reverse
Tooth
Forward
Valley
+B
BOP(REV)b
BOP(FWD)b
BRP(REV)
BRP(FWD)
–B
+V
VPROC(BOP)
100 %
VPROC(BRP)
BRP %
BOP %
–V
t
aSensed Edge: leading (rising) mechanical edge in forward rotation, trailing (falling) mechanical edge in reverse rotation
bB
OP(FWD)
triggers the output transition during forward rotation, and BOP(REV) triggers the output transition during reverse rotation
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 = 100 Ω, CL = 10 pF
38
45
52
µs
Pulse Width, Reverse Rotation
tw(REV)
RL = 100 Ω, CL = 10 pF
76
90
104
µs
Pulse Width, Non-Direction
tw(ND)
RL = 100 Ω, CL = 10 pF
153
180
207
µs
*Measured at a threshold of ( ICC(HIGH) + ICC(LOW) ) / 2.
Allegro MicroSystems, LLC
115 Northeast Cutoff
Worcester, Massachusetts 01615-0036 U.S.A.
1.508.853.5000; www.allegromicro.com
4
Dynamic, Self-Calibrating, Threshold-Detecting, Differential
Speed and Direction Hall-Effect Gear Tooth Sensor IC
ATS657
OPERATING CHARACTERISTICS: Input Characteristics Valid over operating temperature range and using Reference
Target 60-0, unless otherwise noted
Characteristics
Symbol
Test Conditions
Operating Input Range1
BDIFF
Differential magnetic signal; correct direction
output on 6th edge
Maximum Operation Air Gap1
AGmax
Correct direction output on 6th edge
Vibration Immunity (Startup)
Vibration Immunity (Running mode)2
Min.
Typ.
Max.
Unit
60
–
1200
Gpk-pk
–
–
2.2
mm
ErrVIB(SU)
Allowed rotation detected due to vibration;
TTOOTH = period between 2 successive sensed
edges, sinusoidal signal; ∆TA<10°C; BDIFF(AG) = 0
TTOOTH
–
–
–
ErrVIB
Allowed rotation detected due to vibration;
TTOOTH = period between 2 successive sensed
edges, sinusoidal signal; ∆TA<10°C; BDIFF(AG) = 0
TTOOTH
× 0.5
–
–
–
Maximum Sudden Air Gap Change
Induced Signal Reduction3,4
Differential magnetic signal reduction due to
∆BDIFF(AG) instantaneous air gap change; symmetrical
signal reduction, target frequency < 500 Hz
–
–
40
%pk-pk
Axial / Radial Runout / Wobble Induced
Signal Reduction5,6
Differential magnetic signal reduction due to
∆BDIFF(RO) instantaneous runout per edge; symmetrical
signal reduction, multiple edges
–
–
5
%pk-pk
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.
Minimum separation between channels as
a percentage of VPROC amplitude at each
switchpoint (see figure below)
20
–
–
%
Relative Repeatability7
TθE
Switchpoint Separation
VSP(sep)
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 V
SP(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 V
SP(sep) is not maintained, output may be blanked or non-direction pulses may occur.
6Minimum V
PROC(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.
Definition of Terms for Input Characteristics
Tooth
Valley
TTOOTH
TVPROC
VSP
VPROC(BOP)
[BOP]
VPROC(pk-pk)
[BRP]
VPROC(BRP)
VSP
VSP(sep) =
VSP
VPROC(pk-pk)
VPROC = the processed analog signal of the sinusoidal magnetic input (per channel)
Ttooth = period of 2 successive sensed target edges
Allegro MicroSystems, LLC
115 Northeast Cutoff
Worcester, Massachusetts 01615-0036 U.S.A.
1.508.853.5000; www.allegromicro.com
5
Dynamic, Self-Calibrating, Threshold-Detecting, Differential
Speed and Direction Hall-Effect Gear Tooth Sensor IC
ATS657
Reference Target 60-0 (60 Tooth Target)
Characteristics
Symbol
Test Conditions
Typ.
Units
Symbol Key
120
mm
t
Outside Diameter
Do
Outside diameter of target
Face Width
F
Breadth of tooth, with respect
to branded face
6
mm
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
ht
3
mm
–
–
Material
Low Carbon Steel
Do
F
ht
tv
Air Gap
Branded Face of Package
Branded Face
of Package
Reference Target
60-0
Allegro MicroSystems, LLC
115 Northeast Cutoff
Worcester, Massachusetts 01615-0036 U.S.A.
1.508.853.5000; www.allegromicro.com
6
Dynamic, Self-Calibrating, Threshold-Detecting, Differential
Speed and Direction Hall-Effect Gear Tooth Sensor IC
ATS657
Functional Description
Data Protocol Description
When a target passes in front of the branded face of the package, 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.
Pin 4
Non-Direction Output In situations where the IC is not able to
discern direction of target rotation, as occurs during initial calibration 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 occurrences 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.
Pin 1
Branded Face
of Package
Rotating Target
Forward Rotation
Reverse Rotation
Output Pulse
(Forward Rotation)
Pin 1
Branded Face
of Package
Rotating Target
Tooth
∆fwd
tw(FWD) 45 µs
(A) Forward Rotation
Pin 4
Valley
∆rev
tw(REV) 90 µs
Output Pulse
(Reverse Rotation)
t
t
(B) Reverse Rotation
Figure 1. Target rotation
Figure 2. Output pulse timing
Allegro MicroSystems, LLC
115 Northeast Cutoff
Worcester, Massachusetts 01615-0036 U.S.A.
1.508.853.5000; www.allegromicro.com
7
ATS657
Dynamic, Self-Calibrating, Threshold-Detecting, Differential
Speed and Direction Hall-Effect Gear Tooth Sensor IC
Start-Up Detection
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.
Forward Target Rotation (Target passes from pin 4 to pin 1)
Valley
Tooth
Target Differential
Magnetic Profile
tw(ND)
tw(ND)
Power-on
opposite valley
IC Output
Power-on opposite
rising edge
tw(ND)
Power-on
opposite tooth
t
Power-on opposite
falling edge
Device Location at Power-On
Figure 3. Start-up position effect on first device output switching
Allegro MicroSystems, LLC
115 Northeast Cutoff
Worcester, Massachusetts 01615-0036 U.S.A.
1.508.853.5000; www.allegromicro.com
8
Dynamic, Self-Calibrating, Threshold-Detecting, Differential
Speed and Direction Hall-Effect Gear Tooth Sensor IC
ATS657
Continuous Update of Switchpoints
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 output signal polarity. Because the value of VPROC is directly proportional 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.
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.
The operate point, BOP , occurs when VPROC rises through a certain 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 ,
V+
Smaller
TEAG
IC
VPROC (V)
Target
Target
Smaller
TEAG
IC
Hysteresis Band
(Delimited by switchpoints)
Larger
TEAG
0
(A) TEAG varying; cases such as eccentric mount,
out-of-round region, normal operation position shift
Switchpoint
Determinant
Peak Values
(B) Internal analog signal, VPROC, typically resulting in the IC
1
BOP(#1)
BRP(#1)
Pk(#1), Pk(#2)
Pk(#2), Pk(#3)
2
BOP(#2)
BRP(#2)
Pk(#3), Pk(#4)
Pk(#4), Pk(#5)
3
BOP(#3)
BRP(#3)
Pk(#5), Pk(#6)
Pk(#6), Pk(#7)
BOP(#4)
Pk(#7), Pk(#8)
BRP(#4)
Pk(#8), Pk(#9)
4
BOP(#3)
BOP(#2)
BOP(#4)
Pk(#9)
Pk(#1)
Pk(#3)
VPROC (V)
BHYS
360
Target Rotation (°)
BOP(#1)
V+
Smaller
TEAG
Larger
TEAG
Pk(#7)
Pk(#5)
VPROC(BOP)(#1)
VPROC(BOP)(#2)
BHYS(#1)
BHYS(#2)
VPROC(BRP)(#1)
Pk(#4)
BHYS(#3)
VPROC(BOP)(#3)
VPROC(BRP)(#2)
VPROC(BOP)(#4)
VPROC(BRP)(#3)
BHYS(#4)
VPROC(BRP)(#4)
Pk(#6)
Pk(#8)
Pk(#2)
BRP(#1)
BRP(#2)
BRP(#3)
BRP(#4)
t+
(C) Referencing the internal analog signal, VPROC, to continuously update device response
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.
Allegro MicroSystems, LLC
115 Northeast Cutoff
Worcester, Massachusetts 01615-0036 U.S.A.
1.508.853.5000; www.allegromicro.com
9
Dynamic, Self-Calibrating, Threshold-Detecting, Differential
Speed and Direction Hall-Effect Gear Tooth Sensor IC
ATS657
Operation During Running Mode Vibration
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.
Normal Rotation
If the vibration has a low enough amplitude such that its positive 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.
Vibration
+V
VPROC
VPROC(BOP)
}
Switchpoint
Hysteresis
}
Switchpoint
Hysteresis
VPROC(BRP)
+t
+I
IOUT
tw(FWD) or tw(REV)
tw(ND)
+t
Figure 5. Large amplitude vibration during Running mode operation
Normal Rotation
Vibration
+V
VPROC > VPROC(BOP)
VPROC
VPROC(BOP)
VPROC(BRP)
+t
IOUT
+I
tw(FWD) or tw(REV)
tw(FWD)
or tw(REV)
tw(ND)
+t
Figure 6. Small amplitude vibration during Running mode operation
Allegro MicroSystems, LLC
115 Northeast Cutoff
Worcester, Massachusetts 01615-0036 U.S.A.
1.508.853.5000; www.allegromicro.com
10
ATS657
Dynamic, Self-Calibrating, Threshold-Detecting, Differential
Speed and Direction Hall-Effect Gear Tooth Sensor IC
Undervoltage Lockout
When the supply voltage falls below the minimum operating voltage, VCC(UV), ICC goes to the Power-On state and remains regardless 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 unregulated 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 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 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 operation also allows it to compensate for offsets induced by temperature variations over time. Similar to AGC, the AOA is set independently for each channel, so the offset adjust is set per channel,
based on the offset characteristics of that specific channel.
V CC
1
2
3
ATS657
0.01 µF (optional)
CBYPASS
4
RL
100 Ω
CL
Figure 7. Typical application circuit
Ferrous Target
Mechanical Profile
V+
AGLarge
Internal Differential Signal
Response, without AGC
AGSmall
V+
Internal Differential Signal
Response, with AGC
AGSmall
AGLarge
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.
Allegro MicroSystems, LLC
115 Northeast Cutoff
Worcester, Massachusetts 01615-0036 U.S.A.
1.508.853.5000; www.allegromicro.com
11
Dynamic, Self-Calibrating, Threshold-Detecting, Differential
Speed and Direction Hall-Effect Gear Tooth Sensor IC
ATS657
Thermal Characteristics may require derating at maximum conditions, see Power Derating section
Characteristic
Symbol
Test Conditions*
Single layer PCB, with copper limited to solder pads
RθJA
Package Thermal Resistance
Single layer PCB, with copper limited to solder pads and 3.57
(23.03 cm2) copper area each side
in.2
Value
Unit
126
ºC/W
84
ºC/W
Maximum Allowable VCC (V)
*Additional thermal information available on the Allegro website
Power Derating Curve
25
24
23
22
21
20
19
18
17
16
15
14
13
12
11
10
9
8
7
6
5
4
3
2
VCC(absmax)
RθJA = 84 ºC/W
RθJA = 126 ºC/W
VCC(min)
20
40
60
80
100
120
140
160
180
Temperature (ºC)
Power Dissipation, PD (m W)
Power Dissipation versus Ambient Temperature
1900
1800
1700
1600
1500
1400
1300
1200
1100
1000
900
800
700
600
500
400
300
200
100
0
RθJA = 84 ºC/W
RθJA = 126 ºC/W
20
40
60
80
100
120
Temperature (°C)
140
160
180
Allegro MicroSystems, LLC
115 Northeast Cutoff
Worcester, Massachusetts 01615-0036 U.S.A.
1.508.853.5000; www.allegromicro.com
12
Dynamic, Self-Calibrating, Threshold-Detecting, Differential
Speed and Direction Hall-Effect Gear Tooth Sensor IC
ATS657
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 supplied
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, RθJA, is a figure of merit summarizing 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, RθJC, is
a relatively small component of RθJA. 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)
ΔT = PD × RθJA (2)
TJ = TA + ΔT
(3)
Example: Reliability for VCC at TA = 150°C, package SH, using
single layer PCB.
Observe the worst-case ratings for the device, specifically: RθJA = 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:
ΔT(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) = ΔT(max) ÷ RθJA = 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 reliable operation between VCC(est) and VCC(max) requires enhanced
RθJA. If VCC(est) ≥ VCC(max), then operation between VCC(est) and
VCC(max) is reliable under these conditions.
For example, given common conditions such as: TA= 25°C,
VCC = 12 V, ICC = 6.5 mA, and RθJA = 126 °C/W, then:
PD = VCC × ICC = 12 V × 6.5 mA = 78 mW
ΔT = PD × RθJA = 78 mW × 126 °C/W = 9.8°C
TJ = TA + ΔT = 25°C + 9.8°C = 34.8°C
A worst-case estimate, PD(max), represents the maximum allowable power level (VCC(max), ICC(max)), without exceeding
TJ(max), at a selected RθJA and TA.
Allegro MicroSystems, LLC
115 Northeast Cutoff
Worcester, Massachusetts 01615-0036 U.S.A.
1.508.853.5000; www.allegromicro.com
13
Dynamic, Self-Calibrating, Threshold-Detecting, Differential
Speed and Direction Hall-Effect Gear Tooth Sensor IC
ATS657
Package SH 4-Pin SIP
5.50±0.05
F
F
1.50
E
1.50
B
8.00±0.05
LLLLLLL
NNN
5.80±0.05
E1
E2
E3
YYWW
Branded
Face
1.70±0.10
5.00±0.10
D
4.00±0.10
1
2
3
4
= 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
A
0.60±0.10
Standard Branding Reference View
0.71±0.05
For Reference Only, not for tooling use (reference DWG-9003)
Dimensions in millimeters
A Dambar removal protrusion (16X)
24.65±0.10
B Metallic protrusion, electrically connected to pin 4 and substrate (both sides)
C Thermoplastic Molded Lead Bar for alignment during shipment
+0.06
0.38 –0.04
1.00±0.10
13.10±0.10
D Branding scale and appearance at supplier discretion
E Active Area Depth 0.43 mm REF
F
Hall elements (E1, E2, E3); not to scale
A
1.0 REF
1.60±0.10
1.27±0.10
C
0.71±0.10
0.71±0.10
5.50±0.10
Allegro MicroSystems, LLC
115 Northeast Cutoff
Worcester, Massachusetts 01615-0036 U.S.A.
1.508.853.5000; www.allegromicro.com
14
Dynamic, Self-Calibrating, Threshold-Detecting, Differential
Speed and Direction Hall-Effect Gear Tooth Sensor IC
ATS657
Revision History
Revision
Revision Date
Description of Revision
4
December 10, 2013
Update tw(x) , figure 2, terminal list table
5
December 1, 2015
Product status changed to discontinued
Copyright ©2009-2015, Allegro MicroSystems, LLC
Allegro MicroSystems, LLC reserves the right to make, from time to time, such departures from the detail specifications as may be required to
permit improvements in the performance, 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 any devices or systems, including but not limited to life support devices or systems, in which a failure of
Allegro’s product can reasonably be expected to cause bodily harm.
The information included herein is believed to be accurate and reliable. However, Allegro MicroSystems, LLC assumes no responsibility for its
use; nor for any infringement of patents or other rights of third parties which may result from its use.
For the latest version of this document, visit our website:
www.allegromicro.com
Allegro MicroSystems, LLC
115 Northeast Cutoff
Worcester, Massachusetts 01615-0036 U.S.A.
1.508.853.5000; www.allegromicro.com
15