A1684 Datasheet

A1684LUB
Two-Wire, Zero-Speed, High Accuracy
Differential Sensor IC
FEATURES AND BENEFITS
• Integrated capacitor reduces requirement for external
EMI protection component
• Fully optimized differential digital ring magnet and
gear tooth sensor IC
• Running Mode Lockout
• Unique algorithms to assist in mitigation of system
anomalies such as vibration
• AGC and reference adjust circuit
• Air gap independent switchpoints
• Digital output representing target mechanical profile
• Precise duty cycle throughout operating temperature
range
• Short power-on time
• True zero-speed operation
• Undervoltage lockout (UVLO)
• Wide operating voltage range
• Internal current regulator for two-wire operation
• Robust test coverage capability using Scan Path
and IDDQ measurement
• AEC-Q100 automotive qualified
Package: 2-pin SIP (suffix UB)
DESCRIPTION
The A1684LUB is an optimized Hall-effect sensing integrated
circuit that provides a user-friendly solution for true zero-speed
digital ring magnet and, when magnetically back-biased, geartooth sensing in two-wire applications. The Hall-effect IC has
been optimized for the automotive environment. This small
package can be used in conjunction with a wide variety of
target shapes and sizes.
The single integrated circuit incorporates a dual element Hall
effect sensor IC and signal processing circuitry that switches
in response to differential magnetic signals created by a ring
magnet, or by a rotating ferromagnetic target when used in
combination with a back-biasing magnet. The device contains
a sophisticated compensating circuit to eliminate magnetic and
system offsets. Digital tracking of the analog signal is used
to achieve true zero-speed operation. Advanced calibration
algorithms are used to adjust the device gain and offset at
power-up, resulting in air gap independent switchpoints, which
greatly improves output accuracy. In addition, advanced running
mode calibration circuits mitigate the effect of system anomalies
such as target vibration and sudden changes in air gap.
The regulated current output is configured for two-wire
operation. When configured with a back-biasing magnet, this
sensor IC is ideal for obtaining edge and duty cycle information
in gear-tooth–based applications such as transmission speed.
The A1684 is provided in a 2-pin miniature SIP package (suffix
UB) that is lead (Pb) free, with 100% matte tin leadframe plating.
Not to scale
VCC
Voltage
Regulator
PDAC
Hall
Amp
Offset
Adjust
AGC
NDAC
Synchronous Digital Controller
GND
Functional Block Diagram
A1684LUB-DS, Rev. 5
Reference
Generator
and
Lockout
Two-Wire, Zero-Speed, High Accuracy
Differential Sensor IC
A1684LUB
SPECIFICATIONS
SELECTION GUIDE
Part Number
A1684LUBTN-T
Packing*
Tape and reel
*Contact Allegro™ for additional packing options
ABSOLUTE MAXIMUM RATINGS
Characteristic
Symbol
Supply Voltage
VCC
Reverse Supply Voltage
VRCC
Notes
Rating
Units
26.5
V
–18
V
–40 to 150
ºC
Operating Ambient Temperature
TA
Maximum Junction Temperature
TJ(max)
165
ºC
Tstg
–65 to 170
ºC
Rating
Units
10000
pF
Storage Temperature
Range L, refer to Power Derating Curve
INTERNAL DISCRETE CAPACITOR RATINGS
Characteristic
Symbol
Nominal Capacitance
CSUPPLY
Notes
Connected between VCC and GND
PINOUT DIAGRAM AND TERMINAL LIST TABLE
Terminal List Table
Number
1
Name
Function
1
VCC
Supply voltage
2
GND
Ground
2
Package UB, 2-Pin SIP Pin-out Diagram
Allegro MicroSystems, LLC
115 Northeast Cutoff
Worcester, Massachusetts 01615-0036 U.S.A.
1.508.853.5000; www.allegromicro.com
2
Two-Wire, Zero-Speed, High Accuracy
Differential Sensor IC
A1684LUB
OPERATING CHARACTERISTICS: VCC and TA within specification, unless otherwise noted
Characteristics
Symbol
Test Conditions
Min.
Typ.1
Max.
Unit2
4.0
–
24
V
–
3.5
3.95
V
ELECTRICAL CHARACTERISTICS
Supply Voltage3
Undervoltage Lockout
Reverse Supply
Operating, TJ < TJ (max), required across pin 1
to pin 2
VCC
VCC(UV)
Current4
IRCC
Supply Zener Clamp Voltage5
Supply Zener Current
Supply Current
Supply Current Ratio
VCC 0 → 5 V or 5 → 0 V
VCC = –18 V
–
–
–10
mA
VZ
ICC = ICC (max) + 3 mA, TA = 25°C
28
–
–
V
IZ
TA = 25°C, VCC = 28 V
–
–
19
mA
ICC(Low)
Low-current state
4
6
8
mA
ICC(High)
High-current state
12
14
16
mA
ICC(High)
/ ICC(Low)
Ratio of high current to low current
1.85
–
3.05
–
POWER-ON STATE CHARACTERISTICS
Power-On Time6
tPO
Power-On State7
POS
VCC > VCC (min), fOP < 100 Hz
–
1
2
ms
t > tPO
–
ICC(High)
–
A
OUTPUT STAGE
Output Rise Time8
tr
Corresponds to measured output slew rate, from
10% to 90% ICC level, CSUPPLY, RSENSE = 100 Ω
0
2
4
μs
Output Fall Time8
tf
Corresponds to measured output slew rate, from
90% to 10% ICC level, CSUPPLY, RSENSE = 100 Ω
0
2
4
μs
0
–
12
kHz
PERFORMANCE CHARACTERISTICS
Operating Frequency
fOP
Analog Signal Bandwidth
BW
16
20
–
kHz
–
70
–
%
Operate Point
BOP
% of peak-to-peak BSIG , AGOP within
specification
Release Point
BRP
% of peak-to-peak BSIG , AGOP within
specification
–
30
–
%
Running Mode Lockout Enable
Threshold
VLOE(RM)
At peak-to-peak VPROC < VLOE(RM) , output
switching disables
–
170
–
mV
Running Mode Lockout Release
Threshold
VLOR(RM)
At peak-to-peak VPROC > VLOR(RM) , output
switching enables
–
200
–
mV
Continued on the next page…
I+
%
ICC(High)
100
90
10
0
ICC(Low)
tr
tf
Definition of Output Rise Time and Output Fall Time
Output Rise Time (tr) and Fall Time (tf)
VOUT (V)
Output High
Allegro MicroSystems, LLC
115 Northeast Cutoff
Worcester, Massachusetts 01615-0036 U.S.A.
1.508.853.5000; www.allegromicro.com
3
Two-Wire, Zero-Speed, High Accuracy
Differential Sensor IC
A1684LUB
OPERATING CHARACTERISTICS: VCC and TA within specification, unless otherwise noted
Characteristics
Symbol
Test Conditions
Min.
Typ.1
Max.
Unit2
CALIBRATION
Start Mode Hysteresis
Initial Calibration9
POHYS
–
VLOR(RM)
–
mV
CALI
Rising output (current) edges, fOP < 200 Hz
–
–
3
edges
BSIG
Differential magnetic signal
50
–
1500
GPK-PK
30
–
–
GPK-PK
–100
–
+100
G
–
45
–
%
FUNCTIONAL CHARACTERISTICS
Operating Signal Range
Extended Operating Signal Range
BSIGEXT
Differential magnetic signal, output switching (no
missed edges), duty cycle not guaranteed
Allowable User-Induced Differential
Offset
BDIFFEXT
Operation within specification
Maximum Sudden Signal Amplitude
Change
BSIG(INST)
Instantaneous symmetric magnetic signal
amplitude change, measured as a percentage of
peak-to-peak BSIG, fOP < 500 Hz
1 Typical
values are at TA = 25°C and VCC = 12 V. Performance may vary for individual units, within the specified maximum and minimum limits.
G (gauss) = 0.1 mT (millitesla).
3 Maximum voltage must be adjusted for power dissipation and junction temperature; see Power Derating section.
4 Negative current is defined as conventional current coming out of (sourced from) the specified device terminal.
5 Sustained voltages beyond the clamp voltage may cause permanent damage to the IC.
6 Measured from V
CC ≥ VCC (min) to the time when the device is able to switch the output signal in response to a magnetic stimulus.
7 Please refer to the Functional Description, Power-On section.
8 Guaranteed by device characterization.
9 For power-on frequency, f
OP < 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.
21
Allegro MicroSystems, LLC
115 Northeast Cutoff
Worcester, Massachusetts 01615-0036 U.S.A.
1.508.853.5000; www.allegromicro.com
4
Two-Wire, Zero-Speed, High Accuracy
Differential Sensor IC
A1684LUB
THERMAL CHARACTERISTICS: May require derating at maximum conditions; see application information
Characteristic
Symbol
Package Thermal Resistance
Test Conditions*
RθJA
On 1-layer PCB, with copper limited to solder pads
Value
Units
213
ºC/W
*Additional thermal data available on the Allegro Web site.
Power Derating Curve
Maximum Allowable VCC (V)
25
VCC(max)
20
15
10
5
0
VCC(min)
20
40
60
80
100
120
140
160
180
Temperature (°C)
Power Dissipation versus Ambient Temperature
900
Power Dissipation, PD (mW)
800
700
600
500
400
300
200
100
0
20
40
60
80
100
120
140
160
Ambient Temperature, TA (°C)
Allegro MicroSystems, LLC
115 Northeast Cutoff
Worcester, Massachusetts 01615-0036 U.S.A.
1.508.853.5000; www.allegromicro.com
5
Two-Wire, Zero-Speed, High Accuracy
Differential Sensor IC
A1684LUB
FUNCTIONAL DESCRIPTION
Sensing Technology
The A1684 sensor IC contains a single-chip differential Halleffect circuit. As shown in Figure 1, the circuit supports two Hall
elements (spaced at a 2.2 mm pitch), which simultaneously sense
the magnetic profile of a ring magnet, or when coupled with a
back-biasing magnet, the magnetic profile of a ferromagnetic
gear target. The sensed magnetic fields at the two Hall elements
are subtracted one from the other, to generate 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 integrates 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
Mechanical Position (Target moves past device pin 1 to pin 2)
Target
(Radial Ring Magnet)
This pole
sensed earlier
This pole
sensed later
S
N
N
Target Magnetic Profile
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
Under normal operating conditions, the IC is capable of providing digital information that is representative of the mechanical
features of a rotating gear when back biased, or the poles of a
rotating ring magnet. The waveform diagram in Figure 1 presents
the automatic translation of the mechanical profile, through the
magnetic profile that it induces, to the digital output signal of
the A1684. No additional optimization is needed and minimal
processing circuitry is required.
Mechanical Position (Target moves past device pin 1 to pin 2)
This tooth
sensed
earlier
This tooth
sensed
later
Target
(Gear)
Target Magnetic Profile
+B
+B
–B
Device Orientation to Target
IC
(Pin 2 Side)
Device Branded Face
Element Pitch
Device Branded Face
Hall Element 2
Device Orientation to Target
Hall Element 2
Hall Element 1
(Pin 2 Side)
(Pin 1 Side)
Back-biasing
Magnet
(Top View
of Device)
IC Internal Differential Analog Signal, VPROC
BOP(#1)
BRP(#1)
IC Internal Switch State
Off
On
Hall Element 1
(Pin 1 Side)
South Pole
(Top View
of Device)
North Pole
IC Internal Differential Analog Signal, VPROC
BOP(#1)
BOP(#2)
Off
IC
Element Pitch
BRP(#1)
IC Internal Switch State
Off
On
On
IC Output Signal, ICC
BOP(#2)
Off
On
IC Output Signal, ICC
+t
+t
Figure 1: Magnetic Profile Reflecting the Geometry of the Target, Allowing the A1684 to Present an Accurate Digital Output Response.
Allegro MicroSystems, LLC
115 Northeast Cutoff
Worcester, Massachusetts 01615-0036 U.S.A.
1.508.853.5000; www.allegromicro.com
6
Two-Wire, Zero-Speed, High Accuracy
Differential Sensor IC
A1684LUB
Diagnostics
Determining Output Signal Polarity
The regulated current output is configured for two-wire applications, requiring one less wire for operation than do switches with
the traditional open-collector output. Additionally, the system
designer inherently gains diagnostics because there is always
output current flowing, which should be in either of two narrow ranges, shown in Figure 2 as ICC(HIGH) and ICC(LOW). Any
current level not within these ranges indicates a fault condition.
If ICC > ICC(HIGH)(max), then a short condition exists, and if ICC
< ICC(LOW)(min), then an open condition exists. Any value of ICC
between the allowed ranges for ICC(HIGH) and ICC(LOW) indicates
a general fault condition.
In Figure 1, the top of each panel, labeled Mechanical Position,
represents the mechanical features of the target and orientation to
the device. The bottom panels, labeled IC Output Signal, displays
the square waveform corresponding to the digital output signal
(current amplitude) that results from a target configured as shown
in Figure 3. Referring to the target side nearest the face of the
sensor IC, the direction of rotation is: perpendicular to the leads,
across the face of the device, from the pin 1 side to the pin 2 side.
+mA
ICC(HIGH)(max)
ICC(HIGH)(min)
ICC(LOW)(max)
ICC(LOW)(min)
0
Short
Fault

Range for Valid ICC(HIGH)

Range for Valid ICC(LOW)
Rotating Target
BrandedFace
of Device
S
N
S N
Open
RSENSE Location
ICC State
VSENSE State
High side
(VCC pin side)
High
Low
Low
High
PinPin
2 2
Figure 3: Left-to-Right (pin 1 to pin 2) Direction of
Target Rotation.
VS
High
High
Low
Low
ICC
RSENSE
ICC
1
Rotating Target
VSENSE(HighSide)
1
VCC
VCC
A1684
A1684
Pin 1
Pin 4
I+
V+
N
VS
Output Polarity States
ICC
S
SN
Pin 1
Figure 2: Diagnostic Characteristics of Supply Current
Values.
Low side
(GND pin side)
In order to read the output signal as a voltage, VSENSE , a sense
resistor, RSENSE , can be placed on either the VCC signal or on
the GND signal. As shown in Figure 4, when RSENSE is placed on
the GND signal, the output signal voltage, VSENSE(LowSide) , is in
phase with ICC . When RSENSE is placed on the VCC signal, the
output signal voltage, VSENSE(HighSide) , is inverted relative to ICC .
GND
2
VSENSE(LowSide)
VSENSE(LowSide)
Backbiasing magnet with
south pole adjacent to devi
Branded Face
of Device
GND
2
RSENSE
V+
VSENSE(HighSide)
A
B
Figure 4: Alternative Polarity Configurations Using Two-Wire Sensing
The Output Polarity States table provides the permutations of output voltage relative to ICC, given alternative locations for RSENSE. Panel A
shows the low-side, VSENSE(LowSide) , sensing configuration, and panel B shows the high-side, VSENSE(HighSide) , configuration. As shown by the
current and voltage square waves on the left side, VSENSE(LowSide) is in phase with ICC , and VSENSE(HighSide) , is inverted.
Allegro MicroSystems, LLC
115 Northeast Cutoff
Worcester, Massachusetts 01615-0036 U.S.A.
1.508.853.5000; www.allegromicro.com
7
Two-Wire, Zero-Speed, High Accuracy
Differential Sensor IC
A1684LUB
Continuous Update of Switchpoints
the output state changes from low to high.
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 ,
As shown in Figure 5, threshold levels for the switchpoints are
established as a function of the peak input signal levels. The
device 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, VPROC,
typically resulting in the IC
V+
Smaller
TEAG
IC
Target
Smaller
TEAG
Hysteresis Band
(Delimited by switchpoints)
Larger
TEAG
IC
Larger
TEAG
VPROC (V)
Target
Smaller
TEAG
0
Target Rotation (°)
360
(C) Internal analog signal, VPROC, representing
magnetic field for digital output
V+
BOP
VPROC (V)
BOP
BRP
BOP
BRP
BOP
BOP
BRP
BRP
ICC (V)
BRP
BOP
Figure 5: Continuous Update Algorithm
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.
Allegro MicroSystems, LLC
115 Northeast Cutoff
Worcester, Massachusetts 01615-0036 U.S.A.
1.508.853.5000; www.allegromicro.com
8
Two-Wire, Zero-Speed, High Accuracy
Differential Sensor IC
A1684LUB
Power-On
The A1684 is guaranteed to power-on in the high current state,
ICC(High) . When power (VCC > VCC (min) ) is applied to the
device, a short period of time is required to power the various
portions of the circuit. During this period, the A1684 will poweron 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, CALI . However, this period allows the device to optimize
for running mode operation. As shown in Figure 6 (assuming
the south magnetic pole of a back-biasing magnet is adjacent
to the rear of the A1684 case), the first three high peak signals
corresponding to rising output edges are used to calibrate AGC
(Automatic Gain Control). There is a slight variance in the duration of initialization, depending on what target feature is opposite
the sensor IC when power-on occurs. Also, a high speed of target
rotation at power-on may increase the quantity of output edges
required in the CALI period.
Target
(Gear)
3
4
VPR
OC
Power-on 1
opposite
tooth
Start Mode
Hysteresis
Overcome
OC
2
1
VPR
Device
Position
AGC Calibration
Running Mode
ICC
Start Mode
Hysteresis
Overcome
VPR
VPR
OC
Power-on
at falling
2
mechanical
edge
OC
ICC
AGC Calibration
Running Mode
ICC
Start Mode
Hysteresis
Overcome
VPR
VPR
OC
Power-on
opposite 3
valley
OC
ICC
AGC Calibration
Running Mode
ICC
OC
VPR
Start Mode
Hysteresis
Overcome
VPR
Power-on
4
at rising
mechanical
edge
OC
ICC
AGC Calibration
ICC
Running Mode
ICC
Figure 6: Power-On Initial Edge Detection.
This figure demonstrates four typical power-on scenarios. All of these examples assume a south magnetic pole of a back-biasing magnet
is adjacent to the rear of the A1684 case. 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 when fOP ≤ 200 Hz, and more may be required at
greater speeds.
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115 Northeast Cutoff
Worcester, Massachusetts 01615-0036 U.S.A.
1.508.853.5000; www.allegromicro.com
9
Two-Wire, Zero-Speed, High Accuracy
Differential Sensor IC
A1684LUB
Start Mode Hysteresis
A typical scenario is shown in Figure 7 (assuming the south
magnetic pole of a back-biasing magnet is adjacent to the rear
of the A1684 case). 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 A1684 starts to
compute switchpoints.
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 device on such
spurious signals. Calibration can be performed using the actual
target features.
Target (Gear)
Target Magnetic Profile
IC Position
Relative to Target
Differential Signal, VPROC
2
1
3
4
BOP(initial)
BRP
Start Mode
Hysteresis, POHYS
BOP
BRP
BRP(initial)
Output Signal, ICC
If exceed POHYS
on high side
If exceed POHYS
on low side
Figure 7: Operation of Start Mode Hysteresis
(assumes the south magnetic pole of a back-biasing magnet is adjacent to the rear of the A1684 case)
• At power-on (position 1), the A1684 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 rising through the limit on the high side (position 2), the switchpoint is BOP , and if VPROC is falling
through the limit on the low side (position 4), it is BRP . 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 (BOP or BRP), because the switchpoint is immediately passed as soon as it is established, the A1684 enables switching:
▫ If on the high side, at BOP (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 BRP is passed (position 3), the output switches from high to low.
▫ If on the low side, at BRP (position 4) the output switches from high to low.
Allegro MicroSystems, LLC
115 Northeast Cutoff
Worcester, Massachusetts 01615-0036 U.S.A.
1.508.853.5000; www.allegromicro.com
10
Two-Wire, Zero-Speed, High Accuracy
Differential Sensor IC
A1684LUB
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 gradient from the target. This lockout
feature prevents false signals, caused by undervoltage conditions,
from propagating to the output of the device. Because VCC is
below the VCC(min) specification during lockout, the ICC levels
may not be within specification.
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 8 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 is then automatically adjusted. Figure 9 illustrates the effect of this feature.
Running Mode Gain Adjust
The A1684 has a feature during Running mode to compensate
for dynamic air gap variation. If the system increases the mag-
netic input drastically, the device will gradually readjust the gain
downwards, allowing the chip to regain the optimum internal
electrical signal with the new, larger, magnetic signal.
Dynamic Offset Cancellation (DOC)
The offset circuitry when combined with AGC automatically
reduces the effects of chip, magnet, and installation offsets. This
circuitry is continuously active, including both Power-on mode
and Running mode, compensating for any offset drift (within
Allowable User-Induced Differential Offset). Continuous operation also allows it to compensate for offsets induced by temperature variations over time.
Running Mode Lockout
The A1684 has a Running mode lockout feature to prevent
switching on small signals that are characteristic of vibration
signals. The internal logic of the chip evaluates small signal
amplitudes below a certain level to be vibration. In that event, the
output is blanked (locked-out) until the amplitude of the signal
returns to normal operating levels.
Watchdog
The A1684 employs a watchdog circuit to prevent extended loss
of output switching during sudden impulses and vibration in the
system. If the system changes the magnetic input drastically such
that target feature detection is terminated, the device will fully
reset itself, allowing the chip to recalibrate properly on the new
magnetic input signal.
Ferrous Target
Mechanical Profile
VS
1
V+
VCC
Internal Differential
Analog Signal
Response, without AGC
A1684
AGSmall
GND
2
RSENSE
100 AGLarge
V+
CLOAD
Internal Differential
Analog Signal
Response, with AGC
AGSmall
AGLarge
Figure 9: Automatic Gain Control (AGC)
Figure 8: Typical Circuit for Proper Device Operation
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
Two-Wire, Zero-Speed, High Accuracy
Differential Sensor IC
A1684LUB
CHARACTERISTIC PERFORMANCE
SUPPLY CURRENT
Supply Current (High) versus Ambient Temperature
Supply Current (High) versus Supply Voltage
16.0
16.0
15.5
15.5
VCC (V)
14.5
4
14.0
12
13.5
24
13.0
15.0
ICC(HIGH) (mA)
ICC(HIGH) (mA)
15.0
12.5
TA (°C)
14.5
-40
14.0
25
13.5
150
13.0
12.5
12.0
12.0
-60
-40
-20
0
20
40
60
TA (°C)
80
100
120
140
2
160
Supply Current (Low) versus Ambient Temperature
10
14
VCC (V)
18
22
26
Supply Current (Low) versus Supply Voltage
8.0
8.0
7.5
7.5
7.0
VCC (V)
6.5
4
6.0
12
5.5
24
5.0
4.5
7.0
ICC(LOW) (mA)
ICC(LOW) (mA)
6
TA (°C)
6.5
-40
6.0
25
5.5
150
5.0
4.5
4.0
-60
-40
-20
0
20
40
60
TA (°C)
80
100
120
140
160
4.0
2
6
10
14
18
22
26
VCC (V)
Allegro MicroSystems, LLC
115 Northeast Cutoff
Worcester, Massachusetts 01615-0036 U.S.A.
1.508.853.5000; www.allegromicro.com
12
Two-Wire, Zero-Speed, High Accuracy
Differential Sensor IC
A1684LUB
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 website.)
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 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)
For example, given common conditions such as: TA= 25°C,
VCC = 12 V, ICC = 6 mA, and RθJA = 213 °C/W, then:
PD = VCC × ICC = 12 V × 6 mA = 72 mW
ΔT = PD × RθJA = 72 mW × 213 °C/W = 15.3°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.
Example: Reliability for UB package VCC at TA = 150°C, using a
minimum-K PCB using a single layer PCB.
Observe the worst-case ratings for the device, specifically: RθJA = 213°C/W, TJ(max) = 165°C, VCC(max) = 24 V, and
ICC(max) = 16 mA.
Calculate the maximum allowable power level, PD(max). First,
invert equation 3:
ΔTmax = 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) = ΔTmax ÷ RθJA
PD(max) = 15°C ÷ 213°C/W = 70.5 mW
Finally, invert equation 1 with respect to voltage:
VCC(est) = PD(max) ÷ ICC(max) = 70.5 mW ÷ 16 mA = 4.4 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.
TJ = TA + ΔT = 25°C + 15.3°C = 40.3°C
Allegro MicroSystems, LLC
115 Northeast Cutoff
Worcester, Massachusetts 01615-0036 U.S.A.
1.508.853.5000; www.allegromicro.com
13
Two-Wire, Zero-Speed, High Accuracy
Differential Sensor IC
A1684LUB
PACKAGE OUTLINE DRAWING
For Reference Only – Not for Tooling Use
(Reference DWG-9070)
Dimensions in millimeters
Dimensions exclusive of mold flash, gate burrs, and dambar protrusions
Exact case and lead configuration at supplier discretion within limits shown
+0.06
4.00 –0.05
B
4 × 10°
E
1.50
1.50 ±0.05
E
1.25
C
1.34 E
4.00
+0.06
–0.07
E E1
Mold Ejector
Pin Indent
E2 E
Branded
Face
A
4 × 2.50 REF
0.25 REF
0.30 REF
NNN
YYWW
LLLL
45°
0.85 ±0.07
0.42 ±0.10
D Standard Branding Reference View
2.54 REF
N
Y
W
L
4 × 0.85 REF
1
2
1.00 ±0.10
12.20 ±0.10
+0.05
0.25 –0.03
4 × 7.37 REF
1.80
±0.10
0.38 REF
= Supplier emblem
= Last three digits of device part number
= Last 2 digits of year of manufacture
= Week of manufacture
= Lot number
A
Dambar removal protrusion (8×)
B
Gate and tie bar burr area
C
Active Area Depth, 0.38 mm REF
D
Branding scale and appearance at supplier discretion
E
Hall elements (E1 and E2); not to scale
F
Molded Lead Bar for preventing damage to leads during shipment
0.25 REF
4 × 0.85 REF
0.85 ±0.07
1.80
+0.06
–0.07
F
4.00
+0.06
–0.05
1.50 ±0.05
Figure 10: Package UB, 2-Pin SIP
Allegro MicroSystems, LLC
115 Northeast Cutoff
Worcester, Massachusetts 01615-0036 U.S.A.
1.508.853.5000; www.allegromicro.com
14
Two-Wire, Zero-Speed, High Accuracy
Differential Sensor IC
A1684LUB
Revision History
Revision
Date
–
March 7, 2014
1
October 7, 2014
2
December 15, 2014
3
March 24, 2015
4
December 7, 2015
5
March 1, 2016
Change
Initial release
Updated Package Outline Drawing and reformatted document (was Rev. 0.1).
Updated CSUPPLY, tr , tf , and package drawing (was Rev. 0.2).
Updated branding on Package Outline Drawing (was Rev. 0.3).
Added AEC-Q100 qualified bullet to Features and Benefits (was Rev. 0.4)
Updated Package Outline Drawing molded lead bar footnote, Internal Discrete Capacitor Ratings table, corrected
Characteristic Performance labels, and renumbered revisions.
Copyright ©2016, 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
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