Chopper Stabilized Precision Hall Effect Switches

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1 A1, A11, and A11 Features and Benefits Unipolar switchpoints Resistant to physical stress Superior temperature stability Output short-circuit protection Operation from unregulated supply Reverse battery protection Solid-state reliability Small package sizes Packages: 3-pin SOT23W (suffix LH) Not to scale 3-pin SIP (suffix UA) Description The A1, A11, and A11 Hall-effect, unipolar switches are extremely temperature-stable and stress-resistant sensor ICs, especially suited for operation over extended temperature ranges to C. Superior high-temperature performance is made possible through dynamic offset cancellation, which reduces the residual offset voltage normally caused by device overmolding, temperature dependencies, and thermal stress. Each device includes 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 to sink up to ma. An on-board regulator permits operation with supply voltages of 3 to V. The advantage of operating down to 3 V is that the device can be used in 3 V applications or with additional external resistance in series with the supply pin for greater protection against high voltage transient events. For the A1 and A11, a south pole of sufficient strength turns the output on. Removal of the magnetic field turns the output off. The A11 is complementary, in that for these devices, a south pole turns the A11 output off, and removal of the magnetic field turns the output on. Two package styles provide a magnetically optimized package for most applications. Package type LH is a modified SOT23W, surface mount package, while UA is a three-lead ultra-mini SIP for through-hole mounting. Each package type is lead (Pb) free (suffix, T), with a 1% matte tin plated leadframe. Functional Block Diagram VCC Regulator Dynamic Offset Cancellation Amp Sample and Hold Low-Pass Filter To All Subcircuits Control Current Limit VOUT GND A1-DS, Rev. 11

2 A1, A11 and A11 Selection Guide Part Number Packing 1 Mounting Ambient, T A (Typ.) Switchpoints A1ELHLX-T 13-in. reel, 1 pieces/reel 3-pin SOT23W surface mount A1ELHLT-T 2 7-in. reel, 3 pieces/reel 3-pin SOT23W surface mount A1EUA-T Bulk, 5 pieces/bag 3-pin SIP through hole A1LLHLX-T 13-in. reel, 1 pieces/reel 3-pin SOT23W surface mount A1LLHLT-T 2 7-in. reel, 3 pieces/reel 3-pin SOT23W surface mount A1LUA-T Bulk, 5 pieces/bag 3-pin SIP through hole A11ELHLX-T 13-in. reel, 1 pieces/reel 3-pin SOT23W surface mount A11ELHLT-T 2 7-in. reel, 3 pieces/reel 3-pin SOT23W surface mount A11EUA-T Bulk, 5 pieces/bag 3-pin SIP through hole A11LLHLX-T 13-in. reel, 1 pieces/reel 3-pin SOT23W surface mount A11LLHLT-T 2 7-in. reel, 3 pieces/reel 3-pin SOT23W surface mount A11LUA-T Bulk, 5 pieces/bag 3-pin SIP through hole A11ELHLX-T 13-in. reel, 1 pieces/reel 3-pin SOT23W surface mount A11EUA-T Bulk, 5 pieces/bag 3-pin SIP through hole A11LLHLX-T 13-in. reel, 1 pieces/reel 3-pin SOT23W surface mount A11LUA-T Bulk, 5 pieces/bag 3-pin SIP through hole * Contact Allegro for additional packing options. 2Available through authorized Allegro distributors only. 4ºC to 85ºC 4ºC to ºC 4ºC to 85ºC 4ºC to ºC 4ºC to 85ºC 4ºC to ºC B OP B RP Output In South (Positive) Magnetic Field On (logic low) 35 Off (logic high) Worcester, Massachusetts U.S.A ; 2

3 A1, A11 and A11 Absolute Maximum Ratings Characteristic Symbol Notes Rating Units Forward Supply Voltage V CC 26.5 V Reverse Supply Voltage V RCC 3 V Output Off Voltage V OUT 26 V Continuous Output Current I OUT ma Reverse Output Current I ROUT 5 ma Range E 4 to 85 ºC Operating Ambient Temperature T A Range L 4 to ºC Maximum Junction Temperature T J (max) 165 ºC Storage Temperature T stg 65 to 17 ºC GND 3 Pin-out Diagrams Package LH Package UA VCC VOUT VCC GND VOUT Terminal List Name Description Number Package LH Package UA VCC Connects power supply to chip 1 1 VOUT Output from circuit 2 3 GND Ground 3 2 Worcester, Massachusetts U.S.A ; 3

4 A1, A11 and A11 ELECTRICAL CHARACTERISTICS Valid valid over full operating voltage and ambient temperature ranges; unless otherwise noted Characteristics Symbol Test Conditions Min. Typ. 1 Max. Unit 2 Electrical Characteristics Forward Supply Voltage V CC Operating, T J < 165 C 3 V Output Leakage Current I OUTOFF A11 A1, V OUT = V, B B OP 1 μa Output Saturation Voltage V OUT(SAT) A11 A1, I OUT = 2 ma, B > B OP mv A11 I OUT = 2 ma, B B OP 3 6 ma A11 B 3. V, B B OP (max) + 1 G μs Chopping Frequency f C 8 khz Output Rise Time 3,4 t r R L = 82 Ω, C S = 2 pf.2 2 μs Output Fall Time 3,4 t f R L = 82 Ω, C S = 2 pf.1 2 μs Supply Current A1, I A11 CC(ON) V CC = V, B > B OP 4 ma A11 V CC = V, B B OP 4 ma Reverse Supply Current I RCC V RCC = 3 V 5 ma Supply Zener Clamp Voltage V Z I CC = 5 ma; T A = C 28 V Zener Impedance I Z I CC = 5 ma; T A = C 5 Ω Magnetic Characteristics Operate Point B OP A11 A1, 35 5 G A G Release Point B RP A11 A1, 5 G A G A1, Hysteresis B A11 HYS (B OP B RP ) 1 G A G 1Typical data are are at T A = C and V CC = V, and are for initial design estimations only. 1 G (gauss) =.1 mt (millitesla). Guaranteed by device design and characterization. C S = oscilloscope probe capacitance. Worcester, Massachusetts U.S.A ; 4

5 A1, A11 and A11 THERMAL CHARACTERISTICS may require derating at maximum conditions, see application information Characteristic Symbol Test Conditions Value Units Package Thermal Resistance R θja Package LH, 1-layer PCB with copper limited to solder pads 228 ºC/W Package LH, 2-layer PCB with.463 in. 2 of copper area each side connected by thermal vias 11 ºC/W Package UA, 1-layer PCB with copper limited to solder pads 165 ºC/W Maximum Allowable Power Derating Curve T J(max) = 165ºC; I CC = I CC(max) Package LH, 2-layer PCB (R JA = 11 ºC/W) Package UA, 1-layer PCB (R JA = 165 ºC/W) Package LH, 1-layer PCB (R JA = 228 ºC/W) V CC(max) V CC(min) Power Dissipation, PD (mw) Power Dissipation versus Ambient Temperature Package LH, 2-layer PCB (R JA = 11 ºC/W) Package UA, 1-layer PCB (R JA = 165 ºC/W) Package LH, 1-layer PCB (R JA = 228 ºC/W) Temperature ( C) Worcester, Massachusetts U.S.A ; 5

6 A1, A11 and A11 Characteristic Performance A1, A11, and A11 Electrical Characteristics Average Supply Current (On) versus Ambient Temperature Average Supply Current (On) versus Average Supply Voltage I CC(av) (ma) I CC(av) (ma) Average Supply Current (Off) versus Ambient Temperature Average Supply Current (Off) versus Average Supply Voltage ICC(av) (ma) I CC(av) (ma) Average Output Saturation Voltage versus Ambient Temperature 3 Average Output Saturation Voltage versus Supply Voltage 3 VOUT(sat) (V) V OUT(sat) (V) Worcester, Massachusetts U.S.A ; 6

7 A1, A11 and A11 A1 and A11 Magnetic Characteristics Average Operate Point versus Ambient Temperature Average Operate Point versus Average Supply Voltage BOP (G) B OP (G) Average Release Point versus Ambient Temperature Average Release Point versus Average Supply Voltage BRP (G) B RP (G) Average Switchpoint Hysteresis versus Ambient Temperature Average Switchpoint Hysteresis versus Supply Voltage BHYS (G) B HYS (G) Worcester, Massachusetts U.S.A ; 7

8 A1, A11 and A11 A11 Magnetic Characteristics Operate Point versus Ambient Temperature Operate Point versus Average Supply Voltage B OP (G) B OP (G) Release Point versus Ambient Temperature Release Point versus Average Supply Voltage BRP (G) B RP (G) Switchpoint Hysteresis versus Ambient Temperature Switchpoint Hysteresis versus Supply Voltage BHYS (G) B HYS (G) Worcester, Massachusetts U.S.A ; 8

9 A1, A11 and A11 Functional Description Operation The output of the A1 and A11 devices switches low (turns on) when a magnetic field perpendicular to the Hall element exceeds the operate point threshold, B OP (see panel A of figure 1). When the magnetic field is reduced below the release point, B RP, the device output goes high (turns off). The output of the A11 devices switches high (turns off) when a magnetic field perpendicular to the Hall element exceeds the operate point threshold, B OP (see panel B of figure 1). When the magnetic field is reduced below the release point, B RP, the device output goes low (turns on). After turn-on, the output voltage is V OUT(SAT). The output transistor is capable of sinking current up to the short circuit current limit, I OM, which is a minimum of 3 ma. The difference in the magnetic operate and release points is the hysteresis, B HYS, of the device. This built-in hysteresis allows clean switching of the output even in the presence of external mechanical vibration and electrical noise. Powering-on the device in the hysteresis range (less than B OP and higher than B RP ) will give an indeterminate output state. The correct state is attained after the first excursion beyond B OP or B RP. Applications 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 external noise in the application. As is shown in panel B of figure 1, a.1 μf capacitor is typical. Extensive applications information for Hall effect devicers is available in: Hall-Effect IC Applications Guide, Application Note 2771 Guidelines for Designing Subassemblies Using Hall-Effect Devices, Application Note Soldering Methods for Allegro s Products SMT and Through- Hole, Application Note 269 All are provided in Allegro Electronic Data Book, AMS-72, and the Allegro Web site, V+ V CC V+ V CC V S V OUT Switch to High Switch to Low V OUT(SAT) V OUT Switch to Low Switch to High V OUT(SAT) C BYP.1 μf VCC A1x VOUT GND Output R L B RP B OP B+ B RP B OP B+ B HYS B HYS (A) (B) (C) Figure 1. Device switching behavior. In panels A and B, on the horizontal axis, the B+ direction indicates increasing south polarity magnetic field strength. This behavior can be exhibited when using an electrical circuit such as that shown in panel C. Worcester, Massachusetts U.S.A ; 9

10 A1, A11 and A11 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 element. 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 modulationdemodulation process. The undesired offset signal is separated from the magnetic field-induced 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 baseband, 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. This configuration is illustrated in figure 2. The chopper stabilization technique uses a 4 khz high frequency clock. For demodulation process, a sample and hold technique is used, where the sampling is performed at twice the chopper frequency (8 khz). 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 sample-and-hold circuits. The repeatability of magnetic field-induced switching is affected slightly by a chopper technique. However, the Allegro high frequency chopping approach minimizes the affect of jitter and makes it imperceptible in most applications. Applications that are more likely to be sensitive to such degradation are those requiring precise sensing of alternating magnetic fields; for example, speed sensing of ring-magnet targets. For such applications, Allegro recommends its digital device families with lower sensitivity to jitter. For more information on those devices, contact your Allegro sales representative. Regulator Clock/Logic Hall Element Amp Sample and Hold Low-Pass Filter Figure 2. Model of chopper stabilization technique Worcester, Massachusetts U.S.A ; 1

11 A1, A11 and A11 Power Derating The device must be operated below the maximum junction temperature of the device, T J(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 T J. (Thermal data is also available on the Allegro MicroSystems website.) The Package Thermal Resistance, R JA, 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, R JC, is relatively small component of R JA. Ambient air temperature, T A, and air motion are significant external factors, damped by overmolding. The effect of varying power levels (Power Dissipation, P D ), can be estimated. The following formulas represent the fundamental relationships used to estimate T J, at P D. P D = V IN I IN (1) T = P D R JA (2) T J = T A + ΔT (3) For example, given common conditions such as: T A = C, V CC = V, I CC = 1.6 ma, and R JA = 165 C/W, then: A worst-case estimate, P D(max), represents the maximum allowable power level (V CC(max), I CC(max) ), without exceeding T J(max), at a selected R JA and T A. Example: Reliability for V CC at T A = C, package LH, using a minimum-k PCB. Observe the worst-case ratings for the device, specifically: R JA = 228 C/W, T J (max) = 165 C, V CC (max) = V, and I CC (max) = 4 ma. Calculate the maximum allowable power level, P D (max). First, invert equation 3: T max = T J (max) T A = 165 C C = C This provides the allowable increase to T J resulting from internal power dissipation. Then, invert equation 2: P D (max) = T max R JA = C 228 C/W = 66 mw Finally, invert equation 1 with respect to voltage: V CC(est) = P D (max) I CC (max) = 66 mw 4 ma = 16.5 V The result indicates that, at T A, the application and device can dissipate adequate amounts of heat at voltages V CC(est). Compare V CC(est) to V CC (max). If V CC(est) V CC (max), then reliable operation between V CC(est) and V CC (max) requires enhanced R JA. If V CC(est) V CC (max), then operation between V CC(est) and V CC (max) is reliable under these conditions. P D = V CC I CC = V 1.6 ma = 19 mw T = P D R JA = 19 mw 165 C/W = 3 C T J = T A + T = C + 3 C = 28 C Worcester, Massachusetts U.S.A ; 11

12 A1, A11 and A11 Package LH, 3-Pin (SOT-23W) D A D D MIN REF. BSC Seating Plane Gauge Plane B.95 PCB Layout Reference View 8X 1 REF Branded Face 1. ±.13 NNT A.95 BSC Active Area Depth,.28 mm REF.4 ± For Reference Only; not for tooling use (reference dwg. 8284) Dimensions in millimeters Dimensions exclusive of mold flash, gate burrs, and dambar protrusions Exact case and lead configuration at supplier discretion within limits shown C 1 Standard Branding Reference View N = Last two digits of device part number T = Temperature code B Reference land pattern layout All pads a minimum of.2 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 Worcester, Massachusetts U.S.A ;

13 A1, A11 and A11 Package UA, 3-Pin SIP E 2.4 B C 1.52 ± MAX.51 REF E A E Branded Face.79 REF 45 Mold Ejector Pin Indent 1 NNT D Standard Branding Reference View = Supplier emblem N = Last two digits of device part number T = Temperature code.75 ± For Reference Only; not for tooling use (reference DWG-949) 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 B C D E Dambar removal protrusion (6X) Gate burr area Active Area Depth,.5 mm REF Branding scale and appearance at supplier discretion Hall element, not to scale NOM Copyright 29-21, 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, assumes no responsibility 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: Worcester, Massachusetts U.S.A ; 13

Chopper Stabilized Precision Hall Effect Latches

Chopper Stabilized Precision Hall Effect Latches A122, A1221, Features and Benefits Symmetrical latch switchpoints Resistant to physical stress Superior temperature stability Output short-circuit protection Operation from unregulated supply down to 3