Allegro A3250 A3251 Manual
Contents
1.2. 46 TL option The products described herein are manufactured under one or more of the following U S patents 5 045 920 5 264 783 5 442 283 5 389 889 5 581 179 5 517 112 5 619 137 5 621 319 5 650 719 5 686 894 5 694 038 5 729 130 5 917 320 and other patents pending Allegro MicroSystems Inc reserves the right to make from time to time such departures from the detail spec ifications 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 products are not authorized for use as critical components in life support devices or systems without express written approval 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 Copyright 2004 Allegro MicroSystems Inc Allegro MicroSystems Inc 14 115 Northeast Cutoff Box 15036 Worcester Massachusetts 01615 0036 508 853 5000 www allegromicro com A3250 DS A3250 and A3251 Field Programmable Chopper Stabilized Unipolar Hall Effect Switches Allegro MicroSystems Inc 1 5 115 Northeast Cutoff Box 15036 Worcester Massachusetts 01615 0036 508 853 5000 www allegromicro com A3250 DS
3. derating sup plied power or improving the heat dissipation properties of the application This section presents a procedure for correlating factors affecting operating T Thermal data is also available on the Allegro MicroSystems Web site The Package Thermal Resistance Rgy is a figure of merit sum marizing 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 Rgjc is relatively small component of Rg Ambient air temperature T and air motion are significant external factors damped by overmolding The effect of varying power levels Power Dissipation Pp can be estimated The following formulas represent the fundamental relationships used to estimate Tj at Pp Pp Vin X in 1 AT Pp X Roja 2 T T AT 3 For example given common conditions such as T 25 C Vcc 12 V Icc 4 mA and Roya 165 C W then AT Pp X Roya 48 mW x 165 C W 8 C Ty Ta AT 25 C 8 C 33 C A worst case estimate Ppimax represents the maximum allow able power level Vecmax gt Lccimaxy Without exceeding Tymaxy at a selected Roy and T4 A3250 DS Example Reliability for Voc at Ty 150 C package UA using minimum K PCB Observe the worst case rating
4. pulse sequences must be sent one after the other without allow ing Vcc to fall to zero which clears the registers The same pulse sequence is used to provisionally set bitfields as is used to permanently set bitfield level fuses The only differ ence is that when provisionally setting bitfields no fuse blowing pulse is sent at the end of the pulse sequence PROGRAMMING PROTOCOL CHARACTERISTICS T 25 C unless otherwise noted Characteristic Test Conditions Minimum voltage range during programming Programming Voltage Programming Current2 Maximum supply current during programming OFF time between programming bits Pulse duration ON time for enable address fuse Pulse Width blowing or lock bits Pulse duration ON time for fuse blowing Pulse Rise Time Vp to Vey Vp to Vey Pulse Fall Time Vpm to Vp Vpy to Vp 1Programming voltages are measured at the VCC pin 2A bypass capacitor with a minimum capacitance of 0 1 uF must be connected from VCC to the GND pin of the device in order to provide the current necessary to blow the fuse Allegro MicroSystems Inc 9 115 Northeast Cutoff Box 15036 Worcester Massachusetts 01615 0036 508 853 5000 www allegromicro com A3250 DS A3250 and A3251 Field Programmable Chopper Stabilized Unipolar Hall Effect Switches The pulse sequences consist of the following groups of pulses 1 An enable sequence 2 A
5. 3250 DS 115 Northeast Cutoff Box 15036 Worcester Massachusetts 01615 0036 508 853 5000 www allegromicro com 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 Bnysvs Temperature Average Bnysvs Temperature Program Code 1 Vcc 12 V Program Code 16 Vcc 12 V 35 35 30 3 30 oS g 25 m 20 a oa ee 20 e a amp 15 ns ns nie 15 m 5 10 5 10 o o gt gt lt 5 lt 1 5 0 0 50 20 10 40 70 100 130 160 50 20 10 40 70 100 130 160 Ta C Ta C Average Bnysvs Temperature Average Bop vs Temperature Program Code 8 Vcc 12 V 40 C to 25 C and 150 C to 25 C 30 35 30 g7 25 S 10 a 20 Fr H 15 amp i A s S 10 10 Code 1 lt 15 lt a Code 8 ji 20 4 Code 16 3 30 50 20 10 40 70 100 130 160 40 C to 25 C 150 C to 25 C Ta C Ta CO Allegro MicroSystems Inc 5 A3250 DS 115 Northeast Cutoff Box 15036 Worcester Massachusetts 01615 0036 508 853 5000 www allegromicro com A3250 and A3251 Field Programmable Chopper Stabilized Unipolar H
6. Bop and switches HIGH when the field drops below the magnetic release point Bgp The output of the A3251 has the opposite polarity switching HIGH in a south polarity 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 These devices are available in a TO 92 three lead ultra mini SIP Single In line Package with either straight or formed and trimmed lead configuration Features and Benefits m Chopper stabilization for stable switchpoints throughout operating temperature range m On chip protection against e Supply transients m Externally programmable operate point through VCC pin m On board voltage regulator for 4 2 V to 24 V operation e Output short circuits e Reverse battery condition Use the following complete part numbers when ordering Part Number Vout Running Bhysi typ Package G Power On A3250JUA A3250JUATL Straight lead Formed lead 40 to 115 A3250LUA A3250LUATL Straight lead Formed lead 40 to 150 A3251JUA A3251JUATL Straight lead Formed lead 40 to 115 A3251LUA A3251LUATL Straight lead Formed lead 40 to 150 In south polarity magnetic field of sufficient strength Allegro MicroSystems Inc 115 Northeast Cutoff Box 15036 Worcester Massac
7. O 0 A380 0 O A3250 and A3251 Package UA 3 pin SIP TL Option ABSOLUTE MAXIMUM RATINGS Supply Voltage Vcc Reverse Supply Voltage Vecc Zener Overvoltage Vz Output Current Ioyr Magnetic Flux Density B Operating Temperature Ambient Ta Range J Ambient T Range L Maximum Junction T J max Storage Temperature Ts 40 C to 115 C 40 C to 150 C A3250 DS Field Programmable Chopper Stabilized Unipolar Hall Effect Switches The A3250 and A3251 are field programmable chopper stabilized 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 hys teresis remains fixed This advanced feature allows for optimization of the sensor switchpoint and can drastically reduce the effects of variations found in a produc tion 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 mag netic field with a flux density that exceeds the threshold for
8. PCB Package UA Roya 165 C W Maximum Allowable Vcc V a 7 6 5 4 Vec min 3 2 20 40 60 80 100 120 140 160 1 0 Maximum Power Dissipation Ppimax Ty max 165 C Vec Vecymax lec lecimax Power Dissipation Pp mW 20 40 60 80 100 120 140 160 180 Temperature C Allegro MicroSystems Inc 7 115 Northeast Cutoff Box 15036 Worcester Massachusetts 01615 0036 508 853 5000 www allegromicro com A3250 DS A3250 and A3251 Field Programmable Chopper Stabilized Unipolar Hall Effect Switches Functional Description Chopper Stabilized Technique The Hall sensor is based on a Hall element a small sheet of semiconductor material in which a constant bias current flows when a constant voltage source is applied The output takes the form of a voltage measured across the width of the Hall element and has negligible value in the absence of a magnetic field When a magnetic field is applied with flux lines at right angles to the current in the Hall element a small signal voltage directly proportional to the strength of the magnetic field occurs at the output of the Hall element This small signal voltage is disproportionally small relative to the offset produced at the input of the device This makes it very difficult to process the signal and maintain an accurate reliable output over the specified temperature and voltage range There fore it is import
9. all Effect Switches Typical Characterization Data All data are taken with A3250 devices the average of 3 lots 30 pieces per lot Average lcc on vs Temperature Average lcc of vs Temperature 1 10 o loc orty 3 8V 8 8 8 icco 12 0 V 6 z t T 6 a lecior 26 5 V T a i 5 4 emt EE e foe 3 lecion 3 8 V 5 caer 2 E Iccion 12 0 V 2 a a N e Icc on 26 5 V 9 0 50 20 10 40 70 100 130 160 50 20 10 40 70 100 130 160 Ta C Ta C Average Voursat VS Temperature Vcc 3 8 V lout 20 MA 280 _ 260 Z 240 A 220 200 3 gt 180 160 140 50 20 10 40 70 100 130 160 Ta C Allegro MicroSystems Inc 6 A3250 DS 115 Northeast Cutoff Box 15036 Worcester Massachusetts 01615 0036 508 853 5000 www allegromicro com A3250 and A3251 Field Programmable Chopper Stabilized Unipolar Hall Effect Switches THERMAL CHARACTERISTICS may require derating at maximum conditions see application information Characteristic Symbol Test Conditions Conditions TestConditons Min Typ Max Units meree tm a oe ew Power Derating Curve T ymax 165 C leg lcc max Voec max N wo 13 Minimum K
10. ant to reduce any distortion of the signal that could be amplified when the signal is processed Chopper stabilization is a unique approach used to minimize input offset on the Hall IC This technique removes a key source of output drift due to temperature and mechanical stress and produces a 3X reduction in offset in comparison to other conventional methods This offset reduction chopping technique is based on a sig nal modulation demodulation process The undesired offset signal is separated from the magnetically induced signal in the frequency domain The offset and any low frequency noise component of the signal can be seen as signal distortion added after the signal modulation process has taken place Therefore the dc offset is not modulated and remains a low frequency component Consequently the signal demodulation process acts as a modulation process for the offset causing the magnetically induced signal to recover its original spectrum at baseband while the dc offset becomes a high frequency signal Then the signal passes using a low pass filter while the modulated dc offset is suppressed The advantage of this approach is significant offset reduction which desensitizes the Hall IC against the effects of temperature and mechanical stress The disadvantage is that this technique features a demodulator that uses a sample and hold block to store and recover the signal This sampling process can slightly degrade the SNR sig
11. bitfield address sequence 3 When permanently setting the bitfield a long Vpy fuse blow ing pulse Note Blown bit fuses cannot be reset When provisionally trying a value a short Vpy pulse 4 When permanently setting the bitfield the level of Vcc must be allowed to drop to zero between each pulse sequence in order to clear all registers However when provisionally set ting bitfields Vcc must be maintained at Vpr between pulse fuses for 0 value bitfields are never blown This prevents inad vertently setting the bitfield to 1 Instead blowing the device level fuse protects the 0 bitfields from being accidentally set in the future Two pulse sequences for provisionally trying the calibration value 5 are shown in figure 2 Because the bitfields must be set individually 5 9 must be programmed as binary 101 Bit 3 is set to 1 000100 which is 4 9 then bit 1 is set to 1 000001 which is 1 9 Bit 2 is ignored and so remains 0 Two pulse sequences for permanently setting the calibration value 5 are shown in figure 3 The final Vpy pulse which was used as a short delimiter when trying values is maintained for a longer period enough to blow the corresponding bitfield level Bitfields that are not set are evaluated as zeros The bitfield level fuse sequences in order to maintain the prior bitfield settings while preparing to set additional bitfields V 4 VPH VPM VPL EA 7 pulses Addres
12. e Current Vout 24 V Switch state OFF A3250 B lt Bpp Voyt HIGH A3251 B gt Bop Vout HIGH A3250 B gt Bop Voyt LOW A3251 B lt Brp Vour LOW Output Rise Time Rioap 820 O Croan 10 pF Output Fall Time Rioap 820 O Croan 10 pF Supply Current Chopping Frequency Power Up Time Vout HIGH Output Current Limitt 2 lout im Short circuit protection A3250 B lt Bpp t gt ton A3251 B lt Bhp t gt ton Power On State POS MAGNETIC CHARACTERISTICS Initial Operate Point Bop Temperature Drift of Bop ABop Bop lt 500 gauss Package T range J Hysteresis Bop Brp Bh i Package T range L PROGRAMMING CHARACTERISTICS Programmable Bop Values Bop prog Switchpoint set Number of Programming Bits Programming lock Resolution Bres TRANSIENT PROTECTION CHARACTERISTICS Supply Zener Voltage Supply Zener Current Vcc 28 V Reverse Battery Current Vrce 18 V Ty lt Tymax 1 Do not exceed TJ max Additional information on power derating is provided in the applications section 2 Short circuit protection is not intended for continuous operation permanent damage may result 3 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 3 115 Northeast Cutof
13. etic flux G repre sented by each increment is indicated by Bggg see the Operating Characteristics table however testing is the only method for verifying the resulting Bop For programming the 64 incre ments are individually identified using 6 data bits which are physically represented by 6 bitfields in the onboard registers By setting these bitfields the corresponding calibration value is programmed into the device Three voltage levels are used in programming the device a low voltage Vp a minimum required to sustain register settings a mid level voltage Vp used to increment the address counter in the device and a high voltage Vpy used to separate sets of Vpm pulses when short in duration and to blow fuses when long in duration A fourth voltage level essentially 0 V is used to clear the registers between pulse sequences The pulse values are shown in the Programming Protocol Characteristics table and in figure 1 V LT Taa t Figure 1 Pulse amplitudes and durations Additional information on device programming and program ming products is available on www allegromicro com Program ming hardware is available for purchase and programming software is available free of charge Code Programming Each bitfield must be individually set To do so a pulse sequence must be transmitted for each bitfield that is being set to 1 If more than one bitfield is being set to 1 all
14. f Box 15036 Worcester Massachusetts 01615 0036 508 853 5000 www allegromicro com A3250 DS 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 Bopvs Ta Average Brr vs Ta Program Code 1 Vcc 12 V Program Code 1 Vcc 12 V 30 10 5 o a 20 g 0 m 15 iva 5 10 m S M U lt 0 lt 15 pa 5 20 50 20 10 40 70 100 130 160 50 20 10 40 70 100 130 160 Ta C Ta C Average Bopvs Ta Average Bre vs Ta Program Code 8 Vcc 12 V Program Code 8 Vcc 12 V 75 60 g S 65 it oo v 6y o 40 Ee 955 a 9 e o v 50 30 gt ee zZ 45 40 20 50 20 10 40 70 100 130 160 50 20 10 40 70 100 130 160 Ta C Ta C Average Bor vs Ta Average Bre vs Ta Program Code 16 Vcc 12 V Program Code 16 Vcc 12 V 130 110 125 105 3120 amp 100 a fra 8115 g 95 S S E 110 90 mra 105 85 100 80 50 20 10 40 70 100 130 160 50 20 10 40 70 100 130 160 Ta C Ta C Allegro MicroSystems Inc 4 A
15. husetts 01615 0036 508 853 5000 www allegromicro com A3250 and A3251 Field Programmable Chopper Stabilized Unipolar Hall Effect Switches Functional Block Diagram VCC Program Lock Programming Logic Regulator Offset Adjust VOUT Low Pass Filter Dynamic Offset Cancellation Sample and Hold PENISIN I ETIT ETT EE yes Sips eae yas aby Spee tee eee eae 6 4 GND Hysteresis Curves A3250 A3251 Hysteresis of AVouT Hysteresis of AVouT Switching Due to AB Switching Due to AB Vitec dane V VoutTvoff VouTooff c dp op D D T a T 5 2 S 2 5 o E F 7 Vout on sat VouT on sat al w pe w a Be l O D E v T Pa is Buys Buys Output voltage in relation to sensed magnetic flux density ina south polarity magnetic field of sufficient strength Transition through Bop must precede transition through Brp Allegro MicroSystems Inc 2 115 Northeast Cutoff Box 15036 Worcester Massachusetts 01615 0036 508 853 5000 www allegromicro com A3250 DS A3250 and A3251 Field Programmable Chopper Stabilized Unipolar Hall Effect Switches OPERATING CHARACTERISTICS valid over operating T and Vcc unless otherwise specified Characteristic Test Conditions ELECTRICAL CHARACTERISTI Supply Voltage Running mode Output Saturation Voltage lour 20 mA Switch state ON Output Leakag
16. lses Address M S89 as shown in figure 3 When provisionally trying a value this sequence is followed by a short Vpy pulse which serves to delimit the address and set the corresponding bitfield When XPL permanently setting a bitfield the Vpy pulse is continued for a longer period of time suffienct to not only set the bitfield to 1 0 but also to blow the bitfield fuse gt t Figure 5 Pulse sequence to select addresses Falling edge of final Bop address digit Lock Bit Programming After the desired Bop calibration value is programmed and all of the corresponding bitfield level fuses Vem are blown the device level fuse should be blown To do so the lock bit bitfield address 65 should be encoded as 1 and have VPL its fuse blown This is done in the same manner as permanently setting the other bitfields as shown in figure 6 7 pulses 65 pulses l gt Enable Address Encode Lock Bit Blow gt Figure 6 Pulse sequence to encode lock bit Allegro MicroSystems Inc 11 115 Northeast Cutoff Box 15036 A3250 DS Worcester Massachusetts 01615 0036 508 853 5000 www allegromicro com A3250 and A3251 Field Programmable Chopper Stabilized Unipolar Hall Effect Switches Application Information For additional general application information visit the Allegro MicroSystems Web site at www allegromicro com Typical Application Circuit It i
17. nal to noise ratio by producing replicas of the noise spectrum at the baseband This degradation is a function of the ratio between the white noise spectrum and the sampling frequency The effect of the degradation of the SNR is higher jitter also known as signal repeatability However the jitter in a continuous time device can be 5X that of the A3250 A3251 Regulator Sample and Hold LPF rere Chopper stabilization circuit dynamic quadrature offset cancellation A3250 DS Allegro MicroSystems Inc 8 115 Northeast Cutoff Box 15036 Worcester Massachusetts 01615 0036 508 853 5000 www allegromicro com A3250 and A3251 Field Programmable Chopper Stabilized Unipolar Hall Effect Switches Programming Protocol The operate switchpoint Bop can be field programmed To do so a coded series of voltage pulses through the VCC pin is used to set bitfields in onboard registers The effect on the device output can be monitored and the registers can be cleared and set repeatedly until the required Bop is achieved To make the setting permanent bitfield level solid state fuses are blown and finally a device level fuse is blown blocking any further cod ing It is not necessary to program the release switchpoint Bpp because the difference between Bop and Brp referred to as the hysteresis Byys is fixed The range of values between Bop miny and Bopymax 1S Scaled to 64 increments The actual change in magn
18. s 0 Enable Address J Optional T Enable A Optional Clear Monitoring itori Try 001002 410 Try 000012 110 Monitoring Figure 2 Pulse sequence to provisionally try calibration value 5 101 binary or bitfield address 3 and bitfield address 1 V VPH VPM VPL 7 pulses n p Address 0 i Enable Address i Blow i Enable Blow i gt Encode 001002 410 Encode 000012 110 t Figure 3 Pulse sequence to permanently encode calibration value 5 101 binary or bitfield address 3 and bitfield address 1 Allegro MicroSystems Inc 1 0 115 Northeast Cutoff Box 15036 Worcester Massachusetts 01615 0036 508 853 5000 www allegromicro com A3250 DS A3250 and A3251 Field Programmable Chopper Stabilized Unipolar Hall Effect Switches V Enabling Addressing Mode The first segment of code is a keying sequence used to enable the bitfield addressing mode As VPM shown in figure 4 this segment consists of one short Vpy pulse seven or more Vp pulses and one Vpy pulse with no supply interruptions This sequence is designed to prevent the device from being programmed accidentally such as by noise on the supply line VPL Minimum 7 pulses t Figure 4 Addressing mode enable pulse sequence Address Selection After addressing mode is enabled the iii Niece 5 target bitfield address is indicated by a series of VPM pu
19. s for the device specifically Roza 165 C W Ty max 165 C Veconax 24 V and Toc max Calculate the maximum allowable power level Ppmaxy First invert equation 3 AT max Tyma Ta 165 C 150 C 15 C This provides the allowable increase to T resulting from internal power dissipation Then invert equation 2 Pp max AT wax Roya 15 C 165 C W 91 mW Finally invert equation with respect to voltage Veces Pp max lecamaxy 91 mW 10mA 9 V The result indicates that at T the application and device can dissipate adequate amounts of heat at voltages lt Vcc est Compare Voceest to Voc max If Veces lt Vicc max then reli able operation between Vecegt and Vecmax requires enhanced Roya If Voccest gt Vocimax then operation between Voccest and Veccmax S reliable under these conditions Allegro MicroSystems Inc 1 3 115 Northeast Cutoff Box 15036 Worcester Massachusetts 01615 0036 508 853 5000 www allegromicro com A3250 and A3251 Field Programmable Chopper Stabilized Unipolar Hall Effect Switches Package UA 3 Pin TO 92 002 0 05 004 0 10 MAX e AA VA A A sA t 062 1 57 AUKA T e aa os 097 T aa gt lt 050 1 27 Dimensions in inches Metric dimensions mm in brackets for reference only Dimensions without tolerances are basic A Dambar removal protrusion A Hall element Active Area Depth 018 0
20. s strongly recommended that an external ceramic bypass capacitor Cpyp in the range of 0 01 uF to 0 1 uF be connected between the VCC pin and the supply and GND pin to reduce both external noise and noise generated by the chopper stabiliza tion technique The diagram at the right shows Cpyp at 0 1 uF Cpyp Should be installed so that the traces that connect it to the A3250 A3251 are no greater than 5 mm in length The series resistor Rg in combination with Cpyp creates a filter for EMI pulses Additional information on EMC is provided on the Allegro MicroSystems Web site Rg will have a drop of approximately 800 mV This must be taken into consider ation when determining the minimum VCC requirement for the A3250 A3251 The pull up resistor R should be chosen to limit the current through the output transistor do not exceed the maximum continuous output current of the device a 5V R 1 2 KQ Vsuppy A3250 A3251 A Maximum separation 5 mm from Cpyp to device Typical application circuit Allegro MicroSystems Inc 12 A3250 DS 115 Northeast Cutoff Box 15036 Worcester Massachusetts 01615 0036 508 853 5000 www allegromicro com A3250 and A3251 Field Programmable Chopper Stabilized Unipolar Hall Effect Switches Power Derating The device must be operated below the maximum junction temperature of the device Tym Under certain combinations of peak conditions reliable operation may require
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Allegro A3250 A3251 Manual