In­fi­neons’ 3D Mag­netic Sen­sor of­fers great value propo­si­tion

It is ef­fi­cient, con­sumes less power and of­fers high pre­ci­sion

Auto components India - - BY INVITATION - By: Juer­gen Mann, In­fi­neon Tech­nolo­gies

The TLV493D-A1B6 is a mag­netic sen­sor that of­fers pre­cise three-di­men­sional (3D) sens­ing with very low power con­sump­tion in a com­pact, 6-pin TSOP pack­age. It re­li­ably mea­sures three-di­men­sional, lin­ear and ro­tat­ing move­ments. It is well suited for use in joy­sticks, con­trol el­e­ments in ve­hi­cles or house­hold ap­pli­ances and mul­ti­func­tional but­tons. The mag­netic sen­sor can also serve as ma­nip­u­la­tion pro­tec­tion in elec­tric me­ters.

Con­ven­tional lin­ear Hall sen­sors, Hall switches, and an­gle sen­sors are only able to rec­og­nize mag­netic field com­po­nents that are per­pen­dic­u­lar to the sur­face of the chip; Giant Mag­ne­toRe­sis­tive (GMR) an­gle sen­sors mea­sure only the pla­nar-ori­ented field com­po­nents. How­ever, the TLV493D-A1B6 sen­sor from In­fi­neon de­ter­mines the x, y and z co­or­di­nates of the mag­netic field at the same time (fig­ure 1). By recog­nis­ing the mag­netic field com­po­nents of all 3 axes, it re­ceives a holis­tic, three-di­men­sional im­age of the mag­netic field in which the sen­sor lies. Each move­ment by the mag­net in­flu­ences at least one of the 3 mag­netic field com­po­nents.

To en­able three-di­men­sional sen­sors, In­fi­neon in­te­grates ver­ti­cal and hor­i­zon­tal Hall plates on the sen­sor chip. The ver­ti­cal plates de­tect the pla­naror­i­ented x and y field com­po­nents while the hor­i­zon­tal plate de­ter­mines the ver­ti­cally ori­ented field com­po­nent (z di­rec­tion).

Ef­fi­cient Sens­ing

Low­er­ing the power con­sump­tion was a pri­or­ity in the de­vel­op­ment of the TLV493D-A1B6. Thanks to in­no­va­tive de­sign tech­nolo­gies, in­clud­ing an en­ergy-sav­ing os­cil­la­tor, the sen­sor can op­er­ate from just a few nanoamps and down to 7 nA in the pow­er­down mode. How­ever, de­spite the low power con­sump­tion the 3D mag­netic sen­sor is still able to of­fer very high ac­cu­racy. Fur­ther­more, the sil­i­con com­po­nent fits into a very small pack­age – the TSOP-06 pack­age is only 2.9 mm x 1.6 mm in size – mak­ing the de­vice smaller than any other 3D mag­netic sen­sor on the mar­ket.

Thanks to the small pack­age and the low power con­sump­tion, the TLV493D-A1B6 is suit­able for ap­pli­ca­tions that, un­til now, have been un­able to use mag­netic sen­sors. Suit­able for re­place­ment of po­ten­tiome­ters and op­ti­cal so­lu­tions, the con­tact­less po­si­tion­ing and high-tem­per­a­ture sta­bil­ity of the mag­netic switch points makes it pos­si­ble to re­al­ize smaller, more pre­cise and more ro­bust sys­tem con­cepts.

The sen­sor is equipped with a dig­i­tal out­put that uses a two-wire I²C stan­dard in­ter­face. This al­lows high-speed com­mu­ni­ca­tion and use of bus mode for bidi­rec­tional com­mu­ni­ca­tion be­tween the sen­sor and mi­cro­con­troller. The sen­sor ar­chi­tec­ture con­sists of 3 pri­mary func­tion units: power mode con­trol unit, sen­sor unit, and com­mu­ni­ca­tion unit. The power mode con­trol unit serves to dis­trib­ute en­ergy in the IC as well as con­trol­ling sen­sor ac­ti­va­tion.

The sen­sor unit, which con­tains the ver­ti­cal and hor­i­zon­tal Hall plates and a tem­per­a­ture sen­sor, mea­sures the mag­netic field in the x, y, and z di­rec­tions. Each Hall plate is con­nected se­quen­tially with the ana­log-to-

dig­i­tal con­verter (ADC) through a mul­ti­plexer. The tem­per­a­ture sen­sor is also con­nected to the mul­ti­plexer, but it can be de­ac­ti­vated to lower the to­tal power con­sump­tion by about 25 %.

Com­mu­ni­ca­tion

In ev­ery power mode, the mi­cro­con­troller has ac­cess to the com­mu­ni­ca­tion unit through the I2C in­ter­face and to the reg­is­ter data in or­der to read out the reg­is­ter val­ues. The val­ues for the 3 axes and the tem­per­a­ture lie in sep­a­rate reg­is­ters. While the in­ter­face ful­fills the I2C fast­mode spec­i­fi­ca­tion (400 kBit/s), a spe­cial elec­tri­cal assem­bly sup­ports data rates of at least 1 MBit/s. The sen­sor can also work on a shared I2C bus with other de­vices; then the mi­cro­con­troller, as bus mas­ter, con­trols all the slaves. The stan­dard bus ad­dress of the TLV493D-A1B6 is set by the man­u­fac­turer and can be changed through the ad­dress pin when it is switched on. The new ad­dress stays valid dur­ing op­er­a­tion and is re­set to the fac­tory set­ting only when the power sup­ply is in­ter­rupted.

Dur­ing 3D mag­netic field de­tec­tion, the TLV493D-A1B6 of­fers 12-bit data res­o­lu­tion for ev­ery mea­sure­ment di­rec­tion. This al­lows high data res­o­lu­tion of 0.098 mil­liTesla (mT) per bit (LSB, least sig­nif­i­cant bit). The sen­sor can thus mea­sure even the small­est move­ments. Lin­ear mag­netic field mea­sure­ments (B) of Bx, By, and Bz are also pos­si­ble for the large lin­ear field range (+/-130 mT). This makes it pos­si­ble to mea­sure longer mag­netic move­ments. The large mea­sure­ment range also al­lows a sim­ple, ro­bust and flex­i­ble mag­netic switch de­sign. Thanks to the use of ver­ti­cal Hall plates for both pla­nar mag­netic field com­po­nents (x and y di­rec­tion), the sen­sor de­liv­ers a high mag­netic pre­ci­sion (+/- 5 %), which al­lows for ex­act an­gle mea­sure­ments.

Flex­i­ble Power Modes

Af­ter each mea­sure­ment cy­cle, the sen­sor trans­mits a strong in­ter­rupt sig­nal to the con­nected mi­cro­con­troller, which can then read out the mag­netic and tem­per­a­ture val­ues from the sen­sor’s reg­is­ters. The in­ter­rupt can also ac­ti­vate the mi­cro­con­troller from its sleep mode. Be­cause of this, the MCU may stay in low-power mode un­til there is a read-out phase, re­duc­ing power con­sump­tion as a whole. The TLV493D-A1B6 is equipped with 5 user-se­lectable power modes: power down, fast power, low power, ul­tra-low power and mas­ter con­trolled. The dif­fer­ent modes can be con­fig­ured through the I²C in­ter­face dur­ing op­er­a­tion.

When it is switched on, the sen­sor starts with the con­fig­u­ra­tion pre­set by the fac­tory and all func­tional blocks are ac­tive for a short time. Then the sen­sor changes into the power-down mode and switches off all func­tion blocks. In this mode, the sen­sor does not per­form any mag­netic mea­sure­ments and the power con­sump­tion drops to 7 nA. When pow­ered by 2 stan­dard AA bat­ter­ies of 2,400 mAh each, this re­sults in a the­o­ret­i­cal op­er­at­ing time of 39,000 years.

Mea­sure Only When Nec­es­sary

In low-power mode, the sen­sor wakes up from power-down mode ev­ery 10 ms in or­der to per­form mag­netic mea­sure­ments. For this it needs a cur­rent of 100 μA. Reg­u­lar mag­netic mea­sure­ment is ideal for ap­pli­ca­tions such as con­trol el­e­ments (e.g. mul­ti­func­tional but­tons).

Power con­sump­tion drops ten­fold in the ul­tra-low-power mode – wake-up cy­cles are ex­tended to 100 ms and power con­sump­tion is re­duced to 10 μA. Ap­pli­ca­tions that de­mand very low power

con­sump­tion, in­clud­ing bat­tery­op­er­ated sys­tems such as ma­nip­u­la­tion pro­tec­tion de­signs for elec­tric me­ters, will ben­e­fit from this mode.

In fast mode the sen­sor op­ti­mises its read-out speed, start­ing the next con­ver­sion while send­ing the pre­vi­ous mea­sure­ment via the I2C in­ter­face. This mode is par­tic­u­larly suit­able for ap­pli­ca­tions such as joy­sticks that have to rec­og­nize very rapid mag­netic move­ments. In this case, the sen­sor’s power con­sump­tion is at most 3.7 mA at a max­i­mum sam­pling rate of 3.3 kHz.

Dur­ing mas­ter-con­trolled op­er­a­tion, the sen­sor waits af­ter each mea­sure­ment un­til the mi­cro­con­troller (mas­ter) has read out the reg­is­ter. Only then does it ini­ti­ate a new mea­sure­ment cy­cle. This mode is par­tic­u­larly use­ful when sev­eral TLV493D-A1B6 sen­sors, con­nected through an I²C bus, are used to de­tect large lin­ear move­ments. In this sce­nario the mi­cro­con­troller de­cides which sen­sor data are cur­rently rel­e­vant and trig­gers the cor­re­spond­ing sen­sor. Fig­ure 3 shows a com­par­i­son of power con­sump­tion and tem­per­a­ture in the var­i­ous power modes.

Joy­stick and Con­trol El­e­ments

Pre­cise 12-bit res­o­lu­tion and high com­mu­ni­ca­tion speed make the TLV493D-A1B6 ideal for joy­stick ap­pli­ca­tions (fig­ure 4). Tra­di­tional joy­sticks use a me­chan­i­cal po­ten­tiome­ter for ev­ery x, y and z di­rec­tion of move­ment. This ap­proach re­quires a lot of space and ex­hibits high per­for­mance fail­ures over prod­uct life­time as the joy­stick’s zero point drifts out of the cen­ter of move­ment. As a re­sult, com­plex me­chan­i­cal cor­rec­tions of this er­ror are re­quired to avoid com­plete joy­stick re­place­ment.

Re­plac­ing the po­ten­tiome­ter

In choos­ing an ap­proach based on mag­netic 3D sen­sors, a TLV493D-A1B6 sen­sor can re­place the 3 me­chan­i­cal po­ten­tiome­ters. This saves space and makes small joy­stick sys­tems pos­si­ble. In ad­di­tion, con­tact­less mag­netic field iden­ti­fi­ca­tion, high tem­per­a­ture sta­bil­ity and vir­tual lack of ag­ing fea­tures en­able the de­vel­op­ment of new, ro­bust joy­sticks for in­dus­trial ap­pli­ca­tions. The new 3D sen­sors also al­low for in­ex­pen­sive and en­ergy-ef­fi­cient con­trol el­e­ments. These in­clude user-friendly rotary/ push but­tons in elec­tric de­vices or house­hold ap­pli­ances where pre­cise an­gle mea­sure­ments and small sys­tem ar­chi­tec­tures re­sult in high tac­tile user com­fort.

In or­der to re­duce the time needed to de­velop ap­pli­ca­tions us­ing the new sen­sor, In­fi­neon has cre­ated an in­ex­pen­sive eval­u­a­tion sys­tem known as “3D Mag­netic Sen­sor 2Go”. This sys­tem com­bines a TLV493D-A1B6 sen­sor with a 32-bit XMC1100 mi­cro­con­troller. Us­ing the hard­ware with the mag­net and sen­sor soft­ware pro­vided, it only takes a few min­utes un­til the sys­tem is ready for the first mea­sure­ments. In­fi­neon also of­fers a “Joy­stick for 3D Mag­netic 2Go Kit” joy­stick at­tach­ment for fast joy­stick mea­sure­ments. De­sign is fur­ther sim­pli­fied as the XMC1100 mi­cro­con­troller also means that users have ac­cess to the ‘Dave’ free de­vel­op­ment plat­form.

Also Suit­able for Cars

Pro­duc­tion of the new sen­sor tech­nol­ogy has al­ready started. De­vel­oped for in­dus­trial and con­sumer goods, the com­po­nent can work with a volt­age range from 2.7 to 3.5 volts and a tem­per­a­ture range from -40 to +125 °C, and is qual­i­fied ac­cord­ing to the JESD47 in­dus­try stan­dard. In ad­di­tion, for cus­tomers in the au­to­mo­tive in­dus­try In­fi­neon will of­fer a full AEC-Q100 qual­i­fi­ca­tion. Vol­ume pro­duc­tion of 3D mag­netic sen­sor TLE493D-A1B6, cer­ti­fied for the au­to­mo­tive in­dus­try, is planned for early 2017.

In­tro­duc­tion of the TLV493D-A1B6 marks the start of de­vel­op­ment of an en­tire In­fi­neon 3D mag­netic sen­sor port­fo­lio, with ad­di­tional ver­sions of 3D mag­netic sen­sors be­ing in­tro­duced in the com­ing months.

3D Mag­netic Sen­sor

Cur­rent Con­sump­tion

Joy­stick

Juer­gen Mann, In­fi­neon Tech­nolo­gies

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