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description the allegro ? a1205 hall-effect bipolar switch is a next- generation replacement and extension of the popular allegro a3134 bipolar switch. the a1205 has identical specifications as the a1201 but is recommended for applications that require pulsing v cc to conserve power. for standard applications, where v cc is constant, please refer to the a1201 through a1204 devices. overall, the a120x family, produced with bicmos technology, consists of continuous-time devices that feature fast power- on time and low-noise operation. device programming is performed after packaging to ensure increased switchpoint accuracy by eliminating offsets that can be induced by package stress. unique hall element geometries and low- offset amplifiers help to minimize noise and to reduce the residual offset voltage normally caused by device overmolding, temperature excursions, and thermal stress. the a120x hall-effect bipolar switches include the following on a single silicon chip: voltage regulator, hall-voltage generator, a1205-ds, rev. 1 features and benefits ? ideal for applications that require pulsing v cc to conserve power ? continuous-time operation ? fast power-on time ? low noise ? stable operation over full operating temperature range ? reverse battery protection ? solid-state reliability ? factory-programmed at end-of-line for optimum performance ? robust emc performance ? high esd rating ? regulator stability without a bypass capacitor continuous-time bipolar switch continued on the next page packages: functional block diagram not to scale a1205 3 pin sot23w (lh) 3 pin sip (ua) am p r egu l a to r gn d vc c vout o ffset gain tri m co ntro l to all subcircuits
continuous-time bipolar switch a1205 2 allegro microsystems, inc. 115 northeast cutoff, box 15036 worcester, massachusetts 01615-0036 (508) 853-5000 www.allegromicro.com selection guide part number packing* mounting ambient, t a b rp (min) b op (max) A1205ELHLT-T 7-in. reel, 3000 pieces/reel 3-pin sot23w surface mount C40oc to 85oc C50 50 a1205eua-t bulk, 500 pieces/bag 3-pin sip through hole a1205llhlt-t 7-in. reel, 3000 pieces/reel 3-pin sot23w surface mount C40oc to 150oc a1205lua-t bulk, 500 pieces/bag 3-pin sip through hole *contact allegro for additional packing options. description (continued) absolute maximum ratings characteristic symbol notes rating units supply voltage v cc 30 v reverse supply voltage v rcc C30 v output off voltage v out 30 v reverse output voltage v rout C0.5 v output current sink i outsink 25 ma magnetic flux density b unlimited g operating ambient temperature t a range e C40 to 85 oc range l C40 to 150 oc maximum junction temperature t j (max) 165 oc storage temperature t stg C65 to 170 oc small-signal amplifier, schmitt trigger, and nmos output transistor. the integrated voltage regulator permits operation from 3.8 to 24 v. the extensive on-board protection circuitry makes possible a 30 v absolute maximum voltage rating for superior protection in automotive and motor commutation applications, without adding external components. the small geometries of the bicmos process allow these devices to be provided in ultrasmall packages. the package styles available provide magnetically optimized solutions for most applications. package lh is a sot23w miniature thin-profile surface-mount package, while package ua is a three-lead ultramini sip for through- hole mounting. each package is lead (pb) free, with 100% matte tin plated leadframes.
continuous-time bipolar switch a1205 3 allegro microsystems, inc. 115 northeast cutoff, box 15036 worcester, massachusetts 01615-0036 (508) 853-5000 www.allegromicro.com operating characteristics over full operating voltage and ambient temperature ranges, unless otherwise noted characteristic symbol test conditions min. typ. max. units electrical characteristics supply voltage 1 v cc operating, t j < 165c 3.8 C 24 v output leakage current i outoff v out = 24 v, b < b rp C C 10 a output on voltage v out(sat) i out = 20 ma, b > b op C 215 400 mv power-on time 2 t po slew rate (dv cc /dt) < 2.5 v/s, b > b op + 5 g or b < b rp C 5 g C C 4 s output rise time 3 t r v cc = 12 v, r load = 820 ?, c s = 12 pf C C 2 s output fall time 3 t f v cc = 12 v, r load = 820 ?, c s = 12 pf C C 2 s supply current i ccon b > b op C 3.8 7.5 ma i ccoff b < b rp C 3.5 7.5 ma reverse battery current i rcc v rcc = C30 v C C C10 ma supply zener clamp voltage v z i cc = 30 ma; t a = 25c 32 C 40 v supply zener current i z v z = 32 v; t a = 25c C C 30 ma magnetic characteristics 4 operate point b op south pole adjacent to branded face of device C40 15 50 g release point b rp north pole adjacent to branded face of device C50 C15 40 g hysteresis b hys b op C b rp 5 30 55 g 1 maximum voltage must be adjusted for power dissipation and junction temperature, see power derating section. 2 for v cc slew rates greater than 2.5 v/s, and t a = 150c, the power-on time can reach its maximum value. 3 c s =oscilloscope probe capacitance. 4 magnetic flux density, b, is indicated as a negative value for north-polarity magnetic fields, and as a positive value for south-polarity magnetic fields. this so-called algebraic convention supports arithmetic comparison of north and south polarity values, where the relative strength of the field is indicated by the absolute value of b, and the sign indicates the polarity of the field (for example, a C100 g field and a 100 g field have equivalent strength, but opposite polarity). reference to the magnetic field polarity is with respect to the beveled face of the device. device qualification program contact allegro for information. emc (electromagnetic compatibility) requirements contact allegro for information.
continuous-time bipolar switch a1205 4 allegro microsystems, inc. 115 northeast cutoff, box 15036 worcester, massachusetts 01615-0036 (508) 853-5000 www.allegromicro.com thermal characteristics may require derating at maximum conditions, see application information characteristic symbol test conditions* value units package thermal resistance r ja package lh, 1-layer pcb with copper limited to solder pads 228 oc/w package lh, 2-layer pcb with 0.463 in. 2 of copper area each side connected by thermal vias 110 oc/w package ua, 1-layer pcb with copper limited to solder pads 165 oc/w *additional thermal information available on allegro web site. 6 7 8 9 2 3 4 5 1 0 1 1 1 2 1 3 1 4 1 5 1 6 1 7 1 8 1 9 2 0 2 1 2 2 2 3 2 4 2 5 2 0 4 0 6 0 8 0 1 0 0 1 2 0 14 0 1 6 0 18 0 ma xi m u m all o wa b le v c c ( v ) t j( m a x ) = 165oc ; i c c = i cc( m ax ) pow e r der a ting cur v e ( r j a = 2 28 oc/w ) pa c ka g e l h , 1 - l a y e r pcb ( r j a = 1 1 0 oc / w ) pac k a ge l h, 2-l a y e r pcb ( r j a = 1 65 oc/w ) pa c k ag e ua , 1 - l ay e r pc b v cc ( mi n) v cc ( m a x ) 0 1 0 0 2 0 0 3 0 0 4 0 0 5 0 0 6 0 0 7 0 0 8 0 0 9 0 0 1 0 0 0 1 1 0 0 1 2 0 0 1 3 0 0 1 4 0 0 1 5 0 0 1 6 0 0 1 7 0 0 1 8 0 0 1 9 0 0 2 0 4 0 6 0 8 0 1 0 0 1 2 0 1 4 0 1 6 0 1 8 0 t e m p e r a t u r e ( c ) p o w e r d i s s i p a t i o n , p d ( m w ) p o w e r d i s s i p a t i o n v e r s u s a m b i e n t t e m p e r a t u r e ( r j a = 1 6 5 o c / w ) 1 - l a y e r p c b , p a c k a g e u a ( r j a = 2 2 8 o c / w ) 1 - l a y e r p c b , p a c k a g e l h ( r j a = 1 1 0 o c / w ) 2 - l a y e r p c b , p a c k a g e l h
continuous-time bipolar switch a1205 5 allegro microsystems, inc. 115 northeast cutoff, box 15036 worcester, massachusetts 01615-0036 (508) 853-5000 www.allegromicro.com characteristic data ? 50 0 50 100 150 0 5 10 15 20 25 ?50 0 50 100 150 0 5 10 15 20 25 0 50 100 150 200 250 300 350 ?50 0 50 100 150 0 5 10 15 20 25 0 50 100 150 200 250 300 350 t a (c) supply current (on) versus ambient temperature v cc (v) i ccon (ma) 24 3.8 t a (c) supply current (off) versus ambient temperature v cc (v) i ccoff (ma) 24 3.8 i load = 20 ma i load = 20 ma t a (c) output voltage (on) versus ambient temperature v cc (v) v out(sat) (mv) 24 3.8 supply current (on) versus supply voltage t a ( c) i ccon (ma) v cc (v) ? 40 25 150 supply current (off) versus supply voltage t a ( c) i ccoff (ma) v cc (v) ? 40 25 150 output voltage (on) versus supply voltage t a ( c) v out(sat) (mv) v cc (v) ? 40 25 150 0 1.0 2.0 3.0 4.0 5.0 7.0 6.0 8.0 0 1.0 2.0 3.0 4.0 5.0 7.0 6.0 8.0 0 1.0 2.0 3.0 4.0 5.0 7.0 6.0 8.0 0 1.0 2.0 3.0 4.0 5.0 7.0 6.0 8.0
continuous-time bipolar switch a1205 6 allegro microsystems, inc. 115 northeast cutoff, box 15036 worcester, massachusetts 01615-0036 (508) 853-5000 www.allegromicro.com -40 -30 -20 -10 0 10 20 30 40 50 -50 0 50 100 150 -40 -30 -20 0 10 20 30 40 50 0 5 10 15 20 25 -50 -40 -30 -20 -10 0 10 20 30 40 -50 0 50 100 150 -50 -40 -30 -20 -10 0 10 20 30 40 0 5 10 15 20 25 5 10 15 20 25 30 35 40 45 50 55 -50 0 50 100 150 5 10 15 20 25 30 35 40 45 50 55 0 5 10 15 20 25 -10 t a (c) operate point versus ambient temperature b op (g) t a (c) release point versus ambient temperature b rp (g) t a (c) hysteresis versus ambient temperature b hys (g) b op (g) b rp (g) b hys (g) operate point versus supply voltage t a ( c) v cc (v) ?40 25 150 release point versus supply voltage t a ( c) v cc (v) ?40 25 150 hysteresis versus supply voltage t a ( c) v cc (v) ?40 25 150 v cc (v) 24 v cc (v) 24 v cc (v) 24 3.8 3.8 3.8
continuous-time bipolar switch a1205 7 allegro microsystems, inc. 115 northeast cutoff, box 15036 worcester, massachusetts 01615-0036 (508) 853-5000 www.allegromicro.com functional description bipolar device switching the devices of the a120x family provide highly sensitive switching for applications using magnetic fields of alternating polarities, such as ring magnets. there are three switching modes for bipolar devices, referred to as latch , unipolar switch , and negative switch . mode is determined by the switchpoint charac - teristics of the individual device. the characteristic hysteresis, b hys , of the device, is the difference in the relative magnetic strength and polarity of the switchpoints of the device. (note that, in the following descriptions, a negative magnetic value indicates a north polarity field, and a positive magnetic value indicates a south polarity field. for a given value of magnetic strength, b x , the values Cb x and b x indicate two fields of equal strength, but opposite polarity. b = 0 indicates the absence of a magnetic field.) bipolar devices typically behave as latches. in this mode, magnetic fields of opposite polarity and equivalent strengths are needed to switch the output. when the magnetic fields are removed (b 0) the device remains in the same state until a magnetic field of the opposite polarity and of sufficient strength causes it to switch. the hysteresis of latch mode behavior is shown in panel a of figure 1. in contrast to latching, when a device exhibits unipolar switch - ing, it only responds to a south magnetic field. the field must be of sufficient strength, > b op , for the device to operate. when the field is reduced beyond the b rp level, the device switches back to the high state, as shown in panel b of figure 1. devices exhibiting negative switch behavior operate in a similar but opposite manner. a north polarity field of sufficient strength, > b rp , (more north than b rp ) is required for operation, although the result is that v out switches high, as shown in panel c. when figure 1. bipolar device output switching modes. these behaviors can be exhibited when using a circuit such as that shown in panel d. panel a displays the hysteresis when a device exhibits latch mode (note that the b hys band incorporates b= 0), panel b shows unipolar switch behavior (the b hys band is more positive than b = 0), and panel c shows negative switch behavior (the b hys band is more negative than b = 0). bipolar devices, such as the 120x family, can operate in any of the three modes. b op b rp b hys v out v out(sat) switch to low switch to high v+ 0 b op b rp b hys v out v out(sat) switch to low switch to high v+ 0 b op b rp b hys v out v out(sat) switch to low switch to high v+ 0 v cc v cc v cc b+ b? b+ b? 0 0 b+ b? 0 (a) (b) (c) vcc v s sensor output gnd vout r l a120x (d)
continuous-time bipolar switch a1205 8 allegro microsystems, inc. 115 northeast cutoff, box 15036 worcester, massachusetts 01615-0036 (508) 853-5000 www.allegromicro.com the field is reduced beyond the b op level, the device switches back to the low state. the typical output behavior of the a120x devices is latching. however, the a120x family is designed to attain a small hys - teresis, and thereby provide more sensitive switching. although this means that true latching behavior cannot be guaranteed in all cases, proper switching can be ensured by use of both south and north magnetic fields, as in a ring magnet. the hysteresis of the a120x family allows clean switching of the output, even in the presence of external mechanical vibration and electrical noise. bipolar devices adopt an indeterminate output state when pow - ered-on in the absence of a magnetic field or in a field that lies within the hysteresis band of the device. for more information on bipolar switches, refer to application note 27705, understanding bipolar hall effect sensors . continuous-time benefits c ontinuous-time devices, such as the a120x family, offer the fastest available power-on settling time and frequency response. due to offsets generated during the ic packaging process, contin - uous-time devices typically require programming after packaging to tighten magnetic parameter distributions. in contrast, chop - per-stabilized switches employ an offset cancellation technique on the chip that eliminates these offsets without the need for after-packaging programming. the tradeoff is a longer settling time and reduced frequency response as a result of the chopper- stabilization offset cancellation algorithm. the choice between continuous-time and chopper-stabilized designs is solely determined by the application. battery manage - ment is an example where continuous-time is often required. in these applications, v cc is chopped with a very small duty cycle in order to conserve power (refer to figure 2). the duty cycle is controlled by the power-on time, t po , of the device. because figure 2. continuous-time application, b < b rp .. this figure illustrates the use of a quick cycle for chopping v cc in order to conserve battery power. position 1, power is applied to the device. position 2, the output assumes the correct state at a time prior to the maximum power-on time, t po(max) . the case shown is where the correct output state is high . position 3, t po(max) has elapsed. the device output is valid. position 4, after the output is valid, a control unit reads the output. position 5, power is removed from the device . v cc v out output sampled 1 5 4 2 t t t po(max) 3
continuous-time bipolar switch a1205 allegro microsystems, inc. 115 northeast cutoff, box 15036 worcester, massachusetts 01615-0036 (508) 853-5000 www.allegromicro.com continuous-time devices have the shorter power-on time, they are the clear choice for such applications. for more information on the chopper stabilization technique, refer to technical paper stp 97-10, monolithic magnetic hall sensor using dynamic quadrature offset cancellation and technical paper stp 99-1, chopper-stabilized amplifiers with a track-and-hold signal demodulator . additional applications information extensive applications information for hall-effect sensors is available in: ? hall-effect ic applications guide , application note 27701 ? hall-effect devices: gluing, potting, encapsulating, lead welding and lead forming , application note 27703.1 ? soldering methods for allegros products C smt and through- hole , application note 26009 all are provided in allegro electronic data book , ams-702, and the allegro web site, www.allegromicro.com. pin-out diagrams terminal list name description number package lh package ua vcc connects power supply to chip 1 1 vout output from circuit 2 3 gnd ground 3 2 1 3 2 gnd vout vcc package ua package lh 1 2 3 gnd vout vcc
continuous-time bipolar switch a1205 10 allegro microsystems, inc. 115 northeast cutoff, box 15036 worcester, massachusetts 01615-0036 (508) 853-5000 www.allegromicro.com power derating power derating the device must be operated below the maximum junction temperature of the device, t j(max) . under certain combinations of peak conditions, reliable operation may require derating sup - plied power or improving the heat dissipation properties of the application. this section presents a procedure for correlating factors affecting operating t j . (thermal data is also available on the allegro microsystems web site.) the package thermal resistance, r ja , 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, r jc , is relatively small component of r ja . ambient air temperature, t a , and air motion are significant external factors, damped by overmolding. the effect of varying power levels (power dissipation, p d ), can be estimated. the following formulas represent the fundamental relationships used to estimate t j , at p d . p d = v in i in (1) t = p d r ja (2) t j = t a + t (3) for example, given common conditions such as: t a = 25c , v cc = 12 v , i cc = 4 ma, and r ja = 140 c/w, t hen: p d = v cc i cc = 12 v 4 ma = 48 mw t = p d r ja = 48 mw 140 c/w = 7c t j = t a + t = 25c + 7c = 32c a worst-case estimate, p d(max) , represents the maximum allow - able power level (v cc(max) , i cc(max) ), without exceeding t j(max) , at a selected r ja and t a . example : reliability for v cc at t a = 150c, package ua, using minimum-k pcb. observe the worst-case ratings for the device, specifically: r ja = 165c/w, t j(max) = 165c, v cc(max) = 24 v, and i cc(max) = 7.5 ma. calculate the maximum allowable power level, p d(max) . first, invert equation 3: t max = t j(max) C t a = 165 c C 150 c = 15 c this provides the allowable increase to t j resulting from internal power dissipation. then, invert equation 2: p d(max) = t max r ja = 15c 165 c/w = 91 mw finally, invert equation 1 with respect to voltage: v cc(est) = p d(max) i cc(max) = 91 mw 7.5 ma = 12.1 v the result indicates that, at t a , the applicati on and device can dissipate adequate amounts of heat at voltages v cc(est) . compare v cc(est) to v cc(max) . if v cc(est) v cc(max) , then reli - able operation between v cc(est) and v cc(max) requires enhanced r ja . if v cc(est) v cc(max) , then operation between v cc(est) and v cc(max) is reliable under these conditions.
continuous-time bipolar switch a1205 11 allegro microsystems, inc. 115 northeast cutoff, box 15036 worcester, massachusetts 01615-0036 (508) 853-5000 www.allegromicro.com package lh, 3-pin (sot-23w) 0.15 0.00 .006 .000 1.17 0.75 .046 .030 0.50 0.30 .020 .012 2.10 1.85 .083 .073 3.00 2.70 .1 18 .106 1.49 nom .059 0.96 nom .038 0.20 0.08 .008 .003 8o 0o 0.60 0.25 .024 .010 c sea ting plane a b 3x 0.20 [.008] m c a b 0.15 [.006] m c a b c 0.10 [.004] 3x 0.95 .037 1.90 .075 0.25 .010 3.04 2.80 .120 .1 10 2 1 3 gauge plane sea ting plane b a b preliminary dimensions, for reference only dimensions in millimeters u.s. customary dimensions (in.) in brackets, for reference only (reference jedec t o-236 ab, except case width and terminal tip-to-tip) dimensions exclusive of mold flash, gate burrs, and dambar protrusions exact case and lead configuration at supplier discretion within limits shown hall element (not to scale ) active area depth 0.28 [.01 1] a a a
continuous-time bipolar switch a1205 12 allegro microsystems, inc. 115 northeast cutoff, box 15036 worcester, massachusetts 01615-0036 (508) 853-5000 www.allegromicro.com 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 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. the information included herein is believed to be accurate and reliable. however, allegro microsystems, inc. assumes no responsi - bility for its use; nor for any infringement of patents or other rights of third parties which may result from its use. copyright ?2006, allegro microsystems, inc. for the latest version of this document, go to our website at: www.allegromicro.co m package ua, 3-pin sip b d d d .164 .159 4.17 4.04 .122 .117 3.10 2.97 .062 .058 1.57 1.47 .017 .014 0.44 0.35 .019 .014 0.48 0.36 .640 .600 16.26 15.24 .085 max 2.16 .050 nom 1.27 .031 ref 0.79 .091 nom 2.31 1.45 .057 nom dimensions in inches metric dimensions (mm) in brackets, for reference only 2 3 1 a a b c c dambar removal protrusion (6x) active area depth .0195 [0.50] nom d hall element (not to scale) ejector mark on opposite side

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