ATS657 Dynamic, Self-Calibrating, Threshold-Detecting, Differential Speed and Direction Hall-Effect Gear Tooth Sensor IC Features and Benefits Description ▪ Rotational direction detection ▪ High start-up and running mode vibration immunity ▪ Single-chip sensing IC for high reliability ▪ Internal current regulator for two-wire operation ▪ Variable pulse width output protocol ▪ Automatic Gain Control (AGC) and offset adjust circuit ▪ True zero-speed operation ▪ Wide operating voltage range ▪ Undervoltage lockout ▪ ESD and reverse polarity protection The ATS657 includes an optimized Hall-effect sensing integrated circuit (IC) and rare earth pellet to create a userfriendly solution for direction detection and true zero-speed, digital gear tooth sensing in two-wire applications. The small package can be easily assembled and used in conjunction with a wide variety of gear tooth sensing applications. The IC employs patented algorithms for the special operational requirements of automotive transmission applications. The speed and direction of the target are communicated by this two-wire device through a variable pulse width output protocol. The advanced vibration detection algorithm systematically calibrates the IC on the initial teeth of a true rotation signal and not on vibration, always guaranteeing an accurate signal in running mode. Even the high angular vibration caused by engine cranking is completely rejected by the device. Package: 4-pin SIP (suffix SH) Patented running mode algorithms also protect against air gap changes whether or not the target is in motion. Advanced signal processing and innovative algorithms make the ATS657 an ideal solution for a wide range of speed and direction sensing needs. The device package is lead (Pb) free, with 100% matte tin leadframe plating. Not to scale Functional Block Diagram VCC Offset Adjust Internal Regulator AGC Peak Detection Logic Offset Adjust PDAC THRESHP Reference Generator and Update NDAC PDAC NDAC THRESHN THRESHP Reference Generator and Update THRESHN AGC ＋ – Threshold Logic – ＋ ＋ – Speed and Direction Logic Threshold Logic – ＋ GND ATS657-DS, Rev. 3 Output Protocol Control ATS657 Dynamic, Self-Calibrating, Threshold-Detecting, Differential Speed and Direction Hall-Effect Gear Tooth Sensor IC Selection Guide Part Number Packing* ATS657LSHTN-T 800 pieces per 13-in. reel *Contact Allegro® for additional packing options Absolute Maximum Ratings Characteristic Supply Voltage Symbol Notes Rating Unit VSUPPLY See Power Derating curve; proper operation at VSUPPLY = 24 V requires circuit configuration with a series 100 Ω load resistor. Please refer to figure 7. Voltage between pins 1 and 4 of greater than 22 V may partially turn on the ESD protection Zener diode in the IC. 24 V –18 V –40 to 150 ºC TJ(max) 165 ºC Tstg –65 to 170 ºC Reverse Supply Voltage VRCC Operating Ambient Temperature TA Maximum Junction Temperature Storage Temperature Pin-out Diagram 1 2 3 4 Range L Terminal List Number Name Function 1 VCC 2 NC No connection 3 NC Float or tie to GND 4 GND Connects power supply to chip Ground terminal Allegro MicroSystems, Inc. 115 Northeast Cutoff Worcester, Massachusetts 01615-0036 U.S.A. 1.508.853.5000; www.allegromicro.com 2 ATS657 Dynamic, Self-Calibrating, Threshold-Detecting, Differential Speed and Direction Hall-Effect Gear Tooth Sensor IC ELECTRICAL CHARACTERISTICS Valid over operating voltage and temperature ranges, unless otherwise noted Characteristics Supply Voltage Undervoltage Lockout Reverse Supply Current Supply Zener Clamp Voltage Supply Zener Resistance Supply Current Min. Typ.1 Max. Unit2 4.0 – 18 V VCC = 0 → >4 V, or >4 → 0 V – 3.5 4.0 V VCC = –18 V – – –10 mA 24.0 – – V – <5 – Ω Symbol VCC VCC(UV) IRCC Test Conditions Operating, TJ < TJ(max) VZ(SUPPLY) ICC = ICC(max) + 3 mA, TA = 25°C RZ ICC(LOW) Low-current state (Running mode) 5.0 6.5 8.0 mA ICC(HIGH) High-current state (Running mode) 12 14.0 16 mA ICC(SU)(LOW) Startup current level and Power-On mode 5.0 7.0 8.5 mA ICC(SU)(HIGH) High-current state (Calibration) 12 14.5 16.5 mA ICC(HIGH) – ICC(LOW) 5 – – mA Speed < 200 Hz – – 2.0 ms NDIR Speed < 200 Hz, constant rotation direction – – 6 Edge NNONDIR Speed < 200 Hz, constant rotation direction – – 2 Edge Nf Speed < 200 Hz, constant rotation direction – – 5 Edge – 3 – Edge – 5 – ms Non-Direction Pulse Output on Direction NNONDIR_DC Running mode, direction change Change – 1 2 Pulse First Direction Pulse Output on Direction Change Running mode, direction change – 2 3 Pulse Both differential channels – ±60 – G RL = 100 Ω, CL = 10 pF; ICC(HIGH) → ICC(LOW) , ICC(LOW) → ICC(HIGH) , 10% to 90% points 7 16.0 – mA/μs Current Level Difference ∆ICC Power-On Characteristics3 Power-On Time ton Initial Calibration First Output Pulse with Direction4 First Output Pulse5 AGC Disable Vibration Check Time Until Correct Direction Output on High-Speed Startup NVIBCHECK Speed < 200 Hz, after AGC disable tHIGHSU 10 kHz startup, B = 300 Gpk-pk Running Mode Calibration6 NDC DAC Characteristics Allowable User-Induced Differential Offset7 BDIFFEXT Output Stage Output Slew Rate SROUT 1Typical data is at VCC = 8 V and TA = +25°C, unless otherwise noted. Performance may vary for individual units, within the specified maximum and minimum limits. 21 G (gauss) = 0.1 mT (millitesla). 3Power-On Time is the time required to complete the initial internal automatic offset adjust; the DACs are then ready for peak acquisition. 4Direction of the first output pulse on the 6th edge may not be correct when undergoing vibration. 5Non-direction pulse output only. See figure 3 for more details. 6Direction pulse will typically occur on the 2nd output pulse after a direction change. This will hold true unless an offset change at zero speed results in an offset correction event. Note that no output blanking occurs after a direction change. 7The device will compensate for magnetic and installation offsets up to ±60 G. Offsets greater than ±60 G may cause inaccuracies in the output. Allegro MicroSystems, Inc. 115 Northeast Cutoff Worcester, Massachusetts 01615-0036 U.S.A. 1.508.853.5000; www.allegromicro.com 3 Dynamic, Self-Calibrating, Threshold-Detecting, Differential Speed and Direction Hall-Effect Gear Tooth Sensor IC ATS657 OPERATING CHARACTERISTICS: Switchpoint Characteristics Valid over operating voltage and temperature ranges, unless otherwise noted (refer to figure below) Min. Typ. Max. Unit Target Frequency, Forward Rotation Characteristics Symbol fFWD Test Conditions – – 12 kHz Target Frequency, Reverse Rotation fREV – – 6 kHz Target Frequency, Non-Direction Pulses* fND – – 4 kHz Bandwidth f-3dB Cutoff frequency for low-pass filter 15 20 – kHz Operate Point BOP % of peak-to-peak VPROC referenced from PDAC to NDAC, AG < AGmax – 70 – % Release Point BRP % of peak-to-peak VPROC referenced from PDAC to NDAC, AG < AGmax – 30 – % *At power-on, rotational speed or vibration leading to a target frequency greater than 4 kHz may result in a constant high output state until true direction is detected. Sensed Edgea Differential Magnetic Flux Density, BDIFF (G) +B Differential Processed Signal, VProc (V) Reverse +V Tooth Forward Valley BOP(REV)b BOP(FWD)b BRP(REV) BRP(FWD) –B VPROC(BOP) 100 % VPROC(BRP) BRP % BOP % –V t aSensed Edge: leading (rising) mechanical edge in forward rotation, trailing (falling) mechanical edge in reverse rotation bB OP(FWD) triggers the output transition during forward rotation, and BOP(REV) triggers the output transition during reverse rotation OPERATING CHARACTERISTICS: Output Pulse Characteristics* Valid over operating temperature range, unless otherwise noted Characteristics Symbol Test Conditions Min. Typ. Max. Unit Pulse Width, Forward Rotation tw(FWD) RL = 500 Ω, CL = 10 pF 38 45 52 μs Pulse Width, Reverse Rotation tw(REV) RL = 500 Ω, CL = 10 pF 76 90 104 μs Pulse Width, Non-Direction tw(ND) RL = 500 Ω, CL = 10 pF 153 180 207 μs *Measured at a threshold of ( ICC(HIGH) + ICC(LOW) ) / 2. Allegro MicroSystems, Inc. 115 Northeast Cutoff Worcester, Massachusetts 01615-0036 U.S.A. 1.508.853.5000; www.allegromicro.com 4 Dynamic, Self-Calibrating, Threshold-Detecting, Differential Speed and Direction Hall-Effect Gear Tooth Sensor IC ATS657 OPERATING CHARACTERISTICS: Input Characteristics Valid over operating temperature range and using Reference Target 60-0, unless otherwise noted Characteristics Symbol Test Conditions Operating Input Range1 BDIFF Differential magnetic signal; correct direction output on 6th edge Maximum Operation Air Gap1 AGmax Correct direction output on 6th edge Vibration Immunity (Startup) Vibration Immunity (Running mode)2 Min. Typ. Max. Unit 60 – 1200 Gpk-pk – – 2.2 mm ErrVIB(SU) Allowed rotation detected due to vibration; TTOOTH = period between 2 successive sensed edges, sinusoidal signal; ΔTA<10°C; BDIFF(AG) = 0 TTOOTH – – – ErrVIB Allowed rotation detected due to vibration; TTOOTH = period between 2 successive sensed edges, sinusoidal signal; ΔTA<10°C; BDIFF(AG) = 0 TTOOTH × 0.5 – – – Maximum Sudden Air Gap Change Induced Signal Reduction3,4 Differential magnetic signal reduction due to ΔBDIFF(AG) instantaneous air gap change; symmetrical signal reduction, target frequency < 500 Hz – – 40 %pk-pk Axial / Radial Runout / Wobble Induced Signal Reduction5,6 Differential magnetic signal reduction due to ΔBDIFF(RO) instantaneous runout per edge; symmetrical signal reduction, multiple edges – – 5 %pk-pk Differential magnetic signal, BDIFF = 100 Gpk-pk , ideal sinusoidal signal, TA = 150°C, Reference Target rotational speed = 1000 rpm (f = 1000 Hz) – 0.12 – deg. Minimum separation between channels as a percentage of VPROC amplitude at each switchpoint (see figure below) 20 – – % Relative Repeatability7 TθE Switchpoint Separation VSP(sep) 1Under certain extreme conditions, especially for smaller differential magnetic signals, the device may require more than 6 edges to output correct direction on startup. Please contact the Allegro factory for assistance when using this device. 2Small amplitude vibration while in Running mode may result in one additional direction pulse, prior to non-direction pulse. See section Running Small Amplitude Vibration Detection for details. 3If the minimum V SP(sep) is not maintained after a sudden air gap change, output may be blanked or non-direction pulses may occur. 4Sudden air gap change during startup may increase the quantity of edges required to get correct direction pulses. 5If the minimum V SP(sep) is not maintained, output may be blanked or non-direction pulses may occur. 6Minimum V PROC(pk-pk) signal of 200 mV and minimum VSP(sep) must be maintained 7The repeatability specification is based on statistical evaluation of a sample population, evaluated at 1000 Hz. Definition of Terms for Input Characteristics Tooth Valley TTOOTH TVPROC VSP VPROC(BOP) [BOP] VPROC(pk-pk) [BRP] VPROC(BRP) VSP VSP(sep) = VSP VPROC(pk-pk) VPROC = the processed analog signal of the sinusoidal magnetic input (per channel) Ttooth = period of 2 successive sensed target edges Allegro MicroSystems, Inc. 115 Northeast Cutoff Worcester, Massachusetts 01615-0036 U.S.A. 1.508.853.5000; www.allegromicro.com 5 Dynamic, Self-Calibrating, Threshold-Detecting, Differential Speed and Direction Hall-Effect Gear Tooth Sensor IC ATS657 Reference Target 60-0 (60 Tooth Target) Characteristics Symbol Test Conditions Typ. Units Symbol Key 120 mm t Do Outside diameter of target Face Width F Breadth of tooth, with respect to branded face 6 mm Angular Tooth Thickness t Length of tooth, with respect to branded face 3 deg. Angular Valley Thickness tv Length of valley, with respect to branded face 3 deg. Tooth Whole Depth ht 3 mm – – Outside Diameter Material Low Carbon Steel Do ht F tv Air Gap Branded Face of Package Branded Face of Package Reference Target 60-0 Allegro MicroSystems, Inc. 115 Northeast Cutoff Worcester, Massachusetts 01615-0036 U.S.A. 1.508.853.5000; www.allegromicro.com 6 Dynamic, Self-Calibrating, Threshold-Detecting, Differential Speed and Direction Hall-Effect Gear Tooth Sensor IC ATS657 Functional Description Data Protocol Description When a target passes in front of the branded face of the package, each tooth of the target generates a pulse at the output of the IC. Each pulse provides target speed and direction data: speed is provided by the pulse rate, while direction of target rotation is provided by the pulse width. The ATS657 can sense target movement in both the forward and reverse directions. The maximum allowable target rotational speed is limited by the width of the output pulse and the shortest low-state duration the system controller can resolve. Forward Rotation (see panel A in figure 1) When the target is rotating such that a tooth near the package passes from pin 4 to pin 1, this is referred to as forward rotation. Forward rotation is indicated on the output by a tw(FWD) (45 μs typical) pulse width. Reverse Rotation (see panel B in figure 1) When the target is rotating such that a tooth passes from pin 1 to pin 4, it is referred to as reverse rotation. Reverse rotation is indicated on the output by a tw(REV) (90 μs typical) pulse width, twice as long as the pulse generated by forward rotation. Pin 4 Non-Direction Output In situations where the IC is not able to discern direction of target rotation, as occurs during initial calibration or during target vibration, the output pulse width is tw(ND). Timing As shown in figure 2, the pulse appears at the output slightly before the sensed magnetic edge traverses the branded face. For targets in forward rotation, this shift, Δfwd, results in the pulse corresponding to the valley with the sensed mechanical edge, and for targets in reverse rotation, the shift, Δrev, results in the pulse corresponding to the tooth with the sensed edge. The sensed mechanical edge that stimulates output pulses is kept the same for both forward and reverse rotation by using only channel 1 for switching. The overall range between the forward and reverse pulse occurrences is determined by the 1.5 mm spacing between the Hall elements of the corresponding differential channel. In either direction, the pulses appear close to the sensed mechanical edge. The size of the target features, however, can slightly bias the occurrence of the pulses. Pin 1 Branded Face of Package Rotating Target Forward Rotation Reverse Rotation Output Pulse (Forward Rotation) Pin 1 t Branded Face of Package Rotating Target Tooth ∆fwd tw(FWD) 45 μs (A) Forward Rotation Pin 4 Valley ∆rev tw(REV) 90 μs Output Pulse (Reverse Rotation) t (B) Reverse Rotation Figure 1. Target rotation Figure 2. Output pulse timing Allegro MicroSystems, Inc. 115 Northeast Cutoff Worcester, Massachusetts 01615-0036 U.S.A. 1.508.853.5000; www.allegromicro.com 7 ATS657 Dynamic, Self-Calibrating, Threshold-Detecting, Differential Speed and Direction Hall-Effect Gear Tooth Sensor IC Start-Up Detection After the power-on time is complete, the ATS657 internally detects the profile of the target. The output becomes active at the first detected switchpoint. Figure 3 shows where the first output pulse occurs for various starting target phases. After calibration is complete, direction information is available and this information is communicated through the output pulse width. Forward Target Rotation (Target passes from pin 4 to pin 1) Valley Tooth Target Differential Magnetic Profile tw(ND) tw(ND) Power-on opposite valley IC Output Power-on opposite rising edge tw(ND) Power-on opposite tooth t Power-on opposite falling edge Device Location at Power-On Figure 3. Start-up position effect on first device output switching Allegro MicroSystems, Inc. 115 Northeast Cutoff Worcester, Massachusetts 01615-0036 U.S.A. 1.508.853.5000; www.allegromicro.com 8 Dynamic, Self-Calibrating, Threshold-Detecting, Differential Speed and Direction Hall-Effect Gear Tooth Sensor IC ATS657 Continuous Update of Switchpoints The processed differential internal analog signal, VPROC , of each of the two channels is used to determine switchpoints, at which the device determines direction information and changes to output signal polarity. Because the value of VPROC is directly proportional to the differential magnetic flux density, BDIFF, induced by the target and sensed by the Hall elements, the switchpoints occur at threshold levels that correspond to certain levels of BDIFF. occurs and the channel state switches from high to low. As shown in panel C of figure 4, the threshold levels for the ATS657 switchpoints are established as a function of the two previous signal peaks detected. The ATS657 incorporates an algorithm that continuously monitors VPROC and then updates the switching thresholds to correspond to any amplitude reduction. For any given target edge transition, the change in threshold level is limited. Each channel operates in this manner, independent of each other, so independent switchpoint thresholds are calculated for each channel. The operate point, BOP , occurs when VPROC rises through a certain limit, VPROC(BOP) . When BOP occurs, the channel internally switches from low to high. When VPROC falls below VPROC(BOP) through a certain limit, VPROC(BRP) , the release point, BRP , V+ Smaller TEAG IC VPROC (V) Target Target Smaller TEAG IC Hysteresis Band (Delimited by switchpoints) Larger TEAG 0 (A) TEAG varying; cases such as eccentric mount, out-of-round region, normal operation position shift Switchpoint Determinant Peak Values (B) Internal analog signal, VPROC, typically resulting in the IC 1 BOP(#1) BRP(#1) Pk(#1), Pk(#2) Pk(#2), Pk(#3) 2 BOP(#2) BRP(#2) Pk(#3), Pk(#4) Pk(#4), Pk(#5) 3 BOP(#3) BRP(#3) Pk(#5), Pk(#6) Pk(#6), Pk(#7) BOP(#4) Pk(#7), Pk(#8) BRP(#4) Pk(#8), Pk(#9) 4 BOP(#2) BOP(#3) BOP(#4) Pk(#9) Pk(#1) Pk(#3) Pk(#7) Pk(#5) VPROC (V) BHYS 360 Target Rotation (°) BOP(#1) V+ Smaller TEAG Larger TEAG VPROC(BOP)(#1) VPROC(BOP)(#2) BHYS(#1) BHYS(#2) VPROC(BRP)(#1) Pk(#4) BHYS(#3) VPROC(BOP)(#3) VPROC(BRP)(#2) VPROC(BOP)(#4) VPROC(BRP)(#3) BHYS(#4) VPROC(BRP)(#4) Pk(#6) Pk(#8) Pk(#2) BRP(#1) BRP(#2) BRP(#3) BRP(#4) (C) Referencing the internal analog signal, VPROC, to continuously update device response Figure 4. The Continuous Update algorithm allows the Allegro IC to immediately 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, elevation due to lubricant build-up in journal gears, and similar dynamic application problems that affect the TEAG (Total Effective Air Gap). Not detailed in the figure are the boundaries for peak capture DAC movement which intentionally limit the amount of internal signal variation the IC is able to react to over a single transition. The algorithm is used to dynamically establish and subsequently update the device switchpoint levels (VPROC(BOP) and VPROC(BRP)). The hysteresis, BHYS(#x), at each target feature configuration results from this recalibration, ensuring that it remains properly proportioned and centered within the peak-to-peak range of the internal analog signal, VPROC. 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 accurate switchpoint levels based on the fluctuation of VPROC, as shown in panel C. Allegro MicroSystems, Inc. 115 Northeast Cutoff Worcester, Massachusetts 01615-0036 U.S.A. 1.508.853.5000; www.allegromicro.com 9 Dynamic, Self-Calibrating, Threshold-Detecting, Differential Speed and Direction Hall-Effect Gear Tooth Sensor IC ATS657 Operation During Running Mode Vibration During normal running mode, vibration can interfere with the direction detection functions. In that case, during the vibration the device may continue to output speed data with non-directional pulses. If the vibration that occurs has a large enough amplitude such that the peaks of the VPROC signals continue to pass through both switchpoints, non-direction pulses will be outputted during the vibration, as shown in figure 5. Normal Rotation If the vibration has a low enough amplitude such that its positive peak is less than VPROC(BOP) , no pulses are outputted and no switchpoint updating occurs until the vibration becomes large enough that VPROC exceeds VPROC(BOP) . If its negative peak is greater than VPROC(BRP), then there is no output or update until VPROC falls below VPROC(BRP) . As shown in figure 6, when that does occur, a single direction pulse may be outputted, however, regardless of whether or not that single pulse occurs, non-direction pulses are outputted throughout the remainder of the vibration. Vibration +V VPROC VPROC(BOP) } Switchpoint Hysteresis } Switchpoint Hysteresis VPROC(BRP) +t +I IOUT tw(FWD) or tw(REV) tw(ND) +t Figure 5. Large amplitude vibration during Running mode operation Normal Rotation Vibration +V VPROC > VPROC(BOP) VPROC VPROC(BOP) VPROC(BRP) +t IOUT +I tw(FWD) or tw(REV) tw(FWD) or tw(REV) tw(ND) +t Figure 6. Small amplitude vibration during Running mode operation Allegro MicroSystems, Inc. 115 Northeast Cutoff Worcester, Massachusetts 01615-0036 U.S.A. 1.508.853.5000; www.allegromicro.com 10 ATS657 Dynamic, Self-Calibrating, Threshold-Detecting, Differential Speed and Direction Hall-Effect Gear Tooth Sensor IC V CC Undervoltage Lockout When the supply voltage falls below the minimum operating voltage, VCC(UV), ICC goes to the Power-On state and remains 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 IC. ICC levels may not meet datasheet limits when VCC < VCC(min). 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 7 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 of the IC is then automatically adjusted. Figure 8 illustrates the effect of this feature. The two differential channels have their gain set independent of each other, so both channels may or may not have the same gain setting. Automatic Offset Adjust (AOA) The AOA circuitry, when combined with AGC, automatically compensates for the effects of chip, magnet, and installation offsets. (For capability, see Allowable User Induced Differential Offset, in the Electrical Characteristics table.) This circuitry is continuously active, including both during Power-On mode and Running mode, compensating for offset drift. Continuous operation also allows it to compensate for offsets induced by temperature variations over time. Similar to AGC, the AOA is set independently for each channel, so the offset adjust is set per channel, based on the offset characteristics of that specific channel. 1 2 3 ATS657 0.01 MF (optional) CBYPASS 4 RL 100 7 CL Figure 7. Typical application circuit Ferrous Target Mechanical Profile V+ AGLarge Internal Differential Signal Response, without AGC AGSmall V+ Internal Differential Signal Response, with AGC AGSmall AGLarge Figure 8. Automatic Gain Control (AGC). 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, Inc. 115 Northeast Cutoff Worcester, Massachusetts 01615-0036 U.S.A. 1.508.853.5000; www.allegromicro.com 11 Dynamic, Self-Calibrating, Threshold-Detecting, Differential Speed and Direction Hall-Effect Gear Tooth Sensor IC ATS657 Thermal Characteristics may require derating at maximum conditions, see Power Derating section Characteristic Symbol Test Conditions* Single layer PCB, with copper limited to solder pads RθJA Package Thermal Resistance Single layer PCB, with limited to solder pads and 3.57 copper area each side in.2 (23.03 cm2) Value Unit 126 ºC/W 84 ºC/W *Additional thermal information available on the Allegro website 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(absmax) RQJA = 84 ºC/W RQJA = 126 ºC/W VCC(min) 20 40 60 80 100 120 140 160 180 Temperature (ºC) 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 RQJA = 84 ºC/W RQJA = 126 ºC/W 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 12 Dynamic, Self-Calibrating, Threshold-Detecting, Differential Speed and Direction Hall-Effect Gear Tooth Sensor IC ATS657 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 a 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 × IIN T = PD × RJA TJ = TA + ΔT (1) (2) (3) Example: Reliability for VCC at TA = 150°C, package SH, using single layer PCB. Observe the worst-case ratings for the device, specifically: RJA = 126°C/W, TJ(max) = 165°C, VCC(absmax) = 24 V, and ICC = 13 mA (Note: At maximum target frequency, ICC(LOW) = 8 mA, ICC(HIGH) = 16 mA, and maximum pulse widths, the result is a duty cycle of 62.4% and a worst case mean ICC of 13 mA.) Calculate the maximum allowable power level, PD(max). First, invert equation 3: T(max) = 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) = T(max) ÷ RJA = 15°C ÷ 126 °C/W = 119 mW Finally, invert equation 1 with respect to voltage: VCC(est) = PD(max) ÷ ICC = 119 mW ÷ 13 mA = 9.2 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= 25°C, VCC = 12 V, ICC = 6.5 mA, and RJA = 126 °C/W, then: PD = VCC × ICC = 12 V × 6.5 mA = 78 mW T = PD × RJA = 78 mW × 126 °C/W = 9.8°C TJ = TA + T = 25°C + 9.8°C = 34.8°C 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 13 Dynamic, Self-Calibrating, Threshold-Detecting, Differential Speed and Direction Hall-Effect Gear Tooth Sensor IC ATS657 Package SH 4-Pin SIP 5.50±0.05 F F 1.50 1.50 E B 8.00±0.05 LLLLLLL NNN 5.80±0.05 E3 E1 E2 YYWW Branded Face 1.70±0.10 5.00±0.10 D 4.00±0.10 1 2 3 4 = Supplier emblem L = Lot identifier N = Last three numbers of device part number Y = Last two digits of year of manufacture W = Week of manufacture A 0.60±0.10 Standard Branding Reference View 0.71±0.05 For Reference Only, not for tooling use (reference DWG-9003) Dimensions in millimeters A Dambar removal protrusion (16X) 24.65±0.10 B Metallic protrusion, electrically connected to pin 4 and substrate (both sides) C Thermoplastic Molded Lead Bar for alignment during shipment +0.06 0.38 –0.04 1.00±0.10 13.10±0.10 D Branding scale and appearance at supplier discretion E Active Area Depth 0.43 mm REF F Hall elements (E1, E2, E3); not to scale A 1.0 REF 1.60±0.10 C 1.27±0.10 0.71±0.10 0.71±0.10 5.50±0.10 Allegro MicroSystems, Inc. 115 Northeast Cutoff Worcester, Massachusetts 01615-0036 U.S.A. 1.508.853.5000; www.allegromicro.com 14 ATS657 Dynamic, Self-Calibrating, Threshold-Detecting, Differential Speed and Direction Hall-Effect Gear Tooth Sensor IC Copyright ©2009, Allegro MicroSystems, Inc. The products described herein are manufactured under one or more of the following U.S. patents: 5,264,783; 5,389,889; 5,442,283; 5,517,112; 5,581,179; 5,619,137; 5,621,319; 5,650,719; 5,686,894; 5,694,038; 5,729,130; 5,917,320; 6,091,239; 6,100,680; 6,232,768; 6,242,908; 6,265,865; 6,297,627; 6,525,531; 6,690,155; 6,693,419; 6,919,720; 7,046,000; 7,053,674; 7,138,793; 7,199,579; 7,253,614; 7,365,530; 7,368,904; or other patents pending. 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 15