A3290 and A3291 Chopper Stabilized, Precision Hall Effect Latches for Consumer and Industrial Applications Features and Benefits Description ▪ Symmetrical switchpoints ▪ Resistant to physical stress ▪ Superior temperature stability ▪ Output short-circuit protection ▪ Operation from unregulated supply ▪ Reverse battery protection ▪ Solid-state reliability ▪ Small package size The A3290 and A3291 Hall effect latches are extremely temperature-stable and stress-resistant sensors, especially suited for operation over extended temperature ranges (up to 125°C). Superior high-temperature performance is made possible through Dynamic Offset Cancellation, which reduces the residual offset voltage normally caused by device package overmolding, temperature dependencies, and thermal stress. The two devices are identical except for their magnetic switchpoints. They are not intended for automotive applications. Packages: 3 pin SOT23W (suffix LH), and 3 pin SIP (suffix UA) Both devices include, on a single silicon chip, a voltage regulator, a Hall-voltage generator, a small-signal amplifier, chopper stabilization, a Schmitt trigger, and a short-circuit protected open-collector output to sink up to 25 mA. A south polarity magnetic field of sufficient strength is required to turn the output on. A north polarity field of sufficient strength is necessary to turn the output off. An onboard regulator permits operation with supply voltages in the range of 4.2 to 24 volts. Two package styles provide a magnetically optimized package for most applications. Type LH is a miniature SOT23W lowprofile surface-mount package, and type UA is a three-pin ultramini SIP for through-hole mounting. Both packages are lead (Pb) free with 100% matte tin leadframe plating. Not to scale Functional Block Diagram VCC Regulator Amp Sample and Hold Dynamic Offset Cancellation OUT Low-Pass Filter Control Current Limit 17 GND A3290-DS Chopper Stabilized, Precision Hall Effect Latches for Consumer and Industrial Applications A3290 and A3291 Selection Guide Magnetic Switchpoints* Packing1 Part Number Package Type Operate, BOP Release, BRP (G) (G) A3290KLHLT-T 3000 pieces per 7-in. reel Surface mount SOT23W A3290KUA-T 500 pieces per bulk bag Through hole ultramini SIP A3291KLHLT-T 3000 pieces per 7-in. reel Surface mount SOT23W A3291KUA-T 500 pieces per bulk bag Through hole ultramini SIP *Algebraic 5 to 50 –50 to –5 10 to 100 –100 to –10 convention used: (+) south polarity, (–) north polarity. Absolute Maximum Ratings Rating Units Supply Voltage Characteristic Symbol VCC 26.5 V Reverse Battery Voltage VRCC –30 V Output Off Voltage VOUT 26 V Continuous Output Current IOUT 25 mA Reverse Output Current IROUT –50 mA Magnetic Flux Density B Operating Ambient Temperature TA Maximum Junction Temperature Notes Device provides internal current limiting to help protect itself from output short circuits Unlimited G –40 to 125 ºC TJ(max) 165 ºC Tstg –65 to 170 ºC Storage Temperature Range K Pin-out Diagrams Terminal List 3 Name PTCT PTCT 1 2 1 Package LH 2 VCC OUT GND LH 1 2 3 Number UA 1 3 2 Function Power supply Output Ground 3 Package UA Allegro MicroSystems, Inc. 115 Northeast Cutoff Worcester, Massachusetts 01615-0036 U.S.A. 1.508.853.5000; www.allegromicro.com 2 A3290 and A3291 Chopper Stabilized, Precision Hall Effect Latches for Consumer and Industrial Applications ELECTRICAL CHARACTERISTICS over operating temperature range, unless otherwise noted Characteristic Symbol Test Conditions Supply Voltage Range2 VCC Operating, TJ < 165°C Output Leakage Current IOFF VOUT = 24 V, B < BRP Output Saturation Voltage VOUT(SAT) IOUT = 20 mA, B > BOP 3 Output Current Limit ION B > BOP Power-On Time tPO VCC > 4.2 V Chopping Frequency fC RLOAD = 820 Ω, CLOAD = 20 pF Output Rise Time tR Output Fall Time tF RLOAD = 820 Ω, CLOAD = 20 pF B < BRP , VCC = 12 V Supply Current ICC B > BOP , VCC = 12 V Reverse Battery Current IRCC VRCC = –30 V Zener Voltage VZ + VD ICC = 15 mA, TA = 25°C Zener Impedance ZZ + ZD ICC = 15 mA, TA = 25°C Min. 4.2 – – 30 – – – – – – – 28 – Typ.1 – – 185 – – 800 0.2 0.1 3.0 4.0 – 32 50 Max 24 10 500 60 50 – 2.0 2.0 8.0 8.0 –5.0 37 – Units V μA mV mA μs kHz μs μs mA mA mA V Ω !Typical data at TA = 25°C, 12 V VCC must be derated for power dissipation and junction temperature. See application information. 3Non-R device option only. 2Maximum MAGNETIC CHARACTERISTICS1 over VCC range, unless otherwise noted Characteristic Symbol A3290 Operate Point2 BOP A3291 A3290 Release Point3 BRP A3291 A3290 Hysteresis (BOP – BRP) BHYS A3291 Test Conditions TA = 25°C and TA(max) Min. Max. Units 5 50 G TA = –40°C 5 50 G TA = 25°C and TA(max) 10 100 G TA = –40°C 10 100 G TA = 25°C and TA(max) –50 –5 G TA = –40°C –50 –5 G TA = 25°C and TA(max) –100 –10 G TA = –40°C –100 –10 G 10 100 G TA = 25°C and TA(max) TA = –40°C – 100 G TA = 25°C and TA(max) 20 200 G TA = –40°C – 200 G 1The positive polarity symbol (+) indicates south magnetic field, and the negative polarity symbol (–) indicates north magnetic field. 2Required polarity observed and transition of magnetic gradient through B . See functional description. OP 3Required polarity observed and transition of magnetic gradient through B after B . See functional description. RP OP Allegro MicroSystems, Inc. 115 Northeast Cutoff Worcester, Massachusetts 01615-0036 U.S.A. 1.508.853.5000; www.allegromicro.com 3 A3290 and A3291 Chopper Stabilized, Precision Hall Effect Latches for Consumer and Industrial Applications THERMAL CHARACTERISTICS may require derating at maximum conditions, see application information Characteristic Symbol RθJA Package Thermal Resistance Test Conditions* Value Units Package LH, 1-layer PCB with copper limited to solder pads 228 ºC/W Package LH, 2-layer PCB with 0.463 in.2 of copper area each side connected by thermal vias 110 ºC/W Package UA, 1-layer PCB with copper limited to solder pads 165 ºC/W *Additional thermal information available on Allegro website. Maximum Allowable VCC (V) Power Derating Curve 25 24 23 22 21 20 19 18 17 16 15 14 13 12 11 10 9 8 7 6 5 4 3 2 VCC(max) 2-layer PCB, Package LH (RQJA = 110 ºC/W) 1-layer PCB, Package UA (RQJA = 165 ºC/W) 1-layer PCB, Package LH (RQJA = 228 ºC/W) VCC(min) 20 40 60 80 100 120 140 160 180 Temperature (ºC) Power Dissipation, PD (m W) 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 2l (R aye rP θJ C A = 11 B, P 0 º ac 1-la C/ ka W (R yer PC ) ge L θJA = B H 165 , Pac ºC/ kage W) UA 1-lay er P (R CB, θJA = 228 Packag ºC/W e LH ) 20 40 60 80 100 120 Temperature (°C) 140 160 180 Allegro MicroSystems, Inc. 115 Northeast Cutoff Worcester, Massachusetts 01615-0036 U.S.A. 1.508.853.5000; www.allegromicro.com 4 Chopper Stabilized, Precision Hall Effect Latches for Consumer and Industrial Applications A3290 and A3291 Functional Description Chopper-Stabilized Technique The Hall element can be considered as a resistor array similar to a Wheatstone bridge. A basic circuit is shown in figure 1, demonstrating the effect of the magnetic field flux density, B, impinging on the Hall element. When using Hall effect technology, a limiting factor for switchpoint accuracy is the small signal voltage, VHALL, developed across the Hall element. This voltage is disproportionally small relative to the offset that can be produced at the output of the Hall device, caused by device overmolding, temperature dependencies, and thermal stress. A large portion of the offset is a result of the mismatching of these resistors. The A3290 and A3291 use a proprietary dynamic offset cancellation technique, with an internal high-frequency clock, to reduce the ressidual offset. The chopper-stabilizing B +VHALL The signal is then captured by a sample-and-hold circuit and further processed using low-offset bipolar circuitry. This technique produces devices that have an extremely stable quiescent Hall output voltage, are immune to thermal stress, and have precise recoverability after temperature cycling. This technique will also slightly degrade the device output repeatability. A relatively high sampling frequency is used in order to process faster signals. More detailed descriptions of the circuit operation can be found on the Allegro Web site, including: Technical Paper STP 97-10, Monolithic Magnetic Hall Sensor Using Dynamic Quadrature Offset Cancellation, and Technical Paper STP 99-1, ChopperStabilized Amplifiers with a Track-and-Hold Signal Demodulator. Operation The outputs of the A3290 and A3291 switch low (turn on) when a magnetic field perpendicular to the Hall sensor transitions through and exceeds the Operate Point threshold, BOP. This is illustrated in figure 3. After turn-on, the output is capable of sinking 25 mA, and the output voltage reaches VOUT(SAT). Figure 1. Hall element, basic circuit operation Regulator VOUT(on)(sat) BOP BRP LowPass Filter VOUT(off) Switch to Low Amp Sample and Hold V+ Hysteresis of ΔVOUT Switching Due to ΔB Switch to High –V HALL VOUT +V CC technique cancels the mismatching of the resistor circuit by changing the direction of the current flowing through the Hall element. To do so, CMOS switches and Hall voltage measurement taps are used, while maintaining VHALL signal that is induced by the external magnetic flux. B+ BHYS Figure 2. Chopper stabilization circuit (dynamic quadrature offset cancellation) Figure 3. Output voltage responds to sensed magnetic flux density. Allegro MicroSystems, Inc. 115 Northeast Cutoff Worcester, Massachusetts 01615-0036 U.S.A. 1.508.853.5000; www.allegromicro.com 5 A3290 and A3291 Chopper Stabilized, Precision Hall Effect Latches for Consumer and Industrial Applications Note that these devices latch; that is, after a south (+) polarity magnetic field of sufficient strength impinging on the branded face of the device turns on the device, the device remains on until the magnetic field is reduced below the Release Point threshold, BRP . At that transition, 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. When the devices are powered on, if the ambient magnetic field has an intensity that is between BOP and BRP , the initial output state is indeterminate. The first time that the level of B either rises through BOP , or falls through BRP , however, the correct output state is obatined. Application Information 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. This configuration is shown in figure 4. The simplest form of magnet that will operate these devices is a ring magnet.Other methods of operation, such as linear magnets, are possible. 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. The Package Thermal Resistance, RθJA, is a figure of merit summarizing the ability of the application and the device to dissi- pate 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. Sample power dissipation results are given in the Thermal Characteristics section. Additional thermal data is also available on the Allegro website. Extensive applications information for Hall-effect sensors is available in: Hall-Effect IC Applications Guide, Application Note 27701 and Guidelines for Designing Subassemblies Using HallEffect Devices, Application Note 27703.1 VCC VCC A329x VOUT 0.1 uF GND Figure 4. Typical basic application circuit. A bypass capacitor is highly recommended. Allegro MicroSystems, Inc. 115 Northeast Cutoff Worcester, Massachusetts 01615-0036 U.S.A. 1.508.853.5000; www.allegromicro.com 6 Chopper Stabilized, Precision Hall Effect Latches for Consumer and Industrial Applications A3290 and A3291 Package LH, 3-Pin SOT23W 2.975 0.70 1.49 B A 3 4º 0.28 0.180 0.96 B 2.90 1.91 2.40 B 0.38 1.00 2 1 0.25 Seating Plane Gauge Plane 10º PCB Layout Reference View 1.00 10º 0.95 0.40 All dimensions nominal, not for tooling use Dimensions in millimeters 0.05 A Active Area Depth B Hall element, not to scale Allegro MicroSystems, Inc. 115 Northeast Cutoff Worcester, Massachusetts 01615-0036 U.S.A. 1.508.853.5000; www.allegromicro.com 7 A3290 and A3291 Chopper Stabilized, Precision Hall Effect Latches for Consumer and Industrial Applications Package UA, 3-Pin SIP 4.09 45° A B 2.01 C 3X10° 3.02 1.52 1.44 C 45° C 0.79 1.02 MAX 14.99 0.41 1 2 3 0.43 1.27 Matrix leadframe All dimensions nominal, not for tooling use Dimensions in millimeters Exact case and lead configuration at supplier discretion within limits shown A Active Area Depth, 0.50 mm B Gate and tie bar burr area C Hall element, not to scale Copyright ©2005-2008, Allegro MicroSystems, Inc. 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’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 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. For the latest version of this document, visit our website: www.allegromicro.com Allegro MicroSystems, Inc. 115 Northeast Cutoff Worcester, Massachusetts 01615-0036 U.S.A. 1.508.853.5000; www.allegromicro.com 8