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the A3212 integrated circuit is an ultra-sensitive, pole independent hall- effect switch with a latched digital output. this sensor is especially suited for operation in battery-operated, hand-held equipment such as cellular and cordless telephones, pagers, and palmtop computers. a 2.5 volt to 3.5 volt operation and a unique clocking scheme reduce the average operating power requirements to less than 15 w with a 2.75 volt supply. unlike other hall-effect switches, either a north or south pole of sufficient strength will turn the output on; in the absence of a magnetic field, the output is off. the polarity independence and minimal power requirement allow these devices to easily replace reed switches for superior reliability and ease of manufacturing, while eliminating the requirement for signal conditioning. improved stability is made possible through chopper stabilization (dynamic offset cancellation), which reduces the residual offset voltage normally caused by device overmolding, temperature dependencies, and thermal stress. this device includes on a single silicon chip a hall-voltage generator, small-signal amplifier, chopper stabilization, a latch, and a mosfet output. advanced bicmos processing is used to take advantage of low-voltage and low-power requirements, component matching, very low input-offset errors, and small component geometries. three package styles provide a magnetically optimized package for most applications. package suffixes 'eh' and lh are for miniature low-profile (leadless and leaded, respectively) surface-mount packages while suffix ua is for a three-lead sip for through-hole mounting. features micropower operation operation with north or south pole 2.5 v to 3.5 v battery operation chopper stabilized superior temperature stability extremely low switch-point drift insensitive to physical stress esd protected to 5 kv solid-state reliability small size easily manufacturable with magnet pole independence data sheet 27622.61b always order by complete part number: the prefix a + the basic four-digit part number + the suffix e or 'l' to indicate operating temperature range + a suffix to indicate package style, e.g., A3212elh . package suffix lh pinning (sot23w) 3212 absolute maximum ratings at t a = +25 c supply voltage, v dd ............................. 5 v magnetic flux density, b .......... unlimited output off voltage, v out ..................... 5 v output current, i out .......................... 1 ma junction temperature, t j ............... +170 c operating temperature range, t a suffix 'e-' ................... -40 c to +85 c suffix 'l-' ................. -40 c to +150 c storage temperature range, t s .............................. -65 c to +170 c caution: these cmos devices have input static protection (class 3) but are still susceptible to damage if exposed to extremely high static electrical charges. pinning is shown viewed from branded side. micropower, ultra-sensitive hall-effect switch x dwg. ph-016-1 supply ground output v dd 12 3
3212 micropower, ultra-sensitive hall-effect switch 115 northeast cutoff, box 15036 worcester, massachusetts 01615-0036 (508) 853-5000 2 functional block diagram copyright ? 2002, 2003 allegro microsystems, inc. package suffix ua pinning (sip) timing logic dwg. fh-020-5 latch ground output supply x dynamic offset cancellation switch sample & hold dwg. ph-016 1 supply v dd ground 3 2 output x pinning is shown viewed from branded side. package suffix eh pinning (leadless chip carrier) x dwg. ph-016-2 supply ground output v dd ground no connection no connection 5 4 6 1 3 2
3212 micropower, ultra-sensitive hall-effect switch www.allegromicro.com 3 electrical characteristics over operating voltage and temperature range (unless otherwise specified). limits characteristic symbol test conditions min. typ. max. units operate points b ops south pole to branded side C 37 55 g b opn north pole to branded side -55 -40 C g release points b rps south pole to branded side 10 31 C g b rpn north pole to branded side C -34 -10 g hysteresis b hys |b opx - b rpx | C 5.9 C g notes: 1. negative flux densities are defined as less than zero (algebraic convention), i.e., -50 g is less than +10 g. 2. b opx = operate point (output turns on); b rpx = release point (output turns off). 3. typical data is at t a = +25 c and v dd = 2.75 v and is for design information only. 4. 1 gauss (g) is exactly equal to 0.1 millitesla (mt). magnetic characteristics over operating voltage and temperature range (unless otherwise specified). limits characteristic symbol test conditions min. typ. max. units supply voltage range v dd operating 1 2.5 2.75 3.5 v output leakage current i off v out = 3.5 v, b rpn < b < b rps C <1.0 1.0 a output on voltage v out i out = 1 ma, v dd = 2.75 v C 100 300 mv awake time t awake C4590 s period t period C4590ms duty cycle d.c. C 0.1 C % chopping frequency f c C 340 C khz supply current i dd(en) chip awake (enabled) C C 2.0 ma i dd(dis) chip asleep (disabled) C C 8.0 a i dd(avg) v dd = 2.75 v C 5.1 10 a v dd = 3.5 v C 6.7 10 a notes: 1. operate and release points will vary with supply voltage. 2. b opx = operate point (output turns on); b rpx = release point (output turns off). 3. typical data is at t a = +25 c and v dd = 2.75 v and is for design information only.
3212 micropower, ultra-sensitive hall-effect switch 115 northeast cutoff, box 15036 worcester, massachusetts 01615-0036 (508) 853-5000 4 typical operating characteristics supply current switch points 60 switch points in gauss 20 0 -20 -40 2.8 3.0 3.2 3.4 3.6 supply voltage in volts 2.4 dwg. gh-057-2 2.6 b ops -60 40 b rps b rpn b opn t a = 25 c 7.0 average supply current in a 6.0 5.0 4.0 3.0 2.8 3.0 3.2 3.4 3.6 supply voltage in volts 2.4 dwg. gh-058-7 2.6 t a = 25 c 0255075 100 ambient temperature in c -50 dwg. gh-028-11 125 -25 average supply current in a 7.0 6.0 5.0 3.0 v dd =3.5 v 150 v dd =2.75 v v dd =2.5 v 4.0 0 50 100 ambient temperature in c -50 dwg. gh-027-3 switch points in gauss 0 20 40 -20 -40 v dd = 2.75 v 150 60 -60 -25 25 75 125 b ops b rps b rpn b opn
3212 micropower, ultra-sensitive hall-effect switch www.allegromicro.com 5 functional description low average power. internal timing circuitry activates the sensor for 45 s and deactivates it for the remainder of the period (45 ms). a short "awake" time allows for stabilization prior to the sensor sampling and data latching on the falling edge of the timing pulse. the output during the "sleep" time is latched in the last sampled state. the supply current is not affected by the output state. chopper-stabilized technique. the hall element can be considered as a resistor array similar to a wheatstone bridge. a large portion of the offset is a result of the mismatching of these resistors. these devices use a proprietary dynamic offset cancellation technique, with an internal high-frequency clock to reduce the residual offset voltage of the hall element that is normally caused by device overmolding, temperature dependen- cies, and thermal stress. the chopper-stabilizing technique cancels the mismatching of the resistor circuit by changing the direction of the current flowing through the hall plate using cmos switches and hall voltage measurement taps, while maintaing the hall-voltage signal that is induced by the external magnetic flux. the signal is then captured by a sample-and- hold circuit and further processed using low-offset bipolar circuitry. this technique produces devices that have an extremely stable quiescent hall output voltage, are immune to thermal stress, and have precise recoverability after temperature cycling. a relatively high sampling frequency is used for faster signal processing capability can be processed. more detailed descriptions of the circuit operation can be found in: 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 . dwg. eh-012-1 sample & hold x +v +v hall voltage b + dwg. ah-011-2 dwg. wh-017-2 0 period "awake" "sleep" i dd(en) i dd(dis) sample & output latched
3212 micropower, ultra-sensitive hall-effect switch 115 northeast cutoff, box 15036 worcester, massachusetts 01615-0036 (508) 853-5000 6 output dwg. eh-013-2 0.1 f supply (3 v battery) 10 pf 50 k ? x v dd 1 2 3 operation. the output of this device switches low (turns on) when a magnetic field perpendicular to the hall sensor exceeds the operate point b ops (or is less than b opn ). after turn-on, the output is capable of sinking up to 1 ma and the output voltage is v out(on) . when the magnetic field is reduced below the release point b rps (or increased above b rpn ), the device output switches high (turns off). the difference in the magnetic operate and release points is the hysteresis (b hys ) of the device. this built-in hysteresis allows clean switching of the output even in the presence of external mechanical vibration and electrical noise. as used here, negative flux densities are defined as less than zero (algebraic convention), i.e., -50 g is less than +10 g. applications. allegro's pole-independent sensing technique allows for operation with either a north pole or south pole magnet orientation, enhancing the manufacturability of the device. the state-of-the-art technology provides the same output polarity for either pole face. it is strongly recommended that an external bypass capaci- tor be connected (in close proximity to the hall sensor) between the supply and ground of the device to reduce both external noise and noise generated by the chopper-stabilization tech- nique. this is especially true due to the relatively high imped- ance of battery supplies. the simplest form of magnet that will operate these devices is a bar magnet with either pole near the branded surface of the device. many other methods of operation are possible. exten- sive applications information for hall-effect sensors is available in: ? hall-effect ic applications guide , application note 27701; ? hall-effect devices: soldering, gluing, potting, encapsulat- ing, and lead forming , application note 27703.1; ? soldering of through-hole hall-sensor dervices , application note 27703; and ? soldering of surface-mount hall-sensor devices , application note 27703.2. all are provided at www.allegromicro.com 0 +b 0 dwg. gh-043-1 -b output on 5 v max b ops b rps b opn b rpn output voltage magnetic flux output off functional description (cont'd)
3212 micropower, ultra-sensitive hall-effect switch www.allegromicro.com 7 sensor locations package designator lh package designator ua 1 3 2 dwg. mh-011-13 0.0195" 0.50 mm nom branded surface active area depth 0.078" 1.98 mm 0.052" 1.32 mm a 0.033" 0.84 mm 1 2 dw g . mh-025-2 0.011" 0.28 mm nom active area depth 0.056" 1.42 mm a 3 package designator eh 12 dwg. mh-030 0.013" 0.34 mm nom branded surface active area depth 0.035" 0.88 mm 0.062" 1.56 mm a 3 65 4 allegro
3212 micropower, ultra-sensitive hall-effect switch 115 northeast cutoff, box 15036 worcester, massachusetts 01615-0036 (508) 853-5000 8 package designator eh' (mo-229ced) notes: 1. exact body and lead configuration at vendors option within limits shown. 2. where no tolerance is specified, dimension is nominal. 3. add "lt" to part number for tape and reel. dimensions in millimeters (controlling dimensions) 0.80 0.70 0.50 0.05 max 0.20 ref 1 3 6 5 4 2.00 3.00 0.30 0.18 0.65 0.45 1.142 0.890 dw g . mh-029-6 mm index area 2 exposed thermal pad 1.324 0.970 0.25 0.25 1.00 1.00 1.25 0.95 0.40 0.30 1.00 0.50 3.70 dwg. ma-013-6 mm ? 0.3 thermal via (optional)
3212 micropower, ultra-sensitive hall-effect switch www.allegromicro.com 9 package designator eh' (mo-229ced) notes: 1. exact body and lead configuration at vendors option within limits shown. 2. where no tolerance is specified, dimension is nominal. 3. add "lt" to part number for tape and reel. dimensions in inches (for reference only) 0.0118 0.0071 0.0315 0.0276 0.0197 0.002 max 0.00787 ref 1 3 6 5 4 0.118 0.0256 0.0177 0.04496 0.03504 dw g . mh-029-6 in index area 2 exposed thermal pad 0.05213 0.03819 0.0787 0.016 0.020 0.012 0.0098 0.0098 0.039 0.039 0.049 0.037 0.039 0.15 dwg. ma-013-6 mm ? 0.012 thermal via (optional)
3212 micropower, ultra-sensitive hall-effect switch 115 northeast cutoff, box 15036 worcester, massachusetts 01615-0036 (508) 853-5000 10 package designator lh (sot23w, fits sc-59a solder-pad layout) notes: 1. tolerances on package height and width represent allowable mold offsets. dimensions given are measured at the widest point (parting line). 2. exact body and lead configuration at vendors option within limits shown. 3. height does not include mold gate flash. 4. where no tolerance is specified, dimension is nominal. 5. add "lt" to part number for tape and reel. dimensions in inches (for reference only) dimensions in millimeters (controlling dimensions) dwg. ma-011-3 in 12 0.039 0.094 0.03 7 0.028 3 dwg. ma-011-3 mm 12 1.00 2.40 0.95 0.70 3 dwg. ma-010-3d in 12 0.006 0.000 0.0079 0.0050 0.083 0.073 0.118 0.106 0.037 bsc 0.022 ref 0.020 0.012 3 0.045 0.032 0 to 8 0.010 min gauge plane seating plane 0.010 bsc 0.122 0.114 dwg. ma-010-3d mm 12 0.15 0.00 0.20 0.127 2.10 1.85 3.00 2.70 0.95 bsc 0.55 ref 0.50 0.30 3 1.13 0.87 0 to 8 0.25 min gauge plane seating plane 0.25 bsc 3.10 2.90
3212 micropower, ultra-sensitive hall-effect switch www.allegromicro.com 11 dimensions in inches (controlling dimensions) dimensions in millimeters (for reference only) package designator ua notes: 1. tolerances on package height and width represent allowable mold offsets. dimensions given are measured at the widest point (parting line). 2. exact body and lead configuration at vendors option within limits shown. 3. height does not include mold gate flash. 4. recommended minimum pwb hole diameter to clear transition area is 0.035" (0.89 mm). 5. where no tolerance is specified, dimension is nominal. 6. supplied in bulk pack (500 pieces per bag). dwg. mh-014e in 0.164 0.159 0.062 0.058 0.0173 0.0138 0.050 bsc 45 0.640 0.600 0.0189 0.0142 0.085 max 45 0.031 123 0.122 0.117 see note dwg. mh-014e mm 4.17 4.04 1.57 1.47 0.44 0.35 1.27 bsc 45 16.26 15.24 0.48 0.36 2.16 max 45 0.79 123 3.10 2.97 see note radial lead form (order A3212xua-lc) note: lead-form dimensions are the nominals produced on the forming equipment. no dimensional tolerance is implied or guaranteed for bulk packaging (500 pieces per bag). 0.620" 0.500" (15.7 mm 12.7 mm) 0.100" (2.5 mm) dwg. mh-026 0.108" (2.74 mm) 123
3212 micropower, ultra-sensitive hall-effect switch 115 northeast cutoff, box 15036 worcester, massachusetts 01615-0036 (508) 853-5000 12 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. allegro products are not authorized for use as critical components in life-support appliances, devices, or systems without express written approval. 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 infringements of patents or other rights of third parties that may result from its use.

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