A1425 High Accuracy Analog Speed Sensor with Integrated Filter Capacitor and Dual Zero-Crossing Output Signal Package K, 4-pin SIP The A1425 ac-coupled Hall-effect sensor is a monolithic integrated circuit that switches in response to changing differential magnetic fields created by rotating ring magnets and, when coupled with a magnet, by ferrous targets. The device is a true zero-crossing detector: the output switches precisely when the difference in magnetic field strength between the two Hall elements is zero. A unique dual-comparator scheme provides for accurate switching at the zero crossing on both the positive and negative-going regions of the differential signal, while utilizing hysteresis to prevent false switching. The zero-crossing nature of this device provides excellent repeatability and accuracy for crankshaft applications. Changes in field strength at the device face, which are induced by a moving target, are sensed by the two integrated Hall transducers. The transducers generate signals that are differentially amplified by on-chip electronics. This differential sensing design provides immunity to radial vibration within the operating air gap range of the A1425, by rejection of the common mode signal. Steady-state magnet and system offsets are eliminated using an on-chip differential band-pass filter. This filter also provides relative immunity to interference from electromagnetic sources. The device utilizes advanced temperature compensation for the high-pass filter, sensitivity, and Schmitt trigger switchpoints, to guarantee optimal operation to low frequencies over a wide range of air gaps and temperatures. 1 2 3 4 1. VCC 2. VOUT 3. TEST 4. GND ABSOLUTE MAXIMUM RATINGS Supply Voltage*, VCC ........................................ 28 V Reverse-Supply Voltage, VRCC ........................ –18 V Continuous Output Current, IOUT ...................25 mA Continuous Reverse-Output Current, IROUT .–50 mA Operating Temperature Ambient, TA................................ –40ºC to 150ºC Maximum Junction, TJ(max)........................165ºC Storage Temperature, TS .................. –65ºC to 170ºC *Refer to Power Derating section. A1425a-DS Each Hall effect digital integrated circuit includes a voltage regulator, two Hall effect sensing elements, temperature compensating circuitry, a low-level amplifier, band-pass filter, Schmitt trigger, and an output driver, which requires a pull-up resistor. The on-board regulator permits operation with supply voltages from 4.0 to 26.5 V. The output stage can easily switch 20 mA over the full frequency response range of the sensor, and is compatible with both TTL and CMOS logic circuits. The device is packaged in a 4-pin plastic SIP. The lead (Pb) free version (suffix –T) has a 100% matte tin plated leadframe. Features and Benefits • • • • • • • • • • • Senses motion of ring magnet or ferrous targets Integrated filter capacitor Wide operating temperature range Operation with magnetic input signal frequency from 20 Hz to 20 kHz Resistant to EMI Large effective air gaps 4.0 to 26.5 V supply operating range Output compatible with both TTL and CMOS logic families Reverse battery protection Resistant to mechanical and thermal stress Accurate true zero crossing switchpoint Allegro MicroSystems, Inc. 115 Northeast Cutoff, Box 15036 Worcester, Massachusetts 01615-0036 (508) 853-5000 www.allegromicro.com A1425 High Accuracy Analog Speed Sensor with Integrated Filter Capacitor and Dual Zero-Crossing Output Signal Product Selection Guide Part Number A1425LK-T Pb-free1 Ambient, TA (°C) Yes –40 to 150 Switchpoints BRP(MIN) (G) BOP(MAX) (G) –11 11 Packing2 Bulk, 500 pieces/bag 1Pb-based variants are being phased out of the product line. These variants are in production but have been determined to be NOT FOR NEW DESIGN. This classification indicates that sale of this device is currently restricted to existing customer applications. The device should not be purchased for new design applications because obsolescence in the near future is probable. Samples are no longer available. Status change: May 1, 2006. This includes: A1425LK. 2Contact Allegro for additional packing options Functional Block Diagram VS+ VCC (Pin 1) TEST (Pin 3) Diagnostic Circuitry Regulator Bandpass Filter Integrated Tracking Capacitor Dual Hall Transducers VOUT (Pin 2) Comparator 0.1 uF Hall Amp Gain Stage VREF GND (Pin 4) A1425-DS (Required) 2 Allegro MicroSystems, Inc. 115 Northeast Cutoff, Box 15036 Worcester, Massachusetts 01615-0036 (508) 853-5000 www.allegromicro.com A1425 High Accuracy Analog Speed Sensor with Integrated Filter Capacitor and Dual Zero-Crossing Output Signal OPERATING CHARACTERISTICS Valid at TA = – 40ºC to 150ºC, TJ ≤ 165°C; over operational air gap range and VCC within operating range, unless otherwise noted. Typical operating parameters: VCC = 12 V and TA = 25°C. Characteristic Symbol Test Conditions Min. Typ. Max. Units 4.0 – 26.5 V – 4.2 7.0 mA – 140 400 mV – – 5 μA VCC = –18 V – – –1 mA ELECTRICAL CHARACTERISTICS Supply Voltage VCC Supply Current ICC Output Saturation Voltage Output Leakage Current Operating; TJ < TJ(max) VOUT(SAT) ISINK = 20 mA IOFF VOUT = 24 V, Bdiff = 0 PROTECTION COMPONENT CHARACTERISTICS Reverse Supply Current IRCC Supply Zener Current IZSupply VS = 28 V – – 10 mA Supply Zener Clamp Voltage1 VZSupply ICC = 10 mA, TA = 25°C 28 33 37 V Output Zener Current IZOutput VOUT = 28 V – – 3 mA Output Zener Clamp Voltage VZOutput IOUT = 3 mA, TA = 25°C 28 – – V Output Short Circuit Current Limit2 IOUTS(lim) – – 50 mA t < tResponse – High – V tPO VCC > VCC(min) – 4.5 9 ms tSettle fBdiff ≥ 100 Hz 0 – 50 ms RESPONSE CHARACTERISTICS Power-On State Power-On Time3,7 Settling Time4,7 Response Time7 POS 4.5 – 59 ms Upper Corner Frequency tResponse Equal to tPO + tS; fBdiff ≥ 100 Hz fcu –3 dB, single pole 20 – – kHz Lower Corner Frequency fcl –3 dB, single pole – – 20 Hz Output Rise Time5 tr RPU = 1 kΩ, COUT2 = 10 pF – – 200 ns Output Fall Time tf RPU = 1 kΩ, ISINK = 20 mA, COUT2 = 10 pF – – 200 ns –11 0 11 G –11 0 11 G 50 – 1250 G OUTPUT CHARACTERISTICS MAGNETIC CHARACTERISTICS Output Off Switchpoint6,7 BOP Output On Switchpoint6,7 BRP Applied Magnetic Field7,8 Bdiff Bdiff increasing, fBdiff = 200 Hz, Bdiff = 50 Gp-p; digital output signal switches low to high Bdiff decreasing, fBdiff = 200 Hz, Bdiff = 50 Gp-p; digital output signal switches high to low Differential p-p magnetic field 1I CC equivalent to ICC(max) + 3 mA. 2I OUT does not change state when IOUT > IOUTS(lim) , regardless of changes in the sensed magnetic field.. 3Time required to initialize device. 4Time required for the output switchpoints to be within specification. 5Output Rise Time will be dominated by the RC time constant. 6For other sinusoidal signal frequencies and magnetic fields, –B OP = BRP = sinα(Bdiff ⁄ 2) ± 25%, where α is the phase shift shown in the Characteristic Data section. 7See Definitions of Terms section. 8Exceeding the maximum magnetic field may result in compromised absolute accuracy. 3 A1425-DS Allegro MicroSystems, Inc. 115 Northeast Cutoff, Box 15036 Worcester, Massachusetts 01615-0036 (508) 853-5000 www.allegromicro.com A1425 High Accuracy Analog Speed Sensor with Integrated Filter Capacitor and Dual Zero-Crossing Output Signal THERMAL CHARACTERISTICS may require derating at maximum conditions, see application information Characteristic Symbol Test Conditions RθJA Package Thermal Resistance Single-layer PCB, with copper limited to solder pads 177 ºC/W Maximum Power Dissipation, PD(max) Power Derating Curve 30 900 28 850 VCC(max) 26 800 750 24 700 22 650 20 18 16 (RθJA = 177 ºC/W) 14 12 10 8 6 VCC(min) 4 2 Power Dissipation, PD (m W) Maximum Allowable VCC (V) Rating Units 600 (R θJ 550 A 500 450 400 = 17 7 ºC /W ) 350 300 250 200 150 100 50 0 0 20 40 60 80 100 120 140 160 180 Temperature (ºC) 20 40 60 80 100 120 140 160 180 Temperature (°C) Definitions of Terms The following provide additional information about some of the parameters cited in the Operating Characteristics table. For additional information, visit the Allegro Web site at www.allegromicro.com. Applied Magnetic Field, Bdiff – The differential magnetic flux density which is calculated as the arithmetic difference of the flux densities observed by each of the two Hall elements. Output Off Switchpoint (Operate Point), BOP – The value of increasing differential magnetic flux density at which the device output switches from low to high. This value may be greater than or less than 0 G. Output On Switchpoint (Release Point), BRP – The value of decreasing differential magnetic flux density at which the device output switches from high to low. This value may be greater than or less than 0 G. Power-On Time, tPO – The time needed by the device, after power is applied, to initialize all circuitry necessary for proper operation. Settling Time, tSettle – The time required by the device, after tPO, and after a valid magnetic signal has been applied, to provide proper output transitions. Settling time is a function of magnetic offset, offset polarity, signal phase, signal frequency, and signal amplitude. Response Time tResponse – The total time required for generating zero-crossing output transitions after power-up (the sum of power-on time and settling time). 4 A1425-DS Allegro MicroSystems, Inc. 115 Northeast Cutoff, Box 15036 Worcester, Massachusetts 01615-0036 (508) 853-5000 www.allegromicro.com A1425 High Accuracy Analog Speed Sensor with Integrated Filter Capacitor and Dual Zero-Crossing Output Signal Empirical Results Output Voltage by Ambient Temperature Supply Current by Ambient Temperature 7 VCC (V) 6 ICC (mA) 5 VOUT(SAT) (mV) 4.5 12 12.0 26 20.0 4 3 2 1 0 –50 0 50 100 150 200 500 450 400 350 300 250 200 150 100 50 0 –50 ISINK = 20 mA VCC (V) 4.5 12.0 20.0 0 Supply Current by Supply Voltage 7 ICC (mA) 5 VOUT(SAT) (mV) 150 25 –40 4 3 2 1 10 20 VCC (V) 150 200 Output Voltage by Supply Voltage TA (ºC) 6 0 100 TA (ºC) TA (ºC) 0 50 30 500 450 400 350 300 250 200 150 100 50 0 0 ISINK = 20 mA TA (ºC) 150 25 –40 5 10 15 20 25 VCC (V) Continued on next page. 5 A1425-DS Allegro MicroSystems, Inc. 115 Northeast Cutoff, Box 15036 Worcester, Massachusetts 01615-0036 (508) 853-5000 www.allegromicro.com A1425 High Accuracy Analog Speed Sensor with Integrated Filter Capacitor and Dual Zero-Crossing Output Signal Empirical Results, continued Repeatability (º of Rotation) 116 Air Gap (mm) Repeatability (º of Rotation) 116 Air Gap (mm) 6 A1425-DS Allegro MicroSystems, Inc. 115 Northeast Cutoff, Box 15036 Worcester, Massachusetts 01615-0036 (508) 853-5000 www.allegromicro.com A1425 High Accuracy Analog Speed Sensor with Integrated Filter Capacitor and Dual Zero-Crossing Output Signal Simulation Results A1425 Minimum Switching Fields Over the Range of Ambient Operating Temperatures, TA fBdiff(low) = 15 Hz, fBdiff(high) ≈ 30 kHz 40 35 30 25 Bdiff(min) (G) 25 150 20 –40 15 10 5 0 0.01 0.1 1 10 40 Frequency, fBdiff (kHz) A1425 Typical Phase Shift Over the Range of Applied Magnetic Fields, Bdiff fBdiff(low) = 15 Hz, fBdiff(high) = 30 kHz 40 30 50 100 500 10 750 Phase Shift (º) 20 0 –10 1250 Bdiff in Gp-p –20 –30 –40 –50 –60 0.01 0.1 Frequency, fBdiff 1 (kHz) 10 40 Continued on next page. 7 A1425-DS Allegro MicroSystems, Inc. 115 Northeast Cutoff, Box 15036 Worcester, Massachusetts 01615-0036 (508) 853-5000 www.allegromicro.com A1425 High Accuracy Analog Speed Sensor with Integrated Filter Capacitor and Dual Zero-Crossing Output Signal Simulation Results, continued A1425 Typical Delay Over the Range of Applied Magnetic Fields, Bdiff fBdiff(low) = 15 Hz, fBdiff(high) = 30 kHz 15 10 Bdiff in Gp-p 50 75 –10 50 100 12 –5 50 IOUT Lagging 0 0 5 0 IOUT Delay (μs) IOUT Leading 20 –15 –20 0.1 1 Frequency, fBdiff (kHz) 40 10 Positive values of delay indicate a lagging output, while negative values indicate a leading output. IOUT Delay (μs) IOUT Leading A1425 Typical Delay Over the Range of Applied Magnetic Fields, Bdiff fBdiff(low) = 15 Hz, fBdiff(high) = 30 kHz 1000 0 –1000 1250 750 500 –2000 IOUT Lagging –3000 Bdiff in Gp-p –4000 10 –5000 0 50 –6000 0 100 Frequency, fBdiff (Hz) Positive values of delay indicate a lagging output, while negative values indicate a leading output. 8 A1425-DS Allegro MicroSystems, Inc. 115 Northeast Cutoff, Box 15036 Worcester, Massachusetts 01615-0036 (508) 853-5000 www.allegromicro.com A1425 High Accuracy Analog Speed Sensor with Integrated Filter Capacitor and Dual Zero-Crossing Output Signal Sensor Evaluation: EMC Characterization Please contact Allegro MicroSystems for EMC performance information. Test Name Reference Specification ESD – Human Body Model* AEC-Q100-002 ESD – Machine Model* AEC-Q100-003 Conducted Transients ISO 7637-1 Direct RF Injection ISO 11452-7 Bulk Current Injection ISO 11452-4 TEM Cell ISO 11452-3 *ESD testing is performed with no external components. Vs R1 C1 1 RPU VCC 4 GND 1425 VOUT 2 COUT2 TEST 3 (Required) Recommended EMC test circuit. Component RPUa R1b C1 COUT2c Value 1.2 100 0.1 4.7 Units kΩ Ω μF nF aPull-up resistor not required for protection but for normal operation. bFor improved CI performance cFor improved BCI performance 9 A1425-DS Allegro MicroSystems, Inc. 115 Northeast Cutoff, Box 15036 Worcester, Massachusetts 01615-0036 (508) 853-5000 www.allegromicro.com A1425 High Accuracy Analog Speed Sensor with Integrated Filter Capacitor and Dual Zero-Crossing Output Signal Functional Description The A1425 is a versatile high-precision differential sensing device that can be used in a wide range of applications. Proper choice of the target material and shape, and assembly techniques enables large working air gaps and high switchpoint accuracy over the device operating temperature range. Start-up Sensor Operation Also during tPO, a circuit in the A1425 is briefly enabled that charges the on-chip capacitor. This feature reduces tPO, relative to the long RC time constant of a high-pass filter. During power-on time, tPO, the output signal, VOUT, is high. Beyond this time, if the applied magnetic field, Bdiff, is absent or less than 50 G peak-to-peak, the switching state and VOUT polarity are indeterminate. VOUT will be valid for Bdiff > 50 Gp-p, after the additional settling time, tSettle, has also elapsed. The A1425 sensor IC contains two integrated Hall transducers that are used to differentially sense a magnetic field across the surface of the IC. Referring to figure 1, the trigger switches the output off (output high) when the differential magnetic field crosses zero while increasing in strength (referred to as the positive direction), and switches the output on (output low) when the differential magnetic field crosses zero while decreasing (the negative direction). Delay The on-chip band-pass filter induces delay in the output signal, VOUT, relative to the applied magnetic field, Bdiff. Simulation data shown in the Characteristic Data section quantify the effect of the input signal amplitude on the phase shift of the output. AC-Coupled Operation The operation is achieved through the use of two separate comparators. Both comparators use the same reference point, 0 G, to provide high accuracy, but one comparator has a positive hysteresis, BHYS1, and the other a negative hysteresis, BHYS2. Therefore, one comparator switches (BOP) at the zero crossing on an increasing differential signal and the other switches (BRP) at the zero crossing on a decreasing differential signal. The hysteresis on each comparator precludes false switching on noise or target jitter. Steady-state magnet and system offsets are eliminated using an on-chip differential band-pass filter. The low and high frequency poles of this band-pass filter are set using internal integrated capacitors and resistors. The differential structure of this filter improves the ability of the IC to reject single-ended noise on the ground (GND pin) or supply line (VCC pin) and, as a result, makes it more resistant to electromagnetic interference typically seen in hostile remote-sensing environments. 11.0 Applied Magnetic Field, Bdiff BOP(typ) 0.0 A –11.0 BOP(max) / BRP(max) BHYS1 A BRP(typ) BHYS2 BOP(min) / BRP(min) Comparator 1 Comparator 2 Switching State Output Signal, VOUT Off On Off t+ Figure 1. Typical output characteristics with dual comparator operation. Characteristics shown without delay, see characteristic data charts for delay and phase shift contributions. 10 A1425-DS Allegro MicroSystems, Inc. 115 Northeast Cutoff, Box 15036 Worcester, Massachusetts 01615-0036 (508) 853-5000 www.allegromicro.com A1425 High Accuracy Analog Speed Sensor with Integrated Filter Capacitor and Dual Zero-Crossing Output Signal Applications Information Target Selection Power Supply Protection The zero-crossing switchpoints and ac-coupled operation of this device make target selection important. For high-density target geometries or small target features that produce a sinusoidal magnetic signal, the high-pass filter is capable of filtering offsets that may be induced in the final sensor output. If such offset is present, and the target has larger features, then the high-pass filter may not be effective at higher speeds and an accuracy shift may occur. These relationships are shown in figure 2. The A1425 contains an on-chip voltage regulator and can operate over a wide supply voltage range. In applications that operate the device from an unregulated power supply, transient protection must be added externally. For applications using a regulated line, EMI/RFI protection may still be required. The circuit shown in figure 3 is the most basic configuration required for proper device operation. Differential Magnetic Flux Density, Bdiff Large Feature (Tooth) Valley +B (a) 0 –B Differential Magnetic Flux Density, Bdiff Device Output Voltage, VOUT +V VCC 1 RPU 0.1 uF 0 +B t 4 A1425 2 VOUT 3 Output Edge Shift (Required) (b) 0 Figure 3. Basic application circuit. A pull-up resistor, RPU, is required with the output driver. –B Device Output Voltage, VOUT +V 0 t Figure 2. Large Feature Effects. (a) Large target feature but no sensor offset, normal edge position. (b) Large target feature with sensor offset, shifted (advanced) output edge position. 11 A1425-DS Allegro MicroSystems, Inc. 115 Northeast Cutoff, Box 15036 Worcester, Massachusetts 01615-0036 (508) 853-5000 www.allegromicro.com A1425 High Accuracy Analog Speed Sensor with Integrated Filter Capacitor and Dual Zero-Crossing Output Signal 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 application. This section presents a procedure for correlating factors affecting operating TJ. (Thermal data is also available on the Allegro MicroSystems Web site.) The Package Thermal Resistance, RθJA, is a figure of merit summarizing 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 = 5.0 V, ICC = 4.2 mA, and RθJA = 177 °C/W, then: PD = VCC × ICC = 5.0 V × 4.2 mA = 21.0 mW ΔT = PD × RθJA = 21.0 mW × 177 °C/W = 3.7°C TJ = TA + ΔT = 25°C + 3.7°C = 28.7°C A worst-case estimate, PD(max), represents the maximum allowable power level (VCC(max), ICC(max)), without exceeding TJ(max), at a selected RθJA and TA. Example Reliability for VCC at TA = 150°C, using minimum-K PCB Observe the worst-case ratings for the device, specifically: RθJA = 177°C/W, TJ(max) = 165°C, VCC(max) = 26.5 V, and ICC(max) = 7.0 mA. Calculate the maximum allowable power level, PD(max). First, invert equation 3: ΔTmax = 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) = ΔTmax ÷ RθJA = 15°C ÷ 177 °C/W = 84 mW Finally, invert equation 1 with respect to voltage: VCC(est) = PD(max) ÷ ICC(max) = 84 mW ÷ 7.0 mA = 12 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. For example, when a standard diode with a 0.7 V drop is used: VS(max) = 12 V + 0.7 V = 12.7 V 12 A1425-DS Allegro MicroSystems, Inc. 115 Northeast Cutoff, Box 15036 Worcester, Massachusetts 01615-0036 (508) 853-5000 www.allegromicro.com A1425 High Accuracy Analog Speed Sensor with Integrated Filter Capacitor and Dual Zero-Crossing Output Signal Package K, 4-pin SIP .208 5.28 .203 5.16 .0866 2.20 NOM .0592 1.50 NOM .138 3.51 .133 3.38 C .063 1.60 .059 1.50 .0507 1.29 NOM B E1 E2 A .045 1.14 MIN .033 0.84 NOM .021 0.53 MAX .085 2.16 MAX .600 15.24 .560 14.23 .017 0.44 .014 0.35 1 .019 .014 0.48 0.36 2 3 4 .050 1.27 NOM Dimensions in inches Millimeters in brackets, for reference only Case dimensions exclusive of mold flash or gate burrs Mold flash .010 [0.25] MAX, gate burr .008 [0.20] MAX, dambar protrusion .004 [0.10] MAX Exact case and lead configuration at supplier discretion within limits shown A Dambar removal protrusion (8X) B Ejector mark on opposite side C Active Area Depth .0165 [0.42] NOM 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 products are not authorized for use as critical components in life-support devices or systems without express written approval. 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. Copyright © 2005 Allegro MicroSystems, Inc. 13 A1425-DS Allegro MicroSystems, Inc. 115 Northeast Cutoff, Box 15036 Worcester, Massachusetts 01615-0036 (508) 853-5000 www.allegromicro.com