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Description
The A1642 is an optimized Hall effect sensing integrated circuit that provides a user-friendly solution for true zero-speed digital ring-magnet sensing in two-wire applications. This small package can be easily assembled and used in conjunction with a wide variety of target shapes and sizes. The integrated circuit incorporates dual Hall effect elements and signal processing that switches in response to differential magnetic signals created by ring magnet poles. The circuitry contains a sophisticated digital circuit to reduce system offsets, to calibrate the gain for air-gap–independent switchpoints, and to achieve true zero-speed operation. Signal optimization occurs at power-on through the combination of offset and gain adjust and is maintained throughout the operating time with the use of a running-mode calibration. The running-mode calibration allows immunity to environmental effects such as micro-oscillations of the target or sudden air gap changes. The regulated current output is configured for two-wire applications and the A1642 is ideally suited for obtaining speed and duty cycle information in ABS (antilock braking systems). The 1.5 mm spacing between the dual Hall elements is optimized for fine pitch ring-magnet–based configurations. For applications requiring sensing of rotating ferrous gears and targets, refer to the Allegro ATS series of products. The package is lead (Pb) free, with 100% matte tin leadframe plating. A1642LKN-DS, Rev. 4 Features and Benefits ▪ Running mode calibration for continuous optimization ▪ Single chip IC for high reliability ▪ Internal current regulator for 2-wire operation ▪ Precise duty cycle signal over operating temperature range ▪ Large operating air gaps ▪ Automatic Gain Control (AGC) for air gap independent switchpoints ▪ Automatic Offset Adjustment (AOA) for signal processing optimization ▪ True zero-speed operation ▪ Undervoltage lockout ▪ Wide operating voltage range ▪ Wide-lead package suitable for welding external components directly to the package leads or for welding the device to a leadframe. Two-Wire True Zero-Speed Miniature Differential Peak-Detecting Sensor IC with Continuous Calibration Package: 4-pin SIP (Suffix KN) Functional Block Diagram Not to scale A1642 VCC Automatic Offset Control AOA DAC Hall Amplifier AGC DAC Gain Tracking DAC Peak Hold Gain Control Internal Regulator Test Signals GND Test
Two-Wire True Zero-Speed Miniature Differential Peak-Detecting Sensor IC with Continuous CalibrationA1642 2Allegro MicroSystems, LLC
115 Northeast Cutoff
Worcester, Massachusetts 01615-0036 U.S.A. 1234 Pin-out Diagram Absolute Maximum Ratings Characteristic Symbol Notes Rating Units Supply Voltage V CC 28 V Reverse Supply Voltage V RCC –18 V Operating Ambient Temperature T A Range L –40 to 150 ºC Maximum Junction Temperature T J(max) 165 ºC Storage Temperature T stg –65 to 170 ºC Terminal List Table Number Name Function
1 VCC Connects power supply to chip
2 NC No connection
3 Test Float or tie to GND
4 GND Ground connection
Part Number I CC Range Packing* A1642LKNTN-I1-T 4.0 mA Low to 16.0 mA High Tape and reel, 13-inch reel 4000 pieces per reelA1642LKNTN-I2-T 5.9 mA Low to 16.8 mA High A1642LKNTN-I3-T 5.9 mA Low to 16.0 mA High *Contact Allegro for additional packing options
Two-Wire True Zero-Speed Miniature Differential Peak-Detecting Sensor IC with Continuous CalibrationA1642 3Allegro MicroSystems, LLC Worcester, Massachusetts 01615-0036 U.S.A. OPERATING CHARACTERISTICS TA and VCC within specifi cation, unless otherwise noted CHARACTERISTIC Symbol Test Conditions Min. Typ. 1 Max. Units
ELECTRICAL CHARACTERISTICS
2 VCC Operating; TJ < 165°C 4.0 – 24 V Undervoltage Lockout V CC(UV) VCC 0 → 5 V and 5 → 0 V – – 4.0 V Supply Zener Clamp Voltage V Z ICC = ICC(max) + 3 mA; TA = 25°C 28 – – V Supply Zener Current I Z Test conditions only; VZ = 28 V – – ICC(max)+ 3 mA mA Supply Current ICC(Low) A1642LKN-I1 4.0 6.0 8.0 mA A1642LKN-I2, A1642LKN-I3 5.9 7.0 8.4 mA ICC(High) A1642LKN-I1, A1642LKN-I3 12.0 14.0 16.0 mA A1642LKN-I2 11.8 14.0 16.8 mA Supply Current Ratio ICC(High)/ ICC(Low) Ratio of high current to low current 1.85 – 3.05 – Reverse Battery Current I RCC VRCC = –18 V – – –5 mA POWER-ON STATE CHARACTERISTICS Power-On State
3 POS t > t PO –I CC(High) ––
Power-On Time4 tPO fOP < 100 Hz – 1 2 ms OUTPUT STAGE Output Slew Rate 5 dI/dt R LOAD = 100 Ω, CLOAD = 10 pF – 14 – mA/ μs Continued on the next page.
Two-Wire True Zero-Speed Miniature Differential Peak-Detecting Sensor IC with Continuous CalibrationA1642 4Allegro MicroSystems, LLC Worcester, Massachusetts 01615-0036 U.S.A. OPERATING CHARACTERISTICS (continued) TA and VCC within specifi cation, unless otherwise noted Characteristic Symbol Test Conditions Min. Typ. 1 Max. Units SWITCHPOINT CHARACTERISTICS Operating Speed f OP 0 – 8,000 Hz Analog Signal Bandwidth BW Equivalent to f – 3 dB 20 40 – kHz Operate Point B OP Transitioning from ICC(High) to ICC(Low); positive peak referenced; AG < AGMAX – 120 – mV Release Point B RP Transitioning from ICC(Low) to ICC(High); negative peak referenced; AG < AGMAX – 120 – mV CALIBRATION Initial Calibration C I Quantity of rising output (current) edges required for accurate edge detection – – 3 Edge DAC CHARACTERISTICS Allowable User-Induced Differential Offset Operating within specifi cation – – ±90 G FUNCTIONAL CHARACTERISTICS6 Operating Signal Range7 Sig Operating within speci fi cation 30 – 1000 G Minimum Operating Signal Sig OP(min) Output switching (no missed edges); ∆DC not guaranteed 20 – – G 1Typical values are at TA = 25°C and VCC = 12 V. Performance may vary for individual units, within the specifi ed maximum and minimum limits. 2Maximum voltage must be adjusted for power dissipation and junction temperature; see Power Derating section. 3Please refer to Device Operation section. 4Power-On Time includes the time required to complete the internal automatic offset adjust. The DAC is then ready for peak acquisition. 5dI is the difference between 10% of ICC(Low) and 90% of ICC(High), and dt is the time period between those two points. Note: dI/dt is dependent upon the value of the bypass capacitor, if one is used. 6Functional characteristics valid only if magnetic offset is within the specifi ed range for Allowable User Induced Differential Offset. 7In order to remain in specifi cation, the magnetic gradient must induce an operating signal greater than the minimum value speci fi ed. This includes the effect of target wobble.
Two-Wire True Zero-Speed Miniature Differential Peak-Detecting Sensor IC with Continuous CalibrationA1642 5Allegro MicroSystems, LLC Worcester, Massachusetts 01615-0036 U.S.A. Characteristic Data Supply Current (High) versus Ambient Temperature (I1 Trim) -50 0 50 100 150 TA (°C) ICC(HIGH) (mA) Vcc (V) Supply Current (High) versus Supply Voltage (I1 Trim) 0 5 10 15 20 25 VCC (V) ICC(HIGH) (mA) TA (°C) -40 150 Supply Current (Low) versus Ambient Temperature (I1 Trim) -50 0 50 100 150 TA (°C) ICC(LOW) (mA) Vcc (V) Supply Current (Low) versus Supply Voltage (I1 Trim) 0 5 10 15 20 25 VCC (V) ICC(LOW) (mA) TA (°C) -40 150
Two-Wire True Zero-Speed Miniature Differential Peak-Detecting Sensor IC with Continuous CalibrationA1642 6Allegro MicroSystems, LLC Worcester, Massachusetts 01615-0036 U.S.A. ΔTEAGIN (mm) ΔTEAGOUT (mm) Allowable Air Gap Movement from TEAGCAL* -0.2 0.2 0.4 0.6 0.8 1.0 1.2 Characteristic Allowable Air Gap Movement The colored area in the chart above shows the region of allow- able air gap movement within which the device will continue output switching. The output duty cycle is wholly dependent on the target’s magnetic signature across the air gap range of move- ment, and may not always be within specifi cation throughout the entire operating region (to AG (OPmax)). The axis parameters for the chart are defi ned in the drawings below. As an example, assume the case where the air gap is allowed to vary from the nominal installed air gap (TEAG CAL , panel a) within the range defi ned by an increase of TEAGOUT = 0.35 mm (shown in panel b), and a decrease of TEAGIN = 0.65 mm (shown in panel c). This case is plotted with an “x” in the chart above. TEAGINA1642 A1642 TEAGOUT (a) A1642 TEAGCAL (b) (c) *Data based on study performed using spur gear reference target 60-0, and applicable to ring magnet targets with similar magnetic characteristics.
Two-Wire True Zero-Speed Miniature Differential Peak-Detecting Sensor IC with Continuous CalibrationA1642 7Allegro MicroSystems, LLC Worcester, Massachusetts 01615-0036 U.S.A. THERMAL CHARACTERISTICS may require derating at maximum conditions, see application information CHARACTERISTIC Symbol TEST CONDITIONS* Value Units Package Thermal Resistance RθJA Single-layer PCB with copper limited to solder pads 170 ºC/W *Additional information is available on the Allegro Web site. 1300 1200 1100 1000 900 800 700 600 500 400 300 200 100 Power Dissipation versus Ambient Temperature QJA = 170 ºC/W) 20 40 60 80 100 120 140 160 180 Ambient Temperature, TA (°C) Power Dissipation, PD (mW) 20 40 60 80 100 120 140 160 180 Ambient Temperature, TA (ºC) Maximum Allowable VCC (V) Power Derating Curve (RQJA = 170 ºC/W) VCC(min) VCC(max)
Worcester, Massachusetts 01615-0036 U.S.A. a proprietary BiCMOS process. Figure 1. Relative motion of the target is detected by the dual Hall ele- ments mounted on the Hall IC. Figure 2. This left-to-right (pin 1 to pin 4) direction of target rotation 1) rotation inverts the output signal polarity. Figure 4: Voltage profi les for high side and low side two-wire sensing. Figure 3. Output Profi le of a ring magnet target for the polarity
Worcester, Massachusetts 01615-0036 U.S.A. to achieve true zero-speed operation. Figure 5. Automatic Gain Control (AGC). The AGC function corrects for
Two-Wire True Zero-Speed Miniature Differential Peak-Detecting Sensor IC with Continuous CalibrationA1642 10Allegro MicroSystems, LLC Worcester, Massachusetts 01615-0036 U.S.A. Power Supply Protection The device contains an on-chip regulator and can operate over a wide VCC range. For devices 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 may still be required. Contact Allegro Microsystems for information on the circuitry needed for compliance with various EMC specifi cations. Refer to fi gure 7 for an example of a basic application circuit. Undervoltage Lockout When the supply voltage falls below the undervoltage lockout voltage, VCC(UV), the device enters Reset, where the output state returns to the Power-On State (POS) until suffi cient VCC is sup- plied. ICC levels may not meet datasheet limits when VCC < VCC(min). Assembly Description This device is integrally molded into a plastic body that has been optimized for size, ease of assembly, and manufacturability. High operating temperature materials are used in all aspects of construction. Diagnostics The regulated current output is confi gured for two wire appli- cations, requiring one less wire for operation than do switches with the more traditional open-collector output. Additionally, the system designer inherently gains diagnostics because there is always output current flowing, which should be in either of two narrow ranges, shown in figure 8 as I CC(High) and ICC(Low). Any current level not within these ranges indicates a fault condi- tion. If I CC > ICC(High)max, then a short condition exists, and if ICC < ICC(low)min, then an open condition exists. Any value of ICC between the allowed ranges for ICC(High) and ICC(Low) indicates a general fault condition. Figure 7: Typical Application Circuit A1642 VCC GND 0.01 µF ECU Pins 2 and 3 floating R 100 Ω SENSE CBYP Figure 8: Diagnostic Characteristics of Supply Current Values ICC(High)max ICC(High)min Range for Valid ICC(HIGH) Range for Valid ICC(LOW) ICC(Low)max ICC(Low)min +mA Short Fault Open
Two-Wire True Zero-Speed Miniature Differential Peak-Detecting Sensor IC with Continuous CalibrationA1642 11Allegro MicroSystems, LLC Worcester, Massachusetts 01615-0036 U.S.A. DEVICE OPERATION Each operating mode is described in detail below. Power-On When power (VCC > VCC(Min)) is applied to the device, a short period of time is required to power the various portions of the IC. During this period, the A1642 powers-on in the high current state, I CC(High). After power-on, there are conditions that could induce a change in the output state. Such an event could be caused by thermal transients, but would require a static applied magnetic fi eld, proper signal polarity, and particular direction and magnitude of internal signal drift. Initial Offset Adjust The device initially cancels the effects of chip, magnet, and installation offsets. Once offsets have been cancelled, the digital tracking DAC is ready to track the signal and provide output switching. The period of time required for both Power-On and Initial Offset Adjust is defi ned as the Power-On Time. Calibration Mode The calibration mode allows the device to automatically select the proper signal gain and continue to adjust for offsets. The AGC is active, and selects the optimal signal gain based on the amplitude of the VPROC signal. Following each adjustment to the AGC DAC, the Offset DAC is also adjusted to ensure the internal analog signal is properly centered. During this mode, the tracking DAC is active and output switch- ing occurs, but the duty cycle is not guaranteed to be within specifi cation. Running Mode After the Initial Calibration period, C I, establishes a signal gain, the device moves to Running mode. During Running mode, the device tracks the input signal and gives an output edge for every peak of the signal. AOA remains active to compensate for any offset drift over time. The A1642 incorporates a novel algorithm for adjusting the signal gain during Running mode. This algorithm is designed to optimize the V PROC signal amplitude in instances where the magnetic signal “seen” during the calibration period is not repre- sentative of the amplitude of the magnetic signal for the installed device air gap (see fi gure 9). Device Electrical Output, IOUT Internal Differential Signal, V PROC BRP BOP BOP BRP 1 2 3 4 5 Figure 9: Operation of Running Mode Gain Adjust. Position 1. The device is initially powered-on. Self-calibration occurs. Position 2. Small amplitude oscillation of the target sends an erroneously small differential signal to the device. The ampli- tude of V PROC is greater than the switching hysteresis (BOP and BRP), and the device output switches. Position 3. The calibration period completes on the third rising output edge, and the device enters Running mode. Position 4. True target rotation occurs and the correct magnetic signal is generated for the installation air gap. The estab- lished signal gain is too large for the target’s rotational magnetic signal at the given air gap. Position 5. Running Mode Calibration corrects the signal gain to an optimal level for the installation air gap.
Two-Wire True Zero-Speed Miniature Differential Peak-Detecting Sensor IC with Continuous CalibrationA1642 12Allegro MicroSystems, LLC Worcester, Massachusetts 01615-0036 U.S.A. Power Derating Example: Reliability for VCC at TA = 150°C, package KN (I1 trim), using 1-layer PCB Observe the worst-case ratings for the device, specifi cally: RJA = 170 °C/W, TJ(max) = 165°C, VCC(max) = 24 V , and ICC(max) = 16 mA. Calculate the maximum allowable power level, PD(max). First, invert equation 3: Tmax = TJ(max) – TA = 165 °C – 150 °C = 15 °C This provides the allowable increase to TJ resulting from internal power dissipation. Then, invert equation 2: PD(max) = Tmax ÷ RJA = 15°C ÷ 170 °C/W = 88.2 mW Finally, invert equation 1 with respect to voltage: VCC(est) = PD(max) ÷ ICC(max) = 88.2 mW ÷ 16 mA = 5.5 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 reli- able operation between VCC(est) and VCC(max) requires enhanced RJA. If VCC(est) ≥ VCC(max), then operation between VCC(est) and VCC(max) is reliable under these conditions. 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 sup- plied power or improving the heat dissipation properties of the application. This section presents a procedure for correlating factors affecting operating T J. (Thermal data is also available on the Allegro MicroSystems Web site.) The Package Thermal Resistance, RJA, is a fi gure 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 JC, is relatively small component of RJA. Ambient air temperature, TA, and air motion are signifi cant external factors, damped by overmolding. The effect of varying power levels (Power Dissipation, PD), can be estimated. The following formulas represent the fundamental relationships used to estimate T J, at PD. PD = VIN × IIN (1) T J = TA + ΔT (3) For example, given common conditions such as: TA= 25°C, VCC = 12 V, ICC = 6 mA, and RJA = 170 °C/W, then: P D = VCC × ICC = 12 V × 6 mA = 72 mW T = PD × RJA = 72 mW × 170 °C/W = 12.2°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 RJA and TA.
Two-Wire True Zero-Speed Miniature Differential Peak-Detecting Sensor IC with Continuous CalibrationA1642 13Allegro MicroSystems, LLC Worcester, Massachusetts 01615-0036 U.S.A. Package KN, 4-Pin SIP 24 31
1.27 NOM
3.19 NOM
8.12 REF
0.38 REF 2.16 MAX 6.00 REF 45° 45° A
0.84 REF
B B C C Gate and tie bar burr area Dambar removal protrusion (8X) A For Reference Only; not for tooling use (reference DWG-9015) Dimensions in millimeters Dimensions exclusive of mold flash, gate burrs, and dambar protrusions Exact case and lead configuration at supplier discretion within limits shown Standard Branding Reference View N = Device part number Y = Last two digits of year of manufacture W = Week of manufacture Mold Ejector Pin Indent Branded Face YYWW NNNN 5.21 +0.08 –0.05 0.38 +0.06 –0.03 3.43 +0.08 –0.05 1.03 +0.08 –0.05 0.41 +0.07 –0.05 14.74 ±0.51 1.55 ±0.05 Branding scale and appearance at supplier discretion E1 E2 1.85 1.32 1.50 D D Active Area Depth 0.43 mm REF Hall elements (E1,E2), not to scaleE E E E
Two-Wire True Zero-Speed Miniature Differential Peak-Detecting Sensor IC with Continuous CalibrationA1642 14Allegro MicroSystems, LLC Worcester, Massachusetts 01615-0036 U.S.A. Copyright ©2005-2013, Allegro MicroSystems, LLC Allegro MicroSystems, LLC reserves the right to make, from time to time, such de par tures from the detail spec i fi ca tions as may be required to permit improvements in the per for mance, reliability, or manufacturability of its products. Before placing an order, the user is cautioned to verify that the information being relied upon is current. Allegro’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 in for ma tion in clud ed herein is believed to be ac cu rate and reliable. How ev er, Allegro MicroSystems, LLC assumes no re spon si bil i ty for its use; nor for any in fringe ment of patents or other rights of third parties which may result from its use. For the latest version of this document, visit our website: www.allegromicro.com
Revision History
Revision Revision Date Description of Revision Rev. 4 January 16, 2012 Update product variants offered