A1354 Datasheet

A1354
High Precision 2-Wire Linear Hall Effect Sensor IC
With Pulse Width Modulated Output
Discontinued Product
This device is no longer in production. The device should not be
purchased for new design applications. Samples are no longer available.
Date of status change: April 30, 2012
Recommended Substitutions:
For existing customer transition, and for new customers or new applications, contact Allegro Sales.
NOTE: For detailed information on purchasing options, contact your
local Allegro field applications engineer or sales representative.
Allegro MicroSystems, Inc. reserves the right to make, from time to time, revisions to the anticipated product life cycle plan
for a product to accommodate changes in production capabilities, alternative product availabilities, or market demand. The
information included herein is believed to be accurate and reliable. However, Allegro MicroSystems, Inc. assumes no responsibility for its use; nor for any infringements of patents or other rights of third parties which may result from its use.
A1354
High Precision 2-Wire Linear Hall Effect Sensor IC
with Pulse Width Modulated Output
Features and Benefits
Description
▪ Designed for automotive, battery-powered applications
▪ Customer programmable quiescent duty cycle, sensitivity,
and PWM carrier frequency, through VCC pin
▪ Simultaneous programming of duty cycle, sensitivity, and
PWM carrier frequency, for system optimization
▪ Factory programmed sensitivity temperature coefficient
and quiescent duty cycle drift
▪ Selectable unidirectional or bidirectional quiescent
duty cycles
▪ Pulse width modulated (PWM) output provides increased
noise immunity compared to analog output
▪ Temperature-stable quiescent duty cycle output and
sensitivity
The A1354 device is a high precision, programmable 2-wire
Hall effect linear sensor IC with a pulse width modulated
(PWM) output. The duty cycle (D) of the PWM output signal
is proportional to the applied magnetic field. The A1354
device converts an analog signal from its internal Hall circuit
to a digitally encoded PWM output signal. The coupled noise
immunity of the digitally encoded PWM output is far superior
to the noise immunity of an analog output signal.
Continued on the next page…
Package: 4-pin SIP (suffix KT)
1 mm case thickness
The BiCMOS, monolithic circuit inside of the A1354 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. Hall element
offset is normally caused by device overmolding, temperature
dependencies, and thermal stress. The high frequency offset
cancellation (chopping) clock allows a greater sampling rate,
which increases the accuracy of the output signal and results
in faster signal processing capability.
The A1354 device is provided in a lead (Pb) free 4-pin single
inline package (KT suffix), with 100% matte tin leadframe
plating.
Not to scale
Functional Block Diagram
VCC
VCC
PWM Carrier
Generation
and Trimming
Regulator
1
2
Switched
Capacitor
Control
2
Programming
Logic
1
Chopper
Switches
Temperature
Compensation
Programming
Interface
Sensitivity
and Sensitivity
TC Trim
Amp
Signal
Recovery
% Duty
Cycle
Voltage
Controlled
Current
Source
% Duty Cycle
Temperature
Coefficient
GND
RSens
A1354-DS, Rev. 1
High Precision 2-Wire Linear Hall Effect Sensor IC
with Pulse Width Modulated Output
A1354
Features and Benefits (continued)
▪ Output 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 125°C
▪ Resistant to mechanical stress
▪ Extremely thin package: 1 mm case thickness
Selection Guide
Part Number
A1354KKTTN-T
Packing*
4000 pieces per 13-in. reel
*Contact Allegro® for additional packing options
Absolute Maximum Ratings
Characteristic
Symbol
Notes
Rating
Unit
Forward Supply Voltage
VCC
28
V
Reverse Supply Voltage
VRCC
–16
V
Forward Supply Current
ICC
50
mA
Reverse Supply Current
IRCC
–50
mA
–40 to 125
ºC
Range K
Operating Ambient Temperature
TA
Maximum Junction Temperature
TJ(max)
165
ºC
Tstg
–65 to 165
ºC
Storage Temperature
Pin-out Diagram
Branded
Face
1
2
3
Terminal List
Number
Name
Function
1
VCC
2
NC
Not connected
3
NC
Not connected
4
GND
Input power supply; use bypass capacitor to connect to ground
Ground
4
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115 Northeast Cutoff
Worcester, Massachusetts 01615-0036 U.S.A.
1.508.853.5000; www.allegromicro.com
2
A1354
High Precision 2-Wire Linear Hall Effect Sensor IC
with Pulse Width Modulated Output
OPERATING CHARACTERISTICS (A) Valid with CBYPASS = 0.01 μF, over full operating temperature range, TA, and VCC, unless otherwise
noted
Characteristics
Symbol
Test Conditions
Min.
Typ.
Max.
Unit1
ELECTRICAL CHARACTERISTICS
Supply Voltage2
Supply Current
Supply Current Ratio3
Power-On
Time4
Supply Zener Clamp Voltage
VCC
4.5
12
16
V
ICC(LOW)
–
6
9
mA
ICC(HIGH)
13
–
19
mA
ICC(rat)
2
–
–
–
TA = 25°C, CL (of test probe)= 10 pF,
Sens = 0.1%/G, fPWM = fPWM(slow)
–
100
–
ms
TA = 25°C, CL (of test probe)= 10 pF,
Sens = 0.1%/G, fPWM = fPWM(fast)
–
25
–
ms
tPO
28.5
32
–
V
Small signal –3 dB, 100 G(P-P) magnetic input
signal
–
200
–
Hz
TA = 25°C
–
200
–
kHz
TA = 25°C, Impulse magnetic field of 300 G,
Sens = 0.1%/G, fPWM = fPWM(slow)
–
100
–
ms
TA = 25°C, Impulse magnetic field of 300 G,
Sens = 0.1%/G, fPWM = fPWM(fast)
–
25
–
ms
DCLP(HIGH) TA = 25°C
90
92.5
95
%
DCLP(LOW)
TA = 25°C
5
7.5
10
%
Duty Cycle Jitter4,7
JitterPWM
TA = –10°C to 85°C, Sens = 0.12%/G, Measured
over 1000 Output PWM clock periods
–
±0.05
–
%
Duty Cycle Resolution
ResPWM
TA = –10°C to 85°C, Sens = 0.12%/G, Measured
over 1000 Output PWM clock periods
–
±0.42
–
G
Internal Bandwidth
Chopping Frequency5
VZ
BWi
fC
TA = 25°C, ICC = ICC(max) + 3 mA
OUTPUT CHARACTERISTICS
Response
Time4
Clamp Duty Cycles6
tRESPONSE
11
G (gauss) = 0.1 mT (millitesla).
voltage, VCC, is defined as the voltage drop between pin 1 and pin 4 of the device. It does not include the voltage drop across RSENS.
3I
CC ratio is defined as ICC(HIGH) / ICC(LOW) for a given PWM cycle.
4See Characteristic Definitions section.
5f varies up to approximately ±20% over the full operating ambient temperature range, T , and process.
C
A
6Clamp duty cycles are tested with the maximum sensitivity code addressed and an applied magnetic field that is at least 25% greater than
the dynamic range.
7Jitter is dependent on the sensitivity of the device. Values are based on characterization only and are not guaranteed via production testing.
2Supply
Allegro MicroSystems, Inc.
115 Northeast Cutoff
Worcester, Massachusetts 01615-0036 U.S.A.
1.508.853.5000; www.allegromicro.com
3
High Precision 2-Wire Linear Hall Effect Sensor IC
with Pulse Width Modulated Output
A1354
PROGRAMMING CHARACTERISTICS Valid over full operating voltage range and TA = 25°C , unless otherwise noted
Characteristics
Symbol
Test Conditions
Min.
Typ.
Max.
Unit1
–
50
–
%
PRE-PROGRAMMING TARGET2
Pre-Programming Quiescent Duty Cycle
Output
D(Q)PRE
Pre-Programming Sensitivity
SensPRE
–
0.08
–
%/G
Pre-Programming PWM Output Carrier
Frequency
fPWMPRE
–
150
–
Hz
–
20
–
%
B=0G
QUIESCENT DUTY CYCLE PROGRAMMING
Initial Quiescent Duty Cycle Output3
D(Q)UNIinit
Unipolar device, B = 0 G
D(Q)BIinit
Bipolar device, B = 0 G
–
D(Q)PRE
–
%
D(Q)UNI
Unipolar device, B = 0 G
10
–
30
%
Guaranteed Quiescent Duty Cycle
Programming Range4
Quiescent Duty Cycle
Programming Bits
D(Q)BI
Output5
Bipolar device, B = 0 G
40
–
60
%
Coarse (range programming)
–
1
–
bit
Fine (value adjustment)
–
9
–
bit
Average Quiescent Duty Cycle Output
Step Size6,7
StepD(Q)
0.055
0.075
0.095
%
Quiescent Duty Cycle Output
Programming Resolution8
ErrPGD(Q)
–
StepD(Q)
× ±0.5
–
%
Sensinit
–
SensPRE
–
%/G
Sens
0.1
–
0.2
%/G
–
8
–
bit
Average Sensitivity Step Size6,7
StepSENS
600
800
900
μ%/G
Sensitivity Programming Resolution8
ErrPGSENS
–
StepSENS
× ±0.5
–
μ%/G
SENSITIVITY PROGRAMMING
Initial Sensitivity
Guaranteed Sensitivity Programming
Range9
Sensitivity Programming Bits
CARRIER FREQUENCY PROGRAMMING
Initial Carrier Frequency
Guaranteed Carrier Frequency
Programming Range9
fPWM(slow)init
–
19
–
Hz
fPWM(fast)init
–
fPWMPRE
–
Hz
fPWM(slow)
12
–
15.5
Hz
fPWM(fast)
95
–
115
Hz
Coarse (range programming)
–
1
–
bit
Fine (value adjustment)
–
4
–
bit
StepfPWM(slow)
0.5
0.8
1.1
Hz
StepfPWM(fast)
4.5
6.4
8.3
Hz
ErrPGfPWM
–
StepfPWM
× ±0.5
–
Hz
Coarse Carrier Frequency Programming
Bits10
Average Carrier Frequency Step Size6,7
Carrier Frequency Programming
Resolution8
Continued on the next page…
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115 Northeast Cutoff
Worcester, Massachusetts 01615-0036 U.S.A.
1.508.853.5000; www.allegromicro.com
4
A1354
High Precision 2-Wire Linear Hall Effect Sensor IC
with Pulse Width Modulated Output
PROGRAMMING CHARACTERISTICS (continued) Valid over full operating temperature range, TA , and VCC , unless otherwise noted
Characteristics
Symbol
Test Conditions
Min.
Typ.
Max.
Unit1
–
1
–
bit
–
1
–
bit
CALIBRATION TEST MODE PROGRAMMING
Calibration Test Mode Selection Bit
LOCK BIT PROGRAMMING
Overall Programming Lock Bit
11
G (gauss) = 0.1 mT (millitesla).
device characteristic values before any programming.
3D
(Q)UNIinit may be below the clamp duty cycle DCLP(LOW). D(Q) will not appear to respond to programming pulses until D(Q) > DCLP(LOW).
4D (max) is the value guaranteed with all programming fuses blown (maximum programming code set). The D
(Q)
(Q) range is the total range from
D(Q)init up to and including D(Q)(max). See Characteristic Definitions section.
5Bit for selecting between D
(Q)BI and D(Q)UNI programming ranges.
6Step size is larger than required, in order to provide for manufacturing spread. See Characteristic Definitions section.
7Non-ideal behavior in the programming D-to-A converter (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.
8Overall programming value accuracy. See Characteristic Definitions section.
9f
PWM(max) is the value available with all programming fuses blown (maximum programming code set). fPWM range is the total range from fPWMinit up
to and including fPWM(max). See Characteristic Definitions section.
10Bit for selecting between f
PWM(fast) and fPWM(slow) programming ranges.
2Raw
Allegro MicroSystems, Inc.
115 Northeast Cutoff
Worcester, Massachusetts 01615-0036 U.S.A.
1.508.853.5000; www.allegromicro.com
5
High Precision 2-Wire Linear Hall Effect Sensor IC
with Pulse Width Modulated Output
A1354
OPERATING CHARACTERISTICS (B) Valid with CBYPASS = 0.01 μF, over full operating temperature range, TA , and VCC , unless
otherwise noted
Characteristics
Symbol
Test Conditions
Min.
Typ.
Max.
Unit
–
0.12
–
%/°C
–
< ±2
–
%
–
< ±1.2
–
%
B=0G
–
0
–
%
B = 0 G, Sens = SensPRE , D = D(Q)pre
–
< ±0.3
–
%
LinERR
–
< ±1.0
–
%
SymERR
–
< ±1.5
–
%
FACTORY PROGRAMMED SENSITIVITY TEMPERATURE COEFFICIENT AND SENSITIVITY DRIFT
Sensitivity Temperature Coefficient1
TCSens
Maximum Sensitivity Drift Through
Temperature Range2,3
ΔSensTC
Sensitivity Drift Due to Package
Hysteresis3,4
ΔSensPKG TA = 25°C, after temperature cycling
Sens = SensPRE , D = D(Q)PRE, calculated at
125°C
FACTORY PROGRAMMED DUTY CYCLE DRIFT
Duty Cycle Drift1,3
Duty Cycle Drift
Error3
ΔD(Q)
ErrΔD(Q)
ERROR COMPONENTS
Linearity Sensitivity Error3
Symmetry Sensitivity Error3,5
1Programmed
at 125°C and calculated relative to 25°C.
drift from expected value at TA after programming TCSENS. See Characteristic Definitions section.
3Specification unit is defined in percent as result of the calculation shown in the Characteristics Definitions section.
4See Characteristic Definitions section.
5Symmetry error is only valid for bipolar devices.
2Sensitivity
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115 Northeast Cutoff
Worcester, Massachusetts 01615-0036 U.S.A.
1.508.853.5000; www.allegromicro.com
6
High Precision 2-Wire Linear Hall Effect Sensor IC
with Pulse Width Modulated Output
A1354
Thermal Characteristics may require derating at maximum conditions
Characteristic
Symbol
Package Thermal Resistance
RθJA
Test Conditions*
1-layer PCB with copper limited to solder pads
Value
Units
174
ºC/W
*Additional thermal information available on Allegro website.
Power Dissipation versus Ambient Temperature
900
800
600
(R
QJ
500
A
=
17
4
ºC
400
/W
)
Power Dissipation, PD (mW)
700
300
200
100
0
20
40
60
80
100
120
140
Temperature, TA (°C)
160
180
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115 Northeast Cutoff
Worcester, Massachusetts 01615-0036 U.S.A.
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7
A1354
High Precision 2-Wire Linear Hall Effect Sensor IC
with Pulse Width Modulated Output
VCC at Various Duty Cycles
4 μs per division
TPeriod
tHigh
tLow
≈10% Duty Cycle
(Low Clamp)
tHigh – duration of high voltage
tLow – duration of the low voltage
TPeriod – one full frequency cycle
TPeriod
Duty Cycle = (tHigh / TPeriod) × 100%
tHigh
tLow
Unidirectional Field Detection
≈ 50% Duty Cycle
Duty Cycle
Field Detection
10%
0G
10%-90%
0 to +n G (south)
Bidirectional Field Detection
TPeriod
tHigh
tLow
Duty Cycle
Field Detection
50%
0G
50%-90%
0 to +n G (south)
50%-10%
0 to –n G (north)
≈ 90% Duty Cycle
(High Clamp)
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115 Northeast Cutoff
Worcester, Massachusetts 01615-0036 U.S.A.
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8
High Precision 2-Wire Linear Hall Effect Sensor IC
with Pulse Width Modulated Output
A1354
Characteristic Definitions
Quiescent Voltage Output and Duty Cycle The operating
output voltage, VOUT , is determined by the PWM output voltage
duty cycle, D. In turn, D is proportional to a change in air gap
between the A1354 Hall element and the magnetic target. The
output duty cycle in the quiescent state (no significant magnetic
field: B = 0 G), D(Q) , remains steady at the specific programmed
duty cycle throughout the entire operating ranges of VCC and
ambient temperature, TA.
Power-On Time When 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, with no
applied magnetic field (quiescent state), for the PWM output
voltage duty cycle, D(Q) , to settle within ±5% of its steady state
value, after the power supply has reached its minimum specified
operating voltage, VCC(min).
Response Time The time interval, tRESPONSE , between a) when
the applied magnetic field reaches 90% of its final value, and b)
when the device reaches 90% of its output level corresponding to
the applied magnetic field. tRESPONSE depends on the signal delay
defined by the device filter bandwidth, BWi , and a full PWM
period, which is required for output update.
Guaranteed Quiescent Duty Cycle Output Range The
quiescent duty cycle output, D(Q) , can be programmed 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 distributions of the initial duty cycle, D(Q)init , and
of the maximum programming code for setting D(Q) , as shown in
figure 1.
Quiescent Duty Cycle Output Programming Resolution
The programming resolution for any device is half of its programming step size. Therefore, the typical programming resolution is:
ErrPGD(Q)(typ) = 0.5 × StepD(Q)(typ)
D(Q)maxcode – D(Q)mincode
2n –1
,
(2)
Quiescent Output Duty Cycle Drift Through Temperature Range Due to internal component tolerances and thermal
considerations, the quiescent duty cycle temperature coefficient,
TCD(Q), may drift from its nominal value over the range of the
operating ambient temperature, TA. For purposes of specification,
the Quiescent Duty Cycle Output Drift Through Temperature
Range, ∆D(Q) (%), is defined as:
∆D(Q) = D(Q)(∆TA) – D(Q)(25°C) .
(3)
∆D(Q) should be calculated using the actual measured values of
D(Q)(ΔTA) and D(Q)(25°C) rather than ideal programming target
values.
Sensitivity The presence of a south polarity magnetic field,
perpendicular to the branded face of the package, increases the
output duty cycle from its quiescent value toward the maximum
duty cycle limit. The amount of the output duty cycle increase
is proportional to the magnitude of the magnetic field applied.
Conversely, the application of a north polarity field decreases the
output duty cycle from its quiescent value. This proportionality is
specified as the magnetic sensitivity, Sens (%/G), of the device,
and it is defined for bipolar devices as:
Sens =
D(BPOS) – D(BNEG)
BPOS – BNEG
Average Quiescent Duty Cycle Output Step Size The
average quiescent duty cycle output step size, StepD(Q) , for a
single device is determined using the following calculation:
StepD(Q) =
.
,
(4)
Guaranteed D(Q)
Programming
Range
(1)
where:
n is the number of available programming bits in the trim range,
2n –1 is the value of the maximum programming code in the
range, and
D(Q)maxcode is the quiescent output duty cycle at code 2n –1.
Min Code D(Q)
Distribution
Max Code D(Q)
Distribution
Initial D(Q)
Distribution
D(Q)(min)
D(Q)(max)
Figure 1. Quiescent output duty cycle versus time
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115 Northeast Cutoff
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9
High Precision 2-Wire Linear Hall Effect Sensor IC
with Pulse Width Modulated Output
A1354
and for unipolar devices as:
Sens =
D(BPOS) – D(Q)
BPOS
SensEXPECTED(TA), is defined as:
,
(5)
where BPOS and BNEG are two magnetic fields with opposite
polarities.
Guaranteed Sensitivity Range The magnetic sensitivity,
Sens, can be programmed around its nominal value within the
sensitivity range limits: Sens(min) and Sens(max). Refer to the
Guaranteed Quiescent Duty Cycle Output Range section for a
conceptual explanation of how value distributions and ranges are
related.
Average Sensitivity Step Size Refer to the Average Quiescent Duty Cycle Output Step Size section for a conceptual
explanation.
Sensitivity Programming Resolution Refer to the Quiescent Duty Cycle Output Programming Resolution section for a
conceptual explanation.
Guaranteed Carrier Frequency Range The PWM output
signal carrier frequency, fPWM, can be programmed around its
nominal value in fast mode or slow mode.
Average Carrier Frequency Step Size Refer to the Average
Quiescent Duty Cycle Output Step Size section for a conceptual
explanation.
Carrier Frequency Programming Resolution Refer to the
Quiescent Duty Cycle Output Programming Resolution section
for a conceptual explanation.
Sensitivity Temperature Coefficient Device Sensitivity changes as temperature changes, with respect to its programmed sensitivity temperature coefficient, TCSENS. TCSENS
is programmed at 125°C, and calculated relative to the nominal
sensitivity programming temperature of 25°C. TCSENS (%/°C) is
defined as:
 1 
SensT2 – SensT1
TCSens = 
× 100% T2–T1 ,
(6)
Sens
T1



where T1 is the nominal Sens programming temperature of 25°C,
and T2 is the TCSENS programming temperature of 125°C. The
expected value of Sens over the full ambient temperature range,
SensEXPECTED(TA) =
SensT1× [100% +TCSENS (TA –T1)]
(7)
100 %
SensEXPECTED(TA) should be calculated using the actual measured
values of SensT1 and TCSENS rather than ideal programming
target values.
Sensitivity Drift Through Temperature Range Second
order sensitivity temperature coefficient effects cause the magnetic sensitivity, Sens, to drift from its expected value over the
operating ambient temperature range, TA. For purposes of specification, the sensitivity drift through temperature range, ∆SensTC,
is defined as:
∆SensTC =
SensTA – SensEXPECTED(TA)
SensEXPECTED(TA)
× 100% .
(8)
Sensitivity Drift Due to Package Hysteresis Package
stress and stress relaxation can cause the device sensitivity at
TA = 25°C to change during and after temperature cycling.
For purposes of specification, the sensitivity drift due to package
hysteresis, ∆SensPKG, is defined as:
∆SensPKG =
Sens(25°C)2 – Sens(25°C)1
× 100%
Sens(25°C)1
,
(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 125°C, down to –40°C,
and back to up 25°C.
Linearity Sensitivity Error The A1354 is designed to provide
a linear output in response to a ramping applied magnetic field.
Consider two magnetic fields, B1 and B2. Ideally, the sensitivity
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.
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115 Northeast Cutoff
Worcester, Massachusetts 01615-0036 U.S.A.
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10
High Precision 2-Wire Linear Hall Effect Sensor IC
with Pulse Width Modulated Output
A1354
Linearity Error is calculated separately for the positive
(LinERRPOS ) and negative (LinERRNEG ) applied magnetic fields.
Linearity error (%) is measured and defined as:

D(+B) – D(Q) 
 ×% ,
LinERRPOS = ¾–¾
 D(+B½)– D(Q) 

D(–B) – D(Q) 
 ×% ,
LinERRNEG = ¾–¾
 D(–B½)– D(Q) 
(10)
|D(Bx) – D(Q)|
Bx
(11)
where:
SensBx =
.
(12)
Note that unipolar devices only have positive linearity error
(LINERRPOS).
Symmetry Sensitivity Error The magnetic sensitivity of an
A1354 device is constant for any two applied magnetic fields of
equal magnitude and opposite polarities. Symmetry error,

 ×% ,
(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 error specification is only valid
for bipolar devices.
Jitter The duty cycle of the PWM output may vary slightly over
time despite the presence of a constant applied magnetic field and
a constant carrier frequency for the PWM signal. This phenomenon is known as jitter, JitterPWM (%), and is defined as:
JitterPWM = ±
Then:
LinERR = max( LinERRPOS , LinERRNEG ) .
SymERR (%), is measured and defined as:
 D(+B) – D(Q)
SymERR = ¾–¾
D(Q)– D(–B)

DBmax – DBmin
2
,
(14)
where DBmax and DBmin are the maximum and minimum duty
cycles measured the over 1000 PWM clock periods with a constant applied magnetic field.
Resolution The ability to derive the value of the applied magnetic field from the device output is affected by jitter. The resolution of the magnetic field, RESPWM (G), is defined as:
JitterPWM
RESPWM =
.
(15)
Sens
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115 Northeast Cutoff
Worcester, Massachusetts 01615-0036 U.S.A.
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11
High Precision 2-Wire Linear Hall Effect Sensor IC
with Pulse Width Modulated Output
A1354
Typical Application Drawings
VCC
RSENS
VCC
1
1
VCC
VCC
A1354
CBYPASS
0.01 μF
A1354
CBYPASS
0.01 μF
GND
4
GND
4
RSENS
Chopper Stabilization Technique
When using Hall-effect technology, a limiting factor for
switchpoint accuracy is the small signal voltage developed
across the Hall element. This voltage is disproportionally small
relative to the offset that can be produced at the output of the
Hall element. This makes it difficult to process the signal while
maintaining an accurate, reliable output over the specified operating temperature and voltage ranges. Chopper stabilization is a
unique approach used to minimize Hall offset on the chip. The
patented Allegro technique, namely Dynamic Quadrature Offset
Cancellation, removes key sources of the output drift induced by
thermal and mechanical stresses. This offset reduction technique
is based on a signal modulation-demodulation process. The
undesired offset signal is separated from the magnetic fieldinduced signal in the frequency domain, through modulation.
The subsequent demodulation acts as a modulation process for
the offset, causing the magnetic field-induced signal to recover
its original spectrum at base band, while the DC offset becomes
a high frequency signal. The magnetic-sourced signal then can
pass through a low-pass filter, 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 (400 kHz). This high-frequency operation
allows a greater sampling rate, which results in higher accuracy
and faster signal-processing capability. This approach desensitizes the chip to the effects of thermal and mechanical stresses,
and produces devices that have extremely stable quiescent Hall
output voltages and precise recoverability after temperature
cycling. This technique is made possible through the use of a
BiCMOS process, which allows the use of low-offset, low-noise
amplifiers in combination with high-density logic integration and
sample-and-hold circuits.
Regulator
Hall Element
Amp
Sample and
Hold
Clock/Logic
Low-Pass
Filter
Allegro MicroSystems, Inc.
115 Northeast Cutoff
Worcester, Massachusetts 01615-0036 U.S.A.
1.508.853.5000; www.allegromicro.com
12
High Precision 2-Wire Linear Hall Effect Sensor IC
with Pulse Width Modulated Output
A1354
Programming Guidelines
Overview
Programming is accomplished by sending a series of input voltage
pulses serially through the VCC pin of the device. Unique combinations of different voltage amplitude pulses control the internal
programming logic of the device to select a programmable parameter and set its value. There are three voltage levels that must be
taken into account when programming using a high voltage pulse,
VPH (consisting of a VP(LOW) – VP(HIGH) – VP(LOW) sequence),
and a mid voltage pulse, VPM (consisting of a VP(LOW) – VP(MID)
– VP(LOW) sequence). The low voltage level, VP(LOW) , separates the
VPH and VPM programming pulses.
The 1354 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 voltage.
kit is available for download free of charge, and provides additional information on programming these devices.
Definition of Terms
Register The section of the programming logic that controls the
choice of programmable modes and parameters.
Bitfield The internal fuses unique to each register, represented as
a binary number. Incrementing the bitfields of a particular register
causes its programmable parameter to change, based on the internal
programming logic.
Key A series of mid 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 bitfield 0.
Code The number used to identify the combination of fuses
activated in a bitfield, expressed as the decimal equivalent of the
binary value. The LSB of a bitfield is denoted as code 1, or bit 0.
• In Blow mode, the value of a single programmable parameter
may be set, measured, and permanently set by blowing solidstate fuses internal to the device. Additional parameters may be
blown sequentially. This mode is used for blowing the devicelevel fuse, which permanently blocks the further programming
of all parameters.
Addressing Incrementing 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 programming
code (and parameter value) becomes permanent.
• 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 waveforms, Allegro
highly recommends using the Allegro Sensor IC Evaluation Kit,
available on the Allegro website On-line Store. The manual for that
Fuse Blowing Applying a high pulse of sufficient duration to
permanently set an addressed bit by blowing a fuse internal to the
device. Once a bit (fuse) has been blown, it cannot be reset.
Blow Pulse A high 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 programming settings in Try mode.
Programming Pulse Requirements, Protocol at TA = 25 °C
Characteristic
Programming
Voltage
Symbol
Notes
VP(LOW)
VP(MID)
Measured at the VCC pin.
VP(HIGH)
Programming
Current
IP
tLOW
Pulse Width
Minimum supply current required to ensure proper fuse blowing. In addition, a
minimum capacitance, CBLOW = 0.1 μF, must be connected between the VCC 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.
Min.
Typ.
Max.
Unit
4.5
5
5.5
V
13
15
16
V
26
27
28
V
300
–
–
mA
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 bitfield 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
Allegro MicroSystems, Inc.
115 Northeast Cutoff
Worcester, Massachusetts 01615-0036 U.S.A.
1.508.853.5000; www.allegromicro.com
13
High Precision 2-Wire Linear Hall Effect Sensor IC
with Pulse Width Modulated Output
Register 1:
Sensitivity, Sens
Coarse quiescent duty cycle, D(Q)
Register 2:
Fine quiescent duty cycle output, D(Q)
Register 3:
Coarse pulse width modulated carrier frequency
Pulse width modulated carrier frequency, fPWM
Register 5:
Calibration Test Mode
Overall device Lock Bit, LOCK
Fuse Blowing
After the required code is found for a given parameter, its value
can be set permanently by blowing individual fuses in the
appropriate register bitfield. Blowing is accomplished by applying a VPH 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 bitfield must be blown individually. To accomplish this, the code representing the desired parameter value
must be translated to a binary number. For example, as shown
in figure 4, 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
and blown. An appropriate sequence for blowing code 5 is shown
V+
V+
VP(HIGH)
VP(HIGH)
VP(MID)
VP(MID)
Code 2n – 1
Register 1:
Blow and Lock
Register 2:
Try
Also, it has four registers that select among the seven programmable parameters:
When addressing the bitfield, the number of VPM pulses is
represented by a decimal number called the code. Addressing
activates the corresponding fuse locations in the given bitfield by
incrementing the binary value of an internal DAC. The value of
the bitfield (and code) increments by one with the falling edge of
each VPM pulse, up to the maximum possible code for the register (see the Programming Logic table). As the code increases,
the value of the programmable parameter changes. Measurements
can be taken after each VPM pulse to determine if the desired
result for the programmable parameter has been reached. Cycling
the supply voltage resets all the locations in the bitfield that have
unblown fuses to their initial states.
Code 2n – 2
The A1354 has two registers that select among the three programming modes:
Bitfield Addressing
After a parameter register has been selected, a VPH pulse transitions the programming logic into the bitfield addressing state.
Applying a series of VPM pulses to the VCC pin of the device, as
shown in figure 3, increments the bitfield of the selected parameter.
Code 2
Mode and Parameter Register Selection
Each mode and programmable parameter can be accessed through
a specific register. To select a register, a sequence of voltage
pulses consisting of a VPH pulse, a series of VPM pulses, and a
VPH pulse (with no VCC supply interruptions) must be applied
serially to the VCC pin. The number of VPM 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 2.
Code 1
A1354
VP(LOW)
VP(LOW)
tLOW
0
tACTIVE
Figure 2. Parameter selection pulse train. This shows the sequence for
selecting the register corresponding to key 1, indicated by a single VPM
pulse.
0
Figure 3. Bitfield addressing pulse train. Addressing the bitfield by
incrementing 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 bitfield for D(Q) has 6 bits
available, which allows 63 separate codes to be used.
Allegro MicroSystems, Inc.
115 Northeast Cutoff
Worcester, Massachusetts 01615-0036 U.S.A.
1.508.853.5000; www.allegromicro.com
14
High Precision 2-Wire Linear Hall Effect Sensor IC
with Pulse Width Modulated Output
A1354
in figure 5. 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 bitfield 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 desired code for each parameter is programmed, the
device can be locked to prevent further programming of any
parameters.
Additional Guidelines
The additional guidelines in this section should be followed 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 CBLOW blowing capacitor must be replaced in the final application with a 10 nF bypass capacitor for proper operation.
• The application capacitance, CBYPASS, should be used when
measuring the output duty cycle during programming. The
blowing capacitor, CBLOW, should be removed during measurement and should only be applied when blowing fuses.
• The power supply used for programming must be capable of
delivering at least 26 V and 300 mA.
Bit Field Selection
Address Code Format
(Decimal Equivalent)
Code 5
Code in Binary
(Binary)
1 0 1
Fuse Blowing
Target Bits
Fuse Blowing
Address Code Format
Bit 2
• Be careful to observe the tLOW delay time before powering
down the device after blowing each bit.
• The following programming sequence is recommended:
1. Coarse fPWM
2.
3.
4.
5.
6.
Bit 0
Code 4
Code 1
(Decimal Equivalents)
Figure 4. Example of code 5 broken into its binary components, which are
code 4 and code 1.
Fine fPWM
Coarse D(Q)
Sens
Fine D(Q)
LOCK (only after all other parameters have been programmed and validated, because this prevents any further
programming of the device)
V+
VP(HIGH)
VP(MID)
VP(LOW)
0
Cycle VCC
supply
1
Mode
Selection
(Key 1)
1
2
Parameter
Selection
(Key 2)
1
2
3
Addressing
Bitfield 2
(Code 4)
4
Blow
Code 4
tBLOW
tLow
Cycle VCC
supply
Figure 5. Example of Blow mode programming pulses applied to the VCC pin. In this example, Fine D(Q) (Parameter
Key 2) is addressed to code 4 (corresponding to bit 2) and its value is permanently blown.
Allegro MicroSystems, Inc.
115 Northeast Cutoff
Worcester, Massachusetts 01615-0036 U.S.A.
1.508.853.5000; www.allegromicro.com
15
High Precision 2-Wire Linear Hall Effect Sensor IC
with Pulse Width Modulated Output
A1354
Programming Modes
Try Mode This mode allows multiple programmable parameters
to be tested simultaneously without permanently setting any
values. In this mode, each VPH pulse will indefinitely loop the
programming logic through the Mode Select, Register Select, and
Bitfield Select states, as long as there are no interruptions in the
VCC supply.
To enter Try mode, after powering the VCC supply and entering
the Initial state, send one VPH pulse to enter Mode Select state,
and then two VPM pulses (Mode Selection key 2).
Select the required parameter register and address its bitfield.
When addressing the bitfield, each VPM pulse increments the
value of the parameter register, up to the maximum possible
code (see the Programming Logic table). 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 conjunction with the original, enter an additional VPH pulse
on the VCC pin to re-enter the parameter selection field. Select
a different parameter register, and address its bitfield without
any supply interruptions. Both parameter values are stored and
can be measured after removing the programming drive voltage.
Multiple programming combinations can be tested to achieve
optimal application accuracy. See figure 6 for an example of the
Try mode pulse train.
Registers can be addressed and re-addressed an indefinite
number of times, and in any order. After the required code is
found for each register, cycle the supply voltage and blow the
bitfield fuse using Blow mode. Note that for accurate time measurements, the blow capacitor, CBLOW , should be removed during
output voltage measurement.
Blow Mode After 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, select
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 still be addressed in Blow mode before
fuse blowing (simultaneous addressing of multiple parameters,
as in Try mode, is not possible). After powering the VCC supply,
select the required parameter register and address its bitfield.
When addressing the bitfield, each VPM pulse increments the
value of the parameter register, up to the maximum possible code
(see Programming Logic table). 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.
Note that for accurate time measurements, the blow capacitor,
CBLOW, should be removed during output voltage measurement.
It is not possible to decrement the value of the register without
resetting the parameter bitfield. To reset the bit field, and thus the
value of the programmable parameter, cycle the supply voltage.
When testing the device in Try mode, it is recommended to select
parameter register 4, the null register, before tests. This recommendation is because the programming voltage levels overlap the
VCC operating levels, so varying VCC during tests in Try mode may
unintentionally result in device programming.
It is possible to switch between Try and Blow modes where
single programmable parameters can be blown in Blow mode
while other parameters can still be tested in Try mode.
Lock Mode To lock the device, address the LOCK bit, and
apply a blow pulse with CBLOW in place. After locking the
device, no future programming of any parameter is possible.
V+
VP(HIGH)
VP(MID)
VP(LOW)
0
1
2
Mode Selection:
Try Mode
(Key 2)
1
1
2
3
Addressing
Parameter
Selection:
Bitfields 0 and 1
Sens/Coarse D(Q)
(Key 1)
(Code 3)
1
Parameter
Selection:
Fine D(Q)
(Key 2)
2
1
2
Addressing
Bitfield 1
(Code 2)
Figure 6. 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
are stored in the device until the supply is cycled. Permanent fuse blowing cannot be accomplished in Try mode.
Allegro MicroSystems, Inc.
115 Northeast Cutoff
Worcester, Massachusetts 01615-0036 U.S.A.
1.508.853.5000; www.allegromicro.com
16
High Precision 2-Wire Linear Hall Effect Sensor IC
with Pulse Width Modulated Output
A1354
Programming State Machine
Power-up
VPM = VP(LOW) → VP(MID) → VP(LOW)
VPM
Initial
VPH = VP(LOW) → VP(HIGH) → VP(LOW)
VPH
VPH
Mode Select
[Mode Register Key sequence]
VPM
1
Blow
/Lock
2
Try
VPM
VPM
2 s VPH
[Try Mode]
VPH
Register Select
[Parameter Register Key sequence]
VPM
1
Sens/
Coarse
D(Q)
2
Fine
D(Q)
VPM
VPH
No
Fuse
Blowing
Yes
Blow or Lock
Mode?
VPM
4
Null
VPM
5
Calibration
Test Mode
/LOCK
VPM
[Bitfield Code sequence]
VPM
1
(Bitfield 0)
3
fPWM /
Coarse
fPWM
VPH
Bitfield Select
User Power-down
Required
VPM
VPM
2
(Bitfield 1)
VPH
Initial State A known state to which the programming logic is
reset after system power-up. All the bitfield locations that have
intact fuses are reset to logic 0. VPM pulses have no effect. To enter
the Mode Select state, apply a single VPH pulse to the VCC pin.
Mode Select State This state allows the selection of the Mode
register. To select a Mode register, increment through the keys by
applying VPM pulses to the VCC pin. Register keys select among
the following programing modes:
• 1 pulse – Blow and Lock
• 2 pulses – Try
To enter the Parameter Select state, apply 2 VPH pulses to the
VCC pin.
Parameter Select State This state allows the selection of the
Parameter register containing the bitfields to be programmed.
Applying VPM pulses to the VCC pin increments through the
Parameter registers:
• 1 pulse – Sensitivity / Coarse D(Q)
• 2 pulses – Fine D(Q)
• 3 pulses – PWM Frequency / Coarse PWM Frequency
• 4 pulses – Null
• 5 pulses – Calibration Test Mode / Device LOCK
VPM
3
(Bitfields 0
and 1)
VPM
2n – 1
n= bits in
register
VPM
[Optional: test output]
To enter the Bitfield Select state, apply 1 VPH pulse to the VCC pin.
Bitfield Select State This state allows the selection of the individual bitfields to be programmed in the selected Parameter register (see the Programming Logic table). Applying VPM pulses to
the VCC pin increments the bitfield.
In Try mode, to re-enter the Parameter Selection state, apply 1
VPH pulse on the VCC pin. The previously addressed parameter
retains its value as long as VCC is not cycled.
In Blow or Lock mode, to leave the Bitfield Select state requires
either cycling VCC or blowing the fuses for the selected code.
Note: Merely addressing the bitfield does not permanently set
the value of the selected programming parameter; fuses must be
blown to do so.
Fuse Blowing State To blow an addressed bitfield, apply a
VPH pulse to the VCC pin. Power to the device should then be
cycled before additional programming is attempted. Note: Each
bit representing a decimal code must be blown individually (see
the Fuse Blowing section).
Allegro MicroSystems, Inc.
115 Northeast Cutoff
Worcester, Massachusetts 01615-0036 U.S.A.
1.508.853.5000; www.allegromicro.com
17
High Precision 2-Wire Linear Hall Effect Sensor IC
with Pulse Width Modulated Output
A1354
Programming Logic
Bitfield Address
Register Selection Key
Binary Format
(MSB → LSB)
Description
Decimal Equivalent
Code
Mode Register Selection
Blow / Lock
1
01
2
10
1
Blow or Lock
2
Try
Try
Parameter Register Selection
Sensitivity / Coarse D(Q)
Initial value; D(Q) = D(Q)PRE , Sens = SensPRE
000000000
0
011111111
255
Maximum gain value in range
1 00000000
256
Enable Coarse D(Q) bit; switch from bidirectional
programming to unidirectional programming,
D(Q) = D(Q)UNIinit
1
Fine D(Q) (B = 0 gauss)
2
000000000
0
011111111
255
Initial value
Maximum D(Q) in range
1 00000000
256
Switch from programming increasing D(Q) to
programming decreasing D(Q)
111111111
511
Minimum D(Q) in range
PWM Frequency /Coarse PWM Frequency
3
00000
0
Initial value; fPWM = fPWMPRE
01111
15
Minimum fPWM in fPWM(fast) range
1 0000
16
Enable Coarse fPWM bit; switch from fPWM(fast)
programming to fPWM(slow) programming,
fPWM = fPWM(slow)init
11111
63
Minimum fPWM in fPWM(slow) range
–
–
Recommended to be selected before and during test
measurements performed in Try mode
Null
4
Calibration Test Mode / Lock All
5
0000000000
0
Initial value
000001 0000
16
Enable 50% duty cycle Calibration Test Mode bit
1 000000000
512
LOCK bit; lock all device registers
Allegro MicroSystems, Inc.
115 Northeast Cutoff
Worcester, Massachusetts 01615-0036 U.S.A.
1.508.853.5000; www.allegromicro.com
18
A1354
High Precision 2-Wire Linear Hall Effect Sensor IC
with Pulse Width Modulated Output
Programming Example
This example demonstrates the programming of the device. The
recommended sequence for programming is shown in the Additional Guidelines section, but for this example, we start at setting
the register for Fine Duty Cycle and then go on to final locking of
the device.
12. Send two VPH pulses to enter the Register Select state.
13. Send two VPM pulses to select the Fine D(Q) register.
14. Send one VPH pulse to enter the Bitfield Select state.
The Fine D(Q) register is reset to 000000000.
To find the correct duty cycle value:
15. Send one hundred and twenty-eight VPM pulses to set bitfield 7. (The bitfields can be set in any order.)
1. Power-on the system.
This resets all unprogrammed bits in all registers to 0. The
device enters the Initial state.
16. Send one VPH pulse to exit the Bitfield Select state.
The bitfield fuse is blown.
2. Send one VPH pulse to enter the Mode Select state.
3. Send two VPM pulses to select the Try mode.
4. Send two VPH pulses to enter the Register Select state.
5. Send two VPM pulses to select the Fine D(Q) register.
6. Send one VPH pulse to enter the Bitfield Select state.
The Fine D(Q) register is reset to 000000000.
7. For this example, send one hundred and twenty-eight VPM
pulses to set bitfield 7 (010000000, decimal 128).
Now we can measure the device output to see if this is the
required value. Assume for this example that the value is slightly
too low. So we proceed to change it, as follows:
8. Send one VPM pulse to increment the Fine D(Q) code by 1.
This yields a total register value of 129 by setting bitfield 0:
010000001.
Assume we measure the device and find this is the correct duty
cycle value we require. We are finished trying values for this
parameter, and now want to set the value permanently by blowing
the corresponding bitfield fuses. Blowing fuses is done one bitfield (one fuse) at a time. We are setting two bitfields, so we have
to blow them in two stages:
9. Reset the device by powering it off and on.
The device returns to the Initial state.
10. Send one VPH pulse to enter the Mode Select state.
11. Send one VPM pulse to select the Blow mode.
One of the two bitfields is programmed. Now we program the
other bitfield:
17. Repeat steps 9 to 14 to select the Fine D(Q) register again and
enter the Bitfield Select state. This time, however, the register
resets to 010000000, because bit 7 has been permanently set.
18. Send one VPM pulse to set bit 0.
19. Send one VPH pulse to exit the Bitfield Select state.
The bitfield fuse is blown.
Program the remaining parameter by repeating the above steps.
After programming all parameters, we can lock the device:
20. Reset the device by powering it off and on. The device returns
to the Initial state.
21. Send one VPH pulse to enter the Mode Select state.
22. Send one VPM pulse to select the Lock mode.
23. Send two VPH pulses to enter the Register Select state.
24. Send five VPM pulses to select the LOCK register. The register resets either to 0000000000, or to 0000010000 if Calibration Test mode has been previously enabled.
25. Send one VPH pulse to enter the Bitfield Select state.
26. Send five hundred and twelve VPM pulses to set the LOCK
bit, bitfield 9.
27. Send one VPH pulse to exit the Bitfield Select state. The bitfield fuse is blown. Programming of the device is complete.
Optionally, test the results, or power-off the device.
Allegro MicroSystems, Inc.
115 Northeast Cutoff
Worcester, Massachusetts 01615-0036 U.S.A.
1.508.853.5000; www.allegromicro.com
19
High Precision 2-Wire Linear Hall Effect Sensor IC
with Pulse Width Modulated Output
A1354
Calibration Test Mode
The Calibration Test mode is provided so that the user can compensate for differences in the ground potential between the A1354
and any interface circuitry used to measure the pulse width of the
A1354 output. This test mode is optional and must be enabled
by blowing its programming bit. After the test mode bit has been
blown, the device enters Calibration Test mode every time the
device is powered-up.
In customer applications the PWM interface circuitry (body control module: BCM in figure 7) and the A1354 may be powered
via different power and ground circuits. As a result, the ground
reference for the A1354 may differ from the ground reference of
the BCM. In some customer applications this ground difference
can be as large as ± 0.5 V.
Differences in the ground reference for the A1354 and the BCM
can result in variations in the threshold voltage used to measure
the duty cycle of the A1354. 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 waveform. This
problem is shown in figure 8.
The Calibration Test mode allows end users to compensate
for any threshold errors that result from a difference in system
ground potentials. While the A1354 is in the test period, the
VCC
1
VCC
BCM
4.7 kΩ
A1354
CBYPASS
GND
CL
10 nF
10 nF
4
GND1
GND2
Figure 7: In many applications the A1354 may be powered using a different ground
reference than the BCM. This may cause the ground reference for the A1354 (GND 1) to
differ from the ground reference of the BCM (GND 2) by as much as to ±0.5 V.
VOH
VOL
Figure 8. When the threshold voltage is correctly centered between VOH and VOL, the duty cycle accurately coincides with the
applied magnetic field. If the threshold voltage is raised, the output duty cycle appears shorter than expected. Conversely, if
the threshold voltage is lowered, the output duty cycle is longer than expected.
Allegro MicroSystems, Inc.
115 Northeast Cutoff
Worcester, Massachusetts 01615-0036 U.S.A.
1.508.853.5000; www.allegromicro.com
20
A1354
High Precision 2-Wire Linear Hall Effect Sensor IC
with Pulse Width Modulated Output
device output waveform is a fixed 50% duty cycle (the programmed quiescent duty cycle value) regardless of the applied
external magnetic field. After powering-up, the A1354 outputs
its quiescent duty cycle waveform for 800 ms, regardless of the
applied magnetic field (see figure 9). This allows the BCM to
compare the measured quiescent duty cycle with an ideal 50%
duty cycle.
During Calibration Teat mode
PMW output = 50% duty cycle
After the initial 800 ms has elapsed, the duty cycle corresponds to
an applied magnetic field as expected. The 800 ms calibration test
time corresponds to a PWM frequency of 125 Hz. If the PWM
frequency is programmed away from its target of 125 Hz, the
duration of the calibration test time will scale inversely with the
change in PWM frequency.
After the calibration expires, PWM output
proportional to external magnetic field
Figure 9. Calibration Test Mode. After powering-on, the A1354 outputs a 50% duty cycle for
the first 800 ms, regardless of the applied magnetic field (Calibration Test mode in effect).
After the initial 800 ms has elapsed, the output responds to a magnetic field as expected.
The example in this figure assumes that a large +B (south polarity) field is applied to the
device after the initial 800 ms.
Allegro MicroSystems, Inc.
115 Northeast Cutoff
Worcester, Massachusetts 01615-0036 U.S.A.
1.508.853.5000; www.allegromicro.com
21
High Precision 2-Wire Linear Hall Effect Sensor IC
with Pulse Width Modulated Output
A1354
Package KT, 4-Pin SIP
+0.08
5.21 –0.05
B
10°
E
F
2.60
+0.08
1.00 –0.05
1.35 F
+0.08
3.43 –0.05
Mold Ejector
Pin Indent
NNNN
YYWW
F
Branded
Face
A
0.89
MAX
1
0.54
REF
C
Standard Branding Reference View
N = Device part number
Y = Last two digits of year of manufacture
W = Week of manufacture
12.14±0.05
+0.08
0.41 –0.05
+0.08
0.20 –0.05
0.89
MAX
1
2
3
0.54
REF
4
+0.08
1.50 –0.05
For Reference Only; not for tooling use (reference DWG-9202)
Dimensions in millimeters
Dimensions exclusive of mold flash, gate burrs, and dambar protrusions
Exact case and lead configuration at supplier discretion within limits shown
Dambar removal protrusion (16X)
B
Gate and tie bar burr area
C
Branding scale and appearance at supplier discretion
D Thermoplastic Molded Lead Bar for alignment during shipment
D
1.27 NOM
A
+0.08
1.00 –0.05
E
Active Area Depth 0.37 mm REF
F
Hall element, not to scale
+0.08
5.21 –0.05
Copyright ©2009, Allegro MicroSystems, Inc.
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 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 life support devices or systems, if a failure of an Allegro product can reasonably be expected to cause the
failure of that life support device or system, or to affect the safety or effectiveness of that device or system.
The information included herein is believed to be accurate and reliable. However, Allegro MicroSystems, Inc. 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, Inc.
115 Northeast Cutoff
Worcester, Massachusetts 01615-0036 U.S.A.
1.508.853.5000; www.allegromicro.com
22
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