The A1180, A1181, A1182, and A1183 devices are sensitive, two-wire, unipolar,
Hall effect switches. The operate point, BOP, can be fi eld-programmed, after fi nal
3
NC
packaging of the sensor and placement into the application. This advanced feature
allows the optimization of the sensor switching performance, by effectively
accounting for variations caused by mounting tolerances for the device and the
target magnet.
This family of devices are produced on the Allegro MicroSystems advanced
BiCMOS wafer fabrication process, which implements a patented, high-frequency,
chopper-stabilization technique that achieves magnetic stability and eliminates
the offsets that are inherent in single-element devices exposed to harsh application environments. Commonly found in a number of automotive applications,
the A1180-83 family of devices are utilized to sense: seat track position, seat belt
buckle presence, hood/trunk latching, and shift selector position.
1. VCC
2. GND
3. GND
123
AB SO LUTE MAX I MUM RAT INGS
Supply Voltage, V
Reverse-Supply Voltage, V
Magnetic Flux Density, B.........................Unlimited
Operating Temperature
Ambient, T
Ambient, T
Maximum Junction, T
Storage Temperature, T
..........................................28 V
CC
, Range E..................–40ºC to 85ºC
A
, Range L................–40ºC to 150ºC
A
........................–18 V
RCC
........................165ºC
J(max)
.................. –65ºC to 170ºC
S
Two-wire unipolar switches are particularly advantageous in price-sensitive applications, because they require one less wire than the more traditional open-collector output switches. Additionally, the system designer gains inherent diagnostics
because output current normally fl ows in either of two narrowly-specifi ed ranges.
Any output current level outside of these two ranges is a fault condition. The
A1180-83 family of devices also features on-chip transient protection, and a Zener
clamp to protect against overvoltage conditions on the supply line.
The output currents of the A1181 and A1183 switch
HIGH in the presence of a south
polarity magnetic fi eld of suffi cient strength; and switch LOW otherwise, including
when there is no signifi cant magnetic fi eld present. The A1180 and A1182 have
inverted output current levels: switching LOW in the presence of a south polarity
magnetic fi eld of suffi cient strength, and HIGH otherwise. The devices also differ in
their specifi ed LOW current supply levels.
Both devices are offered in two package styles: LH, a SOT-23W miniature lowprofi le package for surface-mount applications, and UA, a three-lead ultramini
Single Inline Package (SIP) for through-hole mounting. Each package is available
in a lead (Pb) free version (suffi x, –T) with 100% matte tin plated leadframe.
Factory-programmed versions are also available. Refer to: A1140, A1141, A1142,
A1143, A1145, and A1146.
Sensitive Two-Wire Field-Programmable Chopper-Stabilized Unipolar Hall Effect Switches
Product Selection Guide
Part Number
A1180ELHLT–
A1180ELHLT-TYes
A1180EUA–
A1180EUA-TYes
A1180LLHLT–
A1180LLHLT-TYes
A1180LUA–
A1180LUA-TYes
A1181ELHLT–
A1181ELHLT-TYes
A1181EUA–
A1181EUA-TYes
A1181LLHLT–
A1181LLHLT-TYes
A1181LUA–
A1181LUA-TYes
A1182ELHLT
A1182ELHLT-TYes
A1182EUA–
A1182EUA-TYes
A1182LLHLT–
A1182LLHLT-TYes
A1182LUA–
A1182LUA-TYes
A1183ELHLT
A1183ELHLT-TYes
A1183EUA–
A1183EUA-TYes
A1183LLHLT–
A1183LLHLT-TYes
A1183LUA–
A1183LUA-TYes
1
Contact Allegro for additional packing options.
2
South (+) magnetic fields must be of sufficient strength.
3
These variants are in production but have been determined to be NOT FOR NEW DESIGN. This classification indicates that sale of this device is cur-
Pb-
free
7-in. reel, 3000 pieces/reelSurface mount
Bulk, 500 pieces/bag4-pin SIP through hole
7-in. reel, 3000 pieces/reelSurface mount
Bulk, 500 pieces/bag4-pin SIP through hole
7-in. reel, 3000 pieces/reelSurface mount
Bulk, 500 pieces/bag4-pin SIP through hole
7-in. reel, 3000 pieces/reelSurface mount
Bulk, 500 pieces/bag4-pin SIP through hole
3
–
7-in. reel, 3000 pieces/reelSurface mount
Bulk, 500 pieces/bag4-pin SIP through hole
7-in. reel, 3000 pieces/reelSurface mount
Bulk, 500 pieces/bag4-pin SIP through hole
3
–
7-in. reel, 3000 pieces/reelSurface mount
Bulk, 500 pieces/bag4-pin SIP through hole
7-in. reel, 3000 pieces/reelSurface mount
Bulk, 500 pieces/bag4-pin SIP through hole
Packing
1
Mounting
Ambient, T
(°C)
–40 to 85
–40 to 150
–40 to 85
–40 to 150
–40 to 85
–40 to 150
–40 to 85
–40 to 150
A
Output
South (+) Field
Low
High
Low
High
Supply Current at
Low Output, I
2
(mA)
2 to 5
5 to 6.9
CC(L)
rently restricted to existing customer applications. The device should not be purchased for new design applications because obsolescence in the near
future is probable. Samples are no longer available. Status date change May 2, 2005.
Sensitive Two-Wire Field-Programmable Chopper-Stabilized Unipolar Hall Effect Switches
Functional Description
Operation
The output, I
, of the A1180 and A1182 devices switch low
CC
after the magnetic fi eld at the Hall sensor exceeds the oper-
ate point threshold, BOP. When the magnetic fi eld is reduced to
below the release point threshold, BRP, the device output goes
high. The differences between the magnetic operate and release
point is called the hysteresis of the device, B
. This built-
HYS
I+
I
CC(H)
I
Switch to Low
CC
Switch to High
I
CC(L)
0
B–
RP
B
B
OP
B+
in hysteresis allows clean switching of the output even in the
presence of external mechanical vibration and electrical noise.
The A1181 and A1183 devices switch with opposite polarity for
similar BOP and BRP values, in comparison to the A1180 and
A1183 (see fi gure 1).
I+
I
CC(H)
I
Switch to Low
CC
Switch to High
I
CC(L)
0
B–
RP
B
B
B+
OP
B
HYS
(A) A1180 and A1182
Figure 1. Alternative switching behaviors are available in the A118x device family. On the horizontal axis, the B+ direction indicates
increasing south polarity magnetic fi eld strength, and the B– direction indicates decreasing south polarity fi eld strength (including the
case of increasing north polarity).
Sensitive Two-Wire Field-Programmable Chopper-Stabilized Unipolar Hall Effect Switches
Chopper Stabilization Technique
A limiting factor for switchpoint accuracy when using Hall
effect technology is the small signal voltage developed across
the Hall element. This voltage is proportionally small relative to
the offset that can be produced at the output of the Hall sensor
device. This makes it diffi cult to process the signal and maintain
an accurate, reliable output over the specifi ed temperature and
voltage range.
Chopper stabilization is a unique approach used to minimize
Hall offset on the chip. The Allegro patented technique, dynamic
quadrature offset cancellation, removes key sources of the output
drift induced by temperature and package stress. This offset
reduction technique is based on a signal modulation-demodulation process. The undesired offset signal is separated from the
magnetically induced signal in the frequency domain through
modulation. The subsequent demodulation acts as a modulation
process for the offset causing the magnetically induced signal
to recover its original spectrum at base band while the dc offset
becomes a high frequency signal. Then, using a low-pass fi lter,
the signal passes while the modulated dc offset is suppressed.
The chopper stabilization technique uses a 200 kHz high frequency clock. For demodulation process, a sample-and-hold
technique is used, where the sampling is performed at twice
the chopper frequency (400KHz). The sampling demodulation
process produces higher accuracy and faster signal processing
capability. Using this chopper stabilization approach, the chip is
desensitized to the effects of temperature and stress. This technique produces devices that have an extremely stable quiescent
Hall output voltage, is immune to thermal stress, and has precise
recoverability after temperature cycling. This technique is made
possible through the use of a BiCMOS process which allows the
use of low-offset and low-noise amplifi ers in combination with
high-density logic integration and sample-and-hold circuits.
The repeatability of switching with a magnetic fi eld is slightly
affected using a chopper technique. The Allegro high frequency
chopping approach minimizes the affect of jitter and makes it
imperceptible in most applications. Applications that may notice
the degradation are those that require the precise sensing of alternating magnetic fi elds such as ring magnet speed sensing. For
those applications, Allegro recommends the “low jitter” family
of digital sensors.
Sensitive Two-Wire Field-Programmable Chopper-Stabilized Unipolar Hall Effect Switches
Application Information
For additional general application information, visit the Allegro
MicroSystems Web site at www. allegromicro.com.
Typical Application Circuit
The A118x family of devices must be protected by an external
bypass capacitor, C
and the ground, GND, of the device. C
noise and the noise generated by the chopper-stabilization function. As shown in fi gure 3, a 0.01 μF capacitor is typical.
, connected between the supply, VCC,
BYP
reduces both external
BYP
Installation of C
must ensure that the traces that connect it to
BYP
the A118x pins are no greater than 5 mm in length.
All high-frequency interferences conducted along the supply
lines are passed directly to the load through C
, and it serves
BYP
only to protect the A118x internal circuitry. As a result, the load
ECU (electronic control unit) must have suffi cient protection,
other than C
, installed in parallel with the A118x.
BYP
A series resistor on the supply side, RS (not shown), in combination with C
, creates a fi lter for EMI pulses. (Additional
BYP
information on EMC is provided on the Allegro MicroSystems
Web site.)
When determining the minimum VCC requirement of the A118x
device, the voltage drops across RS and the ECU sense resistor,
R
, must be taken into consideration. The typical value for
Sensitive Two-Wire Field-Programmable Chopper-Stabilized Unipolar Hall Effect Switches
Power Derating
The device must be operated below the maximum junction
temperature of the device, T
. Under certain combinations of
J(max)
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, R
, is a fi gure of merit sum-
θJA
marizing the ability of the application and the device to dissipate
heat from the junction (die), through all paths to the ambient air.
Its primary component is the Effective Thermal Conductivity,
K, of the printed circuit board, including adjacent devices and
traces. Radiation from the die through the device case, R
relatively small component of R
. Ambient air temperature,
θJA
θJC
, is
TA, and air motion are signifi cant 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 × I
ΔT = PD × R
IN
(2)
θJA
(1)
Example: Reliability for V
minimum-K PCB.
Observe the worst-case ratings for the device, specifi cally:
R
165°C/W, T
θJA =
I
CC(max) = 17
J(max) =
mA.
Calculate the maximum allowable power level, P
invert equation 3:
ΔT
max
= T
– TA = 165 °C – 150 °C = 15 °C
J(max)
This provides the allowable increase to TJ resulting from internal
power dissipation. Then, invert equation 2:
P
D(max)
= ΔT
max
÷ R
Finally, invert equation 1 with respect to voltage:
V
CC(est)
= P
D(max)
÷ I
The result indicates that, at TA, the application and device can
dissipate adequate amounts of heat at voltages ≤V
Compare V
CC(est)
to V
able operation between V
R
θJA
V
CC(max)
. If V
is reliable under these conditions.
CC(est)
≥ V
CC(max)
at TA = 150°C, package UA, using
CC
165°C, V
= 15°C ÷ 165 °C/W = 91 mW
θJA
CC(max)
CC(max)
CC(est)
CC(max) =
= 91 mW ÷ 17 mA = 5 V
. If V
CC(est)
and V
24 V, and
≤ V
CC(max)
requires enhanced
CC(max)
, then operation between V
D(max)
CC(est)
, then reli-
. First,
.
CC(est)
and
TJ = TA + ΔT (3)
For example, given common conditions such as: T
V
= 12 V, I
CC
P
= VCC × I
D
ΔT = PD × R
= 4 mA, and R
CC
= 12 V × 4 mA = 48 mW
CC
= 48 mW × 140 °C/W = 7°C
θJA
θJA
= 140 °C/W, then:
TJ = TA + ΔT = 25°C + 7°C = 32°C
A worst-case estimate, P
able power level (V
at a selected R
Sensitive Two-Wire Field-Programmable Chopper-Stabilized Unipolar Hall Effect Switches
Programming Protocol
The operate switchpoint, B
, can be fi eld-programmed. To do
OP
so, a coded series of voltage pulses through the VCC pin is used
to set bitfi elds in onboard registers. The effect on the device
output can be monitored, and the registers can be cleared and
set repeatedly until the required BOP is achieved. To make the
setting permanent, bitfi eld-level solid state fuses are blown, and fi nally, a device-level fuse is blown, blocking any further coding. It is not necessary to program the release switchpoint, BRP ,
because the difference between BOP and BRP , referred to as the
hysteresis, B
The range of values between B
HYS
, is fi xed.
OP(min)
and B
OP(max)
is scaled to
31 increments. The actual change in magnetic fl ux (G) repre-
sented by each increment is indicated by B
(see the Operating
RES
Characteristics table; however, testing is the only method for
verifying the resulting B
). For programming, the 31 incre-
OP
ments are individually identifi ed using 5 data bits, which are
physically represented by 5 bitfi elds in the onboard registers.
By setting these bitfi elds, the corresponding calibration value is
programmed into the device.
Three voltage levels are used in programming the device: a low
voltage, V
, a minimum required to sustain register settings; a
PL
mid-level voltage, VPM , used to increment the address counter
in the device; and a high voltage, VPH , used to separate sets of
VPM pulses (when short in duration) and to blow fuses (when
long in duration). A fourth voltage level, essentially 0 V, is used
to clear the registers between pulse sequences. The pulse values
are shown in the Programming Protocol Characteristics table and
in fi gure 4.
V+
V
PH
V
PM
V
PL
T
0
T
d(1)
Figure 4. Pulse amplitudes and durations
d(P)
T
d(0)
t
Additional information on device programming and programming products is available on www. allegromicro.com. Programming hardware is available for purchase, and programming
software is available free of charge.
Code Programming. Each bitfi eld must be individually set. To
do so, a pulse sequence must be transmitted for each bitfi eld that
is being set to 1. If more than one bitfi eld is being set to 1, all
pulse sequences must be sent, one after the other, without allowing VCC to fall to zero (which clears the registers).
The same pulse sequence is used to provisionally set bitfi elds as
is used to permanently set bitfi eld-level fuses. The only differ-
ence is that when provisionally setting bitfi elds, no fuse-blowing
pulse is sent at the end of the pulse sequence.
PROGRAMMING PROTOCOL CHARACTERISTICS, over operating temperature range, unless otherwise noted
Sensitive Two-Wire Field-Programmable Chopper-Stabilized Unipolar Hall Effect Switches
The pulse sequences consist of the following groups of pulses:
1. An enable sequence.
2. A bitfi eld address sequence.
3. When permanently setting the bitfi eld, a long VPH fuse-blow-
ing pulse. (Note: Blown bit fuses cannot be reset.)
4. When permanently setting the bitfi eld, the level of VCC must
be allowed to drop to zero between each pulse sequence, in
order to clear all registers. However, when provisionally setting bitfi elds, V
must be maintained at VPL between pulse
CC
sequences, in order to maintain the prior bitfi eld settings while
preparing to set additional bitfi elds.
Bitfi elds that are not set are evaluated as zeros. The bitfi eld-level
fuses for 0 value bitfi elds are never blown. This prevents inad-
V+
V
PH
V
PM
V
PL
vertently setting the bitfi eld to 1. Instead, blowing the device-
level fuse protects the 0 bitfi elds from being accidentally set in
the future.
When provisionally trying the calibration value, one pulse
sequence is used, using decimal values. The sequence for setting
the value 5
is shown in fi gure 5.
10
When permanently setting values, the bitfi elds must be set indi-
vidually, and 510 must be programmed as binary 101. Bit 3 is
set to 1 (0001002, which is 410), then bit 1 is set to 1 (0000012,
which is 1
). Bit 2 is ignored, and so remains 0.Two pulse
10
sequences for permanently setting the calibration value 5 are
shown in fi gure 6. The fi nal V
pulse is maintained for a longer
PH
period, enough to blow the corresponding bitfi eld-level fuse.
0
EnableAddressClear
Try 5
10
Optional
Monitoring
t
Figure 5. Pulse sequence to provisionally try calibration value 5.
V+
V
PH
V
PM
V
PL
0
Enable
Address
Encode 001002 (410)
BlowBlowEnable
Encode 00001
Figure 6. Pulse sequence to permanently encode calibration value 5 (101 binary, or
Sensitive Two-Wire Field-Programmable Chopper-Stabilized Unipolar Hall Effect Switches
V+
V
Enabling Addressing Mode. The fi rst segment of code is a
keying sequence used to enable the bitfi eld addressing mode. As
shown in fi gure 7, this segment consists of one short VPH pulse,
one VPM pulse, and one short VPH pulse, with no supply interruptions. This sequence is designed to prevent the device from
being programmed accidentally, such as by noise on the supply
line.
PH
V
PM
V
PL
0
Address Selection. After addressing mode is enabled, the
target bitfi eld address, is indicated by a series of VPM pulses, as
shown in fi gure 8.
Figure 7. Addressing mode enable pulse sequence
t
V+
V
PH
V
PM
V
PL
0
Address 1
Address 2
Address n ( ≤ 31)
t
Figure 8. Pulse sequence to select addresses
V+
V
PH
Falling edge of final BOP address digit
Lock Bit Programming. After the desired B
calibration value
OP
is programmed, and all of the corresponding bitfi eld-level fuses
are blown, the device-level fuse should be blown. To do so, the
lock bit (bitfi eld address 32) should be encoded as 1 and have
its fuse blown. This is done in the same manner as permanently
setting the other bitfi elds, as shown in fi gure 9.
Sensitive Two-Wire Field-Programmable Chopper-Stabilized Unipolar Hall Effect Switches
A1180-DS, Rev. 2
The products described herein are manufactured under one or
more of the following U.S. patents: 5,045,920; 5,264,783; 5,442,283;
5,389,889; 5,581,179; 5,517,112; 5,619,137; 5,621,319; 5,650,719;
5,686,894; 5,694,038; 5,729,130; 5,917,320; and other patents pending.
Allegro MicroSystems, Inc. reserves the right to make, from time to
time, such de par tures from the detail spec i fi ca tions as may be required
to permit improvements in the per for mance, reliability, or manufacturability of its products. Before placing an order, the user is cautioned to
verify that the information being relied upon is current.
Allegro products are not authorized for use as critical components in
life-support devices or sys tems without express written approval.
The in for ma tion in clud ed herein is believed to be ac cu rate and reliable. How ev er, Allegro MicroSystems, Inc. assumes no re spon si bil i ty
for its use; nor for any in fringe ment of patents or other rights of third
parties which may result from its use.