A3230 Chopper-Stabilized Hall-Effect Bipolar Switch GND Package LH, 3-pin Surface Mount 3 1 3 2 VCC VOUT 2 1 Package UA, 3-pin SIP The A3230 Hall-effect sensor is a temperature stable, stress-resistant bipolar switch. This sensor is the most sensitive Hall-effect device in the Allegro® bipolar switch family and is intended for ring-magnet sensing. Superior high-temperature performance is made possible through an Allegro patented dynamic offset cancellation that utilizes chopper-stabilization. This method reduces the offset voltage normally caused by device overmolding, temperature dependencies, and thermal stress. The A3230 includes the following on a single silicon chip: a voltage regulator, Hall-voltage generator, small-signal amplifier, chopper stabilization, Schmitt trigger, and a short circuit protected open-drain output. Advanced BiCMOS wafer fabrication processing takes advantage of low-voltage requirements, component matching, very low input-offset errors, and small component geometries. The A3230 Hall-effect bipolar switch turns on in a south polarity magnetic field of sufficient strength and switches off in a north polarity magnetic field of sufficient strength. Because the output state is not defined if the magnetic field is diminished or removed, to ensure that the device switches, Allegro recommends using magnets of both polarities and of sufficient strength in the application. 1 2 3 VCC GND VOUT The A3230 is rated for operation between the ambient temperatures –40°C and 85°C for the E temperature range, and –40°C to 150°C for the L temperature range. Two A3230 package styles provide magnetically optimized solutions for most applications. Package LH is a SOT23W, a miniature low-profile surface-mount package, while package UA is a three-lead ultramini SIP for through-hole mounting. Each package is available in a lead (Pb) free version, with 100% matte tin plated leadframes. 1 2 3 ABSOLUTE MAXIMUM RATINGS Supply Voltage, VCC .......................................... 28 V Reverse-Supply Voltage, VRCC ........................ –18 V Output Off Voltage, VOUT ............................... 26.5 V Output Current, IOUTSINK ........... Internally Limited Reverse-Output Current, IROUT ....................–10 mA Magnetic Flux Density, B .........................Unlimited Operating Temperature Ambient, TA, Range E.................. –40ºC to 85ºC Ambient, TA, Range L................ –40ºC to 150ºC Maximum Junction, TJ(MAX) ......................165ºC Storage Temperature, TS .................. –65ºC to 170ºC A3230-DS Features and Benefits Chopper stabilization Output short circuit protection Superior temperature stability Solid state reliability Extremely low switchpoint drift Small size Insensitive to physical stress Reverse battery protection Robust EMC capability High ESD ratings (HBM) Allegro MicroSystems, Inc. 115 Northeast Cutoff, Box 15036 Worcester, Massachusetts 01615-0036 (508) 853-5000 www.allegromicro.com A3230 Chopper-Stabilized Hall Effect Bipolar Switch Product Selection Guide Part Number Pbfree Packing* Ambient, TA (°C) Mounting A3230ELHLT – 7-in. reel, 3000 pieces/reel A3230ELHLT-T Yes A3230EUA – Bulk, 500 pieces/bag A3230EUA-T Yes A3230LLHLT – 7-in. reel, 3000 pieces/reel A3230LLHLT-T Yes A3230LUA – Bulk, 500 pieces/bag A3230LUA-T Yes *Contact Allegro for additional packing options. BRP(MIN) (G) BOP(MAX) (G) –25 25 3-pin SOT23W surface mount –40 to 85 3-pin SIP through hole 3-pin SOT23W surface mount –40 to 150 3-pin SIP through hole Functional Block Diagram VCC Regulator Amp Low-Pass Filter Sample and Hold Dynamic Offset Cancellation To All Subcircuits VOUT Control Current Limit <1Ω GND Terminal List Name Description Number Package LH Package UA Connects power supply to chip 1 1 VOUT Output from circuit 2 3 GND Ground 3 2 VCC 2 A3230-DS Allegro MicroSystems, Inc. 115 Northeast Cutoff, Box 15036 Worcester, Massachusetts 01615-0036 (508) 853-5000 www.allegromicro.com A3230 Chopper-Stabilized Hall Effect Bipolar Switch OPERATING CHARACTERISTICS valid over full operating voltage and ambient temperature ranges, unless otherwise noted Characteristic Symbol Test Conditions Min. Typ. Max. Units Electrical Characteristics Supply Voltage1 Output Leakage Current VCC Operating, TJ < 165°C 3.6 – 24 V IOUTOFF VOUT = 24 V, B < BRP – – 10 µA VOUT(SAT) IOUT = 20 mA, B > BOP – 250 500 mV Output Current Limit IOM B > BOP 30 – 60 mA Power-On Time tPO VCC > 3.6 V Output On Voltage – 8 50 µs – 200 – kHz RLOAD = 820 Ω, CS = 20 pF – 0.2 1 µs RLOAD = 820 Ω, CS = 20 pF – 0.2 1 µs ICCON B > BOP – 1.6 5 mA ICCOFF B < BRP – 1.6 5 mA VRCC = –18 V – – –2 mA VZ ICC = 8 mA; TA = 25°C 28 – – V IZ VS = 28 V – – 8 mA Chopping Frequency fc Output Rise Time2 tr Output Fall Time2 tf Supply Current Reverse Battery Current Supply Zener Clamp Voltage Supply Zener Current3 IRCC Magnetic Characteristics4 Operate Point BOP South pole adjacent to branded face of device –10 7.5 25 G Release Point BRP North pole adjacent to branded face of device –25 –7.5 10 G Hysteresis BHYS BOP – BRP 5 15 25 G 1 Maximum voltage must be adjusted for power dissipation and junction temperature, see Power Derating section. 2 C = oscilloscope probe capacitance. S 3 Maximum current limit is equal to the maximum I CC(MAX) + 3 mA. 4 Magnetic flux density, B, is indicated as a negative value for north-polarity magnetic fields, and as a positive value for south-polarity magnetic fields. This so-called algebraic convention supports arithmetic comparison of north and south polarity values, where the relative strength of the field is indicated by the absolute value of B, and the sign indicates the polarity of the field (for example, a –100 G field and a 100 G field have equivalent strength, but opposite polarity). DEVICE QUALIFICATION PROGRAM Contact Allegro for information. EMC (Electromagnetic Compatibility) REQUIREMENTS Contact Allegro for information. 3 A3230-DS Allegro MicroSystems, Inc. 115 Northeast Cutoff, Box 15036 Worcester, Massachusetts 01615-0036 (508) 853-5000 www.allegromicro.com A3230 Chopper-Stabilized Hall Effect Bipolar Switch Electrical Characteristic Data Supply Current (On) versus Ambient Temperature Supply Current (On) versus Supply Voltage 5.0 5.0 4.0 VCC (V) 3.0 24 3.6 2.0 ICCON (mA) ICCON (mA) 4.0 1.0 3.0 –40 25 150 2.0 1.0 0 –50 TA (°C) 0 0 50 TA (°C) 100 150 0 25 4.0 VCC (V) 3.0 24 3.6 2.0 ICCOFF (mA) ICCOFF (mA) 20 5.0 4.0 TA (°C) –40 25 150 3.0 2.0 1.0 1.0 0 0 0 50 TA (°C) 100 0 150 5 10 15 20 25 VCC (V) Output Voltage (On) versus Ambient Temperature Output Voltage (On) versus Supply Voltage 500 500 450 450 400 400 350 350 300 VCC (V) 250 24 3.6 200 150 VOUT(SAT) (mV) VOUT(SAT) (mV) 15 Supply Current (Off) versus Supply Voltage 5.0 TA (°C) 300 –40 25 150 250 200 150 100 100 50 50 0 –50 10 VCC (V) Supply Current (Off) versus Ambient Temperature –50 5 0 0 50 TA (°C) 100 150 0 5 10 15 20 25 VCC (V) 4 A3230-DS Allegro MicroSystems, Inc. 115 Northeast Cutoff, Box 15036 Worcester, Massachusetts 01615-0036 (508) 853-5000 www.allegromicro.com A3230 Chopper-Stabilized Hall Effect Bipolar Switch Magnetic Characteristic Data Operate Point versus Ambient Temperature Operate Point versus Supply Voltage 25 25 20 20 15 10 VCC (V) 5 24 3.8 TA (°C) 10 BOP (G) BOP (G) 15 –40 25 150 5 0 0 -5 -5 -10 -10 –50 0 50 TA (°C) 100 150 0 15 20 25 Release Point versus Supply Voltage 10 10 5 5 0 -5 VCC (V) -10 24 3.8 BRP (G) 0 BRP (G) 10 VCC (V) Release Point versus Ambient Temperature TA (°C) -5 –40 25 150 -10 -15 -15 -20 -20 -25 -25 –50 0 50 TA (°C) 100 0 150 5 10 15 20 25 VCC (V) Hysteresis versus Ambient Temperature Hysteresis versus Supply Voltage 25 25 20 20 VCC (V) 24 3.8 15 10 BHYS (G) BHYS (G) 5 TA (°C) –40 25 150 15 10 5 5 –50 0 50 TA (°C) 100 150 0 5 10 15 20 25 VCC (V) 5 A3230-DS Allegro MicroSystems, Inc. 115 Northeast Cutoff, Box 15036 Worcester, Massachusetts 01615-0036 (508) 853-5000 www.allegromicro.com A3230 Chopper-Stabilized Hall Effect Bipolar Switch THERMAL CHARACTERISTICS may require derating at maximum conditions, see application information Characteristic Symbol RθJA Package Thermal Resistance Test Conditions Package LH, minimum-K PCB (single-sided with copper limited to solder pads) Package LH, low-K PCB (double-sided with 0.926 in2 copper area) Package UA, minimum-K PCB (single-sided with copper limited to solder pads) Value Units 110 ºC/W 228 ºC/W 165 ºC/W Maximum Allowable V CC (V) Power Derating Curve TJ(max) = 165°C; ICC = ICC(max) 25 24 23 22 21 20 19 18 17 16 15 14 13 12 11 10 9 8 7 6 5 4 3 2 V CC(max) Low-K PCB, Package LH (R θJA= 110 °C/W) Minimum-K PCB, Package UA (R θJA= 165 °C/W) Minimum-K PCB, Package LH (R θJA= 228 °C/W) V CC(min) 20 40 60 80 100 120 140 160 180 Temperature (°C) Power Dissipation, P D (mW) Power Dissipation versus Ambient Temperature 1900 1800 1700 1600 1500 1400 1300 1200 1100 1000 900 800 700 600 500 400 300 200 100 0 Low-K PCB, Package LH (R JA = 110 °C/W) Min-K PCB, Package UA (R JA = 165 °C/W) Min-K PCB, Package LH (R JA = 228 °C/W) 20 40 60 80 100 120 140 160 180 Temperature (°C) 6 A3230-DS Allegro MicroSystems, Inc. 115 Northeast Cutoff, Box 15036 Worcester, Massachusetts 01615-0036 (508) 853-5000 www.allegromicro.com A3230 Chopper-Stabilized Hall Effect Bipolar Switch Functional Description Operation The output of these devices switches low (turns on) when a magnetic field perpendicular to the Hall sensor exceeds the operate point threshold, BOP. After turn-on, the output voltage is VOUT(SAT). The output transistor is capable of sinking current up to the short circuit current limit, IOM, which is a minimum of 30 mA. When the magnetic field is reduced below the release point, BRP, the device output goes high (turns off). The difference in the magnetic operate and release points is the hysteresis, BHYS, of the device. This built-in hysteresis allows clean switching of the output even in the presence of external mechanical vibration and electrical noise. field of the opposite polarity and of sufficient strength causes it to switch. The hysteresis of latch mode behavior is shown in panel A of figure 1. In contrast to latching, when a device exhibits unipolar switching, it only responds to a south magnetic field. The field must be of sufficient strength, > BOP , for the device to operate. When the field is reduced beyond the BRP level, the device switches back to the high state, as shown in panel B of figure 1. Devices There are three switching modes for bipolar devices, referred to as latch, unipolar switch, and negative switch. Mode is determined by the switchpoint characteristics of the individual device. Note that, as shown in figure 1, these switchpoints can lie in either north or south polarity ranges. The values of the magnetic parameters for the A3230 are specified in the Magnetic Characteristics table, on page 3. VS VCC CBYP 0.1 µF A3230 RLOAD Sensor Output VOUT GND Bipolar devices typically behave as latches (although these devices are not guaranteed to do so). In this mode, magnetic fields of opposite polarity and equivalent strengths are needed to switch the output. When the magnetic fields are removed (B → 0) the device remains in the same state until a magnetic (D) (A) (B) V+ V+ Switch to High Switch to High VOUT BHYS B+ B– BRP(MIN) BRP B– 0 VOUT(SAT) 0 BOP BHYS B+ VOUT(SAT) 0 BOP(MAX) 0 BOP B– BRP VOUT(SAT) 0 VCC Switch to Low VOUT VCC Switch to Low Switch to Low Switch to High VCC VOUT V+ (C) 0 B+ BHYS Figure 1. Bipolar Device Output Switching Modes. These behaviors can be exhibited when using a circuit such as that shown in panel D. Panel A displays the hysteresis when a device exhibits latch mode (note that the BHYS band incorporates B= 0), panel B shows unipolar switch behavior (the BHYS band is more positive than B = 0), and panel C shows negative switch behavior (the BHYS band is more negative than B = 0). Bipolar devices, such as the A3230, can operate in any of the three modes. 7 A3230-DS Allegro MicroSystems, Inc. 115 Northeast Cutoff, Box 15036 Worcester, Massachusetts 01615-0036 (508) 853-5000 www.allegromicro.com A3230 Chopper-Stabilized Hall Effect Bipolar Switch exhibiting negative switch behavior operate in a similar but opposite manner. A north polarity field of sufficient strength, > BRP , (more north than BRP) is required for operation, although the result is that VOUT switches high, as shown in panel C. When the field is reduced beyond the BOP level, the device switches back to the low state. Applications It is strongly recommended that an external bypass capacitor be connected (in close proximity to the Hall sensor) between the supply and ground of the device to reduce both external noise and noise generated by the chopper stabilization technique. As is shown in Panel B of figure 1, a 0.1µF capacitor is typical. The A3230 is designed to attain a small hysteresis, and thereby provide more sensitive switching. Although this means that true latching behavior cannot be guaranteed in all cases, proper switching can be ensured by use of both south and north magnetic fields, as in a ring magnet. Extensive applications information on magnets and Hall-effect sensors is available in: Bipolar devices adopt an indeterminate output state when powered-on in the absence of a magnetic field or in a field that lies within the hysteresis band of the device. The correct state is attained after the first excursion beyond BOP or BRP. For more information on Bipolar switches, refer to Application Note 27705, Understanding Bipolar Hall Effect Sensors. • Hall-Effect IC Applications Guide, AN27701, • Hall-Effect Devices: Gluing, Potting, Encapsulating, Lead Welding and Lead Forming, AN27703.1 • Soldering Methods for Allegro’s Products – SMT and ThroughHole, AN26009 All are provided in Allegro Electronic Data Book, AMS-702 and the Allegro Web site: www.allegromicro.com 8 A3230-DS Allegro MicroSystems, Inc. 115 Northeast Cutoff, Box 15036 Worcester, Massachusetts 01615-0036 (508) 853-5000 www.allegromicro.com A3230 Chopper-Stabilized Hall Effect Bipolar Switch 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 sensor. 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 modulationdemodulation process. The undesired offset signal is separated from the magnetic-field-induced signal in the frequency domain, through modulation. The subsequent demodulation acts as a modulation process for the offset, causing the magnetic-fieldinduced signal to recover its original spectrum at baseband, while the dc offset becomes a high-frequency signal. The magnetic-field-induced signal then can pass through a low-pass filter, while the modulated dc offset is suppressed. This configuration is illustrated in figure 2. 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. The repeatability of magnetic-field-induced switching is affected slightly by a chopper technique. However, the Allegro highfrequency chopping approach minimizes the affect of jitter and makes it imperceptible in most applications. Applications that are more likely to be sensitive to such degradation are those requiring precise sensing of alternating magnetic fields; for example, speed sensing of ring-magnet targets. For such applications, Allegro recommends its digital sensor families with lower sensitivity to jitter. For more information on those devices, contact your Allegro sales representative. Regulator Amp Low-Pass Filter Hall Element Sample and Hold Clock/Logic Figure 2. Chopper Stabilization Circuit (Dynamic Quadrature Offset Cancellation) 9 A3230-DS Allegro MicroSystems, Inc. 115 Northeast Cutoff, Box 15036 Worcester, Massachusetts 01615-0036 (508) 853-5000 www.allegromicro.com A3230 Chopper-Stabilized Hall Effect Bipolar Switch 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) ∆T = PD × RθJA (2) TJ = TA + ∆T (3) Example: Reliability for VCC at TA = 150°C, package LH, using a low-K PCB. Observe the worst-case ratings for the device, specifically: RθJA = 228 °C/W, TJ(max) = 165°C, VCC(max) = 24 V, and ICC(max) = 5 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 ÷ RθJA = 15°C ÷ 228 °C/W = 66 mW Finally, invert equation 1 with respect to voltage: VCC(est) = PD(max) ÷ ICC(max) = 66 mW ÷ 5 mA = 13 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, given common conditions such as: TA= 25°C, VCC = 12 V, ICC = 1.5 mA, and RθJA = 165 °C/W, then: PD = VCC × ICC = 12 V × 1.5 mA = 18 mW ∆T = PD × RθJA = 18 mW × 165 °C/W = 3°C TJ = TA + ∆T = 25°C + 3°C = 28°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. 10 A3230-DS Allegro MicroSystems, Inc. 115 Northeast Cutoff, Box 15036 Worcester, Massachusetts 01615-0036 (508) 853-5000 www.allegromicro.com A3230 Chopper-Stabilized Hall Effect Bipolar Switch Package LH, 3-Pin (SOT-23W) Package UA, 3-Pin 11 A3230-DS Allegro MicroSystems, Inc. 115 Northeast Cutoff, Box 15036 Worcester, Massachusetts 01615-0036 (508) 853-5000 www.allegromicro.com A3230 Chopper-Stabilized Hall Effect Bipolar Switch 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. 12 A3230-DS Allegro MicroSystems, Inc. 115 Northeast Cutoff, Box 15036 Worcester, Massachusetts 01615-0036 (508) 853-5000 www.allegromicro.com