A3295 Chopper Stabilized, Precision Hall Effect Switch for Consumer and Industrial Applications FEATURES AND BENEFITS • • • • • • • DESCRIPTION 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 A3295 Hall effect switch is an extremely temperaturestable and stress-resistant sensor IC unipolar switch, 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 device is not intended for automotive applications. Packages: 3-Pin SOT23W (suffix LH) 3-Pin SIP (suffix UA) The device includes, 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-drain output to sink up to 25 mA. A south polarity magnetic field of sufficient strength is required to turn the output on. An onboard regulator permits operation with supply voltages in the range of 3 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-lead ultramini SIP for through-hole mounting. Both packages are lead (Pb) free, with 100% matte tin plated leadframes. Not to scale VCC Amp Sample and Hold Dynamic Offset Cancellation Regulator OUT Low-Pass Filter Control Current Limit 1Ω GND Functional Block Diagram A3295-DS, Rev. 11 Chopper Stabilized, Precision Hall Effect Switch for Consumer and Industrial Applications A3295 SPECIFICATIONS Selection Guide Magnetic Switchpoints2 Part Number Packing1 Package Type A3295KLHLT-T 3000 pieces per 7-in. reel Surface mount SOT23W A3295KLHLX-T 10000 pieces per 13-in. reel Surface mount SOT23W A3295KUA-T 500 pieces per bulk bag Through hole ultramini SIP Operate, BOP (G) Release, BRP (G) 75 max. 5 min. 1Contact Allegro 21 for additional packing options. G (gauss) = 0.1 mT (millitesla). Absolute Maximum Ratings Rating Units Supply Voltage Characteristic Symbol VCC Notes 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 Device provides internal current limiting to help protect itself from output short circuits Magnetic Flux Density B Operating Ambient Temperature TA Maximum Junction Temperature TJ(max) 165 ºC Tstg –65 to 170 ºC Storage Temperature Range K Terminal List 3 Name PTCT PTCT 1 2 1 Package LH, 3-Pin SOT23W Pin-out Diagram 2 VCC OUT GND LH 1 2 3 Number UA 1 3 2 Unlimited G –40 to 125 ºC Function Power supply Output Ground 3 Package UA, 3-Pin SIP Pin-out Diagram Allegro MicroSystems, LLC 115 Northeast Cutoff Worcester, Massachusetts 01615-0036 U.S.A. 1.508.853.5000; www.allegromicro.com 2 Chopper Stabilized, Precision Hall Effect Switch for Consumer and Industrial Applications A3295 ELECTRICAL CHARACTERISTICS over operating temperature range, unless otherwise noted Characteristic Supply Voltage Range2 Output Leakage Current Output Saturation Voltage Symbol Test Conditions Min. Typ.1 Max Units VCC Operating, TJ < 165°C 3.0 – 24 V IOFF VOUT = 24 V, B < BRP – – 10 µA VOUT(SAT) IOUT = 20 mA, B > BOP – 185 500 mV Output Current Limit ION B > BOP 30 – 60 mA Power-On Time tPO VCC > 4.2 V – – 50 µs Chopping Frequency fC – 800 – kHz Output Rise Time tR RLOAD = 820 Ω, CLOAD = 20 pF – 0.2 2.0 µs Output Fall Time tF RLOAD = 820 Ω, CLOAD = 20 pF – 0.1 2.0 µs B < BRP , VCC = 12 V – 3.0 8.0 mA B > BOP , VCC = 12 V – 4.0 8.0 mA VRCC = –30 V – – –5.0 mA ICC = 15 mA, TA = 25°C 28 – – V – 50 – Ω Min. Typ. Max. Units – – 75 G 5 – – G – – 70 G Supply Current ICC Reverse Battery Current IRCC Zener Voltage VZ + VD Zener Impedance ZZ + ZD ICC = 15 mA, TA = 25°C 1Typical data at T = 25°C, 12 V. A 2Maximum V CC must be derated for power dissipation and junction temperature. See Application Information. MAGNETIC CHARACTERISTICS over VCC range, unless otherwise noted Characteristic Operate Point Symbol Test Conditions BOP Release Point BRP Hysteresis BHYS BOP – BRP Allegro MicroSystems, LLC 115 Northeast Cutoff Worcester, Massachusetts 01615-0036 U.S.A. 1.508.853.5000; www.allegromicro.com 3 A3295 Chopper Stabilized, Precision Hall Effect Switch for Consumer and Industrial Applications THERMAL CHARACTERISTICS may require derating at maximum conditions, see application information Characteristic Symbol Package Thermal Resistance Test Conditions* RθJA 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 (RθJA = 110 ºC/W) 1-layer PCB, Package UA (RθJA = 165 ºC/W) 1-layer PCB, Package LH (RθJA = 228 ºC/W) 20 40 60 80 100 120 VCC(min) 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, LLC 115 Northeast Cutoff Worcester, Massachusetts 01615-0036 U.S.A. 1.508.853.5000; www.allegromicro.com 4 Chopper Stabilized, Precision Hall Effect Switch for Consumer and Industrial Applications A3295 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 A3295 uses a proprietary dynamic offset cancellation technique, with an internal high-frequency clock, to reduce the residual offset, see figure 2. The chopper-stabilizing 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. 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 +V CC B +VHALL 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 Sensing Using Dynamic Quadrature Offset Cancellation, and Technical Paper STP 99-1, ChopperStabilized Amplifiers with a Track-and-Hold Signal Demodulator. Operation The output of the A3295 switches low (turns on) when a magnetic field perpendicular to the Hall element 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). Note that 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. –V HALL Figure 1: Hall Element, Basic Circuit Operation V+ Hysteresis of ∆VOUT Switching Due to ∆B VOUT(off) Switch to High VOUT VOUT(on)(sat) BOP BRP LowPass Filter Switch to Low Amp Sample and Hold Regulator B+ BHYS Figure 2: Chopper Stabilization Circuit (Dynamic Quadrature Offset Cancellation) Figure 3: Output Voltage Responds to Magnetic Flux Density. Allegro MicroSystems, LLC 115 Northeast Cutoff Worcester, Massachusetts 01615-0036 U.S.A. 1.508.853.5000; www.allegromicro.com 5 A3295 Chopper Stabilized, Precision Hall Effect Switch for Consumer and Industrial Applications When the device is 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 obtained. APPLICATION INFORMATION It is strongly recommended that an external bypass capacitor be connected (in close proximity to the Hall element) 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 devices is available in: Hall-Effect IC Applications Guide, Application Note 27701 and Guidelines for Designing Subassemblies Using HallEffect Devices, Application Note 27703.1 VCC A3295 VCC 0.1 uF VOUT GND Figure 4: Typical Basic Application Circuit A bypass capacitor is highly recommended. Allegro MicroSystems, LLC 115 Northeast Cutoff Worcester, Massachusetts 01615-0036 U.S.A. 1.508.853.5000; www.allegromicro.com 6 Chopper Stabilized, Precision Hall Effect Switch for Consumer and Industrial Applications A3295 CUSTOMER PACKAGE DRAWINGS For Reference Only – Not for Tooling Use (Reference DWG-2840) Dimensions in millimeters – NOT TO SCALE Dimensions exclusive of mold flash, gate burrs, and dambar protrusions Exact case and lead configuration at supplier discretion within limits shown +0.12 2.98 –0.08 D 1.49 4° ±4° A 3 +0.020 0.180 –0.053 0.96 D +0.19 1.91 –0.06 +0.10 2.90 –0.20 2.40 0.70 D 0.25 MIN 1.00 2 1 0.55 REF 0.25 BSC 0.95 Seating Plane Branded Face Gauge Plane B PCB Layout Reference View 8X 10° REF 1.00 ±0.13 A1101, A1102, A1103, A1104, and A1106 NNT +0.10 0.05 –0.05 0.95 BSC 0.40 ±0.10 N = Last three digits of device part number T = Temperature Code (Letter) A Active Area Depth, 0.28 mm B Reference land pattern layout; all pads a minimum of 0.20 mm from all adjacent pads; adjust as necessary to meet application process requirements and PCB layout tolerances C Branding scale and appearance at supplier discretion A1101, A1102, A1103, and A1104, only NNN D Hall elements, not to scale N = Last three digits of device part number C Standard Branding Reference View Figure 5: Package LH, 3-Pin SOT23W Allegro MicroSystems, LLC 115 Northeast Cutoff Worcester, Massachusetts 01615-0036 U.S.A. 1.508.853.5000; www.allegromicro.com 7 Chopper Stabilized, Precision Hall Effect Switch for Consumer and Industrial Applications A3295 For Reference Only – Not for Tooling Use (Reference DWG-9049) Dimensions in millimeters – NOT TO SCALE Dimensions exclusive of mold flash, gate burrs, and dambar protrusions Exact case and lead configuration at supplier discretion within limits shown 45° B 4.09 +0.08 –0.05 1.52 ±0.05 E 2.04 C 2 X 10° 1.44 E 3.02 E Mold Ejector Pin Indent +0.08 –0.05 45° Branded Face 2.16 MAX 0.51 REF A 1 2 0.79 REF 3 0.43 +0.05 –0.07 0.41 +0.03 –0.06 1.27 NOM NNT 15.75 ±0.25 1 D Standard Branding Reference View = Supplier emblem N = Last three digits of device part number T = Temperature code A Dambar removal protrusion (6X) B Gate and tie bar burr area C Active Area Depth, 0.50 mm REF D Branding scale and appearance at supplier discretion E Hall element, not to scale Figure 6: Package UA, 3-Pin SIP Allegro MicroSystems, LLC 115 Northeast Cutoff Worcester, Massachusetts 01615-0036 U.S.A. 1.508.853.5000; www.allegromicro.com 8 A3295 Chopper Stabilized, Precision Hall Effect Switch for Consumer and Industrial Applications Revision History Revision Revision Date 9 November 11, 2012 10 January 2, 2015 11 July 13, 2015 Description of Revision Conform Description Added LX option to Selection Guide Corrected LH package Active Area Depth value Copyright ©2005-2015, Allegro MicroSystems, LLC Allegro MicroSystems, LLC 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, LLC 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, LLC 115 Northeast Cutoff Worcester, Massachusetts 01615-0036 U.S.A. 1.508.853.5000; www.allegromicro.com 9