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| Static Differential Hall Effect Sensor IC Preliminary Data TLE 4974 Bipolar IC Features q q q q q q q Static operation (zero speed) Digital output signal Two-wire and three-wire configuration possible Large temperature range Protection against overvoltage Protection against reversed polarity Output protection against electrical disturbances P-SSO-4-1 Type TLE 4974 U Ordering Code Q67006-A9133 Package P-SSO-4-1 The TLE 4974 U is a differential Hall effect sensor designed for rotational speed and timing applications using ferromagnetic toothed wheels and slotted shafts such as camshafts, crankshafts, transmissions, and ABS/TCS systems. Since the TLE 4974 U can detect zero rotation speed, it is applicable to position sensing as well. The TLE 4974 U provides a digital signal output with frequency proportional to the speed of rotation. Unlike other rotational sensors differential Hall ICs are not influenced by radial vibration within the effective airgap of the sensor and require no external signal processing. Semiconductor Group 1 09.94 TLE 4974 Pin Configuration (top view) Pin Definitions and Functions Pin 1 2 3 4 Symbol Function Supply voltage Ground Output Not connected VS GND Q N.C. Functional Description The differential Hall sensor IC detects the motion of, and static position of, ferromagnetic and permanent magnet structures by measuring the differential flux density of the magnetic field. To detect ferromagnetic objects the magnetic field must be provided by a back biasing permanent magnet (a magnet attached to the back, unmarked, side of the IC package). Circuit Description (see Figure 1 and 2) The TLE 4974 U is comprised of a supply voltage reference, a pair of Hall probes spaced at 2.5 mm, differential amplifier, Schmitt trigger, an open collector output. Protection is provided at the input/supply (pin 1) for overvoltage and reverse polarity and against overstress such as load dump, etc., in accordance with ISO-TR 7637 and DIN 40839. The output (pin 3) is protected against voltage peaks and electrical disturbances. Semiconductor Group 2 TLE 4974 Operation For ease of explanation the probes will be referred to as sensor 1 and sensor 2, and assumes that the Hall IC is back-biased using the south (positive) pole. Operation is reversed, with respect to the active sensor, if back-biasing uses the north (negative) pole. Applications using a, front (marked side of the IC package) passing, magnet wheel is identical with respect to the Hall sensor operation. Please refer to figure 9 System Operation. As a magnetic source, or target pass in front of sensor 2 the magnetic field or field density creates a positive differential at the input of the differential amplifier, resulting in a proportional output to the Schmitt trigger, and a triggered output to the open collector driver. When the source or target pass in front of sensor 1 (both probes are now influenced by the source/ target) the amplifier inputs are in zero differential state and the output remains "on". As the source or target move past sensor 2 (sensor 1 active) the amplifier inputs are in a negative differential state and the Schmitt trigger remains in the "off" state. When the source or target moves past probe 1 (both probes not influenced by source/target) the amplifier is again in the zero differential state and the output remains in "off" condition, and the cycle repeats. Rotation Sensing Cycle 1. Sensor 2 active (over target) - Output triggered "on" 2. Sensor 1 and 2 active (both probes over target) - Output remains "on". Note: This is not guaranteed over temperature. 3. Sensor 2 inactive (over space), sensor 1 active (over target) - Negative differential mode - Output triggered "off". 4. Sensor 1 and 2 inactive (both probes over space) - Output remains "off". For applications which require larger airgaps (3 mm +) and do not require zero (static) speed sensing, the TLE 4921-2U (dynamic-active high output) should be used. Semiconductor Group 3 TLE 4974 Figure 1 Block Diagram 1 Semiconductor Group 4 TLE 4974 Figure 2 Block Diagram 2 Semiconductor Group 5 TLE 4974 Absolute Maximum Ratings Tj = - 40 to 150 C Parameter Supply voltage Output voltage Output current Output reverse current Junction temperature Junction temperature Junction temperature Storage temperature Thermal resistance Current through inputprotection device Current through outputprotection device Symbol Limit Values min. max. 30 30 50 50 150 170 210 150 190 200 200 V V mA mA C C C C K/W mA mA - - - - - 1000 h 40 h - - - 40 - 0.7 - - - - - - 40 - - - 200 Unit Remarks VS VQ IQ - IQ Tj Tj Tj Tstg Rth JA ISZ IQZ t < 2 ms; v = 0.1 t < 2 ms; v = 0.1 Electro Magnetic Compatibility ref. DIN 40839 part 1; test circuit 1 Testpulse 1 Testpulse 2 Testpulse 3a Testpulse 3b Testpulse 4 Testpulse 5 Operating Range Supply voltage Junction temperature Junction temperature Pre-induction VLD VLD VLD VLD VLD VLD - 100 - - 150 - -7 - - 100 - 100 - 120 V V V V V V td = 2 ms td = 0.05 ms td = 0.1 s td = 0.1 s td 20 s td = 400 ms; Rp = 450 VS Tj Tj BO 4.5 - 40 - 40 - 500 24 150 170 500 V C C mT - - threshold may exceed the limits - Semiconductor Group 6 TLE 4974 AC/DC Characteristics 4.5 V VS 24 V; - 40 C Tj 150 C Parameter Supply current Symbol Limit Values min. typ. 8 8.5 max. 12 13.5 mA mA Unit Test Condition Test Circuit 1 1 IS IS IS IS Output saturation voltage VQSat Output leakage current Switching frequency Switching flux density Hysteresis Overvoltage protection - at supply voltage - at output 3.0 3.5 VQ = high, IQ = 0 mA VS = 4.5 V VS 7 V VQ = low, IQ = 40 mA VS = 4.5 V VS 7 V IQ = 40 mA VQ = 24 V B = 20 mT - - 3.5 4.0 - - 0 -6 3 27 27 8.5 9 0.25 - - 2.5 5 - - 12.5 14.5 0.6 10 20 17 10 35 35 mA mA V A kHz mT mT V V 1 1 1 1 2 2 2 1 1 IQL f BOP BHy VSZ VQZ IS = 16 mA IS = 16 mA Semiconductor Group 7 TLE 4974 Figure 3 Test Circuit 1 Figure 4 Test Circuit 2 - - - - BO = 100 mT; tooth wheel with module m = 2 mm Distance IC-object L = 1 mm Southpole at back of IC Semiconductor Group 8 TLE 4974 Application Notes Two possible applications are shown in figure 7 and 8 (Tooth and Magnet Wheel). The differences between two-wire and three-wire application is shown in figure 10. Tothed Wheel Sensing In the case of ferromagnetic toothed wheel application the IC has to be biased by a permanent magnet (e.g. SECo5 (Vacuumschmelze VX145) with the dimensions 8 mm x 5 mm x 3 mm) which should cover both hallprobes. The maximum air gap depends on - the magnetic field strength (magnet used), - the toothed wheel that is used (dimensions, material, etc), - the ambient temperature a b L centred distance of hall probes hall-probes to IC surface IC surface to tooth wheel a = 2.5 mm b= 0.25 mm Figure 5 Sensor Spacing Conversion DIN - ASA m = 25.4 mm/p t = 25.4 mm x CP DIN d z m t diameter (mm) number of teeth module m = d/z (mm) pitch t = x m (mm) ASA p diametral pitch p = z/d (inch) PD pitch diameter PD = z/p (inch) CP circular pitch CP = 1 inch x /p Figure 6 Toothed Wheel Dimensions Semiconductor Group 9 TLE 4974 Figure 7 TLE 4974 U, with Ferromagnetic Toothed Wheel Semiconductor Group 10 TLE 4974 Figure 8 TLE 4974 U, with Magnet Wheel Semiconductor Group 11 TLE 4974 For Southpole or Northpole at the back of the IC release point: B2-B1 < BRP switches the output OFF (VQ = HIGH) operate point: B2-B1 > BOP switches the output ON (VQ = LOW) BOP = BRP + BHy Figure 9 System Operation Semiconductor Group 12 TLE 4974 Figure 10 Application Circuits Semiconductor Group 13 TLE 4974 Quiescent Current versus Supply Voltage Quiescent Current versus Junction Temperature Quiescent Current Difference versus Supply Voltage Saturation Voltage versus Output current Semiconductor Group 14 TLE 4974 Maximum Preinduction versus Junction Temperature Switching Induction versus Temperature Hysteresis Induction versus Junction Temperature Semiconductor Group 15 TLE 4974 Distance IC-Toothed Wheel versus Junction Temperature Relative Distance versus Module Fall and Rise Time versus Junction Temperature Semiconductor Group 16 |
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