(A3250 / A3251) Chopper-Stabilized Unipolar Hall-Effect Switches

A3250 and A3251 Field-Programmable, Chopper-Stabilized Unipolar Hall-Effect Switches Features and Benefits ▪ Chopper stabilization for stable switchpoints throughout operating temperature range ▪ Externally programmable operate point (through VCC pin) ▪ On-board voltage regulator for 4.2 V to 24 V operation ▪ On-chip protection against: ▫ Supply transients ▫ Output short-circuits ▫ Reverse-battery condition Description The A3250 and A3251 are field-programmable, chopperstabilized, unipolar Hall-effect switches designed for use in high-temperature applications. These devices use a chopper-stabilization technique to eliminate offset inherent in single-element devices. The A3250 and A3251 are externally programmable devices. The devices have a wide range of programmability of the magnetic operate point (BOP) while the hysteresis remains fixed. This advanced feature allows for optimization of the sensor switchpoint and can drastically reduce the effects of variations found in a production environment, such as magnet and device placement tolerances. These devices provide on-chip transient protection. A Zener clamp on the power supply protects against overvoltage conditions on the supply line. These devices also include short-circuit protection on the output. The output of the A3250 switches LOW when subjected to a south-polarity magnetic field with a flux density that exceeds the threshold for BOP , and switches HIGH when the Package: 3 pin SOT89 (suffix LT) and 3 pin SIP (suffix UA) www.DataSheet4U.com Continued on the next page… Not to scale Functional Block Diagram VCC Program/Lock Programming Logic Regulator Offset Adjust Sample and Hold Dynamic Offset Cancellation VOUT Amp Current Limit Low-Pass Filter GND 3250-DS Rev. 3 A3250 and A3251 Field-Programmable, Chopper-Stabilized, Unipolar Hall-Effect Switches Three package styles provide a magnetically optimized package for most applications. Type LT is a miniature SOT89/TO-243AA surface mount package that is thermally enhanced with an exposed ground tab, and type UA is a three-lead ultramini SIP for through-hole mounting. The packages are lead (Pb) free, with 100% matte tin plated leadframes (suffix, –T). Description (continued) field drops below the magnetic release point, BRP . The output of the A3251 has the opposite polarity, switching HIGH in a southpolarity magnetic field that BOP , and switching LOW when the field drops below BRP . The other differences in the devices are the power-on state. The A3250 powers-on in the HIGH state, while the A3251 powers-on in the LOW state. Selection Guide Part Number A3250ELT-T A3250ELTTR-T A3250EUA-T A3250LLT-T A3250LLTTR-T A3250LUA-T A3251ELT-T A3251ELTTR-T A3251EUA-T A3251LLT-T A3251LLTTR-T A3251LUA-T 1Pb-based Pb-free1 Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Yes Packing2 Bulk, 500 pieces/bag 7-in. reel, 1000 pieces/reel Bulk, 500 pieces/bag Bulk, 500 pieces/bag 7-in. reel, 1000 pieces/reel Bulk, 500 pieces/bag Bulk, 500 pieces/bag 7-in. reel, 1000 pieces/reel Bulk, 500 pieces/bag Bulk, 500 pieces/bag 7-in. reel, 1000 pieces/reel Bulk, 500 pieces/bag Package Surface mount SIP through hole Surface mount SIP through hole Surface mount SIP through hole Surface mount SIP through hole TA (ºC) –40 to 85 VOUT Power-On High Running3 Low –40 to 150 High Low –40 to 85 Low High –40 to 150 Low High variants are being phased out of the product line. a. Certain variants cited in this footnote are in production but have been determined to be LAST TIME BUY. This classification indicates that sale of this device is currently restricted to existing customer applications. The device should not be purchased for new design applications because obsolescence in the near future is probable. Samples are no longer available. Status change: October 31, 2006. Deadlilne for receipt of LAST TIME BUY ORDERS: April 27, 2007. These variants include: A3250ELT, A3250ELTTR, A3250EUA, A3251ELT, A3251ELTTR, A3251EUA, A3251LLT, A3251LLTTR, and A3251LUA. b. Certain variants cited in this footnote are in production but have been determined to be NOT FOR NEW DESIGN. This classification indicates that sale of this device is currently restricted to existing customer applications. The device should not be purchased for new design applications because obsolescence in the near future is probable. Samples are no longer available. Status change: May 1, 2006. These variants include: A3250LLT, A3250LLTTR, A3250LUA. 2Contact Allegro for additional packing options. 3In south polarity magnetic field of sufficient strength. Absolute Maximum Ratings Characteristic Supply Voltage Reverse Supply Voltage Zener Overvoltage Output Current Magnetic Flux Density Operating Ambient Temperature Maximum Junction Temperature Storage Temperature Symbol VCC VRCC VZ IOUT B TA TJ(max) Tstg Range E Range L Notes Rating 26.5 –18 30 20 Unlimited –40 to 85 –40 to 150 165 –65 to 170 Units V V V mA G ºC ºC ºC ºC Allegro MicroSystems, Inc. 115 Northeast Cutoff, Box 15036 Worcester, Massachusetts 01615-0036 (508) 853-5000 www.allegromicro.com 2 A3250 and A3251 Characteristic ELECTRICAL CHARACTERISTICS Supply Voltage1 Output Saturation Voltage Output Leakage Current VCC VOUT(sat) IOFF ICC(off) Supply Current ICC(on) Output Rise Time Output Fall Time Chopping Frequency Power-Up Time Output Current Limit1,2 tr tf fC ton IOUT(lim) POS Symbol Field-Programmable, Chopper-Stabilized, Unipolar Hall-Effect Switches Test Conditions Min. Typ. Max. Units OPERATING CHARACTERISTICS valid over operating TA and VCC, unless otherwise specified Running mode IOUT = 20 mA; Switch state = ON VOUT = 24 V; Switch state = OFF A3250; B < BRP; VOUT = HIGH A3251; B > BOP; VOUT = HIGH A3250; B > BOP; VOUT = LOW A3251; B < BRP; VOUT = LOW RLOAD = 820 Ω, CLOAD = 10 pF RLOAD = 820 Ω, CLOAD = 10 pF 4.2 – – – – – – – – – – 175 – 4.0 4.0 6.0 6.0 – – 340 20 90 HIGH LOW 24 400 10 7.0 7.0 10.0 10.0 5.0 5.0 – 50 120 – – V mV μA mA mA mA mA μs μs kHz μs mA mV mV VOUT = HIGH Short-circuit protection A3250; B < BRP, t > ton A3251; B < BRP, t > ton – 60 – – Power-On State MAGNETIC CHARACTERISTICS Initial Operate Point Temperature Drift of BOP Hysteresis (BOP – BRP) BOP ΔBOP Bhys BOP ≤ 500 gauss Package TA range = J Package TA range = L –20 –35 5.0 5.0 13 – 18 13 50 35 35 35 G G G G PROGRAMMING CHARACTERISTICS Programmable BOP Values3 Number of Programming Bits Resolution BOP(prog) – BRES Switchpoint set Programming lock 50 – – – – 6 1 7.0 ≥350 – – – G Bit Bit G TRANSIENT PROTECTION CHARACTERISTICS Supply Zener Voltage Supply Zener Current Reverse Battery Current 1 2 3 VZ IZ IRCC VCC = 28 V VRCC = –18 V, TJ < TJ(max) 28 – – – – – – 13 –5.0 V mA mA Do not exceed TJ(max): Additional information on power derating is provided in the applications section. Short-circuit protection is not intended for continuous operation; permanent damage may result. Device can be used below 50 G but is not guaranteed to be a unipolar switch. It is the responsibility of the programmer to verify that the desired switchpoint has been achieved. Allegro MicroSystems, Inc. 115 Northeast Cutoff, Box 15036 Worcester, Massachusetts 01615-0036 (508) 853-5000 www.allegromicro.com 3 A3250 and A3251 Field-Programmable, Chopper-Stabilized, Unipolar Hall-Effect Switches Typical Characterization Data All data are taken with A3250 devices, the average of 3 lots, 30 pieces per lot Average BOP vs. TA Program Code: 1, VCC = 12 V 30 Average BRP vs. TA Program Code: 1, VCC = 12 V 10 Average BRP (G) -20 10 40 70 TA (°C) 100 130 160 Average BOP (G) 25 20 15 10 5 0 -5 -50 5 0 -5 -10 -15 -20 -50 -20 10 40 70 TA (°C) 100 130 160 Average BOP vs. TA Program Code: 8, VCC = 12 V 75 Average BRP vs. TA Program Code: 8, VCC = 12 V 60 Average BOP (G) Average BRP (G) 70 65 60 55 50 45 40 -50 -20 10 40 70 TA (°C) 100 130 160 50 40 30 20 -50 -20 10 40 70 TA (°C) 100 130 160 Average BOP vs. TA Program Code: 16, VCC = 12 V 130 Average BRP vs. TA Program Code: 16, VCC = 12 V 110 Average BOP (G) 125 120 115 110 105 100 -50 -20 10 40 70 TA (°C) 100 130 160 Average BRP (G) 105 100 95 90 85 80 -50 -20 10 40 70 TA (°C) 100 130 160 Allegro MicroSystems, Inc. 115 Northeast Cutoff, Box 15036 Worcester, Massachusetts 01615-0036 (508) 853-5000 www.allegromicro.com 4 A3250 and A3251 Field-Programmable, Chopper-Stabilized, Unipolar Hall-Effect Switches Typical Characterization Data All data are taken with A3250 devices, the average of 3 lots, 30 pieces per lot Average B hys vs. Temperature Program Code: 1, VCC = 12 V 35 Average BHYS (G) Average B hys vs. Temperature Program Code: 16, VCC = 12 V 35 Average BHYS (G) 30 25 20 15 10 5 0 -50 -20 10 40 TA (°C) 30 25 20 15 10 5 0 -50 -20 10 40 70 TA (°C) 100 130 160 70 100 130 160 Average B hys vs. Temperature Program Code: 8, VCC = 12 V 30 Average BOP vs. Temperature -40°C to 25°C and 150°C to 25°C 20 10 0 Code 1 Code 8 Code 16 35 Average BHYS (G) 30 25 20 15 10 5 0 -50 -20 10 40 TA (°C) 70 100 130 160 Average BOP (G) -10 -20 -30 -40°C to 25°C 150°C to 25°C TA (°C) Allegro MicroSystems, Inc. 115 Northeast Cutoff, Box 15036 Worcester, Massachusetts 01615-0036 (508) 853-5000 www.allegromicro.com 5 A3250 and A3251 Field-Programmable, Chopper-Stabilized, Unipolar Hall-Effect Switches Typical Characterization Data All data are taken with A3250 devices, the average of 3 lots, 30 pieces per lot Average ICC(on) vs. Temperature 10 8 10 Average ICC(off) vs. Temperature ICC(off) @ 3.8 V 8 ICC(off) @ 12.0 V ICC(off) @ 26.5 V ICC(on) (mA) 6 4 ICC(on) @ 3.8 V ICC(off) (mA) 160 6 4 2 0 -50 2 0 -50 ICC(on) @ 12.0 V ICC(on) @ 26.5 V -20 10 40 70 100 130 -20 10 40 70 100 130 160 TA (°C) TA (°C) Average VOUT(SAT) vs. Temperature VCC = 3.8 V, Iout = 20 mA 280 260 240 220 200 180 160 140 -50 -20 10 4