DESCRIPTION
The A1667 is a true zero-speed ring magnet sensor integrated
circuit (IC) consisting of an optimized Hall IC available in
two package options that provides a user-friendly solution for
digital ring magnet sensing applications.
The sensor incorporates a dual element Hall IC that switches
in response to differential magnetic signals created by a
ring magnet. The IC contains a sophisticated compensating
circuit designed to eliminate the detrimental effects of magnet
and system offsets. Digital processing of the analog signal
provides zero-speed performance independent of air gap and
also dynamic adaptation of device performance to the typical
operating conditions found in automotive applications (reduced
vibration sensitivity). High-resolution peak detecting DACs
are used to set the adaptive switching thresholds of the device.
Hysteresis in the thresholds reduces the negative effects of any
anomalies in the magnetic signal associated with the targets
used in many automotive applications.
The open-drain output is configured for three-wire applications.
This sensor is ideal for obtaining speed and duty cycle
A1667-DS, Rev. 3
MCO-0000168
FEATURES AND BENEFITS
▪Optimizedrobustnesstomagneticoffsetvariation
▪Smallsignallockoutforimmunityagainstvibration
▪Tightdutycycleandtimingaccuracyoverfulloperating
temperature range
▪Truezero-speedoperation
▪Airgapindependentswitchpoints
▪Largeoperatingairgapsachievedthroughuseofgain
adjust and offset adjust circuitry
▪Definedpower-onstate(POS)
▪Wideoperatingvoltagerange
▪Digitaloutputrepresentingtargetprofile
▪SinglechipsensingICforhighreliability
▪Smallmechanicalsize
▪Faststartup
▪Undervoltagelockout(UVLO)
True Zero-Speed, High Accuracy, Ring Magnet Sensor IC
Functional Block Diagram
A1667
Not to scale
PACKAGES:
GND
VOUT
VCC
TEST
Output
Transistor
Current
Limit
Voltage
Regulator
Hall
Amp
Automatic
Gain
Control VPROC
PThresh
NThresh
Threshold
Logic
Threshold
Comparator
Offset
Adjust
Reference
Generator
PDAC
NDAC
4-Pin SIP (su󰀩x K)
8-Pin SOIC (su󰀩x L)
KEY APPLICATIONS
• Automotive – Transmissions Applications
• 2-and3-WheelerSpeedApplications
• WhiteGoods–DrumSpeedApplications
Continued on the next page…
October 4, 2018
True Zero-Speed, High Accuracy, Ring Magnet Sensor IC
A1667
2
Allegro MicroSystems, LLC
955 Perimeter Road
Manchester, NH 03103-3353 U.S.A.
www.allegromicro.com
ABSOLUTE MAXIMUM RATINGS
Characteristic Symbol Notes Rating Unit
Supply Voltage VCC See Power Derating section 26.5 V
Reverse Supply Voltage VRCC –18 V
Reverse Supply Current IRCC –50 mA
Reverse Output Voltage VROUT –0.5 V
Output Sink Current IOUT 25 mA
Operating Ambient Temperature TARange L –40 to 150 °C
Maximum Junction Temperature TJ(max) 165 °C
Storage Temperature Tstg –65 to 170 °C
SELECTION GUIDE
Part Number Packaging Packing*
A1667LK-T 4-pin SIP through hole Bulk, 500 pieces per bag
A1667LLTR-T 8-pin SOIC surface mount 3000 pieces per 13-in. reel
*Contact Allegro™ for additional packing options
Terminal List
Number Name Function
KL
1 1 VCC Supply voltage
2 2 VOUT Device output
3 3 TEST Test pin (float or tie to GND)
4 4 GND Ground
– 5,6,7,8 NC No connect*
* Pins 5, 6, 7, and 8 should be externally connected to Ground.
1 2 3 4
PINOUT DIAGRAMS AND TERMINAL LIST TABLE
8
7
6
5
1
2
3
4
Package L, 8-Pin SOICPackage K, 4-Pin SIP
DESCRIPTION (continued)
information using ring magnet based systems in applications such
as automotive transmissions and industrial equipment.
TheA1667isavailableina4-pinSIPthrough-holepackage(suf-
fixK)andan8-pinSOICsurface-mountpackage(suffixL).Both
packagesarelead(Pb)freewith100%matte-tin-platedleadframes.
True Zero-Speed, High Accuracy, Ring Magnet Sensor IC
A1667
3
Allegro MicroSystems, LLC
955 Perimeter Road
Manchester, NH 03103-3353 U.S.A.
www.allegromicro.com
OPERATING CHARACTERISTICS: Valid over operating voltage and temperature ranges, unless otherwise noted
Characteristics Symbol Test Conditions Min. Typ. [1] Max. Unit
Continued on the next page…
ELECTRICAL CHARACTERISTICS
Supply Voltage VCC Operating, TJ < TJ(max) 4 – 24 V
Undervoltage Lockout (UVLO) VCC(UV) 2.7 3.5 3.95 V
Reverse Supply Current IRCC VCC = –18 V – – –10 mA
Supply Zener Clamp Voltage VZICC = 15 mA, TA = 25 °C 26.5 – – V
Supply Zener Current IZTA = 25°C, TJ < TJ(max), continuous, VZ = 26.5 V – – 15 mA
Supply Current ICC
Output off 4 7 12 mA
Output on 4 7 12 mA
Test Pin Zener Clamp Voltage
[2] VTESTZ – 6 – V
POWER-ON STATE CHARACTERISTICS
Power-On State POS Connected as in figure 6 – High – –
Power-On Time
[3] tPO fOP < 200 Hz; VCC > VCC(min) – – 2 ms
OUTPUT STAGE
Low Output Voltage VOUT(SAT) ISINK = 10 mA, Output = on – 100 250 mV
Output Zener Clamp Voltage VZOUT 26.5 – – V
Output Current Limit IOUT(LIM) VOUT = 12 V, TJ < TJ(max) 25 45 70 mA
Output Leakage Current IOUT(OFF) Output = off, VOUT = 24 V – – 10 µA
Output Rise Time tr
RL = 1 kΩ, CL = 4.7 nF, VPULLUP = 12 V,
10% to 90%, connected as in figure 6 – 10 – µs
Output Fall Time tf
RL = 1 kΩ, CL = 4.7 nF, VPULLUP = 12 V,
10% to 90%, connected as in figure 6 – 0.6 2 µs
DIGITAL-TO-ANALOG CONVERTER (DAC) CHARACTERISTICS
Allowable User-Induced Differential
Offset
[4][5] BDIFFEXT User induced differential offset –150 – 150 G
SWITCHPOINT CHARACTERISTICS
Operational Switching Frequency fOP 0 – 12 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, BSIG > BSIG(MIN),
VOUT high to low
65 70 75 %
Release Point BRP
% of peak-to-peak VPROC referenced from
PDAC to NDAC, BSIG > BSIG(MIN),
VOUT low to high
25 30 35 %
Running Mode Lockout Enable (LOE) VLOE(RM)
VPROC(PK-PK) < VLOE(RM) = output switching
disabled – 100 – mV
Running Mode Lockout Release (LOR) VLOR(RM)
VPROC(PK-PK) < VLOR(RM) = output switching
enabled – 220 – mV
True Zero-Speed, High Accuracy, Ring Magnet Sensor IC
A1667
4
Allegro MicroSystems, LLC
955 Perimeter Road
Manchester, NH 03103-3353 U.S.A.
www.allegromicro.com
OPERATING CHARACTERISTICS (continued): Valid over operating voltage and temperature ranges, unless otherwise noted
Characteristics Symbol Test Conditions Min. Typ. [1] Max. Unit
CALIBRATION
Initial Calibration
[6] CALI
Possible reduced edge detection accuracy, duty
cycle not guaranteed – 1 6 electrical
edge
Update Method Running mode operation, bounded for
decreasing BSIG, unlimited for increasing BSIG
–Continuous – –
OPERATING CHARACTERISTICS
Operating Signal Range BSIG
Differential magnetic signal
operation within specification 30 – 1400 G
Relative Repeatability
[7] TθE
60 pole-pair target, using 100 GPK-PK ideal
sinusoidal signal, TA = 150°C, and fOP = 1000 Hz – 0.12 – degrees
Maximum Single Outward Sudden Air
Gap Change
[8] ∆AGMAX
Single instantaneous air gap peak-to-peak
amplitude change, fOP < 500 Hz, VPROC(pk-pk) >
VLOE after sudden AG change
– 40 – %PK-PK
[1] Typical data is at VCC = 12 V and TA = 25°C, unless otherwise noted. Performance may vary for individual units, within the specified maximum and
minimum limits.
[2] Sustained voltages beyond the clamp voltage may cause permanent damage to the IC.
[3] Power-On Time is the time required to complete the internal Automatic Offset Adjust; the DACs are then ready for peak acquisition.
[4] The device compensates for magnetic and installation offsets. Offsets greater than specification in gauss may cause inaccuracies in the output.
[5] 1 G (gauss) = 0.1 mT (millitesla).
[6] For power-on frequency, fOP < 200 Hz. Higher power-on frequencies may result in more input magnetic cycles until full output edge accuracy is
achieved, including the possibility of missed output edges.
[7] The repeatability specification is based on statistical evaluation of a sample population, evaluated at 1000 Hz.
[8] Single maximum allowable air gap change in outward direction (increase in air gap).
True Zero-Speed, High Accuracy, Ring Magnet Sensor IC
A1667
5
Allegro MicroSystems, LLC
955 Perimeter Road
Manchester, NH 03103-3353 U.S.A.
www.allegromicro.com
CHARACTERISTIC PERFORMANCE
T
A
(°C)
Supply Current (Off) versus Ambient Temperature
ICCOFF (mA)
14
12
10
8
6
4
2
0
0 10050-50 150
V
CC
(V)
V
CC
(V)
Supply Current (Off) versus Supply Voltage
ICCOFF (mA)
14
12
10
8
6
4
2
0
10 200 30
10 200 30
T
A
(°C)
Supply Current (On) versus Ambient Temperature
ICCON (mA)
14
12
10
8
6
4
2
0
0 10050-50 150
Supply Current (On) versus Supply Voltage
ICCON (mA)
14
12
10
8
6
4
2
0
T
A
(°C)
Output Saturation Voltage versus Ambient Temperature
VCC = 12 V
VOUT(SAT) (mV)
180
160
140
120
100
80
60
40
20
0
0 10050-50 150
TA (°C)
25
150
–40
TA (°C)
25
150
–40
VCC (V)
12
24
4
VCC (V)
12
24
4
0
10
20
30
40
50
60
70
80
90
100
-
50 0 50 100 150
BOP
,
BRP
(%)
TA(°C)
Switchpoints versus Ambient Temperature
B
OP
BRP
True Zero-Speed, High Accuracy, Ring Magnet Sensor IC
A1667
6
Allegro MicroSystems, LLC
955 Perimeter Road
Manchester, NH 03103-3353 U.S.A.
www.allegromicro.com
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
P ,noitapissiD rewoP D(mW)
Temperature (°C)
Power Dissipation versus Ambient Temperature
Package L, 1-layer PCB
(RθJA = 140 °C/W)
Package K, 1-layer PCB
(RθJA = 177
°
C/W)
Package L, 4-layer PCB
(RθJA = 80 °C/W)
6
7
8
9
2
3
4
5
10
11
12
13
14
15
16
17
18
19
20
20 40 60 80 100 120 180140 160
Temperature (ºC)
Maximum Allowable VCC (V)
Power Derating Curve
(RθJA = 140ºC/W)
Package L, 1-layer PCB
(RθJA = 177ºC/W)
Package K, 1-layer PCB
(RθJA = 80ºC/W)
Package L, 4-layer PCB
VCC(min)
VCC(max)
THERMAL CHARACTERISTICS: May require derating at maximum conditions; see application information
Characteristic Symbol Test Conditions* Value Units
Package Thermal Resistance RθJA
Package K, 1-layer PCB with copper limited to solder pads 177 °C/W
Package L, 1-layer PCB with copper limited to solder pads 140 °C/W
Package L, 4-layer PCB based on JEDEC standard 80 °C/W
*Additional thermal data available on the Allegro Website.
True Zero-Speed, High Accuracy, Ring Magnet Sensor IC
A1667
7
Allegro MicroSystems, LLC
955 Perimeter Road
Manchester, NH 03103-3353 U.S.A.
www.allegromicro.com
FUNCTIONAL DESCRIPTION
HALL TECHNOLOGY
The single-chip differential Hall-effect sensor IC contains two
Hall elements as shown in figure 1, which simultaneously sense
the magnetic profile of the ring magnet. The magnetic fields are
sensed 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 temperature-
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
An operating device 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 transla-
tion of the mechanical profile, through the magnetic profile that
it induces, to the digital output signal of the A1667. No addi-
tional optimization is needed and minimal processing circuitry is
required. This ease of use reduces design time and 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 ring magnet and orienta-
tion to the device. The bottom panel, labeled Device Output
Signal, displays the square waveform corresponding to the digital
output signal that results from a rotating ring magnet configured
as shown in figure 2. That direction of rotation (of the target
side adjacent to the package face) is: perpendicular to the leads,
across the face of the device, from the pin 1 side to the pin 4
side. This results in the device output switching from low to high
output state as the leading edge of a north magnetic pole passes
the device face. In this configuration, the device output voltage
switches to its high polarity when a north pole is the target feature
nearest to the device. If the direction of rotation is reversed, then
the output polarity inverts.
Target
(Ring Magnet)
(Pin 1 Side)(Pin 4 Side)
Hall IC
Element Pitch
Hall Element 1
Hall Element 2
NN
S
S
N
N
N
N
N
N
S
S
N
N
S
S
S
S
S
S
Pin 1
Pin 1
Pin 4
Pin 4
Branded Face
of K Package
Branded Face
of L Package
Rotatin
Rotatin
g
g
T
T
arget
arget
B
RP(#1)
B
OP(#1)
B
RP(#2)
Off OnOn Off
Device Internal Switch State
Device Orientation to Target
Device Internal Differential Analog Signal, V
PROC
Device Output Signal, V
OUT
(Pin 1 Side)(Pin 4 Side) IC
Element Pitch
Hall Element 1
Hall Element 2
Sensor Branded Face
Target Magnetic Profile
+B
–B
+t
Mechanical Position (Target moves past device pin 1 to pin 4)
NS
S
Target
(Radial Ring Magnet)
This pole
sensed earlier
This pole
sensed later
(View of Sensor
Opposite Pins)
Figure 1. Relative motion of the target is detected by the dual Hall
elements 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 state when a north magnetic pole of the target is nearest
the face of the device (see figure 3). A right-to-left (pin 4 to pin 1) rotation
inverts the output signal polarity.
Figure 3. The magnetic profile reflects the geometry of the target, allowing
the A1667 to present an accurate digital output response.
True Zero-Speed, High Accuracy, Ring Magnet Sensor IC
A1667
8
Allegro MicroSystems, LLC
955 Perimeter Road
Manchester, NH 03103-3353 U.S.A.
www.allegromicro.com
CONTINUOUS UPDATE OF SWITCHPOINTS
Switchpoints are the threshold levels of the differential internal
analogsignal,VPROC
, at which the device changes output signal
state.ThevalueofVPROC is directly proportional to the magnetic flux
density,B,inducedbythetargetandsensedbytheHallelements.
AsVPROC rises through a certain limit, referred to as the operate
point,BOP,theoutputstatechangesfromhightolow.AsVPROC
fallsbelowBOP to a certain limit, the release point,BRP, the output
state changes from low to high.
As shown in figure 5, threshold levels for the A1667 switchpoints
are established as a function of the peak input signal levels. The
A1667 incorporates an algorithm that continuously monitors the
input signal and updates the switching thresholds accordingly with
limitedinwardmovementofVPROC. The switchpoint for each edge
is determined by the detection of the previous two signal edges. In
this manner, variations are tracked in real time.
(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
0
B
OP
B
RP
B
OP
B
RP
B
OP
B
RP
B
OP
B
RP
B
OP
B
OP
B
RP
360
Target Rotation (°)
Hysteresis Band
(Delimited by switchpoints)
V
PROC
(V)
V+
(C) Internal analog signal, VPROC, representing
magnetic field for digital output
V
PROC
(V)V
OUT
(V)
V+
Larger
TEAG
Smaller
TEAG
IC
Target
Larger
TEAG
Target
IC
Smaller
TEAG
Smaller
TEAG
Figure 4. The Continuous Update algorithm allows the Allegro IC to 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, and similar dynamic application problems that affect the TEAG (Total
Effective Air Gap). 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 switchpoints based on the fluctuation of VPROC, as shown in panel C.
True Zero-Speed, High Accuracy, Ring Magnet Sensor IC
A1667
9
Allegro MicroSystems, LLC
955 Perimeter Road
Manchester, NH 03103-3353 U.S.A.
www.allegromicro.com
Chart
Index
Magnetic Field
Peak VPROC
Amplitude
Centered Calculated Range, BHYS
Target Behavior
(Example only)
Peak Magnetic
Signal, BPK
Operate Point. BOP
(70% B(PKPK) ∝
70% VPROC(PKPK))
Release Point. BRP
(30% B(PKPK) ∝
30% VPROC(PKPK))
BHYS
PK(1) TEAG small +BPK
(South Polarity) VPROCPK(1)
BOP(A)
(Previous state)
A
PK(2) TEAG small –BPK
(North Polarity) VPROCPK(2) BRP(A)
PK(3) TEAG mid +BPK
(South Polarity) VPROCPK(3)
BOP(B) BPK(4) TEAG mid –BPK
(North Polarity) VPROCPK(4) BRP(B)
PK(5) TEAG large +BPK
(South Polarity) VPROCPK(5)
BOP(C)
CPK(6) TEAG large –BPK
(North Polarity) VPROCPK(6)
BRP(C)
PK(7) TEAG mid +BPK
(South Polarity) VPROCPK(7)
BOP(D)
DPK(8) TEAG mid –BPK
(North Polarity) VPROCPK(8)
BRP(D)
PK(9) TEAG small +BPK
(South Polarity) VPROCPK(9)
(Next state)
PK(2)
PK(1)
PK(3)
PK(5)
PK(6)
PK(8)
PK(9)
PK(7)
PK(4)
V
PROC
(V)
B
SIG
(G)
B
HYS(D)
B
HYS(C)
t+
V++B
–B
B
RP(A)
B
OP(A)
B
RP(B)
B
RP(C)
B
OP(C)
B
RP(D)
B
OP(D)
B
OP(B)
B
HYS(A)
B
HYS(B)
Figure 5. The Continuous Update algorithm operation. Not detailed in the figure are the boundaries for peak capture DAC
movement which intentionally limit the amount of inward signal variation the IC is able to react to over a single transition. The
algorithm is used to 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.
True Zero-Speed, High Accuracy, Ring Magnet Sensor IC
A1667
10
Allegro MicroSystems, LLC
955 Perimeter Road
Manchester, NH 03103-3353 U.S.A.
www.allegromicro.com
BRP
BOP
BOP
BOP(initial)
BRP(initial)
1 4
23
Start Mode
Hysteresis, POHYS
Output Signal, VOUT
If exceed POHYS
on high side
If exceed POHYS
on low side
IC Position
Relative to Target
Target Magnetic Profile
Differential Signal, VPROC
Target, Ring Magnet NS
S
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.
Atypicalscenarioisshowninfigure6.TheStartMode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 A1667 starts to compute switchpoints.
Figure 6. Operation of Start Mode Hysteresis
• At power-on (position 1), the A1667 begins sampling VPROC.
• At the point where the Start Mode Hysteresis, POHYS , is exceeded, the device establishes an initial switching threshold, by using the Continuous
Update algorithm. If VPROC is falling through the limit on the low side (position 2), the switchpoint is BRP , and if VPROC is rising through the limit on the
high side (position 4), it is BOP . 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.
• In either case, because the switchpoint is immediately passed as soon as it is established, the A1667 enables switching:
--If on the low side, at BRP (position 2) the output would switch from low to high. However, because output is already high, no output switching occurs.
At the next switchpoint, where BOP is passed (position 3), the output switches from high to low.
--If on the high side, at BOP (position 4) the output switches from high to low.
As this example demonstrates, initial output switching occurs with the same polarity, regardless of whether the Start Mode Hysteresis is exceeded on the
high side or on the low side.
True Zero-Speed, High Accuracy, Ring Magnet Sensor IC
A1667
11
Allegro MicroSystems, LLC
955 Perimeter Road
Manchester, NH 03103-3353 U.S.A.
www.allegromicro.com
UNDERVOLTAGE LOCKOUT
Whenthesupplyvoltagefallsbelowtheundervoltagelockout
voltage,VCC(UV) , the device enters Reset, where the output
statereturnstothePower-OnState(POS)untilsufficientVCC
is supplied. ICClevelsmaynotmeetdatasheetlimitswhenVCC
<VCC(min). 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must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.
AUTOMATIC OFFSET ADJUST (AOA)
TheAOAcircuitryautomaticallycompensatesfortheeffectsof
chip, magnet, and installation offsets. This circuitry is continu-
ously active, including during both power-on mode and running
mode, compensating for any offset drift (within the Allowable
UserInducedDifferentialOffset).Continuousoperationalso
allows it to compensate for offsets induced by temperature varia-
tions over time.
RUNNING MODE LOCKOUT
The A1667 has a running mode lockout feature to prevent switch-
ing in response to small signals that are characteristic of vibra-
tion signals. The internal logic of the chip considers small signal
amplitudes below a certain level to be vibration. The output is
held to the state prior to lockout until the amplitude of the signal
returns to normal operational levels.
Figure 7. Typical circuit for proper device operation. 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.
AGSmall
AGLarge
AGSmall
AGLarge
Internal Differential
Analog Signal
Response, with AGC
Internal Differential
Analog Signal
Response, without AGC
V+
V+
N N
SS
Target
Ring Magnet
4 3
VCC
VCC VPULLUP
RL
GND TEST
VOUT
CBYPASS
0.1 µF
(Optional)
CL
A1667
12
True Zero-Speed, High Accuracy, Ring Magnet Sensor IC
A1667
12
Allegro MicroSystems, LLC
955 Perimeter Road
Manchester, NH 03103-3353 U.S.A.
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 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 website.)
ThePackageThermalResistance,RθJA, 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, RθJC, is 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)
∆T = PD × RθJA (2)
TJ = TA + ΔT (3)
Forexample,givencommonconditionssuchas:TA= 25°C,
VCC = 12V, ICC = 7.5 mA, and RθJA =177°C/W,then:
PD = VCC × ICC = 12 V × 7.5 mA = 90 mW
∆T = PD × RθJA = 90 mW × 177°C/W = 11.3°C
TJ = TA + ∆T = 25°C + 11.3°C = 36.3°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 RθJA and TA.
Example:ReliabilityforVCC at TA
=
150°C,packageK,usinga
single-layerPCB.
Observetheworst-caseratingsforthedevice,specifically:
RθJA=
177°C/W,TJ(max)
=
165°C,VCC(max)
=
24 V,and
ICC(max) = 12
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 ÷ RθJA = 15°C ÷ 177°C/W = 84.7 mW
Finally,invertequation1withrespecttovoltage:
 VCC(est)=PD(max) ÷ ICC(max) =119mW÷12 mA = 7.1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
RθJA.IfVCC(est)≥VCC(max),thenoperationbetweenVCC(est) and
VCC(max) is reliable under these conditions.
True Zero-Speed, High Accuracy, Ring Magnet Sensor IC
A1667
13
Allegro MicroSystems, LLC
955 Perimeter Road
Manchester, NH 03103-3353 U.S.A.
www.allegromicro.com
Package K, 4-Pin SIP
2 431
E1 E2
1.50
2.20
0.84 REF
1.27 NOM
2.16
MAX
45°
45°
DActive Area Depth, 0.43 ±0.011 mm
Hall elements (E1 and E2); not to scale
D
E
E
E
E
E
B
1.32
Gate and tie bar burr area
A
B
C
Dambar removal protrusion (8×)
A
C
For Reference Only; not for tooling use (reference DWG-9010)
Dimensions in millimeters
Dimensions exclusive of mold flash, gate burrs, and dambar protrusions
Exact case and lead configuration at supplier discretion within limits shown
Standard Branding Reference View
N = Device part number
Y = Last two digits of year of manufacture
W = Week of manufacture
Mold Ejector
Pin Indent
Branded
Face
YYWW
NNNN
1
5.21 +0.08
–0.05
0.38 +0.06
–0.03
3.43 +0.08
–0.05
0.41 +0.07
–0.05
14.73 ±0.51
1.55 ±0.05
Branding scale and appearance at supplier discretion
True Zero-Speed, High Accuracy, Ring Magnet Sensor IC
A1667
14
Allegro MicroSystems, LLC
955 Perimeter Road
Manchester, NH 03103-3353 U.S.A.
www.allegromicro.com
For Reference Only – Not for Tooling Use
(Reference DWG-0000385)
Dimensions in millimeters–NOTTO SCALE
Dimensions exclusive of mold flash, gate burrs, and dambar protrusions
Exact case and lead configuration at supplier discretion within limits shown
SEATING
PLANE
21
21
1
8
1.27 BSC
A
B
B
C
D
E
C
A
D
Branding scale and appearance at supplier discretion
B
B
0.65 1.27
5.60
1.75
0.10
8×
0.25 BSC
4.90 BSC
3.90 BSC
0.41 ±0.10
6.00 BSC
0.21 ±0.04
0.84+0.43
–0.44
8°
0°
0.15+0.10
–0.05
1.62 +0.13
–0.27
8
1.95
2.20
E
E
E1 E2
SEATING PLANE
GAUGE PLANE
PCB Layout Reference View
Standard Branding Reference View
= Device part number
= Supplier emblem
= Last two digits of year of manufacture
= Week of manufacture
= Lot number
N
Y
W
L
NNNNNNN
LLLL
YYWW
Active Area Depth, 0.40 mm NOM
Reference land pattern layout (reference IPC7351 SOIC127P600X175-8M);
all pads a minimum of 0.20 mm from all adjacent pads; adjust as necessary
to meet application process requirements and PCB layout tolerances
Terminal #1 mark area
Hall elements (E1 and E2); not to scale
1.35
Package L, 8-Pin SOIC
True Zero-Speed, High Accuracy, Ring Magnet Sensor IC
A1667
15
Allegro MicroSystems, LLC
955 Perimeter Road
Manchester, NH 03103-3353 U.S.A.
www.allegromicro.com
For the latest version of this document, visit our website:
www.allegromicro.com
Copyright ©2018, 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.
Copies of this document are considered uncontrolled documents.
Revision History
Number Date Description
1 May 13, 2016 Added L package option
2 April 4, 2017 Corrected K package active area depth
3 October 4, 2018 Corrected L package Hall element spacing; minor editorial updates