A17501POKATN-SDFUOKWA

A17501

Dual Output Differential Speed and Direction Sensor IC

FEATURES AND BENEFITS

DESCRIPTION

• High-speed switching bandwidth up to 40 kHz

• Two independent output channels with options for high

resolution XOR speed, pulse, and direction protocol

• ASIL B(D) compliant (ISO 26262), assessment pending

• Optional fault detection output protocol

• Immune to common external magnetic disturbance

• EEPROM enables factory traceability throughout product

life cycle

The A17501 is a single IC solution designed for rotational

position sensing of a ring magnet target found in automotive

and industrial electric motor applications (often with specific

application and safety requirements).

ThreeHallelementsareincorporatedtocreatetwoindependent

differential channels. These inputs are processed by digital

circuits and robust algorithms designed to eliminate the

detrimental effects of magnetic and system offsets, and to

address false output transitions caused by target vibrations

in electric motors at startup and low speed operation. The

differential signals are used to produce a highly accurate

speed output and, if desired, provide information on the

direction of rotation.

• Ideally suited for asynchronous electric motor applications

• Also available with integrated magnet (see ATS17501

datasheet)

2

-

Advanced calibration techniques are used to optimize signal

offset and amplitude. This calibration, combined with the

digital tracking of the signal, results in accurate switch points

over air gap, speed, and temperature.

PACKAGE:

The IC can be programmed for a variety of applications

requiring dual-phase target speed and position signal

information or simultaneous high-resolution target speed

and direction information. It can be configured to enable

Fault Detection mode for ASIL B(D) utilization (assessment

pending).

4-Pin SIP

(suffix K)

The A17501 K package is a lead (Pb) free 4-pin SIP package

with a 100% matte-tin-plated lead frame.

Not to scale

Functional Block Diagram

Analog

Regulator

EEPROM

VCC

Diagnostics

Digital

Regulator

Temperature

Sensor

OUTA

Digital

Controller

Oscillator

Hall

Elements

Analog

Gain

OUTB

GND

ADC

Filter

Analog

Filter

Gain

ADC

A17501-DS

MCO-0000793

March 19, 2020

Advance Information Datasheet • Subject to Change Without Notice

A17501

Dual Output Differential Speed and Direction Sensor IC

SELECTION GUIDE ^[1]

Part Number

Packing

A17501POKATN-SDFUYJE

4000 pieces per 13-inch reel

^[1]Not all selectable combinations are available, contact Allegro for additional

selections and packing options.

2

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A17501

Dual Output Differential Speed and Direction Sensor IC

ABSOLUTE MAXIMUM RATINGS

Characteristic

Symbol

V_CC

Notes

Refer to Power Derating section

Rating

28

Unit

V

Supply Voltage

Reverse Supply Voltage

Output Voltage

V_RCC

–18

28

V

V_OUT

Each output pin

V

Reverse Output Voltage

V_ROUT

Each output pin; R_PULLUP≥ 1 kΩ

–0.5

V

Short-term output current for OUTA and OUTB independently,

not intended for continuous operation

Output Sink Current

I_OUT

50

mA

Operating Ambient Temperature Range

Junction Temperature

T_A

T_J

–40 to 160

175

°C

Storage Temperature Range

T_stg

–65 to 170

PINOUT DIAGRAM

Branded

Face

1

2

3

4

K Package, 4-Pin SIP

PINOUT TABLE

Name

Function

VCC

1

2

3

4

Supply Voltage

OUTA

OUTB

GND

Configurable Output A

Configurable Output B

Ground

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A17501

Dual Output Differential Speed and Direction Sensor IC

TYPICAL APPLICATION CIRCUIT

[2]

V_PULLUP

V_SUPPLY

R_SERIES

R_PULLUP(A)

VCC

OUTA

V_OUT(A)

C_LOAD(A)

V_PULLUP

[2]

C_BYPASS

A17501

R_PULLUP(B)

GND

OUTB

V_OUT(B)

C_LOAD(B)

COMPONENTS ^[3]

Characteristic

Symbol

Notes

Value (Typ.)

Unit

Series Resistance

R_SERIES

Recommended for typical EMC requirements

100

1

Ω

Required for functional operation; recommended value

dependent on programming options

OUTA Pullup Resistance

R_PULLUP(A)

kΩ

Required for functional operation; recommended value

dependent on programming options

OUTB Pullup Resistance

Bypass Capacitance

R_PULLUP(B)

C_BYPASS

C_LOAD(A)

1

kΩ

nF

Recommended for typical EMC requirements

100

2.2

Recommended for typical EMC requirements; required for

certain programming options

OUTA Load Capacitance

Recommended for typical EMC requirements; required for

certain programming options

OUTB Load Capacitance

C_LOAD(B)

2.2

nF

[2]

V

may be connected to V_CCif V_CCmeets V_PULLUPrequirements. See Operating Characteristics section.

PULLUP

^[3]Components listed are typical recommended values and are not suited for all applications and/or programmable options. See Operating Characteristics and Selection Guide for more information.

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A17501

Dual Output Differential Speed and Direction Sensor IC

OPERATING CHARACTERISTICS: Valid throughout operating ranges, unless otherwise speciﬁed

Characteristic

Symbol

Test Conditions

Min.

Typ. ^[4]

Max.

Unit

ELECTRICAL SUPPLY CHARACTERISTICS

Supply Voltage ^[5]

V_CC

V_CC(UV)

I_CC

Voltage across VCC and GND

4

–

24

3.99

15

V

Undervoltage Lockout

Supply Current

V

–

10

–

mA

Reverse Supply Current

I_RCC

V_CC= –18 V

–10

–

ELECTRICAL PROTECTION CHARACTERISTICS

Supply Clamp Voltage

V_CSUPPLYT_A= 25°C; I_CC= 18 mA

V_RCSUPPLYT_A= 25°C; I_CC= –3 mA

28

–

–18

–

V

Reverse Supply Clamp Voltage

Output Clamp Voltage

V_COUT

T_A= 25°C; I_OUT= 3 mA

28

Current limited by design for short circuit event

on OUTA and OUTB independently;

low impedance output state

Output Current Internal Limiter

I_OUT(LIM)

30

55

85

mA

POWER-ON CHARACTERISTICS

Power-On State

POS

t_PO

For OUTA and OUTB

V_OUT(HIGH)

–

V

Time from V_CC> V_CC(min)to when sensor IC

output is valid

Power-On Time

–

1

ms

CALIBRATION CHARACTERISTICS

Amount of target rotation with constant direction

following power-on until first electrical output

transition; Dynamic Threshold option; see Figure 1

First Output Edge

–

1

2

T_CYCLE

–

Amount of target rotation with constant direction

following power-on until calibration is complete;

Dynamic Threshold option; see Figure 1

Initial Calibration

–

T_CYCLE

OUTPUT CHARACTERISTICS ^[6]

Fault Detection Mode disabled; I_OUT= 10 mA

–

0.165

–

0.35

1.25

V

5 V, 1 kΩ or 5 V, 3 kΩ

option

Output Low Voltage

V_OUT(LOW)

0.5

Fault Detection Mode

enabled

12 V, 1 kΩ option

1.2

–

3.6

–

V

Fault Detection Mode disabled

5 V, 1 kΩ or 5 V, 3 kΩ

V_PULLUP

Output High Voltage

V_OUT(HIGH)

3.75

8.4

–

4.5

V

Fault Detection Mode

enabled

option

12 V, 1 kΩ option

10.8

Continued on next page...

^[4]Typical values are at T_A= 25°C and V_CC= 5 V. Performance may vary for individual units, within the speciﬁed maximum and minimum limits.

^[5]Maximum voltage must be adjusted for power dissipation and junction temperature; see representative for Power Derating discussions.

^[6]Output characteristics are valid for each output independently, unless otherwise speciﬁed.

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A17501

Dual Output Differential Speed and Direction Sensor IC

OPERATING CHARACTERISTICS (continued): Valid throughout operating ranges, unless otherwise speciﬁed

Characteristic

Symbol

Test Conditions

Min.

Typ. ^[7]

Max.

Unit

OUTPUT CHARACTERISTICS (continued) ^[8]

Fault Detection

Mode enabled;

5 V, 1 kΩ or

High fault (V_FAULT(HIGH)

)

4.5

1.25

–

1

–

3.75

0.5

–

V

Mid fault (V_FAULT(MID)

Low fault (V_FAULT(LOW)

High fault (V_FAULT(HIGH)

Mid fault (V_FAULT(MID)

Low fault (V_FAULT(LOW)

)

V

5 V, 3 kΩ option

Fault Voltage ^[9]

V_FAULT

)

10.8

3.6

–

V

Fault Detection

Mode enabled;

12 V, 1 kΩ option

)

8.4

1.2

24

V

)

V

Fault Detection Mode disabled

4

V

Allowable Pullup Voltage

V_PULLUP

5 V, 1 kΩ or 5 V, 3 kΩ option

12 V, 1 kΩ option

4.75

11.4

–

5.25

12.6

–

V

Fault Detection

Mode enabled

V

Fault Detection Mode disabled

5 V, 1 kΩ option

Fault Detection

Mode enabled

kΩ

nF

µA

0.8

1.46

0.9

1

1.46

3.4

1.1

–

Allowable Pullup Resistor ^[10]

R_PULLUP

5 V, 3 kΩ option

12 V, 1 kΩ option

Allowable Load Capacitor ^[11]

Output Leakage Current

C_LOAD

Fault Detection Mode enabled

I_OUT(OFF)Fault Detection Mode disabled; V_OUT= V_OUT(HIGH)

–

10

Speed output protocol; Dynamic Threshold

option; sinusoidal input signal; f_OP< 1 kHz

Duty Cycle

D

45

–

50

5

55

–

%

µs

10%→90%; V_PULLUP= 5 V; R_PULLUP= 1 kΩ;

C_LOAD= 2.2 nF

Output Rise Time

t_r

Fault Detection Mode disabled;

–

0.5

3.5

6

–

Fast fall time option

90%→10%;

V_PULLUP= 5 V;

Fault Detection Mode disabled;

Output Fall Time

t_f

–

R_PULLUP= 1 kΩ; Slow fall time option

C_LOAD= 2.2 nF

Fault Detection Mode

–

enabled

Forward Pulse Width ^[12]

Reverse Pulse Width ^[12]

t_w(FWD)

t_w(REV)

38

76

45

90

52

µs

104

Delay from the magnetic signal crossing a switch

point threshold to the start of the output transition

Propagation Delay

t_d

–

8

–

µs

target degrees

B_DIFF(pk-pk)= 100 G

–

0.13

0.086

0.064

σ×6; sinusoidal

input signal;

f_OP= 1 kHz

Jitter ^[13]

B_DIFF(pk-pk)= 150 G

B_DIFF(pk-pk)= 200 G

–

Continued on next page...

^[7]Typical values are for V_CC= 5 V and T_A= 25°C, unless otherwise speciﬁed.

^[8]Output characteristics are valid for each output independently, unless otherwise speciﬁed.

^[9]Valid with Fault Detection Mode enabled and correct programming of the Fault Detection Load Circuit option; see Selection Guide.

^[10]See Application Circuit section.

^[11]Minimum capacitor required when Fault Detection Mode is enabled to ensure correct output levels over operating conditions. Increased load capacitance will directly impact maximum operating

frequency due to the increased rise and fall times; see Application Circuit section.

^[12]Time from start of output transition from V_OUT(HIGH)to V_OUT(LOW)to start of output transition from V_OUT(LOW)to V_OUT(HIGH). Measured pulse width will vary with load circuit conﬁgurations and measure-

ment thresholds. Valid with Pulse or Pulse Inverted output protocol; see Programming Options section.

^[13]Guaranteed by design and characterization only. Characterization performed by measuring greater than 1,000 falling output edges of the same target feature at constant temperature using Reference

Target 60-0, see Reference Target Characteristics section. Value representative of a 6-σ distribution, such that 99.76% of the measured values are within the speciﬁed target degree.

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A17501

Dual Output Differential Speed and Direction Sensor IC

OPERATING CHARACTERISTICS (continued): Valid over operating ranges, unless otherwise speciﬁed

Characteristic

Symbol

Test Conditions

Min.

Typ. ^[14]

Max.

Unit

SWITCH POINT CHARACTERISTICS

% of B_DIFF(PKPK); V_OUT= V_OUT(LOW)→ V_OUT

V_OUT(HIGH); Dynamic Threshold option

=

Operate Point

B_OP

B_RP

–

70

30

–

%

% of B_DIFF(PKPK); V_OUT= V_OUT(HIGH)→ V_OUT

V_OUT(LOW); Dynamic Threshold option

=

Release Point

Hysteresis

ΔB_DIFFafter

switch point

% of B_DIFF(PKPK);

Dynamic Threshold option

–

40

10

–

%

G

B_HYS

to allow next

output transition

Fixed Threshold option

INPUT CHARACTERISTICS

Sinusoidal input signal; forward and reverse

target rotation; not valid for Pulse or Inverse

Pulse output protocol

Operating Frequency

f_OP

0

–

40

kHz

Forward Pulse Operating Frequency

Reverse Pulse Operating Frequency

f_OP(FWD)

f_OP(REV)

Pulse or Inverse Pulse output protocol

0

–

9

6

kHz

Dynamic Threshold option;

f_OP≤ 20 kHz

30

40

–

G

Operating Magnetic Input ^[15]

B_DIFF(pk-pk)See Figure 2

Dynamic Threshold option;

f_OP> 20 kHz

Fixed Threshold option

100

–

G

Operating Magnetic Input Peak ^[15]

B_DIFF

See Figure 2

–1150

1150

Bounded amplitude ratio within T_WINDOW; no

missed output transitions; possible incorrect

direction information and/or reduction in switch

point accuracy; see Figure 3 and Figure 4

Operating Magnetic Input Signal

Variation ^[16]

ΔB_DIFF(pk-pk)

0.6

8

–

2

–

Operating Magnetic Input Signal

Variation Window

Rolling window in which ΔB_DIFF(pk-pk)cannot

exceed bounded ratio; see Figure 3 and Figure 4

T_WINDOW

T_CYCLE

THERMAL CHARACTERISTICS

Single-sided PCB, with copper limited to solder

pads

Package Thermal Resistance

R_θJA

–

177

–

°C/W

^[14]Typical values are for V_CC= 5 V and T_A= 25°C, unless otherwise speciﬁed.

^[15]Diﬀerential magnetic ﬁeld is measured for Left Channel (E1-E2) and Right Channel (E2-E3) independently; see Package Diagram. Magnetic ﬁeld is measured orthogonally to the branded package

face.

^[16]Operating magnetic input variation is valid for symmetrical peak variation about the signal oﬀset. B_DIFF(pk-pk)must always be greater than B_{DIFF(pk-pk,min)}

.

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A17501

Dual Output Differential Speed and Direction Sensor IC

REFERENCE

Typical Application Circuit

T_CYCLE

Target

S

N

S

N

S

T_CYCLE

B_DIFF

Figure 1: Deﬁnition of T_CYCLE

T_CYCLE= Target Cycle; the amount of rotation that moves one tooth and valley across the sensor.

B_DIFF= The differential magnetic flux density sensed by the IC.

Diﬀerential Magnetic Input

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Figure 2: Diﬀerential Magnetic Input

B_DIFF= The differential magnetic flux density sensed by the IC.

B_DIFF(pk-pk)= The peak-to-peak magnetic flux density sensed by the IC.

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A17501

Dual Output Differential Speed and Direction Sensor IC

Operating Magnetic Signal Variation and Window

Figure 3: Repeated Period Variation

Figure 4: Single Period Variation

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A17501

Dual Output Differential Speed and Direction Sensor IC

CHARACTERIZATION PLOTS ^[17]

^[17]Characterization data representative of distribution averages. Characterization tested with Dynamic Threshold algorithm at f_OP= 1 kHz, V_CC= 5 V, V_PULLUP= 5 V,

R_PULLUP= 1 kΩ, and C_LOAD= 2.2 nF unless otherwise speciﬁed.

10

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955 Perimeter Road

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A17501

Dual Output Differential Speed and Direction Sensor IC

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A17501

Dual Output Differential Speed and Direction Sensor IC

FUNCTIONAL DESCRIPTION

General

As shown in Figure 5, the A17501 supports three Hall elements

that sense the magnetic profile of the ring magnet target simulta-

neously but at different points (each channel spaced at 1.75 mm

pitch), generating two differential internal signals processed

for precise switching of the digital output signals. Direction of

rotation can be determined based on the phase relationship of the

two differential internal signals. The A17501 is intended for use

with ring magnet targets, or ferromagnetic targets when properly

back-biased.

N

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The Hall-effect sensor IC is self-calibrating and possesses a tem-

perature compensated amplifier as well as a full-range analog-to-

digital converter (ADC). This allows for accurate processing of

a wide range of target magnetic profile amplitudes and offsets.

The on-chip voltage regulator provides supply noise rejection

throughout the operating voltage range. Changes in tempera-

ture do not greatly affect the A17501 due to the stable amplifier

design and full-range ADC. The Hall elements and signal pro-

cessing electronics are integrated on the same silicon substrate.

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The A17501 is capable of providing digital information that is

representative of the mechanical features of a rotating target. Fig-

ure 5 shows the automatic translation of the mechanical profile

to the digital output signal. No additional optimization is needed,

and minimum processing circuitry is required. This ease of use

reduces design time and incremental assembly costs for most

applications.

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Figure 5: Magnetic Proﬁle and Switch Points

(B_OP= 70%, B_RP= 30%)

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A17501

Dual Output Differential Speed and Direction Sensor IC

Threshold Algorithms

The A17501 contains selectable algorithms for determining when

to produce an output transition from the magnetic input signal. For

all options, a threshold is set within the sensor IC that triggers the

output transition when crossed by the digitized magnetic signals

(switch point).

Ring Magnet

S N S N S N S N S

B_DIFF

Dynamic Threshold

With the A17501 programmed for the Dynamic Threshold option,

each switch point is calculated from information learned from the

previous target feature. This algorithm allows for robust tracking to

produce accurate output transitions for inconsistent magnetic input

signals (offset drift, amplitude changes, etc.).

Speed Output Protocol

After power-on, the magnetic input signal is tracked to find the

peaks of the signal. After each new peak is found, the switch points

are updated based on a percentage of the previous two peaks.

Figure 6: Dynamic Threshold Option

Switch Point Algorithm (B_OP= 70%, B_RP= 30%)

Fixed Threshold

With the A17501 programmed for the Fixed Threshold option, an

absolute threshold stored in memory is used to set the switch point

for both the operate point and release point. This algorithm allows

for accurate output transitions immediately after power-on for

consistent magnetic input signals without the need to “learn” the

signal. The threshold stored in memory and loaded during power-

on contains threshold levels over temperature to allow for offset

drift adjustment of the magnetic input signal over temperature. The

A17501 sensor IC contains a temperature sensor used continu-

ously to adjust the switch point over temperature as needed by the

application.

Ring Magnet

S N S N S N S N S

B_DIFF

The fixed thresholds stored in memory can be pre-programmed

for unique switch points over temperature for each application.

Additionally, the A17501 can find and set the threshold for each

installation over temperature during end-of-line calibration.

Speed Output Protocol

If during the application the magnetic input signal offset does not

match the programmed threshold stored in memory (due to inac-

curate programming, mechanical shift, etc.), the A17501 identifies

the threshold as “out of range”, calculates the threshold for the

current temperature, and updates the threshold to produce correct

output transitions. After the update, algorithms use the current

temperature to recharacterize the threshold over the operational

temperature range. This prevents the update from overcompensat-

ing the threshold at a distant temperature relative to the update

temperature. After the updated threshold is confirmed to be within

the magnetic input signal’s switch point range over several target

features, the updated threshold is stored into memory such that it

can be used for subsequent power-on cycles.

Figure 7: Fixed Threshold Option

Switch Point Algorithm

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A17501

Dual Output Differential Speed and Direction Sensor IC

from the magnetic input signal, the algorithm will transition from

using the fixed threshold switch point to using the dynamic thresh-

old switch points. This transition occurs only when the magnetic

input signal is near a maximum or minimum value, such that

“double-switching” on the transition can be avoided.

Hybrid Threshold

With the A17501 programmed for the Hybrid Threshold option,

the threshold is determined from the Fixed Threshold option at

startup, then transitions to the Dynamic Threshold option after

tracking signals have correctly acquired the magnetic input

signals. This algorithm allows for both accurate output transi-

tions immediately following power-on for consistent magnetic

input signals as well as robust tracking to produce accurate output

transitions of inconsistent magnetic input signals (offset drift,

amplitude changes, etc.).

While the majority of the power-on will use the Dynamic Thresh-

old option for robust signal tracking, the A17501 will continue to

monitor the fixed threshold for comparison to the fixed threshold

stored in memory. Should the fixed threshold require an update, the

A17501 will update and write the new threshold to memory for use

in subsequent power-on cycles.

Once the tracking signals have identified consistent peak values

14

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955 Perimeter Road

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A17501

Dual Output Differential Speed and Direction Sensor IC

put transitions. These channels are determined by the Hall elements

used to produce the differential signal, where the left channel

Output

The A17501 contains a number of selectable options to change the

output protocol or adjust the output behavior. These options allow for

the A17501 to be programmed to application-level needs.

differential signal is determined by the left and center element (E1-

E2), and the right channel is referenced from the center and right

element (E2-E3); see Package Diagram. XOR Speed and Direction

output protocols are channel-independent, as both channels are

used to determine the output transitions.

Output Protocol

The A17501 contains several programmable output protocols; see

Figure 8. These protocols can be programmed for either output

pin (OUTA or OUTB) independently. For example, Left Chan-

nel Speed can be programmed as the output protocol for OUTA,

OUTB, or both output pins.

For Speed, XOR Speed and Direction output protocols, the polarity

of the signal can be inverted by selecting the “Inverse” option of

the corresponding protocol. Selecting one of these options will

invert the polarity of the output (V_OUT(HIGH)and V_OUT(LOW)) rela-

tive to the B_DIFFsignal(s). For the Pulse output protocols, selecting

the “Inverse” option will invert the pulse width for forward and

reverse rotation (t_w(FWD)and t_w(REV)).

The A17501 contains two independent signal paths. Most out-

put protocols reference a specific magnetic input signal channel

(B_DIFF(LEFT)or B_DIFF(RIGHT)), which is used to determine the out-

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Cꢊanꢋe in Direction

ꢀ_{DIꢁꢁꢂꢇIꢈꢉꢅꢆ}

ꢃeft Cꢊannel

Speed

ꢇiꢋꢊt Cꢊannel

Speed

ꢃeft Cꢊannel

Speed Inꢌerted

ꢇiꢋꢊt Cꢊannel

Speed Inꢌerted

ꢍOꢇ

ꢍOꢇ Inꢌerted

Direction

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ꢏ_{OꢐꢅꢂꢉIꢈꢉꢆ}

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Direction Inꢌerted

ꢏ_{OꢐꢅꢂꢉIꢈꢉꢆ}

ꢃeft Cꢊannel

ꢎulse

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ꢎulse

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ꢎulse Inꢌerted

ꢇiꢋꢊt Cꢊannel

ꢎulse Inꢌerted

Figure 8: Output Protocol Options

15

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A17501

Dual Output Differential Speed and Direction Sensor IC

Fault Detection Mode

t_PO

The A17501 allows for the output to transition between one

of two sets of values. With Fault Detection mode disabled, the

output will transition between approximately 0% and 100% of

V_PULLUP. With Fault Detection mode disabled, the output transi-

V_HIGH= V_PULLUP

tions between approximately 20% and 80% of V_PULLUP

.

At the beginning of power-on, the A17501 outputs initialize to

the V_PULLUPlevel. With Fault Detection mode enabled, the output

levels transition from V_PULLUPto V_HIGHbefore the end of power-

on. After power-on, the output transitions as determined by the

programmed algorithm and output protocol between V_OUT(HIGH)

V_LOW

and V_OUT(LOW)

.

Figure 9: Fault Detection Mode Disabled Output

Enabling Fault Detection mode allows for additional communica-

tion for cases of open wire or short circuit, as well as allowing

for the A17501 to communicate a fault detected from the internal

diagnostics. For a typical application load circuit, these cases can

be detected by observing either OUTA or OUTB transition to

t_PO

V_PULLUP

V_HIGH

approximately 0 V or V_PULLUPafter t_PO

.

V_LOW

0 V

Figure 10: Fault Detection Mode Enabled Output

16

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A17501

Dual Output Differential Speed and Direction Sensor IC

Fault Voltage

>1 ms

The A17501 communicates a fault condition by configuring

either output to hold within one of three V_FAULTranges (high,

mid, and low) for greater than 1 millisecond. Normal operation

allows for output transitions to occur over the V_FAULT(MID)range;

as such, it is necessary to ignore fast transients for less than

1 millisecond through this range.

V_{FAULT (HIGH,min)}

V_{FAULT (MID,max)}

For internal diagnostics that trigger fault conditions (force the

output to go to V_FAULT), both outputs will go to the V_FAULT(HIGH)

range. As there may exist internal or external faults that cause

either or both output pins to hold a V_FAULT(MID)or V_FAULT(LOW)

level, these fault ranges should also be monitored. Examples of

these fault conditions could be a short circuit of the output to

ground, forcing the output to V_FAULT(LOW), or a fault in the IC

V_{FAULT (MID,min)}

output controller that forces the output to V_FAULT(MID)

.

See Figure 11, Figure 12, and Figure 13 for examples of the out-

put communicating a fault condition.

Normal Opera�on

Assumed Fault

Figure 11: Assumed Fault Example: High Fault

>1 ms

V_{FAULT (HIGH,min)}

V_{FAULT (MID,max)}

V_{FAULT (MID,min)}

Normal Opera�on

Assumed Fault

Figure 12: Assumed Fault Example: Mid Fault

Figure 13: Assumed Fault Example: Low Fault

17

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A17501

Dual Output Differential Speed and Direction Sensor IC

DEVICE FEATURES

Undervoltage Lockout

Vibration Robust Signal Tracking

When supply voltage falls below the Undervoltage Lockout volt-

age (V_CC(UV)), the A17501 enters Reset, where the output state

returns to the Power-On State (POS) until sufficient V_CCis sup-

plied. This feature prevents false signals, caused by undervoltage

conditions, from propagating to the output of the sensor IC.

During vibration events, the magnetic input signals can produce

oscillations with a sufficient amplitude for the peak tracking

algorithms to bound in and produce a non-ideal peak-to-peak.

When the A17501 detects a direction change, inward bounding

of the peak tracking signals is prevented. This prevents cases of

erroneous output transitions from switch points being incorrectly

set from vibration signals. Additionally, this allows for immediate

acquisition of the magnetic input signals once real target rotation

resumes following a vibration event.

Power Supply Protection

The A17501 contains an on-chip regulator and can operate over

a wide V_CCrange. For applications that need to operate from an

unregulated power supply, transient protection must be added

externally. For applications using a regulated line, EMI/RFI pro-

tection is recommended. Contact Allegro for more information

Signature Region Robust Signal Tracking

Signature teeth (characterized by an extra target tooth and/or

about circuitry to address EMC requirement compliance. Refer to valley) can produce significant variations of the magnetic input

the Typical Application Circuit section.

signals. The bounded updating of the tracking signals prevent

overcompensation for these signature variations to provide robust

and accurate switch points for the signature region, as well as the

features about the signature region.

Startup Hysteresis

With a Power-On and a target held at zero-speed (f_OP≈ 0 Hz),

noise and/or vibration can produce magnetic input signals.

Startup hysteresis prevents peak tracking and switch point setting

at startup immediately following power-on. This occurs until

the sensed differential magnetic signal has moved sufficiently

to satisfy the hysteresis band for signal tracking. This feature

helps to ensure optimal self-calibration of the magnetic signals

by rejecting electrical noise and low-amplitude target vibrations

during startup and ensures that calibration occurs on actual target

features.

Temperature Drift Robust Signal Tracking

As temperature changes can impact both the amplitude and offset

of the magnetic signal, a full-range ADC, advanced algorithms,

temperature compensation, watchdog timers, and an internal tem-

perature sensor ensure robust signal tracking over temperature.

To compensate for amplitude changes over temperature, tempera-

ture compensated gain is first applied to normalize the amplitude

over temperature. The full-range ADC and peak tracking algo-

rithms track and acquire the signal to accurately set the switch

points.

Small Signal Lockout

When B_DIFF(pk-pk)falls below specification, the internal logic of

the sensor IC will indicate a reduced signal, as measured in an

excessive air gap or a vibration condition. Small Signal Lockout

will hold the output state at the level when B_DIFF(pk-pk)was last

in-specification. Once B_DIFF(pk-pk)returns to an in-specification

value, the output state is released to transition as expected during

normal operation. When direction information is not explicitly

defined by the selected output protocol, Small Signal Lockout

is controlled independently for each channel. For example, Left

Channel Speed + Right Channel Speed output protocol will allow

for one channel to continue switching while the other is in lock-

out. When direction information is explicitly communicated, for

example XOR + Direction output protocol, Small Signal Lockout

will occur when either channel’s B_DIFF(pk-pk)falls below specifi-

cation.

To compensate for offset changes over temperature, two algo-

rithms are implemented to ensure the signal tracking accurately

follows and updates the switch points to follow the offset. With

nominal target rotation, peak-tracking algorithms automatically

follow and update the switch points over offset drift. With no

target rotation (stopped condition), a watchdog timer is imple-

mented which adjust the algorithms to track together, allowing

for preservation of the correct signal peak-to-peak and switch

points once rotation resumes.

With the Fixed Threshold algorithm option selected, algorithms

are implemented for continuous monitoring and updating of the

fixed threshold over temperature to follow the offset drift of the

system. This compensation is implemented for each channel

independently to provide robust tracking of both signal channels

over temperature.

18

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955 Perimeter Road

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www.allegromicro.com

A17501

Dual Output Differential Speed and Direction Sensor IC

to-peak and phase relationship of the magnetic input signals can

meet the conditions to calibrate. Once normal rotation resumes,

Diagnostics and Fault Reporting

The A17501 contains diagnostics monitors of analog and digital

circuits of the IC. These continuously monitor and report if any

defect, calculation error, or invalid input stimulus is found. If a

diagnostic monitor fires, the outputs of the A17501 will transi-

tion to a V_FAULTlevel. For all faults, the outputs will remain at

the V_FAULTlevel for enough time to allow the system controller

to monitor that a fault has occurred. For some diagnostics, it is

possible to clear the fault with a reset of the internal controller

of the sensor IC. If any of those diagnostic monitors triggers the

fault event, the A17501 will automatically perform a reset of the

internal controller after the output is held V_FAULTfor enough time

to allow the system controller to monitor the fault event.

the actual signal amplitudes can be much larger than the peak

signals acquired during calibration. Rather than wait several

T_CYCLEevents for the peak signal to be tracked to actual levels,

the A17501 will detect the difference and recalibrate on the new

signal. Recalibration allows for fast and robust correction from

cases of calibration on vibration events.

Pulse Collision Prevention

In cases of “high-speed” vibration, output transitions can occur at

very high frequencies, to prevent pulse collision (truncation of the

pulse width), the A17501 will prevent output transitions until the

current output pulse transition is complete to ensure the system

controller can accurately interpret the output signal. This feature

is only implemented when a pulse protocol option is selected.

For diagnostics and fault reporting to perform correctly, proper

programming and adherence to the specifications and assump-

tions stated in this datasheet, the A17501 Safety Manual, and any

other addendum, corrigendum, and application note that applies

to the A17501. For more information on diagnostics and fault

reporting, see the A17501 Safety Manual.

High Conﬁgurability

The A17501 contains programmable parameters, as shown in the

Selection Guide, that can be configured to provide application-

level optimization.

Recalibration

Under large amplitude vibration conditions at startup, the peak-

19

Allegro MicroSystems

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955 Perimeter Road

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A17501

Dual Output Differential Speed and Direction Sensor IC

POWER DERATING

The device must be operated below the maximum junction tem-

perature of the device (T_J(max)). Under certain combinations of

peak conditions, reliable operation may require derating supplied

power or improving the heat dissipation properties of the appli-

cation. This section presents a procedure for correlating factors

affecting operating T_J. (Thermal data is also available on the

Allegro MicroSystems website.)

A worst-case estimate, P_D(max), represents the maximum allow-

able power level (V_CC(max), I_CC(max)), without exceeding T_J(max)

at a selected R_θJAand T_A.

,

For example, calculating reliability of V_CCgiven observed worst-

case ratings, specifically:

T_A= 160°C, R_θJA=177°C/W, T_J(max)=175°C, V_CC(max)= 24 V,

and I_CC(max)= 15 mA.

The Package Thermal Resistance (R_θJA) is a figure of merit sum-

marizing the ability of the application and the device to dissipate

heat from the junction (die), through all paths to the ambient air.

Its primary component is the Effective Thermal Conductivity (K)

of the printed circuit board, including adjacent devices and traces.

Radiation from the die through the device case (R_θJC) is a rela-

tively small component of R_θJA. Ambient air temperature (T_A) and

air motion are significant external factors, damped by overmolding.

Calculation of the maximum allowable power, P_D(max), can be

done by first inverting equation 3 and calculating the maximum

allowable increase to T_J:

ΔT_max= T_J(max)– T_A= 175°C–160°C = 15°C

Then, maximum allowable power can be calculated by:

P_D(max)= ΔT_max÷R_θJA=15°C÷177°C/W=84.7mW

The effect of varying power levels (Power Dissipation or P_D), can

be estimated. The following formulas represent the fundamental

relationships used to estimate T_J, at P_D.

Finally, invert equation 1 with respect to voltage:

V_CC(est)= P_D(max)÷ I_CC(max)= 84.7mW÷15mA=5.65 V

The results indicate that, at T_A, the application and A17501 can

dissipate adequate amounts of heat at voltages less than or equal

P_D= V_IN

I

(1)

(2)

(3)

×

IN

ꢀ

ΔT = P_D

R

×

θJA

to V_CC(est)

.

T_J= T_A+ ΔT

Compare V_CC(est)to V_CC(max). If V_CC(est)≤ V_CC(max), then reli-

able operation between V_CC(est)and V_CC(max)requires enhanced

R_θJA. If V_CC(est)≥ V_CC(max), then operation between V_CC(est)and

V_CC(max)is reliable under these conditions.

For example, given common conditions such as: T_A= 25°C,

V_CC= 12 V, I_CC(avg)= 8.5 mA, and R_θJA= 177°C/W, then:

P_D= V_CC

I

= 12 V 8.5 mA = 102 mW

CC(avg)

×

ΔT = P_D

R

= 102 mW 177°C/W = 18.1°C

×

θJA

T_J= T_A+ ΔT = 25°C + 18.1°C = 43.1°C

20

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March 19, 2020

A17501

Dual Output Differential Speed and Direction Sensor IC

PACKAGE OUTLINE DRAWING

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Exact case and lead conﬁguration at supplier discretion within limits shown

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ꢓ

ꢐꢐꢐꢐ

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ꢄꢅꢁꢃ

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ꢓ

ꢈ

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ꢃꢅꢀꢊ ꢋꢌꢍ

Figure 14: Package K, 4-Pin SIP

21

Allegro MicroSystems

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March 19, 2020

955 Perimeter Road

Manchester, NH 03103-3353 U.S.A.

www.allegromicro.com

A17501

Dual Output Differential Speed and Direction Sensor IC

Revision History

Number

Date

March 19, 2020

Description

–

Initial release

Allegro MicroSystems reserves the right to make, from time to time, such departures from the detail specifications as may be required to permit

improvements in the performance, reliability, or manufacturability of its products. Before placing an order, the user is cautioned to verify that the

information being relied upon is current.

Allegro’s products are not to be used in any devices or systems, including but not limited to life support devices or systems, in which a failure of

Allegro’s product can reasonably be expected to cause bodily harm.

The information included herein is believed to be accurate and reliable. However, Allegro MicroSystems assumes no responsibility for its use; nor

for any infringement of patents or other rights of third parties which may result from its use.

Copies of this document are considered uncontrolled documents.

For the latest version of this document, visit our website:

www.allegromicro.com

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型号：	A17501POKATN-SDFUOKWA
厂家：	ALLEGRO MICROSYSTEMS
描述：	Dual Output Differential Speed and Direction Sensor IC
文件：	总22页 (文件大小：1778K)
中文：	中文翻译
下载：	下载PDF数据表文档文件

A17501POKATN-SDFUOKWA [ALLEGRO]

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