A1357-DS, Rev. 1
MCO-0000602
Features and Benefits
▪Two-wireoutputenablesreducedwiringcostsin
longwiresystems
▪SimultaneousprogrammingofPWMcarrierfrequency,
quiescentdutycycle(QDC),andsensitivityforsystem
optimization
▪FullydifferentialsignalpathincreasesEMCimmunityand
reducesoutputoffsetdrifts
▪Factoryprogrammedsensitivitytemperaturecoefficient
andquiescentdutycycledrift
▪Programmabilityatend-of-line
▪Pulsewidthmodulated(PWM)currentoutputprovides
increasednoiseandEMCimmunitycomparedtoan
analogoutput
▪Preciserecoverabilityaftertemperaturecycling
•Dutycycleclampsprovideshortcircuitdiagnostic
capabilities
▪Optional50%dutycyclecalibrationtestmodeatdevice
powerup
▪Wideambienttemperaturerange:–40°Cto150°C
▪Resistanttomechanicalstress
Two-Wire High Precision Linear Hall-Effect Sensor IC
With Pulse Width Modulated Output Current
Package: 3-pin SIP (suffix KB)
Functional Block Diagram
Not to scale
A1357
Description
TheA1357deviceisahighprecision,programmabletwo-wire
Hall-effect linear sensor IC with a pulse width modulated
(PWM)current.TheA1357deviceconvertsananalogsignal
fromitsinternalHallsensorelementtoadigitallyencoded
PWM signal. The coupled noise immunity of the digitally
encoded PWM is far superior to the noise immunity of an
analogoutputsignal.
TheBiCMOS,monolithiccircuitinsideoftheA1357integrates
aHallelement,precisiontemperature-compensatingcircuitry
toreducetheintrinsicsensitivityandoffsetdriftoftheHall
element, a small-signal high-gain amplifier, proprietary
dynamic offset cancellation circuits, and PWM conversion
circuitry.Thedynamicoffsetcancellationcircuitsreducethe
residualoffsetvoltage ofthe Hall element thatis normally
caused by device overmolding, temperature dependencies,
and thermal stress. The high frequency offset cancellation
(chopping)clock allows for a greatersampling rate, which
increasestheaccuracyoftheoutputcurrentsignalandresults
infastersignalprocessingcapability.
TheA1357sensorisprovidedinalead(Pb)free3-pinsingle
inlinepackage(KBsuffix),with100%matte tinleadframe
plating.
VCC (and
programming)
CBYBASS
VSUPPLY
GND
1
2
2
1
Temperature
Compensation
Chopper
Switches
Voltage Controlled
Current Source
PWM
Frequency Trim
Signal
Recovery
PWM Carrier
Generation
Regulator
Signal
Conditioning
% Duty Cycle
Temperature
Coefficient
% Duty
Cycle
Sensitivity
Trim
Amp
February 19, 2019
Two-Wire High Precision Linear Hall-Effect Sensor IC
With Pulse Width Modulated Output Current
A1357
2
Allegro MicroSystems, LLC
955 Perimeter Road
Manchester, NH 03103-3353 U.S.A.
www.allegromicro.com
Pin-out Diagram
Absolute Maximum Ratings
Characteristic Symbol Notes Rating Unit
Forward Supply Voltage VCC 28 V
Reverse Supply Voltage VRCC –18 V
Forward Supply Current ICC 50 mA
Reverse Supply Current IRCC –50 mA
Operating Ambient Temperature TAL temperature range –40 to 150 ºC
Maximum Junction Temperature TJ(max) 165 ºC
Storage Temperature Tstg VCC = 0 V –65 to 170 ºC
Selection Guide
Part Number Packing*
A1357LKB-T 500 pieces per bag
A1357LKBTN-T 4000 pieces per 13-in. reel
*Contact Allegro™ for additional packing options
2 31
Terminal List Table
Number Name Function
1 VCC Input power supply; use bypass capacitor to connect to ground; also
used for programming
2 GND Ground
3 NC No connect
Two-Wire High Precision Linear Hall-Effect Sensor IC
With Pulse Width Modulated Output Current
A1357
3
Allegro MicroSystems, LLC
955 Perimeter Road
Manchester, NH 03103-3353 U.S.A.
www.allegromicro.com
Continued on the next page…
OPERATING CHARACTERISTICS Valid over full operating temperature range, TA , VCC = 4.5 to 18 V, CBYPASS = 0.1 µF, unless
otherwise noted
Characteristics Symbol Test Conditions Min. Typ. Max. Unit1
Electrical Characteristics
Supply Voltage2VCC 4.5 – 18 V
Supply Current ICC_LOW – 6 8 mA
ICC_HIGH 12 – 16.5 mA
Supply Current Ratio 2 – – –
Supply Zener Clamp Voltage VZsupply ICC = 18 mA, TA = 25ºC 28 – – V
Power-On Time3,4 tPO fpwm = 1 kHz – – 5 ms
Internal Bandwidth BWi
Small signal –3 dB, 100 G(P-P) magnetic input
signal, TA = 25 C° – 400 – Hz
Chopping Frequency5fCTA = 25°C – 200 – kHz
Output Current Characteristics
PWMOUT Rise Time3,4 trVCC pin, No CBYPASS
or RSENSE, TA = 25 C° – 6.5 – mA/µs
PWMOUT Fall Time3,4 tfVCC pin, No CBYPASS
or RSENSE, TA = 25 C° – 6.5 – mA/µs
Maximum Propagation Delay3,4 tPROP TA = 25 C° – 2 3 ms
Response Time3,4 tRESPONSE
Impulse magnetic field of 300 G, fpwm = 1 kHz,
slew rate < 120 G/ms, TA = 25 C° – 2 3.125 ms
Duty Cycle Jitter3,4,6 JitterPWM
Measured over 1000 output PWM clock periods,
3 sigma values, Sens = 60 m% / G, TA = 25 C° – – ±0.090 % D
Clamp Duty Cycle DCLP(HIGH) 90 – 95 % D
DCLP(LOW) 5 – 10 % D
Pre-Programming Target7
Pre-Programming Quiescent Current
Duty Cycle D(Q)PRE B = 0 G, TA = 25°C – 50 – % D
Pre-Programming Sensitivity SensPRE TA = 25°C – 25 – (m% D)/G
Pre-Programming PWMOUT Carrier
Frequency fPWMPRE TA = 25°C – 1.5 – kHz
Quiescent Current Duty Cycle Programming
Initial Quiescent Current Duty Cycle D(Q)init B = 0 G, TA = 25°C – D(Q)PRE – % D
Guaranteed Quiescent Current Duty
Cycle Output Range8D(Q) B = 0 G, TA = 25°C 40 – 60 % D
Quiescent Current Duty Cycle
Programming Bits – 9 – bit
Average Quiescent Current Duty Cycle
Step Size9,10 StepD(Q) TA = 25°C 0.091 0.103 0.115 % D
Quiescent Current Duty Cycle
Programming Resolution11 ErrPGD(Q) TA = 25°C – StepD(Q)
× ±0. 5 – % D
Two-Wire High Precision Linear Hall-Effect Sensor IC
With Pulse Width Modulated Output Current
A1357
4
Allegro MicroSystems, LLC
955 Perimeter Road
Manchester, NH 03103-3353 U.S.A.
www.allegromicro.com
Continued on the next page…
Sensitivity Programming
Initial Sensitivity Sensinit TA = 25°C – SensPRE – (% D)/G
Sensitivity Programming Bits
Range_
Selection TA = 25°C – 1 – bit
Fine TA = 25°C – 8 – bit
Guaranteed Sensitivity Range SensRange1 TA = 25°C 35 – 70 (m% D)/G
SensRange2 TA = 25°C 70 – 145 (m% D)/G
Average Sensitivity Step Size9,10 StepSENS1 TA = 25°C 215 300 375 (µ% D)/G
StepSENS2 TA = 25°C 430 600 750 (µ% D)/G
Sensitivity Programming Resolution11 ErrPGSENS TA = 25°C – StepSENS
× ±0. 5 – (µ% D)/G
Carrier Frequency Programming
Initial Carrier Frequency fPWMinit TA = 25°C – fPWMPRE – Hz
Carrier Frequency Programming Range fPWM TA = 25°C 0.9 1 1.1 kHz
Carrier Frequency Programming Bits – 4 – bit
Average Carrier Frequency Step Size9,10 StepfPWM TA = 25°C 38 54 70 Hz
Carrier Frequency Programming
Resolution11 ErrPGfPWM TA = 25°C – StepfPWM
× ±0. 5 – Hz
Calibration Test Mode
Calibration Test Mode Selection Bit – 1 – bit
Calibration Test Mode Duration4tCAL fPWM = 1 kHz 45 50 55 ms
Output Duty Cycle During Calibration
Mode4DCAL 49 50 51 % D
Lock Bit Programming
Overall Programming Lock Bit LOCK – 1 – bit
Factory Programmed Sensitivity Temperature Coefficient And Drift Characteristics
Sensitivity Temperature Coefficient12 SensTC_
NdFeB
TA = 150°C – 0.11 – %/°C
Sensitivity Drift Through Temperature
Range13 ΔSensTC TA = 150°C – < ±3 – %
Sensitivity Drift Due to Package
Hysteresis3ΔSensPKG TA = 150°C, after temperature cycling – < ±1 – %
OPERATING CHARACTERISTICS (continued) Valid over full operating temperature range, TA , VCC = 4.5 to 18 V,
CBYPASS = 0.1 µF, unless otherwise noted
Characteristics Symbol Test Conditions Min. Typ. Max. Unit
Two-Wire High Precision Linear Hall-Effect Sensor IC
With Pulse Width Modulated Output Current
A1357
5
Allegro MicroSystems, LLC
955 Perimeter Road
Manchester, NH 03103-3353 U.S.A.
www.allegromicro.com
OPERATING CHARACTERISTICS (continued) Valid over full operating temperature range, TA , VCC = 4.5 to 18 V,
CBYPASS = 0.1 µF, unless otherwise noted
Characteristics Symbol Test Conditions Min. Typ. Max. Unit
Factory Programmed Quiescent Current Duty Cycle Drift
Quiescent Current Duty Cycle
Temperature Coefficient12 DTC(Q) TA = 150°C – 0 – (% D)/°C
Quiescent Current Duty Cycle Drift
Through Temperature Range14 ΔD(Q) Sens = SensPRE, TA = 150°C – < ±0.35 – % D
Error Components
Linearity Sensitivity Error LinERR – < ±1.5 – %
Symmetry Sensitivity Error SymERR – < ±1.5 – %
11 G (gauss) = 0.1 mT (millitesla).
2Supply Voltage is the voltage drop between device supply and ground pins. It does not include a drop through a sense resistor.
3See Characteristic Definitions section.
4Guaranteed by design only. Characterized but not tested in production.
5fC varies up to approximately ±20% through the full operating ambient temperature range, TA
, and process.
6Jitter is dependent on the sensitivity of the device.
7Raw device characteristic values before any programming.
8D(Q)(max) is the value available with all programming fuses blown (maximum programming code set). The D(Q) range is the total range from D(Q)(min)
up to and including D(Q)(max). See Characteristic Definitions section.
9Step size is larger than required, in order to provide for manufacturing spread. See Characteristic Definitions section.
10Non-ideal behavior in the programming DAC can cause the step size at each significant bit rollover code to be greater than twice the maximum
specified value of StepD(Q) , StepSENS , or StepfPWM
.
11Overall programming value accuracy. See Characteristic Definitions section.
12Programmed at 150°C and calculated relative to 25°C.
13Sensitivity drift from expected value at TA after programming SENSTC. See Characteristic Definitions section.
14D(Q) drift from expected value at TA after programming DTC(Q).
Two-Wire High Precision Linear Hall-Effect Sensor IC
With Pulse Width Modulated Output Current
A1357
6
Allegro MicroSystems, LLC
955 Perimeter Road
Manchester, NH 03103-3353 U.S.A.
www.allegromicro.com
THERMAL CHARACTERISTICS may require derating at maximum conditions, see application information
Characteristic Symbol Test Conditions* Value Units
Package Thermal Resistance RθJA 1-layer PCB with copper limited to solder pads 177 ºC/W
*Additional thermal data available on the Allegro Web site.
Ambient Temperature, TA (ºC)
Ambient Temperature, TA (ºC)
Maximum Allowable VCC (V)
Power Dissipation, P
D
(mW)
VCC(max)
VCC(min)
20
15
10
5
0
900
800
700
600
500
400
300
200
100
0
20 40 8060 100 120 140 160
20 40 8060 100 120 140 160
Power Dissipation versus Ambient Temperature
Power Derating Curve
Two-Wire High Precision Linear Hall-Effect Sensor IC
With Pulse Width Modulated Output Current
A1357
7
Allegro MicroSystems, LLC
955 Perimeter Road
Manchester, NH 03103-3353 U.S.A.
www.allegromicro.com
Characteristic Definitions
Power-On TimeWhenthesupplyisrampedtoitsoperating
voltage,thedevicerequiresafinitetimetopoweritsinternal
componentsbeforesupplyingavalidPWMoutputduty-cycle.
Power-OnTime,tPO,isdefinedasthetimeittakesfortheoutput
voltagetosettlewithin±10%ofitssteadystatevalueafterthe
powersupplyhasreacheditsminimumspecifiedoperatingvolt-
age,VCC(min).(Seefigure1.)
Propagation DelayTravelingtimeofsignalfrominputHall
platetooutputstageofdevice.(Seefigure2.)
Response Time Thetimeinterval,tRESPONSE
,between
a)whentheappliedmagneticfieldreaches90%ofitsfinalvalue,
andb)whenthesensorICreaches90%ofitsoutputcorrespond-
ingtotheappliedmagneticfield.(Seefigure2.)
PWMOUT Rise TimeThetime,tr
,elapsedbetween10%and
90%oftherisingsignalvaluewhenoutputcurrentswitchesfrom
lowtohighstates.
PWMOUT Fall TimeThetime,tf
,elapsedbetween90%and
10%ofthefallingsignalvaluewhenoutputcurrentswitches
fromhightolowstates.
Quiescent Current Duty CycleInthequiescentstate(no
significantmagneticfield:B=0G),theQuiescentCurrentDuty
Cycle,D(Q),equalsaspecificprogrammeddutycyclethroughout
theentireoperatingrangesofVCCandambienttemperature,TA.
Guaranteed Quiescent Current Duty Cycle RangeThe
QuiescentCurrentDutyCycle,D(Q),canbeprogrammedaround
itsnominalvalueof50%D,withintheGuaranteedQuiescent
DutyCycleRangelimits:D(Q)(min)andD(Q)(max).Theavailable
guaranteedprogrammingrangeforD(Q)fallswithinthedistribu-
tionsoftheminimumandthemaximumprogrammingcodefor
settingD(Q).(Seefigure3.)
Average Quiescent Current Duty Cycle Step SizeThe
AverageQuiescentCurrentDutyCycleStepSize,StepD(Q),fora
singledeviceisdeterminedusingthefollowingcalculation:
D
(Q)
(max)
– D
(Q)
(min)
2
n
–1
StepD(Q) =,(1)
where:
nisthenumberofavailableprogrammingbitsinthetrimrange,
2n–1isthevalueofprogrammingstepsintherange,
D(Q)(max)isthemaximumreachedquiescentdutycycle,and
D(Q)(min)isminimumreachedquiescentdutycycle.
Figure 1. Definition of Power-On Time
Figure 2. Definitions of Propagation Delay and Response Time
Figure 3. Definition of Guaranteed Quiescent Voltage Output Range
Guaranteed D(Q)
Programming
Range
D(Q)(min) D(Q)(max)
Max Code D(Q)
Distribution
Min Code D(Q)
Distribution
Initial D(Q)
Distribution
Time
Time
VCC(min)
tPO
First valid duty cycle
VCC
ICC
Time
B-field
Icc
Propagation
Delay
1 ms
AB
ADC BDC
ADC – DC corresponds to the A field
BDC – DC corresponds to the B field
C
Response
Time
0.9×
C
CDC
CDC – DC corresponds to the 0.9
×
C field
Two-Wire High Precision Linear Hall-Effect Sensor IC
With Pulse Width Modulated Output Current
A1357
8
Allegro MicroSystems, LLC
955 Perimeter Road
Manchester, NH 03103-3353 U.S.A.
www.allegromicro.com
Quiescent Current Duty Cycle Output Programming
ResolutionTheprogrammingresolutionforanydeviceishalf
ofitsprogrammingstepsize.Therefore,thetypicalprogramming
resolutionwillbe:
ErrPGD(Q)(typ) =0.5 × StepD(Q)(typ) .(2)
Quiescent Duty Cycle Output Drift through Tempera-
ture RangeDuetointernalcomponenttolerancesandthermal
considerations,theQuiescentDutyCycleTemperatureCoef-
ficient,DTC(Q),maydriftfromitsnominalvalueovertheoperat-
ingambienttemperature,TA.Forpurposesofspecification,the
QuiescentDutyCycleOutputDriftThroughTemperatureRange,
∆D(Q)(%D),isdefinedas:
D(Q)(TA) – D(Q)(25°C)
∆D(Q) =,(3)
whereD(Q)(TA)isthequiescentdutycyclemeasuredatTAand
D(Q)(25°C)isthequiescentdutycyclemeasuredat25°C.
SensitivityThepresenceofasouthpolaritymagneticfield,
perpendiculartothebrandedsurfaceofthepackageface,
increasesthecurrentdutycyclefromitsquiescentvaluetoward
themaximumdutycyclelimit.Theamountofthecurrentduty
cycleincreaseisproportionaltothemagnitudeofthemagnetic
fieldapplied.Conversely,theapplicationofanorthpolarity
fielddecreasesthecurrentdutycyclefromitsquiescentvalue.
ThisproportionalityisspecifiedasthemagneticSensitiv-
ity,Sens((%D)/G),ofthedevice,anditisdefinedforbipolar
devicesas:
D(BPOS) – D(BNEG)
BPOS – BNEG
Sens =,(4)
andforunipolardevicesas:
D(BPOS) – D(Q)
BPOS
Sens =,(5)
whereBPOSandBNEGaretwomagneticfieldswithopposite
polarities.
Guaranteed Sensitivity RangeThemagneticSensitivitycan
beprogrammedfromitsinitialvalue,Sensinit,toavaluewithin
theGuaranteedSensitivityRangelimits:SensRange(min)and
SensRange(max).
Average Sensitivity Step SizeRefertotheAverageQui-
escentCurrentDutyCycleStepSizesectionforaconceptual
explanation.
Sensitivity Programming ResolutionRefertotheQuies-
centCurrentDutyCycleProgrammingResolutionsectionfora
conceptualexplanation.
Carrier Frequency TargetThePWMOUTsignalCarrier
FrequencyProgrammingRange,fPWM,canbeprogrammedtoits
typicalvalueof1kHz.
Average Carrier Frequency Step SizeRefertotheAverage
QuiescentCurrentDutyCycleStepSizesectionforaconceptual
explanation.
Carrier Frequency Programming ResolutionRefertothe
QuiescentDurrentDutyCycleProgrammingResolutionsection
foraconceptualexplanation.
Sensitivity Temperature CoefficientDevicesensitiv-
itychangesastemperaturechanges,withrespecttoitspro-
grammedSensitivityTemperatureCoefficient,SensTC.SensTC
isprogrammedat150°C,andcalculatedrelativetothenominal
sensitivityprogrammingtemperatureof25°C.SensTC(%/°C)is
definedas:
SensT2 – SensT1
SensT1 T2–T1
1
SensTC =×
100% ,
(6)
whereT1isthenominalSensprogrammingtemperatureof25°C,
andT2istheprogrammingtemperatureof150°C.Theexpected
valueofSensthroughthefullambienttemperaturerange,
SensEXPECTED(TA),isdefinedas:
SensT1× [100% +SensTC (TA –T1)]
SensEXPECTED(TA) =.
100 % (7)
SensEXPECTED(TA)shouldbecalculatedusingtheactualmeasured
valuesofSensT1andSensTCratherthanprogrammingtarget
values.
Sensitivity Drift Through Temperature RangeSecond
orderSensitivityTemperatureCoefficienteffectscausethemag-
neticSensitivity,Sens,todriftfromitsexpectedvaluethrough
theoperatingambienttemperaturerange,TA.Forpurposesof
specification,theSensitivityDriftThroughTemperatureRange,
∆SensTC
,isdefinedas:
SensTA – SensEXPECTED(TA)
SensEXPECTED(TA)
∆SensTC =×
100% .
(8)
Sensitivity Drift Due to Package HysteresisPackage
stressandrelaxationcancausethedeviceSensitivityatTA=
25°Ctochangeduringandaftertemperaturecycling.
Two-Wire High Precision Linear Hall-Effect Sensor IC
With Pulse Width Modulated Output Current
A1357
9
Allegro MicroSystems, LLC
955 Perimeter Road
Manchester, NH 03103-3353 U.S.A.
www.allegromicro.com
Forpurposesofspecification,theSensitivityDriftDuetoPack-
ageHysteresis,∆SensPKG,isdefinedas:
Sens(25°C)2 – Sens(25°C)1
Sens(25°C)1
∆SensPKG =×
100% ,
(9)
whereSens(25°C)1istheprogrammedvalueofsensitivityatTA=
25°C,andSens(25°C)2isthevalueofsensitivityatTA=25°C,
aftertemperaturecyclingTAupto150°C,downto–40°C,and
backtoup25°C.
Linearity Sensitivity ErrorTheA1357isdesignedtoprovide
alinearcurrentoutputinresponsetoarampingappliedmagnetic
field.Considertwomagneticfields,B1andB2.Ideally,thesen-
sitivityofadeviceisthesameforbothfields,foragivensupply
voltageandtemperature.Linearityerrorispresentwhenthereisa
differencebetweenthesensitivitiesmeasuredatB1andB2.
LinearitySensitivityErroriscalculatedseparatelyforthepositive
(LinERRPOS)andnegative(LinERRNEG)appliedmagneticfields.
Linearityerror(%)ismeasuredanddefinedas:
SensBPOS2
SensBPOS1
SensBNEG2
SensBNEG1
1–
LinERRPOS =×
100% ,
1–
LinERRNEG =×
100% ,
(10)
where:
|D(Bx) – D(Q)|
Bx
SensBx=.
(11)
andBPOSxandBNEGxarepositiveandnegativemagneticfields,
withrespecttothequiescentcurrentdutycyclesuchthatBPOS2=
2×BPOS1andBNEG2=2×BNEG1.
Then:
LinERR max(
LinERRPOS
, LinERRNEG)
=.
(12)
Notethatunipolardevicesonlyhavepositivelinearityerror
(LinERRPOS).
Symmetry Sensitivity ErrorThemagneticsensitivityofthe
A1357deviceisconstantforanytwoappliedmagneticfieldsof
equalmagnitudeandoppositepolarities.SymmetrySensitivity
Error,SymERR(%),ismeasuredanddefinedas:
Sens
BPOS
SensBNEG
1–
SymERR =×
100% ,
(13)
whereSensBxisasdefinedinequation11,andBPOSandBNEG
arepositiveandnegativemagneticfieldssuchthat|BPOS|=
|BNEG|.NotethattheSymmetrySensitivityErrorspecificationis
validonlyforbipolardevices.
Duty Cycle JitterThedutycycleofthePWMOUToutputmay
varyslightlyovertimedespitethepresenceofaconstantapplied
magneticfieldandaconstantCarrierFrequency,fPWM,forthe
PWMOUTsignal.Thisphenomenonisknownasjitter,andis
definedas:
JitterPWM = ,
3 σ
DBi±
1
n
n
i=1 (14)
whereDB1,…,DBnarethesampleddutycyclesinaconstant
appliedmagneticfield,B,measuredover1000PWMclockperi-
ods,andJitterPWMisgivenin%D.
Two-Wire High Precision Linear Hall-Effect Sensor IC
With Pulse Width Modulated Output Current
A1357
10
Allegro MicroSystems, LLC
955 Perimeter Road
Manchester, NH 03103-3353 U.S.A.
www.allegromicro.com
Typical Application Circuit
GND
A1357
VCC
1
2
VSUPPLY
RSENSE
CBYPASS
0.1 µF
GND
A1357
VCC
1
2
VSUPPLY
RSENSE
CBYPASS
0.1 µF
ThecurrentswitchingperformedbytheHallsensorICcanbe
observedasvoltageswitching.Todoso,placeasenseresistor,
RSENSE,betweenthesupplyandtheA1357VCCpin(seefigure
4),orbetweentheA1357GNDpinandground(figure5).There
isanadvantagetoputtingthesenseresistorbetweenthesupply
andtheA1357VCCpin,becausetheresistorcanthenprovide
additionaldeviceprotectionfromsupplytransients.
WhenspecifyingvalueoftheRSENSEandtheappliedsupplyvolt-
ageintheapplication,thefollowingequationmustbeapplied,in
ordertoprovideenoughvoltagetoallowtheA1357topower-up:
VSUPPLY>RSENSE×ICC_HIGH(max)+VCC(min), (15)
whereICC(max)isthemaximumA1357supplycurrentand
VCC(min)istheA1357minimumsupplyvoltage.
Substitutingintoequation15:
12V>RSENSE×16.5mA+4.5V,
therefore:
RSENSE≤(12–4.5)V/16.5mA
≤454Ω.
ItcanbeseenthatRSENSEisproportionaltoVSUPPLY.Thehigher
thevalueofRSENSE,thehighertheapplicationsupplyvoltage
required.
TherecommendedminimumCBYPASSvalueis0.01µF.
Figure 4. High-side PWM voltage sensing configuration Figure 5. Low-side PWM voltage sensing configuration
Two-Wire High Precision Linear Hall-Effect Sensor IC
With Pulse Width Modulated Output Current
A1357
11
Allegro MicroSystems, LLC
955 Perimeter Road
Manchester, NH 03103-3353 U.S.A.
www.allegromicro.com
Overview
Programmingisaccomplishedbysendingaseriesofinputvolt-
agepulsesseriallythroughtheVCCpinofthedevice.Aunique
combinationofdifferentvoltagelevelpulsescontrolstheinternal
programminglogicofthedevicetoselectaprogrammable
parameterandchangeitsvalue.Therearethreevoltagelevels
thatmustbetakenintoaccountwhenprogramming.Theselevels
arereferredtoashigh,VP(HIGH)
,mid,VP(MID),andlow,VP(LOW)
.
TheA1357featuresTrymode,BlowmodeandLockmode:
•InTrymode,thevalueofmultipleprogrammableparameters
maybesetandmeasuredsimultaneously.Theparametervalues
arestoredtemporarily,andresetaftercyclingthesupplyvolt-
age.
•InBlowmode,thevalueofasingleprogrammableparameter
maybesetandmeasured,andthenpermanentlysetbyblowing
solid-statefusesinternaltothedevice.Additionalparameters
maybeblownsequentially.Thismodealsoisusedforblow-
ingthedevice-levelfuse(whenLockmodeisenabled),which
permanentlyblocksthefurtherprogrammingofallparameters.
•Lockmodepreventsallfutureprogrammingofthedevice.This
isaccomplishedbyblowingaspecialfuseusingBlowmode.
Theprogrammingsequenceisdesignedtohelppreventthe
devicefrombeingprogrammedaccidentally;forexample,asa
resultofnoiseonthesupplyline.Althoughanyprogrammable
variablepowersupplycanbeusedtogeneratethepulsewave-
forms,AllegrohighlyrecommendsusingtheAllegroSensor
EvaluationKit,availableontheAllegrowebsiteOn-lineStore.
Themanualforthatkitisavailablefordownloadfreeofcharge,
andprovidesadditionalinformationonprogrammingthisdevice.
Definition of Terms
RegisterThesectionoftheprogramminglogicthatcontrolsthe
choiceofprogrammablemodesandparameters.
Bit FieldTheinternalfusesuniquetoeachregister,represented
asabinarynumber.Changingthebitfieldsettingsofaparticular
registercausesitsprogrammableparametertochange,basedon
theinternalprogramminglogic.
KeyAseriesofmid-levelvoltagepulsesusedtoselectaregister,
withavalueexpressedasthedecimalequivalentofthebinary
value.TheLSBofaregisterisdenotedaskey1,orbit0.
CodeThenumberusedtoidentifythecombinationoffuses
activatedinabitfield,expressedasthedecimalequivalentofthe
binaryvalue.TheLSBofabitfieldisdenotedascode1,orbit0.
AddressingIncreasingthebitfieldcodeofaselectedregister
byseriallyapplyingapulsetrainthroughtheVCCpinofthe
device.Eachparametercanbemeasuredduringtheaddressing
process,buttheinternalfusesmustbeblownbeforetheprogram-
mingcode(andparametervalue)becomespermanent.
Fuse BlowingApplyingahighvoltagepulseofsufficient
durationtopermanentlysetanaddressedbitbyblowingafuse
internaltothedevice.Afterabit(fuse)hasbeenblown,itcannot
bereset.
Blow PulseAhighvoltagepulseofsufficientdurationtoblow
theaddressedfuse.
Cycling the SupplyPowering-down,andthenpowering-upthe
supplyvoltage.Cyclingthesupplyisusedtocleartheprogram-
mingsettingsinTrymode.
Programming Guidelines
Programming Pulse Requirements, Protocol at TA = 25 °C
Characteristic Symbol Notes Min. Typ. Max. Unit
Programming
Voltage
VP(LOW)
Measured at the VCC pin.
4.5 5 5.5 V
VP(MID) 13 15 16 V
VP(HIGH) 26 27 28 V
Programming
Current IP
Minimum supply current required to ensure proper fuse blowing. In addition, a
minimum capacitance, CBLOW = 0.1 µF, must be connected between the supply and
GND pins during programming to provide the current necessary for fuse blowing.
The blowing capacitor should be removed and the load capacitance used for properly
programming duty cycle measurements.
300 – – mA
Pulse Width
tLOW Duration of VP(LOW) for separating VP(MID) and VP(HIGH) pulses. 40 – – µs
tACTIVE Duration of VP(MID) and VP(HIGH) pulses for register selection or bit field addressing. 40 – – µs
tBLOW Duration of VP(HIGH) pulses for fuse blowing. 40 – – µs
Pulse Rise Time tPr Rise time required for transitions from VP(LOW) to either VP(MID) or VP(HIGH). 5 – 100 µs
Pulse Fall Time tPf Fall time required for transitions from VP(HIGH) to either VP(MID) or VP(LOW). 5 – 100 µs
Two-Wire High Precision Linear Hall-Effect Sensor IC
With Pulse Width Modulated Output Current
A1357
12
Allegro MicroSystems, LLC
955 Perimeter Road
Manchester, NH 03103-3353 U.S.A.
www.allegromicro.com
Mode and Parameter Selection
Eachprogrammablemodeandparametercanbeaccessedthrough
specificregisters.Toselectaregister,asequenceofvoltage
pulsesconsistingofaVP(HIGH)pulse,aseriesofVP(MID)pulses,
andaVP(HIGH)pulse(withnoVCCsupplyinterruptions)mustbe
appliedseriallytothesupplypin.ThequantityofVP(MID)pulses
iscalledthekey,anduniquelyidentifieseachregister.Thepulse
trainusedforselectionofthefirstregister,key1,isshownin
figure6.
TheA1357hastworegistersthatselectamongthethreeprogram-
mablemodes:
•RegisterMode1:
BlowandLockmodes
•RegisterMode2:
Trymode
Andtherearefourregistersthatselectamongthefourprogram-
mableparameters:
•Register1:
Sensitivity,Sens
•Register2:
QuiescentCurrentDutyCycle,D(Q)
•Register3:
Pulsewidthmodulatedcarrierfrequency,fPWM
•Register6:
Lock(devicelocking)
Bit Field Addressing
Afteraprogrammableparameterhasbeenselected,aVP(HIGH)
pulsetransitionstheprogramminglogicintothebitfieldaddress-
ingstate.ApplyingaseriesofVP(MID)pulsestotheVCCpinof
thedevice,asshowninfigure7,increasesbyonethebitfieldof
theselectedparameter.
Whenaddressingthebitfield,thequantityofVP(MID)pulses
isrepresentedbyadecimalnumbercalledacode.Addressing
activatesthecorrespondingfuselocationsinthegivenbitfield
byincreasingthebinaryvalueofaninternalDAC.Thevalueof
thebitfield(andcode)increasesbyonewiththefallingedge
ofeachVP(MID)pulse,uptothemaximumpossiblecode(see
theProgrammingLogictable).Asthevalueofthebitfieldcode
increases,thevalueoftheprogrammableparameterchanges.
Measurementscanbetakenaftereachpulsetodetermineifthe
requiredresultfortheprogrammableparameterhasbeenreached.
Cyclingthesupplyvoltageresetsallthelocationsinthebitfield
thathaveunblownfusestotheirinitialstates.
Fuse Blowing
Aftertherequiredcodeisfoundforagivenparameter,itsvalue
canbesetpermanentlybyblowingindividualfusesintheappro-
priateregisterbitfield.Blowingisaccomplishedbyapplyinga
VP(HIGH)pulse,calledablowpulse,ofsufficientdurationatthe
VP(HIGH)leveltopermanentlysetanaddressedbitbyblowinga
fuseinternaltothedevice.Duetopowerrequirements,thefuse
foreachbitinthebitfieldmustbeblownindividually.Toaccom-
plishthis,thecoderepresentingtherequiredparametervalue
mustbetranslatedtoabinarynumber.Forexample,asshown
infigure8,decimalcode5isequivalenttothebinarynumber
101.Thereforebit2(code4)mustbeaddressedandblown,the
devicepowersupplycycled,andthenbit0(code1)addressed
Programming Procedures
Figure 6. Parameter selection pulse train. This shows the sequence for
selecting the register corresponding to key 1, indicated by a single VP(MID)
pulse.
V+
0
t
LOW
t
ACTIVE
V
P(HIGH)
V
P(MID)
V
P(LOW)
Figure 7. Bit field addressing pulse train. Addressing the bit field by
increasing the code causes the programmable parameter value to change.
The number of bits available for a given programming code, n, varies
among parameters; for example, the bit field for D(Q) has 8 bits available,
which allows 255 separate codes to be used.
V+
0
V
P(HIGH)
V
P(MID)
V
P(LOW)
Code 1
Code 2
Code 2
n
– 2
Code 2
n
– 1
Two-Wire High Precision Linear Hall-Effect Sensor IC
With Pulse Width Modulated Output Current
A1357
13
Allegro MicroSystems, LLC
955 Perimeter Road
Manchester, NH 03103-3353 U.S.A.
www.allegromicro.com
andblown.Anappropriatesequenceforblowingcode5isshown
infigure9.Theorderofblowingbits,however,isnotimportant.
Blowingbit0first,andthenbit2isacceptable.
Note:Afterblowing,theprogrammingisnotreversible,even
aftercyclingthesupplypower.Althougharegisterbitfieldfuse
cannotberesetafteritisblown,additionalbitswithinthesame
registercanbeblownatanytimeuntilthedeviceislocked.For
example,ifbit1(binary10)hasbeenblown,itisstillpossibleto
blowbit0.Theendresultwouldbebinary11(decimalcode3).
Locking the Device
Aftertherequiredcodeforeachparameterisprogrammed,the
devicecanbelockedtopreventfurtherprogrammingofany
parameters.
Additional Guidelines
Theadditionalguidelinespresentedinthissectionshouldbefol-
lowedtoensuretheproperbehaviorofthesedevices:
•A0.1μFblowingcapacitor,CBLOW
,mustbemountedbetween
theVCCpinandtheGNDpinduringprogramming,toensure
enoughcurrentisavailabletoblowfuses.
•Theapplicationloadcapacitance,CL,shouldbeusedwhen
measuringthedutycycleduringprogramming.Theblowing
capacitor,CBLOW
,shouldberemovedduringmeasurementand
shouldonlybeappliedwhenblowingfuses.
•Theblowingcapacitor,CBLOW
,mustbereplacedinthefinal
applicationwiththeloadcapacitance,CL,forproperoperation.
•Thepowersupplyusedforprogrammingmustbecapableof
deliveringatleast26Vand300mA.
•BecarefultoobservethetLOWdelaytimebeforepowering
downthedeviceafterblowingeachbit.
•Thefollowingprogrammingorderisrecommended:
1.fPWM
2.Sens
3.D(Q)
4.Lockthedevice(onlyafterallotherparametershavebeen
programmedandvalidated,becausethispreventsanyfurther
programmingofthedevice)
Programming Modes
Try ModeTrymodeallowsmultipleprogrammableparameters
tobetestedsimultaneouslywithoutpermanentlysettingany
values.Inthismode,eachVP(HIGH)pulsewillindefinitelyloop
theprogramminglogicthroughthemode,register,andbitfield
selectionstates.TheremustbenointerruptionsintheVCCsupply.
AfterpoweringtheVCCsupply,selectmodekey2,followed
bytheparameterregister,andthenaddressitsbitfield.When
addressingthebitfield,eachVP(MID)pulseincreasesthevalue
oftheparameterregisterbyone,uptothemaximumpossible
code(seeProgrammingLogicsection).Theaddressedparameter
valueisstoredinthedeviceevenaftertheprogrammingdrive
voltageisremovedfromtheVCCpin,allowingitsvaluetobe
measured.Totestanadditionalprogrammableparameterin
Figure 9. Example of Blow Mode programming pulses applied to the VCC pin. In this example, D(Q)
(Parameter Key 2) is addressed to code 4 (i.e bit 2) and its value is permanently blown.
V+
0
Mode
Selection
Parameter
Selection
(Key 1)
V
P(HIGH)
V
P(MID)
V
P(LOW)
(Key 2) (Code 4)
Addressing
Bitfield 2
t
BLOW
Code 4
Blow
t
Low
Cycle VCC
supply
Cycle VCC
supply
1 1 2 1 2 3 4
Figure 8. Example of code 5 broken into its binary components, which are
code 4 and code 1.
(Decimal Equivalent)
Code 5
Bit Field Selection
Address Code Format
Code in Binary
Fuse Blowing
Target Bits
Fuse Blowing
Address Code Format
(Binary)
1 0 1
Bit 2 Bit 0
Code 4 Code 1
(Decimal Equivalents)
Two-Wire High Precision Linear Hall-Effect Sensor IC
With Pulse Width Modulated Output Current
A1357
14
Allegro MicroSystems, LLC
955 Perimeter Road
Manchester, NH 03103-3353 U.S.A.
www.allegromicro.com
conjunctionwiththeoriginal,enteranadditionalVP(HIGH)pulse
ontheVCCpintoreentertheparameterselectionfield.Selecta
differentparameterregister,andaddressitsbitfield,withoutany
supplyinterruptions.Bothparametervalueswillbestoredand
canbemeasuredafterremovingtheprogrammingdrivevoltage.
Multipleprogrammingcombinationscanbetestedtoachieve
optimalapplicationaccuracy.Seefigure10foranexampleofthe
Trymodepulsetrain.
Registerscanbeaddressedandre-addressedanindefinitenumber
oftimesinanyorder.Aftertherequiredcodeisfoundforeach
register,cyclethesupplyandblowthebitfieldusingBlowmode.
Blow ModeAftertherequiredvalueoftheprogrammable
parameterisfoundusingTrymode,thecorrespondingcode
shouldbeblowntomakethevaluepermanent.Todothis,first
selectBlowmodeaskey1,thentherequiredparameterregister,
andaddressandbloweachrequiredbitseparately(asdescribed
intheFuseBlowingsection).Thesupplymustbecycledbetween
blowingeachbitofagivencode.Afterabitisblown,cyclingthe
supplywillnotresetitsvalue.
SingleparameterscanbestilladdressedintheBlowmodebefore
fuseblowing.Simultaneousaddressingofmultipleparameters,
asinTrymode,isnotpossible.AfterpoweringtheVCCsupply,
selectthedesiredparameterregisterandaddressitsbitfield.
Whenaddressingthebitfield,eachVP(MID)pulseincreases
thevalueoftheparameterregisterbyone,uptothemaximum
possiblecode(seeProgrammingLogictable).Theaddressed
parametervalueisstoredinthedeviceevenaftertheprogram-
mingdrivevoltageisremovedfromtheVCCpin,allowingits
valuetobemeasured.Itisnotpossibletodecreasethevalueof
theregisterwithoutresettingtheparameterbitfield.Toresetthe
bitfield,andthusthevalueoftheprogrammableparameter,cycle
thesupply,VCC,voltage.
ItispossibletoswitchbetweenTryandBlowmodesinthat,after
individualprogrammableparametershavebeenblowninBlow
mode,otherparameterscanbestilltestedinTrymode.
Lock ModeTolockthedevice,firstselectLockmode,then
addresstheLockbitandapplyablowpulsewithCBLOWinplace.
Afterlockingthedevice,nofutureprogrammingofanyparam-
eterispossible.
V+
0
Mode
Selection
Parameter
Selection
(Key 2, Try Mode)
V
P(HIGH)
V
P(MID)
V
P(LOW)
(Key 1) (Code 3)
Addressing Parameter
Selection
(Key 2) (Code 2)
Addressing
1 2 1 1 2 1 2 1 23
Figure 10. Example of Try mode programming pulses applied to the VCC pin. In this example,
Sensitivity (parameter key 1) is addressed to code 3, and D(Q) (parameter key 2) is addressed
to code 2. The values set in the Sensitivity and D(Q) registers will be held in the device until the
supply is cycled. Permanent fuse blowing cannot be accomplished in Try mode.
Two-Wire High Precision Linear Hall-Effect Sensor IC
With Pulse Width Modulated Output Current
A1357
15
Allegro MicroSystems, LLC
955 Perimeter Road
Manchester, NH 03103-3353 U.S.A.
www.allegromicro.com
Programming State Machine
VP(HIGH) VP(HIGH)
VP(HIGH)
VP(HIGH)
VP(HIGH)
VP(HIGH)
2 x VP(HIGH)
VP(MID)
VP(MID)
VP(MID)
VP(MID) VP(MID) VP(MID)
VP(MID) 1
(Sens
Range1/
Range2)
2
(D(Q))
Select Mode
3
(fPWM/
Calibration
Test Mode)
6
(Lock All)
VP(MID) VP(MID) VP(MID)
VP(MID) VP(MID) VP(MID)
Two-Wire High Precision Linear Hall-Effect Sensor IC
With Pulse Width Modulated Output Current
A1357
16
Allegro MicroSystems, LLC
955 Perimeter Road
Manchester, NH 03103-3353 U.S.A.
www.allegromicro.com
Programming Logic Table
Mode or Parameter
Name
(Register Key)
Bit Field Address
Description
Binary Format
[MSB → LSB] Decimal Equivalent Code
Programmable Mode
Lock, Blow
(1) 01 1 Entry to Lock or Blow mode
Try
(2) 10 2 Entry to Try mode
Programmable Parameter
Sens
(Range1/Range2)
(1)
0 0000 0000 0Minimum Sens value in SensRange1, Sens =
SensPRE
0 1111 1111 255 Maximum Sens value in SensRange1
1 0000 0000 256 Minimum Sens value in SensRange2
1 1111 1111 511 Maximum Sens value in SensRange2
D(Q)
(2)
0 0000 0000 0 Initial value, D(Q) = D(Q)PRE
0 1111 1111 255 Maximum quiescent current duty cycle in range
1 0000 0000 256 Switch from programming increasing D(Q) to
programming decreasing D(Q)
1 1111 1111 511 Minimum quiescent current duty cycle in range
fPWM
/
Calibration Test Mode
(3)
0 0000 0000 0 Initial value; fPWM = fPWMPRE
0 0000 1111 15 Minimum PWM frequency in range
0 0001 0000 16 Enable 50% Duty Cycle Calibration Test Mode
Lock All
(6) 10 0000 0000 512 Enable blowing Lock fuse to lock device
Sens
(%/gauss)
D(Q)
(%)
Quiescent Current
Duty Cycle Range
D(Q)(max)
D(Q)(min)
D(Q)PRE
fPWM
(Hz)
fPWMPRE
fPWM(max)
fPWM(min)
Two-Wire High Precision Linear Hall-Effect Sensor IC
With Pulse Width Modulated Output Current
A1357
17
Allegro MicroSystems, LLC
955 Perimeter Road
Manchester, NH 03103-3353 U.S.A.
www.allegromicro.com
Thecalibrationmodeisprovidedsothattheusercancompensate
fordifferencesinthegroundpotentialbetweentheA1357and
anyinterfacecircuitryusedtomeasurethepulsewidthofthe
A1357current.Thetestmodeisoptionalandmustbeenabled
byblowingprogrammingbits.Afterthebitforthetestmodehas
beenblown,thedeviceenters50%DutyCycleCalibrationTest
modeeverytimethedeviceispowered-up.Thebitenablingtest
modeiskey3,bit4.
Incustomerapplications,thePWMinterfacecircuitry(shown
asthesystemcontrollerinfigure11)andtheA1357maybe
poweredviadifferentpowerandgroundcircuits.Asaresult,the
groundreferencefortheA1357maydifferfromthegroundrefer-
enceofthesystemcontroller.Insomecustomerapplications,this
grounddifferencecanbeaslargeas±0.5V.
DifferencesinthegroundreferencefortheA1357andthesystem
controllercanresultinvariationsinthethresholdvoltageused
tomeasurethedutycycleoftheA1357.IfthePWMconversion
thresholdvoltagevaries,thenthedutycyclewillvarybecause
thereisafiniterisetime,tr,andfalltime,tf,inthePWMwave-
form.Thisproblemisshowninfigure12.
50% Duty Cycle Calibration Test Mode
PWM period
Duty Cycle
shorter than
expected
Duty Cycle at
expected duration
Duty Cycle longer
than expected
Vth (high)
∆tr∆tf
Vth (centered)
Vth (low)
2.5
3.5
1.5
Threshold Voltage,
Vth (V)
Time
Figure 12. When the threshold voltage, Vth , is correctly centered between Vth (high) and Vth (low) , the current duty cycle
accurately coincides with the applied magnetic field. If the threshold voltage is raised, the current duty cycle appears shorter
than expected. Conversely, if the threshold voltage is lowered, the current duty cycle is longer than expected.
GND1 GND2
System
Controller
GND
A1357
VCC
1
2
VSUPPLY
RSENSE
CBYPASS
0.1 µF
Figure 11. In many applications the A1357 may be powered using a different ground reference
than the system controller. This may cause the ground reference for the A1357 (GND1) to differ
from the ground reference of the system controller (GND2) by as much as to ± 0.5 V.
Two-Wire High Precision Linear Hall-Effect Sensor IC
With Pulse Width Modulated Output Current
A1357
18
Allegro MicroSystems, LLC
955 Perimeter Road
Manchester, NH 03103-3353 U.S.A.
www.allegromicro.com
The50%DutyCycleCalibrationTestmodeallowsendusersto
compensateforanythresholderrorsthatresultfromadifference
insystemgroundpotentials.Whencalibrationmodehasbeen
enabled,atpower-upthedeviceoperatesinitiallyincalibration
modefortCAL,50ms,duringwhichthedevicecurrentwaveform
hasafixed50%dutycycle(theprogrammedquiescentduty
cycle,D(Q),value)regardlessoftheappliedexternalmagnetic
field(seefigure13).Thisallowsthesystemcontrollertocom-
parethemeasuredquiescentdutycyclewithanideal50%duty
cycle.AftertCALhaselapsed,thedutycyclewillcorrespondto
anappliedmagneticfieldasexpected.Thecalibrationtesttime
(tCAL)correspondswithatargetPWMfrequencyof1kHz.Ifthe
PWMfrequencyisprogrammedawayfromitstargetof1kHz,
thedurationofthecalibrationtesttimewillscaleinverselywith
thechangeinPWMfrequency.
Figure 13. With calibration mode in effect, after powering-on the A1357 outputs a 50%
duty cycle for the first 50 ms, tCAL , regardless of the applied magnetic field. After tCAL has
elapsed, the output responds to a magnetic field as expected. The example in this figure
assumes that a large +B field is applied to the device after tCAL has elapsed.
Calibration sequence PWM proportional to
magnetic field
Two-Wire High Precision Linear Hall-Effect Sensor IC
With Pulse Width Modulated Output Current
A1357
19
Allegro MicroSystems, LLC
955 Perimeter Road
Manchester, NH 03103-3353 U.S.A.
www.allegromicro.com
Package KB, 3-Pin SIP
1.90 NOM
2.16
MAX
45°
45°
0.84 REF
2 31
A
Gate and tie bar burr area
A
B
B
C
D
E
E
Dambar removal protrusion (6X)
Mold Ejector
Pin Indent
Branded
Face
Standard Branding Reference View
N = Device part number
Y = Last two digits of year of manufacture
W = Week of manufacture
YYWW
NNNN
1
5.21 +0.08
–0.05
0.38 +0.06
–0.03
3.43 +0.08
–0.05
0.51 +0.07
–0.05
14.73 ±0.51
1.55 ±0.05
For Reference Only; not for tooling use (reference DWG-9009)
Dimensions in millimeters
Dimensions exclusive of mold flash, gate burrs, and dambar protrusions
Exact case and lead configuration at supplier discretion within limits shown
Branding scale and appearance at supplier discretion
D
D
D
1.33
2.60
C
Hall element (not to scale)
Active Area Depth 0.43 mm REF
Two-Wire High Precision Linear Hall-Effect Sensor IC
With Pulse Width Modulated Output Current
A1357
20
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
Revision History
Number Date Description
– April 23, 2013 Initial release
1 February 19, 2019 Minor editorial updates
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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.
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