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A1667 Schematic ( PDF Datasheet ) - Allegro

Teilenummer A1667
Beschreibung Ring Magnet Sensor IC
Hersteller Allegro
Logo Allegro Logo 




Gesamt 15 Seiten
A1667 Datasheet, Funktion
A1667
True Zero-Speed, High Accuracy, Ring Magnet Sensor IC
FEATURES AND BENEFITS
▪ Optimized robustness to magnetic offset variation
▪ Small signal lockout for immunity against vibration
▪ Tight duty cycle and timing accuracy over full operating
temperature range
▪ True zero-speed operation
▪ Air gap independent switch points
▪ Large operating air gaps achieved through use of gain
adjust and offset adjust circuitry
▪ Defined power-on state (POS)
▪ Wide operating voltage range
▪ Digital output representing target profile
▪ Single chip sensing IC for high reliability
▪ Small mechanical size
▪ Fast startup
▪ Undervoltage lockout (UVLO)
Packages:
8-Pin SOIC (suffix L)
4-Pin SIP (suffix K)
Not to scale
DESCRIPTION
The A1667 is a true zero-speed ring magnet sensor integrated
circuit (IC) consisting of an optimized Hall IC available in
two package options that provides a user-friendly solution for
digital ring magnet sensing applications.
The sensor incorporates a dual element Hall IC that switches
in response to differential magnetic signals created by a
ring magnet. The IC contains a sophisticated compensating
circuit designed to eliminate the detrimental effects of magnet
and system offsets. Digital processing of the analog signal
provides zero-speed performance independent of air gap and
also dynamic adaptation of device performance to the typical
operating conditions found in automotive applications (reduced
vibration sensitivity). High-resolution peak detecting DACs
are used to set the adaptive switching thresholds of the device.
Hysteresis in the thresholds reduces the negative effects of any
anomalies in the magnetic signal associated with the targets
used in many automotive applications.
The open-drain output is configured for three-wire applications.
This sensor is ideal for obtaining speed and duty cycle
Continued on the next page…
KEY APPLICATIONS
• Automotive – Transmissions Applications
2- and 3-Wheeler Speed Applications
White Goods – Drum Speed Applications
Functional Block Diagram
VCC
Voltage
Regulator
Hall
Amp
Offset
Adjust
Automatic
Gain
Control
VPROC
PDAC
NDAC
PThresh
Reference
Generator
NThresh
Threshold
Comparator
Threshold
Logic
TEST
A1667-DS, Rev. 1
GND
Current
Limit
Output
Transistor
VOUT






A1667 Datasheet, Funktion
A1667
True Zero-Speed, High Accuracy, Ring Magnet Sensor IC
THERMAL CHARACTERISTICS: May require derating at maximum conditions; see application information
Characteristic
Symbol
Test Conditions*
Value Units
Package K, 1-layer PCB with copper limited to solder pads
177 ºC/W
Package Thermal Resistance
RθJA Package L, 1-layer PCB with copper limited to solder pads
140 ºC/W
Package L, 4-layer PCB based on JEDEC standard
80 ºC/W
*Additional thermal data available on the Allegro Website.
Power Derating Curve
20
19
18
17
16
15
14
Package L, 4-layer PCB
13 (RθJA = 80ºC/W)
12
11
Package L, 1-layer PCB
10 (RθJA = 140ºC/W)
9
8
Package K, 1-layer PCB
7 (RθJA = 177ºC/W)
6
5
4
3
2
VCC(max)
VCC(min)
20 40 60 80 100 120 140 160 180
Temperature (ºC)
Power Dissipation versus Ambient Temperature
1900
1800
1700
1600
1500
1400
1300
1200
1100
1000
900
Package L, 4-layer PCB
(RθJA = 80°C/W)
Package L, 1-layer PCB
(RθJA = 140°C/W)
800
700
Package K, 1-layer PCB
(RθJA = 177°C/W)
600
500
400
300
200
100
0
20 40 60 80 100 120 140 160 180
Temperature (°C)
Allegro MicroSystems, LLC
115 Northeast Cutoff
Worcester, Massachusetts 01615-0036 U.S.A.
1.508.853.5000; www.allegromicro.com
6

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A1667 pdf, datenblatt
A1667
True Zero-Speed, High Accuracy, Ring Magnet Sensor IC
Power Derating
The device must be operated below the maximum junction
temperature of the device, TJ(max). Under certain combinations of
peak conditions, reliable operation may require derating supplied
power or improving the heat dissipation properties of the appli-
cation. This section presents a procedure for correlating factors
affecting operating TJ. (Thermal data is also available on the
Allegro website.)
The Package Thermal Resistance, RθJA, 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, RθJC, is relatively
small component of RθJA. Ambient air temperature, TA, and air
motion are significant external factors, damped by overmolding.
The effect of varying power levels (Power Dissipation, PD), can
be estimated. The following formulas represent the fundamental
relationships used to estimate TJ, at PD. 
×PD = VIN IIN
(1)
ΔT = PD × RθJA
(2)
TJ = TA + ΔT
(3)
For example, given common conditions such as: TA= 25°C,
VCC = 12 V, ICC = 7.5 mA, and RθJA = 177 °C/W, then:
Example: Reliability for VCC at TA =150°C, package K, using a
single-layer PCB.
Observe the worst-case ratings for the device, specifically:
RθJA =177 °C/W, TJ(max)  =165°C, VCC(max) =24 V, and
ICC(max)= 12 mA.
Calculate the maximum allowable power level, PD(max). First,
invert equation 3:
ΔTmax = TJ(max) – TA = 165°C150°C = 15°C
This provides the allowable increase to TJ resulting from internal
power dissipation. Then, invert equation 2:
PD(max) = ΔTmax ÷ RθJA = 15°C ÷ 177 °C/W = 84.7 mW
Finally, invert equation 1 with respect to voltage:
  VCC(est) = PD(max) ÷  ICC(max) = 119 mW ÷ 12 mA = 7.1 V
The result indicates that, at TA, the application and device can
dissipate adequate amounts of heat at voltages ≤ VCC(est).
Compare VCC(est) to VCC(max). If VCC(est) ≤ VCC(max), then
reliable operation between VCC(est) and VCC(max) requires
enhanced RθJA. If VCC(est) ≥ VCC(max), then operation between
VCC(est) and VCC(max) is reliable under these conditions.
 PD = VCC × ICC = 12 V × 7.5 mA = 90 mW
ΔT = PD × RθJA = 90 mW × 177 °C/W = 11.3°C
 TJ = TA + ΔT = 25°C + 11.3°C = 36.3°C
A worst-case estimate, PD(max), represents the maximum allow-
able power level (VCC(max), ICC(max)), without exceeding
TJ(max), at a selected RθJA and TA.
Allegro MicroSystems, LLC
115 Northeast Cutoff
Worcester, Massachusetts 01615-0036 U.S.A.
1.508.853.5000; www.allegromicro.com
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