A1684LUB Two-Wire, Zero-Speed, High Accuracy Differential Sensor IC FEATURES AND BENEFITS • Integrated capacitor reduces requirement for external EMI protection component • Fully optimized differential digital ring magnet and gear tooth sensor IC • Running Mode Lockout • Unique algorithms to assist in mitigation of system anomalies such as vibration • AGC and reference adjust circuit • Air gap independent switchpoints • Digital output representing target mechanical profile • Precise duty cycle throughout operating temperature range • Short power-on time • True zero-speed operation • Undervoltage lockout (UVLO) • Wide operating voltage range • Internal current regulator for two-wire operation • Robust test coverage capability using Scan Path and IDDQ measurement • AEC-Q100 automotive qualified Package: 2-pin SIP (suffix UB) DESCRIPTION The A1684LUB is an optimized Hall-effect sensing integrated circuit that provides a user-friendly solution for true zero-speed digital ring magnet and, when magnetically back-biased, geartooth sensing in two-wire applications. The Hall-effect IC has been optimized for the automotive environment. This small package can be used in conjunction with a wide variety of target shapes and sizes. The single integrated circuit incorporates a dual element Hall effect sensor IC and signal processing circuitry that switches in response to differential magnetic signals created by a ring magnet, or by a rotating ferromagnetic target when used in combination with a back-biasing magnet. The device contains a sophisticated compensating circuit to eliminate magnetic and system offsets. Digital tracking of the analog signal is used to achieve true zero-speed operation. Advanced calibration algorithms are used to adjust the device gain and offset at power-up, resulting in air gap independent switchpoints, which greatly improves output accuracy. In addition, advanced running mode calibration circuits mitigate the effect of system anomalies such as target vibration and sudden changes in air gap. The regulated current output is configured for two-wire operation. When configured with a back-biasing magnet, this sensor IC is ideal for obtaining edge and duty cycle information in gear-tooth–based applications such as transmission speed. The A1684 is provided in a 2-pin miniature SIP package (suffix UB) that is lead (Pb) free, with 100% matte tin leadframe plating. Not to scale VCC Voltage Regulator PDAC Hall Amp Offset Adjust AGC NDAC Synchronous Digital Controller GND Functional Block Diagram A1684LUB-DS, Rev. 5 Reference Generator and Lockout Two-Wire, Zero-Speed, High Accuracy Differential Sensor IC A1684LUB SPECIFICATIONS SELECTION GUIDE Part Number A1684LUBTN-T Packing* Tape and reel *Contact Allegro™ for additional packing options ABSOLUTE MAXIMUM RATINGS Characteristic Symbol Supply Voltage VCC Reverse Supply Voltage VRCC Notes Rating Units 26.5 V –18 V –40 to 150 ºC Operating Ambient Temperature TA Maximum Junction Temperature TJ(max) 165 ºC Tstg –65 to 170 ºC Rating Units 10000 pF Storage Temperature Range L, refer to Power Derating Curve INTERNAL DISCRETE CAPACITOR RATINGS Characteristic Symbol Nominal Capacitance CSUPPLY Notes Connected between VCC and GND PINOUT DIAGRAM AND TERMINAL LIST TABLE Terminal List Table Number 1 Name Function 1 VCC Supply voltage 2 GND Ground 2 Package UB, 2-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 Two-Wire, Zero-Speed, High Accuracy Differential Sensor IC A1684LUB OPERATING CHARACTERISTICS: VCC and TA within specification, unless otherwise noted Characteristics Symbol Test Conditions Min. Typ.1 Max. Unit2 4.0 – 24 V – 3.5 3.95 V ELECTRICAL CHARACTERISTICS Supply Voltage3 Undervoltage Lockout Reverse Supply Operating, TJ < TJ (max), required across pin 1 to pin 2 VCC VCC(UV) Current4 IRCC Supply Zener Clamp Voltage5 Supply Zener Current Supply Current Supply Current Ratio VCC 0 → 5 V or 5 → 0 V VCC = –18 V – – –10 mA VZ ICC = ICC (max) + 3 mA, TA = 25°C 28 – – V IZ TA = 25°C, VCC = 28 V – – 19 mA ICC(Low) Low-current state 4 6 8 mA ICC(High) High-current state 12 14 16 mA ICC(High) / ICC(Low) Ratio of high current to low current 1.85 – 3.05 – POWER-ON STATE CHARACTERISTICS Power-On Time6 tPO Power-On State7 POS VCC > VCC (min), fOP < 100 Hz – 1 2 ms t > tPO – ICC(High) – A OUTPUT STAGE Output Rise Time8 tr Corresponds to measured output slew rate, from 10% to 90% ICC level, CSUPPLY, RSENSE = 100 Ω 0 2 4 μs Output Fall Time8 tf Corresponds to measured output slew rate, from 90% to 10% ICC level, CSUPPLY, RSENSE = 100 Ω 0 2 4 μs 0 – 12 kHz PERFORMANCE CHARACTERISTICS Operating Frequency fOP Analog Signal Bandwidth BW 16 20 – kHz – 70 – % Operate Point BOP % of peak-to-peak BSIG , AGOP within specification Release Point BRP % of peak-to-peak BSIG , AGOP within specification – 30 – % Running Mode Lockout Enable Threshold VLOE(RM) At peak-to-peak VPROC < VLOE(RM) , output switching disables – 170 – mV Running Mode Lockout Release Threshold VLOR(RM) At peak-to-peak VPROC > VLOR(RM) , output switching enables – 200 – mV Continued on the next page… I+ % ICC(High) 100 90 10 0 ICC(Low) tr tf Definition of Output Rise Time and Output Fall Time Output Rise Time (tr) and Fall Time (tf) VOUT (V) Output High Allegro MicroSystems, LLC 115 Northeast Cutoff Worcester, Massachusetts 01615-0036 U.S.A. 1.508.853.5000; www.allegromicro.com 3 Two-Wire, Zero-Speed, High Accuracy Differential Sensor IC A1684LUB OPERATING CHARACTERISTICS: VCC and TA within specification, unless otherwise noted Characteristics Symbol Test Conditions Min. Typ.1 Max. Unit2 CALIBRATION Start Mode Hysteresis Initial Calibration9 POHYS – VLOR(RM) – mV CALI Rising output (current) edges, fOP < 200 Hz – – 3 edges BSIG Differential magnetic signal 50 – 1500 GPK-PK 30 – – GPK-PK –100 – +100 G – 45 – % FUNCTIONAL CHARACTERISTICS Operating Signal Range Extended Operating Signal Range BSIGEXT Differential magnetic signal, output switching (no missed edges), duty cycle not guaranteed Allowable User-Induced Differential Offset BDIFFEXT Operation within specification Maximum Sudden Signal Amplitude Change BSIG(INST) Instantaneous symmetric magnetic signal amplitude change, measured as a percentage of peak-to-peak BSIG, fOP < 500 Hz 1 Typical values are at TA = 25°C and VCC = 12 V. Performance may vary for individual units, within the specified maximum and minimum limits. G (gauss) = 0.1 mT (millitesla). 3 Maximum voltage must be adjusted for power dissipation and junction temperature; see Power Derating section. 4 Negative current is defined as conventional current coming out of (sourced from) the specified device terminal. 5 Sustained voltages beyond the clamp voltage may cause permanent damage to the IC. 6 Measured from V CC ≥ VCC (min) to the time when the device is able to switch the output signal in response to a magnetic stimulus. 7 Please refer to the Functional Description, Power-On section. 8 Guaranteed by device characterization. 9 For power-on frequency, f OP < 200 Hz. Higher power-on frequencies may result in more input magnetic cycles until full output edge accuracy is achieved, including the possibility of missed output edges. 21 Allegro MicroSystems, LLC 115 Northeast Cutoff Worcester, Massachusetts 01615-0036 U.S.A. 1.508.853.5000; www.allegromicro.com 4 Two-Wire, Zero-Speed, High Accuracy Differential Sensor IC A1684LUB THERMAL CHARACTERISTICS: May require derating at maximum conditions; see application information Characteristic Symbol Package Thermal Resistance Test Conditions* RθJA On 1-layer PCB, with copper limited to solder pads Value Units 213 ºC/W *Additional thermal data available on the Allegro Web site. Power Derating Curve Maximum Allowable VCC (V) 25 VCC(max) 20 15 10 5 0 VCC(min) 20 40 60 80 100 120 140 160 180 Temperature (°C) Power Dissipation versus Ambient Temperature 900 Power Dissipation, PD (mW) 800 700 600 500 400 300 200 100 0 20 40 60 80 100 120 140 160 Ambient Temperature, TA (°C) Allegro MicroSystems, LLC 115 Northeast Cutoff Worcester, Massachusetts 01615-0036 U.S.A. 1.508.853.5000; www.allegromicro.com 5 Two-Wire, Zero-Speed, High Accuracy Differential Sensor IC A1684LUB FUNCTIONAL DESCRIPTION Sensing Technology The A1684 sensor IC contains a single-chip differential Halleffect circuit. As shown in Figure 1, the circuit supports two Hall elements (spaced at a 2.2 mm pitch), which simultaneously sense the magnetic profile of a ring magnet, or when coupled with a back-biasing magnet, the magnetic profile of a ferromagnetic gear target. The sensed magnetic fields at the two Hall elements are subtracted one from the other, to generate a differential internal analog voltage, VPROC , that is processed for precise switching of the digital output signal. The Hall IC is self-calibrating and also integrates a temperature compensated amplifier and offset cancellation circuitry. Its voltage regulator provides supply noise rejection throughout the operating voltage range. Changes in temperature do not greatly Mechanical Position (Target moves past device pin 1 to pin 2) Target (Radial Ring Magnet) This pole sensed earlier This pole sensed later S N N Target Magnetic Profile affect this device due to the stable amplifier design and the offset rejection circuitry. The Hall transducers and signal processing electronics are integrated on the same silicon substrate, using a proprietary BiCMOS process. Target Profiling During Operation Under normal operating conditions, the IC is capable of providing digital information that is representative of the mechanical features of a rotating gear when back biased, or the poles of a rotating ring magnet. The waveform diagram in Figure 1 presents the automatic translation of the mechanical profile, through the magnetic profile that it induces, to the digital output signal of the A1684. No additional optimization is needed and minimal processing circuitry is required. Mechanical Position (Target moves past device pin 1 to pin 2) This tooth sensed earlier This tooth sensed later Target (Gear) Target Magnetic Profile +B +B –B Device Orientation to Target IC (Pin 2 Side) Device Branded Face Element Pitch Device Branded Face Hall Element 2 Device Orientation to Target Hall Element 2 Hall Element 1 (Pin 2 Side) (Pin 1 Side) Back-biasing Magnet (Top View of Device) IC Internal Differential Analog Signal, VPROC BOP(#1) BRP(#1) IC Internal Switch State Off On Hall Element 1 (Pin 1 Side) South Pole (Top View of Device) North Pole IC Internal Differential Analog Signal, VPROC BOP(#1) BOP(#2) Off IC Element Pitch BRP(#1) IC Internal Switch State Off On On IC Output Signal, ICC BOP(#2) Off On IC Output Signal, ICC +t +t Figure 1: Magnetic Profile Reflecting the Geometry of the Target, Allowing the A1684 to Present an Accurate Digital Output Response. Allegro MicroSystems, LLC 115 Northeast Cutoff Worcester, Massachusetts 01615-0036 U.S.A. 1.508.853.5000; www.allegromicro.com 6 Two-Wire, Zero-Speed, High Accuracy Differential Sensor IC A1684LUB Diagnostics Determining Output Signal Polarity The regulated current output is configured for two-wire applications, requiring one less wire for operation than do switches with the traditional open-collector output. Additionally, the system designer inherently gains diagnostics because there is always output current flowing, which should be in either of two narrow ranges, shown in Figure 2 as ICC(HIGH) and ICC(LOW). Any current level not within these ranges indicates a fault condition. If ICC > ICC(HIGH)(max), then a short condition exists, and if ICC < ICC(LOW)(min), then an open condition exists. Any value of ICC between the allowed ranges for ICC(HIGH) and ICC(LOW) indicates a general fault condition. In Figure 1, the top of each panel, labeled Mechanical Position, represents the mechanical features of the target and orientation to the device. The bottom panels, labeled IC Output Signal, displays the square waveform corresponding to the digital output signal (current amplitude) that results from a target configured as shown in Figure 3. Referring to the target side nearest the face of the sensor IC, the direction of rotation is: perpendicular to the leads, across the face of the device, from the pin 1 side to the pin 2 side. +mA ICC(HIGH)(max) ICC(HIGH)(min) ICC(LOW)(max) ICC(LOW)(min) 0 Short Fault Range for Valid ICC(HIGH) Range for Valid ICC(LOW) Rotating Target BrandedFace of Device S N S N Open RSENSE Location ICC State VSENSE State High side (VCC pin side) High Low Low High PinPin 2 2 Figure 3: Left-to-Right (pin 1 to pin 2) Direction of Target Rotation. VS High High Low Low ICC RSENSE ICC 1 Rotating Target VSENSE(HighSide) 1 VCC VCC A1684 A1684 Pin 1 Pin 4 I+ V+ N VS Output Polarity States ICC S SN Pin 1 Figure 2: Diagnostic Characteristics of Supply Current Values. Low side (GND pin side) In order to read the output signal as a voltage, VSENSE , a sense resistor, RSENSE , can be placed on either the VCC signal or on the GND signal. As shown in Figure 4, when RSENSE is placed on the GND signal, the output signal voltage, VSENSE(LowSide) , is in phase with ICC . When RSENSE is placed on the VCC signal, the output signal voltage, VSENSE(HighSide) , is inverted relative to ICC . GND 2 VSENSE(LowSide) VSENSE(LowSide) Backbiasing magnet with south pole adjacent to devi Branded Face of Device GND 2 RSENSE V+ VSENSE(HighSide) A B Figure 4: Alternative Polarity Configurations Using Two-Wire Sensing The Output Polarity States table provides the permutations of output voltage relative to ICC, given alternative locations for RSENSE. Panel A shows the low-side, VSENSE(LowSide) , sensing configuration, and panel B shows the high-side, VSENSE(HighSide) , configuration. As shown by the current and voltage square waves on the left side, VSENSE(LowSide) is in phase with ICC , and VSENSE(HighSide) , is inverted. Allegro MicroSystems, LLC 115 Northeast Cutoff Worcester, Massachusetts 01615-0036 U.S.A. 1.508.853.5000; www.allegromicro.com 7 Two-Wire, Zero-Speed, High Accuracy Differential Sensor IC A1684LUB Continuous Update of Switchpoints the output state changes from low to high. Switchpoints are the threshold levels of the differential internal analog signal, VPROC , at which the device changes output signal state. The value of VPROC is directly proportional to the magnetic flux density, B, induced by the target and sensed by the Hall elements. As VPROC rises through a certain limit, referred to as the operate point, BOP , the output state changes from high to low. As VPROC falls below BOP to a certain limit, the release point, BRP , As shown in Figure 5, threshold levels for the switchpoints are established as a function of the peak input signal levels. The device incorporates an algorithm that continuously monitors the input signal and updates the switching thresholds accordingly with limited inward movement of VPROC. The switchpoint for each edge is determined by the detection of the previous two signal edges. In this manner, variations are tracked in real time. (A) TEAG varying; cases such as eccentric mount, out-of-round region, normal operation position shift (B) Internal analog signal, VPROC, typically resulting in the IC V+ Smaller TEAG IC Target Smaller TEAG Hysteresis Band (Delimited by switchpoints) Larger TEAG IC Larger TEAG VPROC (V) Target Smaller TEAG 0 Target Rotation (°) 360 (C) Internal analog signal, VPROC, representing magnetic field for digital output V+ BOP VPROC (V) BOP BRP BOP BRP BOP BOP BRP BRP ICC (V) BRP BOP Figure 5: Continuous Update Algorithm The Continuous Update algorithm allows the Allegro IC to interpret and adapt to variances in the magnetic field generated by the target as a result of eccentric mounting of the target, out-of-round target shape, and similar dynamic application problems that affect the TEAG (Total Effective Air Gap). As shown in panel A, the variance in the target position results in a change in the TEAG. This affects the IC as a varying magnetic field, which results in proportional changes in the internal analog signal, VPROC, shown in panel B. The Continuous Update algorithm is used to establish switchpoints based on the fluctuation of VPROC, as shown in panel C. Allegro MicroSystems, LLC 115 Northeast Cutoff Worcester, Massachusetts 01615-0036 U.S.A. 1.508.853.5000; www.allegromicro.com 8 Two-Wire, Zero-Speed, High Accuracy Differential Sensor IC A1684LUB Power-On The A1684 is guaranteed to power-on in the high current state, ICC(High) . When power (VCC > VCC (min) ) is applied to the device, a short period of time is required to power the various portions of the circuit. During this period, the A1684 will poweron in the high current state, ICC(High) . Initial Edge Detection The device self-calibrates using the initial teeth sensed, and then enters running mode. This results in reduced accuracy for a brief period, CALI . However, this period allows the device to optimize for running mode operation. As shown in Figure 6 (assuming the south magnetic pole of a back-biasing magnet is adjacent to the rear of the A1684 case), the first three high peak signals corresponding to rising output edges are used to calibrate AGC (Automatic Gain Control). There is a slight variance in the duration of initialization, depending on what target feature is opposite the sensor IC when power-on occurs. Also, a high speed of target rotation at power-on may increase the quantity of output edges required in the CALI period. Target (Gear) 3 4 VPR OC Power-on 1 opposite tooth Start Mode Hysteresis Overcome OC 2 1 VPR Device Position AGC Calibration Running Mode ICC Start Mode Hysteresis Overcome VPR VPR OC Power-on at falling 2 mechanical edge OC ICC AGC Calibration Running Mode ICC Start Mode Hysteresis Overcome VPR VPR OC Power-on opposite 3 valley OC ICC AGC Calibration Running Mode ICC OC VPR Start Mode Hysteresis Overcome VPR Power-on 4 at rising mechanical edge OC ICC AGC Calibration ICC Running Mode ICC Figure 6: Power-On Initial Edge Detection. This figure demonstrates four typical power-on scenarios. All of these examples assume a south magnetic pole of a back-biasing magnet is adjacent to the rear of the A1684 case. The length of time required to overcome Start Mode Hysteresis, as well as the combined effect of whether it is overcome in a positive or negative direction plus whether the next edge is in that same or opposite polarity, affect the point in time when AGC calibration begins. Three high peaks are always required for AGC calibration when fOP ≤ 200 Hz, and more may be required at greater speeds. Allegro MicroSystems, LLC 115 Northeast Cutoff Worcester, Massachusetts 01615-0036 U.S.A. 1.508.853.5000; www.allegromicro.com 9 Two-Wire, Zero-Speed, High Accuracy Differential Sensor IC A1684LUB Start Mode Hysteresis A typical scenario is shown in Figure 7 (assuming the south magnetic pole of a back-biasing magnet is adjacent to the rear of the A1684 case). The hysteresis, POHYS , is a minimum level of the peak-to-peak amplitude of the internal analog electrical signal, VPROC , that must be exceeded before the A1684 starts to compute switchpoints. This feature helps to ensure optimal self-calibration by rejecting electrical noise and low-amplitude target vibration during initialization. This prevents AGC from calibrating the device on such spurious signals. Calibration can be performed using the actual target features. Target (Gear) Target Magnetic Profile IC Position Relative to Target Differential Signal, VPROC 2 1 3 4 BOP(initial) BRP Start Mode Hysteresis, POHYS BOP BRP BRP(initial) Output Signal, ICC If exceed POHYS on high side If exceed POHYS on low side Figure 7: Operation of Start Mode Hysteresis (assumes the south magnetic pole of a back-biasing magnet is adjacent to the rear of the A1684 case) • At power-on (position 1), the A1684 begins sampling VPROC . • At the point where the Start Mode Hysteresis, POHYS, is exceeded, the device establishes an initial switching threshold, by using the Continuous Update algorithm. If VPROC is rising through the limit on the high side (position 2), the switchpoint is BOP , and if VPROC is falling through the limit on the low side (position 4), it is BRP . After this point, Start Mode Hysteresis is no longer a consideration. Note that a valid VPROC value exceeding the Start Mode Hysteresis can be generated either by a legitimate target feature or by excessive vibration. • In either case (BOP or BRP), because the switchpoint is immediately passed as soon as it is established, the A1684 enables switching: ▫ If on the high side, at BOP (position 2) the output would switch from low to high. However, because output is already high, no output switching occurs. At the next switchpoint, where BRP is passed (position 3), the output switches from high to low. ▫ If on the low side, at BRP (position 4) the output switches from high to low. Allegro MicroSystems, LLC 115 Northeast Cutoff Worcester, Massachusetts 01615-0036 U.S.A. 1.508.853.5000; www.allegromicro.com 10 Two-Wire, Zero-Speed, High Accuracy Differential Sensor IC A1684LUB Undervoltage Lockout When the supply voltage falls below the minimum operating voltage, VCC(UV) , ICC goes high and remains high regardless of the state of the magnetic gradient from the target. This lockout feature prevents false signals, caused by undervoltage conditions, from propagating to the output of the device. Because VCC is below the VCC(min) specification during lockout, the ICC levels may not be within specification. Power Supply Protection The device contains an on-chip regulator and can operate over a wide VCC range. For devices that need to operate from an unregulated power supply, transient protection must be added externally. For applications using a regulated line, EMI/RFI protection may still be required. Contact Allegro for information on the circuitry needed for compliance with various EMC specifications. Refer to Figure 8 for an example of a basic application circuit. Automatic Gain Control (AGC) This feature allows the device to operate with an optimal internal electrical signal, regardless of the air gap (within the AG specification). At power-on, the device determines the peak-to-peak amplitude of the signal generated by the target. The gain is then automatically adjusted. Figure 9 illustrates the effect of this feature. Running Mode Gain Adjust The A1684 has a feature during Running mode to compensate for dynamic air gap variation. If the system increases the mag- netic input drastically, the device will gradually readjust the gain downwards, allowing the chip to regain the optimum internal electrical signal with the new, larger, magnetic signal. Dynamic Offset Cancellation (DOC) The offset circuitry when combined with AGC automatically reduces the effects of chip, magnet, and installation offsets. This circuitry is continuously active, including both Power-on mode and Running mode, compensating for any offset drift (within Allowable User-Induced Differential Offset). Continuous operation also allows it to compensate for offsets induced by temperature variations over time. Running Mode Lockout The A1684 has a Running mode lockout feature to prevent switching on small signals that are characteristic of vibration signals. The internal logic of the chip evaluates small signal amplitudes below a certain level to be vibration. In that event, the output is blanked (locked-out) until the amplitude of the signal returns to normal operating levels. Watchdog The A1684 employs a watchdog circuit to prevent extended loss of output switching during sudden impulses and vibration in the system. If the system changes the magnetic input drastically such that target feature detection is terminated, the device will fully reset itself, allowing the chip to recalibrate properly on the new magnetic input signal. Ferrous Target Mechanical Profile VS 1 V+ VCC Internal Differential Analog Signal Response, without AGC A1684 AGSmall GND 2 RSENSE 100 AGLarge V+ CLOAD Internal Differential Analog Signal Response, with AGC AGSmall AGLarge Figure 9: Automatic Gain Control (AGC) Figure 8: Typical Circuit for Proper Device Operation The AGC function corrects for variances in the air gap. Differences in the air gap cause differences in the magnetic field at the device, but AGC prevents that from affecting device performance, as shown in the lowest panel. Allegro MicroSystems, LLC 115 Northeast Cutoff Worcester, Massachusetts 01615-0036 U.S.A. 1.508.853.5000; www.allegromicro.com 11 Two-Wire, Zero-Speed, High Accuracy Differential Sensor IC A1684LUB CHARACTERISTIC PERFORMANCE SUPPLY CURRENT Supply Current (High) versus Ambient Temperature Supply Current (High) versus Supply Voltage 16.0 16.0 15.5 15.5 VCC (V) 14.5 4 14.0 12 13.5 24 13.0 15.0 ICC(HIGH) (mA) ICC(HIGH) (mA) 15.0 12.5 TA (°C) 14.5 -40 14.0 25 13.5 150 13.0 12.5 12.0 12.0 -60 -40 -20 0 20 40 60 TA (°C) 80 100 120 140 2 160 Supply Current (Low) versus Ambient Temperature 10 14 VCC (V) 18 22 26 Supply Current (Low) versus Supply Voltage 8.0 8.0 7.5 7.5 7.0 VCC (V) 6.5 4 6.0 12 5.5 24 5.0 4.5 7.0 ICC(LOW) (mA) ICC(LOW) (mA) 6 TA (°C) 6.5 -40 6.0 25 5.5 150 5.0 4.5 4.0 -60 -40 -20 0 20 40 60 TA (°C) 80 100 120 140 160 4.0 2 6 10 14 18 22 26 VCC (V) Allegro MicroSystems, LLC 115 Northeast Cutoff Worcester, Massachusetts 01615-0036 U.S.A. 1.508.853.5000; www.allegromicro.com 12 Two-Wire, Zero-Speed, High Accuracy Differential Sensor IC A1684LUB 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 website.) The Package Thermal Resistance, RθJA, 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, RθJC, is relatively small component of RθJA. 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 × IIN (1) ΔT = PD × RθJA (2) TJ = TA + ΔT (3) For example, given common conditions such as: TA= 25°C, VCC = 12 V, ICC = 6 mA, and RθJA = 213 °C/W, then: PD = VCC × ICC = 12 V × 6 mA = 72 mW ΔT = PD × RθJA = 72 mW × 213 °C/W = 15.3°C A worst-case estimate, PD(max), represents the maximum allowable power level (VCC(max), ICC(max)), without exceeding TJ(max), at a selected RθJA and TA. Example: Reliability for UB package VCC at TA = 150°C, using a minimum-K PCB using a single layer PCB. Observe the worst-case ratings for the device, specifically: RθJA = 213°C/W, TJ(max) = 165°C, VCC(max) = 24 V, and ICC(max) = 16 mA. Calculate the maximum allowable power level, PD(max). First, invert equation 3: ΔTmax = 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) = ΔTmax ÷ RθJA PD(max) = 15°C ÷ 213°C/W = 70.5 mW Finally, invert equation 1 with respect to voltage: VCC(est) = PD(max) ÷ ICC(max) = 70.5 mW ÷ 16 mA = 4.4 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 RθJA. If VCC(est) ≥ VCC(max), then operation between VCC(est) and VCC(max) is reliable under these conditions. TJ = TA + ΔT = 25°C + 15.3°C = 40.3°C Allegro MicroSystems, LLC 115 Northeast Cutoff Worcester, Massachusetts 01615-0036 U.S.A. 1.508.853.5000; www.allegromicro.com 13 Two-Wire, Zero-Speed, High Accuracy Differential Sensor IC A1684LUB PACKAGE OUTLINE DRAWING For Reference Only – Not for Tooling Use (Reference DWG-9070) Dimensions in millimeters Dimensions exclusive of mold flash, gate burrs, and dambar protrusions Exact case and lead configuration at supplier discretion within limits shown +0.06 4.00 –0.05 B 4 × 10° E 1.50 1.50 ±0.05 E 1.25 C 1.34 E 4.00 +0.06 –0.07 E E1 Mold Ejector Pin Indent E2 E Branded Face A 4 × 2.50 REF 0.25 REF 0.30 REF NNN YYWW LLLL 45° 0.85 ±0.07 0.42 ±0.10 D Standard Branding Reference View 2.54 REF N Y W L 4 × 0.85 REF 1 2 1.00 ±0.10 12.20 ±0.10 +0.05 0.25 –0.03 4 × 7.37 REF 1.80 ±0.10 0.38 REF = Supplier emblem = Last three digits of device part number = Last 2 digits of year of manufacture = Week of manufacture = Lot number A Dambar removal protrusion (8×) B Gate and tie bar burr area C Active Area Depth, 0.38 mm REF D Branding scale and appearance at supplier discretion E Hall elements (E1 and E2); not to scale F Molded Lead Bar for preventing damage to leads during shipment 0.25 REF 4 × 0.85 REF 0.85 ±0.07 1.80 +0.06 –0.07 F 4.00 +0.06 –0.05 1.50 ±0.05 Figure 10: Package UB, 2-Pin SIP Allegro MicroSystems, LLC 115 Northeast Cutoff Worcester, Massachusetts 01615-0036 U.S.A. 1.508.853.5000; www.allegromicro.com 14 Two-Wire, Zero-Speed, High Accuracy Differential Sensor IC A1684LUB Revision History Revision Date – March 7, 2014 1 October 7, 2014 2 December 15, 2014 3 March 24, 2015 4 December 7, 2015 5 March 1, 2016 Change Initial release Updated Package Outline Drawing and reformatted document (was Rev. 0.1). Updated CSUPPLY, tr , tf , and package drawing (was Rev. 0.2). Updated branding on Package Outline Drawing (was Rev. 0.3). Added AEC-Q100 qualified bullet to Features and Benefits (was Rev. 0.4) Updated Package Outline Drawing molded lead bar footnote, Internal Discrete Capacitor Ratings table, corrected Characteristic Performance labels, and renumbered revisions. Copyright ©2016, 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 any devices or systems, including but not limited to life support devices or systems, in which a failure of Allegro’s product can reasonably be expected to cause bodily harm. 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 15