A1244 Chopper-Stabilized, Two Wire Hall-Effect Latch Features and Benefits Description High speed, 4-phase chopper stabilization Low switchpoint drift throughout temperature range Low sensitivity to thermal and mechanical stresses On-chip protection Supply transient protection Reverse battery protection On-board voltage regulator 3.0 to 24 V operation Solid-state reliability Robust EMC and ESD performance Industry leading ISO 7637-2 performance through use of proprietary, 40-V clamping structures The A1244 is a two-wire Hall-effect latch. The devices are produced on the Allegro(R) advanced BiCMOS wafer fabrication process, which implements a patented high frequency, 4-phase, chopper-stabilization technique. This technique achieves magnetic stability over the full operating temperature range, and eliminates offsets inherent in devices with a single Hall element that are exposed to harsh application environments. Two-wire latches are particularly advantageous in cost-sensitive applications because they require one less wire for operation versus the more traditional open-collector output switches. Additionally, the system designer inherently gains diagnostics because there is always output current flowing, which should be in either of two narrow ranges. Any current level not within these ranges indicates a fault condition. Packages: 3-pin ultramini SIP 1.5 mm x 4 mm x 3 mm (suffix UA) 3-pin SOT23-W 2 mm x 3 mm x 1 mm (suffix LH) The Hall-effect latch will be in the high output current state in the presence of a magnetic south polarity field of sufficient magnitude and will remain in this state until a sufficient north polarity field is present. The device is offered in two package styles. The LH is a SOT-23W style, miniature low profile package for surfacemount applications. The UA is a 3-pin ultra-mini single inline package (SIP) for through-hole mounting. Both packages are lead (Pb) free, with 100% matte tin leadframe plating. Approximate footprint Not to scale Functional Block Diagram V+ VCC Regulator To all subcircuits Amp Sample and Hold 0.01 F Dynamic Offset Cancellation Clock/Logic Low-Pass Filter Schmitt Trigger Polarity GND UA package only A1244-DS, Rev. 1 GND Chopper-Stabilized, Two Wire Hall-Effect Latch A1244 Selection Guide Operating Ambient Temperature, TA (C) Supply Current at ICC(L) (mA) A1244LLHLX-I1-T 13-in. reel, 10000 pieces/reel 3-pin SOT23W surface mount -40 to 150 5 to 6.9 A1244LLHLX-I2-T 13-in. reel, 10000 pieces/reel 3-pin SOT23W surface mount -40 to 150 2 to 5 A1244LUA-I1-T Bulk, 500 pieces/bag 3-pin SIP through hole -40 to 150 5 to 6.9 A1244LUA-I2-T Bulk, 500 pieces/bag 3-pin SIP through hole -40 to 150 2 to 5 Part Number Packing* Package *Contact Allegro(R) for additional packing options Absolute Maximum Ratings Characteristic Symbol Notes Rating Unit 28 V Forward Supply Voltage VCC Reverse Supply Voltage VRCC -18 V B Unlimited G Magnetic Flux Density Operating Ambient Temperature TA -40 to 150 C Maximum Junction Temperature TJ(max) 165 C Tstg -65 to 170 C Storage Temperature Range L Pin-out Diagrams Terminal List Table 3 Name Number Function LH UA VCC 1 1 Connects power supply to chip NC 2 - No connection GND 3 2,3 NC 1 2 LH Package 3-pin SOT23W 1 2 3 Ground UA Package 3-pin SIP Allegro MicroSystems, Inc. 115 Northeast Cutoff Worcester, Massachusetts 01615-0036 U.S.A. 1.508.853.5000; www.allegromicro.com 2 Chopper-Stabilized, Two Wire Hall-Effect Latch A1244 ELECTRICAL CHARACTERISTICS Valid at TA = -40C to 150C, TJ < TJ(max), CBYP = 0.01 F, through operating supply voltage range; unless otherwise noted Characteristics Supply Voltage1,2 Supply Current Supply Zener Clamp Voltage Symbol VCC ICC(L) Test Conditions Operating, TJ 165 C -I1 B < BRP -I2 B < BRP Min. Typ. Max. Unit 3.0 - 24 V 5 - 6.9 mA 2 - 5 mA ICC(H) B > BOP 12 - 17 mA VZ(sup) ICC(L)(max) + 3 mA, TA = 25C 28 - - V mA Supply Zener Clamp Current IZ(sup) VZ(sup) = 28 V - - ICC(L)(max) + 3 mA Reverse Supply Current IRCC VRCC = -18 V - - -1.6 mA Output Slew Rate3 di/dt No bypass capacitor, capacitance of probe CS = 20 pF - 90 - mA / s - 700 - kHz - - 25 s - ICC(H) - - Chopping Frequency Power-Up Time2,4,5 Power-Up State4,6,7 fc ton POS ton < ton(max) , VCC slew rate > 25 mV / s 1V represents the generated voltage between the VCC pin and the GND pin. VCC slew rate must exceed 600 mV/ms from 0 to 3 V. A slower slew rate through this range can affect device performance. 3Measured without bypass capacitor between VCC and GND. Use of a bypass capacitor results in slower current change. 4Power-Up Time is measured without and with bypass capacitor of 0.01 F, B < B RP - 10 G. Adding a larger bypass capacitor would cause longer Power-Up Time. 5Guaranteed by characterization and design. 6Power-Up State as defined is true only with a V CC slew rate of 25 mV / s or greater. 7For t > t on and BRP < B < BOP , Power-Up State is not defined. CC 2The MAGNETIC CHARACTERISTICS1 Valid at TA = -40C to 150C, TJ < TJ (max); unless otherwise noted Characteristics Magnetic Operating Point Symbol Test Conditions BOP Magnetic Release Point BRP Hysteresis BHYS BOP - BRP Min. Typ. Max. Unit2 5 - 80 G -80 - -5 G 40 - 110 G 1Relative values of B use the algebraic convention, where positive values indicate south magnetic polarity, and negative values indicate north magnetic polarity; therefore greater B values indicate a stronger south polarity field (or a weaker north polarity field, if present). 2 1 G (gauss) = 0.1 mT (millitesla). Allegro MicroSystems, Inc. 115 Northeast Cutoff Worcester, Massachusetts 01615-0036 U.S.A. 1.508.853.5000; www.allegromicro.com 3 Chopper-Stabilized, Two Wire Hall-Effect Latch A1244 THERMAL CHARACTERISTICS may require derating at maximum conditions, see application information Application Information Characteristic Symbol RJA Package Thermal Resistance Test Conditions* Value Units Package LH, 1-layer PCB with copper limited to solder pads 228 C/W Package LH, 2-layer PCB with 0.463 in.2 of copper area each side connected by thermal vias 110 C/W Package UA, 1-layer PCB with copper limited to solder pads 165 C/W *Additional thermal information available on Allegro Web site. 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) LH, 2-layer PCB (RQJA = 110 C/W) UA, 1-layer PCB (RQJA = 165 C/W) LH, 1-layer PCB (RQJA = 228 C/W) VCC(min) 20 40 60 80 100 120 140 160 180 Temperature (C) 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 J C A = 11 B, P 0 ac 1-la C/ ka y W (R er PC ) ge L JA = B H 165 , Pac k C/ a W) ge U A 1-lay er P (R CB, JA = 228 Packag C/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, Two Wire Hall-Effect Latch A1244 Characteristic Performance A1244-I1 A1244-I1 Average Supply Current (Low) versus Temperature Average Supply Current (Low) versus Supply Voltage 7.0 Supply Current, ICC(L) (mA) Supply Current, ICC(L) (mA) 7.0 6.5 VCC = 24 V 6.0 VCC = 3.0 V 5.5 5.0 -60 6.0 -20 0 20 40 60 80 100 120 140 160 5.5 2 6 10 A1244-I1,I2 18 22 26 A1244-I1,I2 Average Supply Current (High) versus Temperature Average Supply Current (High) versus Supply Voltage 17 Supply Current, ICC(H) (mA) 17 Supply Current, ICC(H) (mA) 14 Supply Voltage, VCC (V) Ambient Temperature, TA (C) 16 VCC = 24 V 15 VCC = 3.0 V 14 13 12 -60 TA = -40C TA = 25C 5.0 -40 TA = 150C 6.5 16 15 TA = 25C 14 13 12 -40 -20 0 20 40 60 80 100 Ambient Temperature, TA (C) 120 140 160 TA = -40C TA = 150C 2 6 10 14 18 22 26 Supply Voltage, VCC (V) Allegro MicroSystems, Inc. 115 Northeast Cutoff Worcester, Massachusetts 01615-0036 U.S.A. 1.508.853.5000; www.allegromicro.com 5 Chopper-Stabilized, Two Wire Hall-Effect Latch A1244 A1244-I1,I2 Average Operate Point versus Supply Voltage 85 85 75 75 Applied Flux Density at Operate Point, BOP (G) Applied Flux Density at Operate Point, BOP (G) A1244-I1,I2 Average Operate Point versus Temperature 65 55 45 VCC = 3.0 V 35 VCC = 24 V 25 15 5 65 55 45 TA = -40C 25 15 5 -60 -40 -20 0 20 40 60 80 100 120 140 2 160 6 -5 -5 -15 -15 -25 VCC = 3.0 V -45 VCC = 24 V -55 -65 -75 -85 -60 -20 0 20 40 60 80 100 120 140 160 TA = 25C -45 TA = 150C -55 -65 -75 2 6 100 90 VCC = 24 V 80 VCC = 3.0 V 60 50 -20 0 20 40 60 80 100 Ambient Temperature, TA (C) 10 14 18 22 26 120 A1244-I1,I2 Average Switchpoint Hysteresis versus Supply Voltage Applied Flux Density at Switchpoint Hysteresis, BHYS (G) 110 -40 26 Supply Voltage, VCC (V) A1244-I1,I2 Average Switchpoint Hysteresis versus Temperature 40 -60 22 TA = -40C -35 Ambient Temperature, TA (C) 70 18 -25 -85 -40 14 A1244-I1,I2 Average Release Point versus Supply Voltage Applied Flux Density at Release Point, BRP (G) Applied Flux Density at Release Point, BRP (G) A1244-I1,I2 Average Release Point versus Temperature -35 10 Supply Voltage, VCC (V) Ambient Temperature, TA (C) Applied Flux Density at Switchpoint Hysteresis, BHYS (G) TA = 150C TA = 25C 35 140 160 110 100 90 TA = 150C 80 TA = 25C 70 TA = -40C 60 50 40 2 6 10 14 18 22 26 Supply Voltage, VCC (V) Allegro MicroSystems, Inc. 115 Northeast Cutoff Worcester, Massachusetts 01615-0036 U.S.A. 1.508.853.5000; www.allegromicro.com 6 Chopper-Stabilized, Two Wire Hall-Effect Latch A1244 Functional Description The A1244 output, ICC, switches high after the magnetic field at the Hall sensor IC exceeds the operate point threshold, BOP . When the magnetic field is reduced to below the release point threshold, BRP , the device output goes low. This is shown in figure 1. The difference between the magnetic operate and release points is called the hysteresis of the device, BHYS . This built-in hysteresis allows clean switching of the output even in the presence of external mechanical vibration and electrical noise. I+ ICC Switch to Low Switch to High ICC(H) ICC(L) BRP B- BOP 0 B+ BHYS Figure 1. Hysteresis for the A1244. On the horizontal axis, the B+ direction indicates increasing south polarity magnetic field strength, and the B- direction indicates decreasing south polarity field strength (including the case of increasing north polarity). Allegro MicroSystems, Inc. 115 Northeast Cutoff Worcester, Massachusetts 01615-0036 U.S.A. 1.508.853.5000; www.allegromicro.com 7 Chopper-Stabilized, Two Wire Hall-Effect Latch A1244 RSENSE V+ V+ VCC A1244 VCC CBYP 0.01 F A1244 GND ECU CBYP 0.01 F GND RSENSE (A) Low side sensing (B) High side sensing Figure 2. Typical application circuits 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 IC. 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 modulation-demodulation process. The undesired offset signal is separated from the magnetic fieldinduced signal in the frequency domain, through modulation. The subsequent demodulation acts as a modulation process for the offset, causing the magnetic field-induced signal to recover its original spectrum at base band, while the DC offset becomes a high-frequency signal. The magnetic-sourced signal then can pass through a low-pass filter, while the modulated DC offset is suppressed. The chopper stabilization technique uses a 350 kHz high frequency clock. For demodulation process, a sample and hold technique is used, where the sampling is performed at twice the chopper frequency. 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 sampleand-hold circuits. Regulator Hall Element Amp Sample and Hold Clock/Logic Low-Pass Filter Figure 3. Chopper stabilization circuit (Dynamic Quadrature Offset Cancellation) Allegro MicroSystems, Inc. 115 Northeast Cutoff Worcester, Massachusetts 01615-0036 U.S.A. 1.508.853.5000; www.allegromicro.com 8 Chopper-Stabilized, Two Wire Hall-Effect Latch A1244 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, RJA, 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, RJC, is relatively small component of RJA. 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 x IIN T = PD x RJA TJ = TA + T (1) (2) (3) Example: Reliability for VCC at TA = 150C, package LH, using a low-K PCB. Observe the worst-case ratings for the device, specifically: RJA = 110 C/W, TJ(max) = 165C, VCC(max) = 24 V, and ICC(max) = 17 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 = 15C / 110 C/W = 136 mW Finally, invert equation 1 with respect to voltage: VCC(est) = PD(max) / ICC(max) = 136 mW / 17 mA = 8 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 RJA. 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= 25C, VCC = 12 V, ICC = 4 mA, and RJA = 140 C/W, then: PD = VCC x ICC = 12 V x 4 mA = 48 mW T = PD x RJA = 48 mW x 140 C/W = 7C TJ = TA + T = 25C + 7C = 32C A worst-case estimate, PD(max), represents the maximum allowable power level (VCC(max), ICC(max)), without exceeding TJ(max), at a selected RJA and TA. Allegro MicroSystems, Inc. 115 Northeast Cutoff Worcester, Massachusetts 01615-0036 U.S.A. 1.508.853.5000; www.allegromicro.com 9 Chopper-Stabilized, Two Wire Hall-Effect Latch A1244 Package LH, 3-Pin SOT23W +0.12 2.98 -0.08 1.49 D 44 3 A +0.020 0.180-0.053 0.96 D +0.10 2.90 -0.20 +0.19 1.91 -0.06 2.40 0.70 D 0.25 MIN 1.00 2 1 0.55 REF 0.25 BSC 0.95 Seating Plane Gauge Plane 8X 10 REF B PCB Layout Reference View Branded Face 1.00 0.13 +0.10 0.05 -0.05 0.95 BSC 0.40 0.10 NNN 1 C Standard Branding Reference View N = Last three digits of device part number For Reference Only; not for tooling use (reference DWG-2840) Dimensions in millimeters Dimensions exclusive of mold flash, gate burrs, and dambar protrusions Exact case and lead configuration at supplier discretion within limits shown A Active Area Depth, 0.28 mm REF 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 D 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 10 Chopper-Stabilized, Two Wire Hall-Effect Latch A1244 Package UA, 3-Pin SIP +0.08 4.09 -0.05 45 B E C 2.04 1.52 0.05 1.44 E +0.08 3.02 -0.05 10 Mold Ejector Pin Indent E Branded Face 45 0.79 REF A 1.02 MAX NNN 1 1 2 D Standard Branding Reference View 3 = Supplier emblem N = Last three digits of device part number +0.03 0.41 -0.06 14.99 0.25 For Reference Only; not for tooling use (reference DWG-9065) Dimensions in millimeters Dimensions exclusive of mold flash, gate burrs, and dambar protrusions Exact case and lead configuration at supplier discretion within limits shown +0.05 0.43 -0.07 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) 1.27 NOM Allegro MicroSystems, Inc. 115 Northeast Cutoff Worcester, Massachusetts 01615-0036 U.S.A. 1.508.853.5000; www.allegromicro.com 11 Chopper-Stabilized, Two Wire Hall-Effect Latch A1244 Revision History Revision Revision Date Rev. 1 July 12, 2012 Description of Revision Update package drawing Copyright (c)2011-2012, Allegro MicroSystems, Inc. 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 12