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Technical content
Description
The A1250 Hall-effect sensor IC is a temperature stable, stress-resistant bipolar switch. This device 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 A1250 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 A1250 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. A1250-DS, Rev. 1 Features and Benefits
- High speed, 4-phase chopper stabilization
- Low operating voltage down to 3.0 V
- High Sensitivity
- Stable switchpoints
- Robust EMC Hall Effect Latch / Bipolar Switch Functional Block Diagram A1250 Control Current Limit Clock / Logic Low-Pass Filter 1 Ω Regulator GND VC C VOUT Dynamic Offset Cancellation Sample and Hold To All Subcircuits Amp Not to scale 3-pin SIP (suffix UA) Continued on the next page…
Hall Effect Latch / Bipolar SwitchA1250 2Allegro MicroSystems, LLC
115 Northeast Cutoff
Worcester, Massachusetts 01615-0036 U.S.A. Pin-out Diagrams Absolute Maximum Ratings Characteristic Symbol Notes Rating Unit* Forward Supply Voltage V CC 28 V Reverse Supply Voltage V RCC –18 V Output Off Voltage V OUT 28 V Reverse Output Voltage V ROUT –0.6 V Output Current I OUTSINK Internally limited A Reverse Output Current I ROUT –10 mA Magnetic Flux Density B Unlimited G Operating Ambient Temperature T A Range L –40 to 150 ºC Maximum Junction Temperature T J(max) 165 ºC Storage Temperature T stg –65 to 170 ºC *1 G (gauss) = 0.1 mT (millitesla). Terminal List Table Name Number FunctionPackage LH Package UA VCC 1 1 Device supply VOUT 2 3 Device output GND 3 2 Ground The A1250 is rated for operation in the ambient temperature range L, –40°C to 150°C. Two package styles provide magnetically optimized solutions for most applications. Each package is lead (Pb) free version, with 100% matte tin plated leadframe. Description (continued) Selection Guide Part Number Packing * Mounting Ambient, TA (°C) A1250LLHLT-T 7-in. reel, 3000 pieces/reel Surface mount –40 to 150A1250LLHLX-T 13-in. reel, 10 000 pieces/reel Surface mount A1250LUA-T Bulk, 500 pieces/bag SIP through hole *Contact Allegro for additional packing options. 1 2 GND VOUT VCC 1 32GND VOUT VCC Package UAPackage LH
Hall Effect Latch / Bipolar SwitchA1250 3Allegro MicroSystems, LLC Worcester, Massachusetts 01615-0036 U.S.A.
ELECTRICAL CHARACTERISTICS
Supply Voltage V CC Operating TJ < 165°C 3.0 – 24 V Output Leakage Current I OUTOFF VOUT = 24 V, B < BRP –– 1 0 μA Output On Voltage V OUT(SAT) IOUT = 20 mA, B > BOP – – 500 mV Output Current Limit I OM B > BOP 3 0–6 0m A Power-On Time t PO VCC > 3.0 V – – 25 μs Chopping Frequency f c – 160 – kHz Output Rise Time1 tr RLOAD = 820 Ω, CS = 20 pF – – 2 μs Output Fall Time1 tf RLOAD = 820 Ω, CS = 20 pF – – 2 μs Supply Current ICCON B > BOP ––4m A ICCOFF B < BRP ––4m A Reverse Battery Current I RCC VRCC = –18 V – – –2 mA Supply Zener Clamp Voltage V Z ICC = 6.5 mA, TA = 25°C 28 – – V Supply Zener Current I Z VCC = 28 V – – 7 mA MAGNETIC CHARACTERISTICS2 Valid at TA = –40°C to 150°C, TJ ≤ TJ(max), unless otherwise noted Operate Point B OP –10 5 25 G Release Point B RP –25 –5 10 G Hysteresis B HYS 51 0 2 5 G 1Guaranteed by design. 2Magnetic flux density, B, is indicated as negative value for north-polarity fields, and positive for south-polarity fields. OPERATING CHARACTERISTICS Valid at TA = –40°C to 150°C, CBYPASS = 0.1 μF, unless otherwise noted Characteristics Symbol Test Conditions Min. Typ. Max. Unit
Hall Effect Latch / Bipolar SwitchA1250 4Allegro MicroSystems, LLC Worcester, Massachusetts 01615-0036 U.S.A. THERMAL CHARACTERISTICS may require derating at maximum conditions, see application information Characteristic Symbol Test Conditions* Value Units Package Thermal Resistance RθJA 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 Web site. 20 40 60 80 100 120 140 160 180 Temperature (ºC) Maximum Allowable VCC (V) Power Derating Curve (RQJA = 228 ºC/W) 1-layer PCB, Package LH (RQJA = 110 ºC/W) 2-layer PCB, Package LH (RQJA = 165 ºC/W) 1-layer PCB, Package UA VCC(min) VCC(max) 100 200 300 400 500 600 700 800 900 1000 1100 1200 1300 1400 1500 1600 1700 1800 1900 20 40 60 80 100 120 140 160 180 Temperature (°C) Power Dissipation, PD (mW) Power Dissipation versus Ambient Temperature QJA = 165 ºC/W) 1-layer PCB, Package UA QJA = 228 ºC/W) 1-layer PCB, Package LH QJA = 110 ºC/W) 2-layer PCB, Package LH
Hall Effect Latch / Bipolar SwitchA1250 5Allegro MicroSystems, LLC Worcester, Massachusetts 01615-0036 U.S.A. Characteristic Performance Data 0.5 1.0 1.5 2.0 2.5 3.0 3.5 4.0 0 5 10 15 20 25 ICCON (mA) VCC (V) Supply Current (On) versus Supply Voltage -40°C 25°C 150°C 0.5 1.0 1.5 2.0 2.5 3.0 3.5 4.0 -50 -25 0 25 50 75 100 125 150 ICCON (mA) TA (°C) Supply Current (On) versus Ambient Temperature Vcc: 24 V Vcc: 3 V 0.5 1.0 1.5 2.0 2.5 3.0 3.5 4.0 0 5 10 15 20 25 ICCOFF (mA) VCC (V) Supply Current (Off) versus Supply Voltage -40°C 25°C 150°C 0.5 1.0 1.5 2.0 2.5 3.0 3.5 4.0 -50 -25 0 25 50 75 100 125 150 ICCOFF (mA) TA (°C) Supply Current (Off) versus Ambient Temperature Vcc: 24 V Vcc: 3 V 100 150 200 250 300 350 400 450 500 -50 -25 0 25 50 75 100 125 150 VOUT(SAT) TA (°C) VOUT(SAT) versus Ambient Temperature IOUT = 20 mA Vcc: 3 V Vcc: 24 V
Hall Effect Latch / Bipolar SwitchA1250 6Allegro MicroSystems, LLC Worcester, Massachusetts 01615-0036 U.S.A. -10 -50 -25 0 25 50 75 100 125 150 BOP (G) TA (°C) Operate Point versus Ambient Temperature Vcc: 24 V Vcc: 3 V -25 -20 -15 -10 -50 -25 0 25 50 75 100 125 150 BRP (G) TA (°C) Release Point versus Ambient Temperature Vcc: 24 V Vcc: 3 V -50 -25 0 25 50 75 100 125 150 BOP (G) TA (°C) Hysteresis versus Ambient Temperature Vcc: 24 V Vcc: 3 V
Worcester, Massachusetts 01615-0036 U.S.A. OP . After turn-on, the output voltage is VOUT(SAT) . BRP , the device will operate as a latch, as shown in figure 1a. the output will retain its state when the magnetic field is removed. switch to the low state if the magnetic field is removed. Figure 1. Bipolar Device Output Switching Modes. These behaviors can be exhibited when using a circuit such as can operate in any of the three modes.
Hall Effect Latch / Bipolar SwitchA1250 8Allegro MicroSystems, LLC Worcester, Massachusetts 01615-0036 U.S.A.
Application Information
Figure 2. Typical Application Circuit Figure 3. Concept of Chopper Stabilization Technique density logic integration and sample-and-hold circuits.
Hall Effect Latch / Bipolar SwitchA1250 9Allegro MicroSystems, LLC Worcester, Massachusetts 01615-0036 U.S.A. The device must be operated below the maximum junction temperature of the device, T J(max) . Under certain combina- tions 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 T J. (Thermal data is also available on the Allegro MicroSystems Web site.) The Package Thermal Resistance, RJA, is a figure of merit sum- marizing 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, R JC, 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 T J, at PD. P D = VIN × IIN (1) T J = TA + ΔT (3) For example, given common conditions such as: TA= 25°C, VIN = 12 V, IIN = 4 mA, and RJA = 140 °C/W, then: P D = VIN × IIN = 12 V × 4 mA = 48 mW T = PD × RJA = 48 mW × 140 °C/W = 7°C A worst-case estimate, PD(max) , represents the maximum allow- able power level, without exceeding TJ(max) , at a selected RJA and TA. Example: Reliability for VCC at TA = 150°C, package UA, using a single-layer PCB. Observe the worst-case ratings for the device, specifically: RJA = 165 °C/W, TJ(max) = 165°C, VCC(max) = 24 V , and ICC(max) = 4 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 = 15°C ÷ 165 °C/W = 91 mW Finally, invert equation 1 with respect to voltage: VCC(est) = PD(max) ÷ ICC(max) = 91 mW ÷ 4 mA = 23 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 condi- tions. Power Derating
Hall Effect Latch / Bipolar SwitchA1250 10Allegro MicroSystems, LLC Worcester, Massachusetts 01615-0036 U.S.A.
0.55 REF
0.25 BSC
0.95 BSC
0.95 1.00 0.70 2.40 A Active Area Depth, 0.28 mm REF B C C 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 Branding scale and appearance at supplier discretion A PCB Layout Reference View Standard Branding Reference View Branded Face N = Last three digits of device part number NNN 2.90 +0.10 –0.20 4°±4° 8X 10° REF 0.180+0.020 –0.053 0.05 +0.10 –0.05
0.25 MIN
1.91 +0.19 –0.06 2.98 +0.12 –0.08 1.00 ±0.13 0.40 ±0.10 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 D Hall element, not to scale D D D1.49 0.96
Hall Effect Latch / Bipolar SwitchA1250 11Allegro MicroSystems, LLC Worcester, Massachusetts 01615-0036 U.S.A. Package UA 3-Pin SIP 231
1.27 NOM
2.16 MAX 0.51 REF 45° C 45°
0.79 REF
B E E E 2.04 1.44 Gate burr area A B C Dambar removal protrusion (6X) A D E D Branding scale and appearance at supplier discretion Hall element, not to scale Active Area Depth, 0.50 mm REF For Reference Only; not for tooling use (reference DWG-9049) Dimensions in millimeters Dimensions exclusive of mold flash, gate burrs, and dambar protrusions Exact case and lead configuration at supplier discretion within limits shown Standard Branding Reference View = Supplier emblem N = Last three digits of device part number NNN Mold Ejector Pin Indent Branded Face 4.09 +0.08 –0.05 0.41 +0.03 –0.06 3.02 +0.08 –0.05 0.43 +0.05 –0.07 15.75 ±0.51 1.52 ±0.5
Hall Effect Latch / Bipolar SwitchA1250 12Allegro MicroSystems, LLC Worcester, Massachusetts 01615-0036 U.S.A. Copyright ©2010-2013, Allegro MicroSystems, LLC Allegro MicroSystems, LLC reserves the right to make, from time to time, such de par tures from the detail spec i fi ca tions as may be required to permit improvements in the per for mance, 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 in for ma tion in clud ed herein is believed to be ac cu rate and reliable. How ev er, Allegro MicroSystems, LLC assumes no re spon si bil i ty for its use; nor for any in fringe ment 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
Revision History
Revision Revision Date Description of Revision Rev. 1 March 22, 2012 Update product selection