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ip+ ip+ ipC ipC i p 5 gnd 2 4 1 3 ACS712 7 8 +5 v viout v out 6 filter vcc c byp 0.1 f c f 1 nf application 1. the ACS712 outputs an analog signal, v out . that varies linearly with the uni- or bi-directional ac or dc primary sampled current, i p , within the range specified. c f is recommended for noise management, with values that depend on the application. ACS712 description the allegro ? ACS712 provides economical and precise solutions for ac or dc current sensing in industrial, commercial, and communications systems. the device package allows for easy implementation by the customer. typical applications include motor control, load detection and management, switch- mode power supplies, and overcurrent fault protection. the device is not intended for automotive applications. the device consists of a precise, low-offset, linear hall circuit with a copper conduction path located near the surface of the die. applied current flowing through this copper conduction path generates a magnetic field which the hall ic converts into a proportional voltage. device accuracy is optimized through the close proximity of the magnetic signal to the hall transducer. a precise, proportional voltage is provided by the low-offset, chopper-stabilized bicmos hall ic, which is programmed for accuracy after packaging. the output of the device has a positive slope (>v iout(q) ) when an increasing current flows through the primary copper conduction path (from pins 1 and 2, to pins 3 and 4), which is the path used for current sampling. the internal resistance of this conductive path is 1.2 m typical, providing low power loss. the thickness of the copper conductor allows survival of ACS712-ds, rev. 13 features and benefits ? low-noise analog signal path ? device bandwidth is set via the new filter pin ? 5 s output rise time in response to step input current ? 80 khz bandwidth ? total output error 1.5% at t a = 25c ? small footprint, low-profile soic8 package ? 1.2 m internal conductor resistance ? 2.1 kvrms minimum isolation voltage from pins 1-4 to pins 5-8 ? 5.0 v, single supply operation ? 66 to 185 mv/a output sensitivity ? output voltage proportional to ac or dc currents ? factory-trimmed for accuracy ? extremely stable output offset voltage ? nearly zero magnetic hysteresis ? ratiometric output from supply voltage fully integrated, hall effect-based linear current sensor ic with 2.1 kvrms isolation and a low-resistance current conductor continued on the next page? approximate scale 1:1 package: 8 lead soic (suffix lc) typical application tv america certificate number: u8v 06 05 54214 010
fully integrated, hall effect-based linear current sensor ic with 2.1 kvrms isolation and a low-resistance current conductor ACS712 2 allegro microsystems, inc. 115 northeast cutoff worcester, massachusetts 01615-0036 u.s.a. 1.508.853.5000; www.allegromicro.com absolute maximum ratings characteristic symbol notes rating units supply voltage v cc 8v reverse supply voltage v rcc ?0.1 v output voltage v iout 8v reverse output voltage v riout ?0.1 v reinforced isolation voltage v iso pins 1-4 and 5-8; 60 hz, 1 minute, t a =25c 2100 vac maximum working voltage according to ul60950-1 184 v peak basic isolation voltage v iso(bsc) pins 1-4 and 5-8; 60 hz, 1 minute, t a =25c 1500 vac maximum working voltage according to ul60950-1 354 v peak output current source i iout(source) 3ma output current sink i iout(sink) 10 ma overcurrent transient tolerance i p 1 pulse, 100 ms 100 a nominal operating ambient temperature t a range e ?40 to 85 oc maximum junction temperature t j (max) 165 oc storage temperature t stg ?65 to 170 oc selection guide part number packing* t a (c) optimized range, i p (a) sensitivity, sens (typ) (mv/a) ACS712elctr-05b-t tape and reel, 3000 pieces/reel ?40 to 85 5 185 ACS712elctr-20a-t tape and reel, 3000 pieces/reel ?40 to 85 20 100 ACS712elctr-30a-t tape and reel, 3000 pieces/reel ?40 to 85 30 66 *contact allegro for additional packing options. the device at up to 5 overcurrent conditions. the terminals of the conductive path are electrically isolated from the signal leads (pins 5 through 8). this allows the ACS712 to be used in applications requiring electrical isolation without the use of opto-isolators or other costly isolation techniques. the ACS712 is provided in a small, surface mount soic8 package. the leadframe is plated with 100% matte tin, which is compatible with standard lead (pb) free printed circuit board assembly processes. internally, the device is pb-free, except for flip-chip high-temperature pb-based solder balls, currently exempt from rohs. the device is fully calibrated prior to shipment from the factory. description (continued) parameter specification fire and electric shock can/csa-c22.2 no. 60950-1-03 ul 60950-1:2003 en 60950-1:2001
fully integrated, hall effect-based linear current sensor ic with 2.1 kvrms isolation and a low-resistance current conductor ACS712 3 allegro microsystems, inc. 115 northeast cutoff worcester, massachusetts 01615-0036 u.s.a. 1.508.853.5000; www.allegromicro.com vcc (pin 8) (pin 7) viout r f(int) gnd (pin 5) filter (pin 6) dynamic offset cancellation ip+ (pin 1) ip+ (pin 2) ip ? (pin 3) ip ? (pin 4) sense trim signal recovery sense temperature coefficient trim 0 ampere offset adjust hall current drive +5 v ip+ ip+ ip? ip? vcc viout filter gnd 1 2 3 4 8 7 6 5 terminal list table number name description 1 and 2 ip+ terminals for current being sampled; fused internally 3 and 4 ip? terminals for current being sampled; fused internally 5 gnd signal ground terminal 6 filter terminal for external capacitor that sets bandwidth 7 viout analog output signal 8 vcc device power supply terminal functional block diagram pin-out diagram
fully integrated, hall effect-based linear current sensor ic with 2.1 kvrms isolation and a low-resistance current conductor ACS712 4 allegro microsystems, inc. 115 northeast cutoff worcester, massachusetts 01615-0036 u.s.a. 1.508.853.5000; www.allegromicro.com common operating characteristics 1 over full range of t a , c f = 1 nf, and v cc = 5 v, unless otherwise specified characteristic symbol test conditions min. typ. max. units electrical characteristics supply voltage v cc 4.5 5.0 5.5 v supply current i cc v cc = 5.0 v, output open ? 10 13 ma output capacitance load c load viout to gnd ? ? 10 nf output resistive load r load viout to gnd 4.7 ? ? k primary conductor resistance r primary t a = 25c ? 1.2 ? m rise time t r i p = i p (max), t a = 25c, c out = open ? 5 ? s frequency bandwidth f ?3 db, t a = 25c; i p is 10 a peak-to-peak ? 80 ? khz nonlinearity e lin over full range of i p ? 1.5 ? % symmetry e sym over full range of i p 98 100 102 % zero current output voltage v iout(q) bidirectional; i p = 0 a, t a = 25c ? v cc 0.5 ?v power-on time t po output reaches 90% of steady-state level, t j = 25c, 20 a present on leadframe ?35 ? s magnetic coupling 2 ? 12 ? g/a internal filter resistance 3 r f(int) 1.7 k 1 device may be operated at higher primary current levels, i p , and ambient, t a , and internal leadframe temperatures, t a , provided that the maximum junction temperature, t j (max), is not exceeded. 2 1g = 0.1 mt. 3 r f(int) forms an rc circuit via the filter pin. common thermal characteristics 1 min. typ. max. units operating internal leadframe temperature t a e range ?40 ? 85 c value units junction-to-lead thermal resistance 2 r jl mounted on the allegro asek 712 evaluation board 5 c/w junction-to-ambient thermal resistance r ja mounted on the allegro 85-0322 evaluation board, includes the power con- sumed by the board 23 c/w 1 additional thermal information is available on the allegro website. 2 the allegro evaluation board has 1500 mm 2 of 2 oz. copper on each side, connected to pins 1 and 2, and to pins 3 and 4, with thermal vias connect- ing the layers. performance values include the power consumed by the pcb. further details on the board are available from the frequently asked questions document on our website. further information about board design and thermal performance also can be found in the appl ications informa- tion section of this datasheet.
fully integrated, hall effect-based linear current sensor ic with 2.1 kvrms isolation and a low-resistance current conductor ACS712 5 allegro microsystems, inc. 115 northeast cutoff worcester, massachusetts 01615-0036 u.s.a. 1.508.853.5000; www.allegromicro.com x05b performance characteristics 1 t a = ?40c to 85c, c f = 1 nf, and v cc = 5 v, unless otherwise specified characteristic symbol test conditions min. typ. max. units optimized accuracy range i p ?5 ? 5 a sensitivity sens over full range of i p, t a = 25c 180 185 190 mv/a noise v noise(pp) peak-to-peak, t a = 25c, 185 mv/a programmed sensitivity, c f = 47 nf, c out = open, 2 khz bandwidth ?21 ? mv zero current output slope ? i out(q) t a = ?40c to 25c ? ?0.26 ? mv/c t a = 25c to 150c ? ?0.08 ? mv/c sensitivity slope ? sens t a = ?40c to 25c ? 0.054 ? mv/a/c t a = 25c to 150c ? ?0.008 ? mv/a/c total output error 2 e tot i p =5 a, t a = 25c ? 1.5 ? % 1 device may be operated at higher primary current levels, i p , and ambient temperatures, t a , provided that the maximum junction temperature, t j(max) , is not exceeded. 2 percentage of i p , with i p = 5 a. output filtered. x20a performance characteristics 1 t a = ?40c to 85c, c f = 1 nf, and v cc = 5 v, unless otherwise specified characteristic symbol test conditions min. typ. max. units optimized accuracy range i p ?20 ? 20 a sensitivity sens over full range of i p, t a = 25c 96 100 104 mv/a noise v noise(pp) peak-to-peak, t a = 25c, 100 mv/a programmed sensitivity, c f = 47 nf, c out = open, 2 khz bandwidth ?11 ? mv zero current output slope ? i out(q) t a = ?40c to 25c ? ?0.34 ? mv/c t a = 25c to 150c ? ?0.07 ? mv/c sensitivity slope ? sens t a = ?40c to 25c ? 0.017 ? mv/a/c t a = 25c to 150c ? ?0.004 ? mv/a/c total output error 2 e tot i p =20 a, t a = 25c ? 1.5 ? % 1 device may be operated at higher primary current levels, i p , and ambient temperatures, t a , provided that the maximum junction temperature, t j (max), is not exceeded. 2 percentage of i p , with i p = 20 a. output filtered. x30a performance characteristics 1 t a = ?40c to 85c, c f = 1 nf, and v cc = 5 v, unless otherwise specified characteristic symbol test conditions min. typ. max. units optimized accuracy range i p ?30 ? 30 a sensitivity sens over full range of i p , t a = 25c 63 66 69 mv/a noise v noise(pp) peak-to-peak, t a = 25c, 66 mv/a programmed sensitivity, c f = 47 nf, c out = open, 2 khz bandwidth ?7 ? mv zero current output slope ? i out(q) t a = ?40c to 25c ? ?0.35 ? mv/c t a = 25c to 150c ? ?0.08 ? mv/c sensitivity slope ? sens t a = ?40c to 25c ? 0.007 ? mv/a/c t a = 25c to 150c ? ?0.002 ? mv/a/c total output error 2 e tot i p = 30 a , t a = 25c ? 1.5 ? % 1 device may be operated at higher primary current levels, i p , and ambient temperatures, t a , provided that the maximum junction temperature, t j (max), is not exceeded. 2 percentage of i p , with i p = 30 a. output filtered.
fully integrated, hall effect-based linear current sensor ic with 2.1 kvrms isolation and a low-resistance current conductor ACS712 6 allegro microsystems, inc. 115 northeast cutoff worcester, massachusetts 01615-0036 u.s.a. 1.508.853.5000; www.allegromicro.com ?40 25 85 150 t a (c) ?40 25 85 150 t a (c) i p = 0 a i p = 0 a v cc = 5 v v cc = 5 v v cc = 5 v v cc = 5 v; i p = 0 a, after excursion to 20 a mean supply current versus ambient temperature sensitivity versus sensed current 200.00 190.00 180.00 170.00 160.00 150.00 140.00 130.00 120.00 110.00 100.00 sens (mv/a) 186.5 186.0 185.5 185.0 184.5 184.0 183.5 183.0 182.5 182.0 181.5 181.0 sens (mv/a) ip (a) -6-4-20246 t a (c) t a (c) t a (c) mean i cc (ma) 10.30 10.25 10.20 10.15 10.10 10.05 10.00 9.95 9.90 9.85 9.80 9.75 -50 -25 0 25 50 75 125 100 150 i om (ma) 0 ?0.5 ?1.0 ?1.5 ?2.0 ?2.5 ?3.0 ?3.5 ?4.0 ?4.5 ?5.0 -50 -25 0 25 50 75 125 100 150 supply current versus supply voltage 10.9 10.8 10.7 10.6 10.5 10.4 10.3 10.2 10.1 10.0 4.5 4.6 4.8 4.7 4.9 5.0 5.3 5.1 5.2 5.4 5.5 v cc (v) i cc (ma) t a (c) v iout(q) (mv) 2520 2515 2510 2505 2500 2495 2490 2485 -50 -25 0 25 50 75 125 100 150 t a (c) i out(q) (a) 0.20 0.15 0.10 0.05 0 ?0.05 ?0.10 ?0.15 -50 -25 0 25 50 75 125 100 150 nonlinearity versus ambient temperature 0.6 0.5 0.4 0.3 0.2 0.1 0 ?50 0 ?25 25 50 125 75 100 150 e lin (%) t a (c) mean total output error versus ambient temperature 8 6 4 2 0 ?2 ?4 ?6 ?8 ?50 0 ?25 25 50 125 75 100 150 e tot (%) t a (c) sensitivity versus ambient temperature ?50 0 ?25 25 50 125 75 100 150 i p (a) output voltage versus sensed current 4.0 3.5 3.0 2.5 2.0 1.5 1.0 0.5 0 ?7 ?6 ?5 ?4 ?3 ?2 ?1 0 1 234567 v iout (v) magnetic offset versus ambient temperature v cc = 5 v 0 a output voltage versus ambient temperature 0 a output voltage current versus ambient temperature characteristic performance i p = 5 a, unless otherwise specified
fully integrated, hall effect-based linear current sensor ic with 2.1 kvrms isolation and a low-resistance current conductor ACS712 7 allegro microsystems, inc. 115 northeast cutoff worcester, massachusetts 01615-0036 u.s.a. 1.508.853.5000; www.allegromicro.com ?40 25 85 150 t a (c) ?40 25 ?20 85 125 t a (c) i p = 0 a i p = 0 a v cc = 5 v v cc = 5 v v cc = 5 v v cc = 5 v; i p = 0 a, after excursion to 20 a mean supply current versus ambient temperature sensitivity versus sensed current 110.00 108.00 106.00 104.00 102.00 100.00 98.00 96.00 94.00 92.00 90.00 sens (mv/a) ip (a) t a (c) t a (c) mean i cc (ma) 9.7 9.6 9.5 9.4 9.3 9.2 9.1 -50 -25 0 25 50 75 125 100 150 supply current versus supply voltage 10.4 10.2 10.0 9.8 9.6 9.4 9.2 9.0 v cc (v) i cc (ma) nonlinearity versus ambient temperature 0.35 0.30 0.25 0.20 0.15 0.10 0.05 0 ?50 0 ?25 25 50 125 75 100 150 e lin (%) t a (c) mean total output error versus ambient temperature 8 6 4 2 0 ?2 ?4 ?6 ?8 ?50 0 ?25 25 50 125 75 100 150 e tot (%) i p (a) output voltage versus sensed current 5.0 4.5 4.0 3.5 3.0 2.5 2.0 1.5 1.0 0.5 0 ?25 ?20 ?15 ?10 ?5 0 5 10152025 v iout (v) 4.5 4.6 4.8 4.7 4.9 5.0 5.3 5.15.2 5.45.5 ?25 ?20 ?15 ?10 ?5 0 51015 20 25 100.8 100.6 100.4 100.2 100.0 99.8 99.6 99.4 99.2 99.0 sens (mv/a) t a (c) sensitivity versus ambient temperature ?50 0 ?25 25 50 125 75 100 150 t a (c) i om (ma) 0 ?0.5 ?1.0 ?1.5 ?2.0 ?2.5 ?3.0 ?3.5 ?4.0 ?4.5 ?5.0 -50 -25 0 25 50 75 125 100 150 magnetic offset versus ambient temperature 0 a output voltage versus ambient temperature t a (c) v iout(q) (mv) 2525 2520 2515 2510 2505 2500 2495 2490 2485 -50 -25 0 25 50 75 125 100 150 0 a output voltage current versus ambient temperature t a (c) i out(q) (a) 0.25 0.20 0.15 0.10 0.05 0 ?0.05 ?0.10 ?0.15 -50 -25 0 25 50 75 125 100 150 characteristic performance i p = 20 a, unless otherwise specified
fully integrated, hall effect-based linear current sensor ic with 2.1 kvrms isolation and a low-resistance current conductor ACS712 8 allegro microsystems, inc. 115 northeast cutoff worcester, massachusetts 01615-0036 u.s.a. 1.508.853.5000; www.allegromicro.com characteristic performance i p = 30 a, unless otherwise specified ?40 25 85 150 t a (c) ?40 25 ?20 85 125 t a (c) i p = 0 a i p = 0 a v cc = 5 v v cc = 5 v v cc = 5 v v cc = 5 v; i p = 0 a, after excursion to 20 a v cc = 5 v mean supply current versus ambient temperature sensitivity versus sensed current 70.00 69.00 68.00 67.00 66.00 65.00 64.00 63.00 62.00 61.00 60.00 sens (mv/a) ip (a) t a (c) t a (c) mean i cc (ma) 9.6 9.5 9.4 9.3 9.2 9.1 9.0 8.9 -50 -25 0 25 50 75 125 100 150 supply current versus supply voltage 10.2 10.0 9.8 9.6 9.4 9.2 9.0 v cc (v) i cc (ma) nonlinearity versus ambient temperature 0.45 0.40 0.35 0.30 0.25 0.20 0.15 0.10 0.05 0 ?50 0 ?25 25 50 125 75 100 150 e lin (%) t a (c) mean total output error versus ambient temperature 8 6 4 2 0 ?2 ?4 ?6 ?8 ?50 0 ?25 25 50 125 75 100 150 e tot (%) i p (a) output voltage versus sensed current 5.0 4.5 4.0 3.5 3.0 2.5 2.0 1.5 1.0 0.5 0 ?30 ?20 ?10 0 10 20 30 v iout (v) 4.5 4.6 4.8 4.7 4.9 5.0 5.3 5.1 5.2 5.4 5.5 ?30 ?20 ?10 0 10 20 30 66.6 66.5 66.4 66.3 66.2 66.1 66.0 65.9 65.8 65.7 sens (mv/a) t a (c) sensitivity versus ambient temperature ?50 0 ?25 25 50 125 75 100 150 t a (c) i om (ma) 0 ?0.5 ?1.0 ?1.5 ?2.0 ?2.5 ?3.0 ?3.5 ?4.0 ?4.5 ?5.0 -50 -25 0 25 50 75 125 100 150 magnetic offset versus ambient temperature t a (c) v iout(q) (mv) 2535 2530 2525 2520 2515 2510 2505 2500 2495 2490 2485 -50 -25 0 25 50 75 125 100 150 t a (c) i out(q) (a) 0.35 0.30 0.25 0.20 0.15 0.10 0.05 0 ?0.05 ?0.10 ?0.15 -50 -25 0 25 50 75 125 100 150 0 a output voltage versus ambient temperature 0 a output voltage current versus ambient temperature
fully integrated, hall effect-based linear current sensor ic with 2.1 kvrms isolation and a low-resistance current conductor ACS712 9 allegro microsystems, inc. 115 northeast cutoff worcester, massachusetts 01615-0036 u.s.a. 1.508.853.5000; www.allegromicro.com sensitivity (sens). the change in device output in response to a 1 a change through the primary conductor. the sensitivity is the product of the magnetic circuit sensitivity (g / a) and the linear ic amplifier gain (mv/g). the linear ic amplifier gain is pro- grammed at the factory to optimize the sensitivity (mv/a) for the full-scale current of the device. noise (v noise ). the product of the linear ic amplifier gain (mv/g) and the noise floor for the allegro hall effect linear ic ( 1 g). the noise floor is derived from the thermal and shot noise observed in hall elements. dividing the noise (mv) by the sensitivity (mv/a) provides the smallest current that the device is able to resolve. linearity (e lin ). the degree to which the voltage output from the ic varies in direct proportion to the primary current through its full-scale amplitude. nonlinearity in the output can be attrib- uted to the saturation of the flux concentrator approaching the full-scale current. the following equation is used to derive the linearity: where v iout_full-scale amperes = the output voltage (v) when the sampled current approximates full-scale i p . symmetry (e sym ). the degree to which the absolute voltage output from the ic varies in proportion to either a positive or negative full-scale primary current. the following formula is used to derive symmetry: quiescent output voltage (v iout(q) ). the output of the device when the primary current is zero. for a unipolar supply voltage, it nominally remains at v cc 2. thus, v cc = 5 v translates into v iout(q) = 2.5 v. variation in v iout(q) can be attributed to the resolution of the allegro linear ic quiescent voltage trim and thermal drift. electrical offset voltage (v oe ). the deviation of the device out- put from its ideal quiescent value of v cc / 2 due to nonmagnetic causes. to convert this voltage to amperes, divide by the device sensitivity, sens. accuracy (e tot ). the accuracy represents the maximum devia- tion of the actual output from its ideal value. this is also known as the total output error. the accuracy is illustrated graphically in the output voltage versus current chart at right. accuracy is divided into four areas: ?? 0 a at 25c. accuracy at the zero current flow at 25c, with- out the effects of temperature. ?? 0 a over temperature. accuracy at the zero current flow including temperature effects. ?? full-scale current at 25c. accuracy at the the full-scale current at 25c, without the effects of temperature. ?? full-scale current over temperature. accuracy at the full- scale current flow including temperature effects. ratiometry . the ratiometric feature means that its 0 a output, v iout(q) , (nominally equal to v cc /2) and sensitivity, sens, are proportional to its supply voltage, v cc . the following formula is used to derive the ratiometric change in 0 a output voltage, ? v iout(q)rat (%). the ratiometric change in sensitivity, ? sens rat (%), is defined as: definitions of accuracy characteristics 100 1? [ { [ { v iout _full-scale amperes ? v iout(q) gain % sat ( ) 2 ( v iout _half-scale amperes ? v iout(q) ) 100 v iout _+ full-scale amperes ? v iout(q) v iout(q) ? v iout _?full-scale amperes ?? 100 v iout(q)vcc / v iout(q)5v v cc / 5 v ?? 100 sens vcc / sens 5v v cc / 5 v output voltage versus sampled current accuracy at 0 a and at full-scale current increasing v iout (v) +i p (a) accuracy accuracy accuracy 25c only accuracy 25c only accuracy 25c only accuracy 0 a vr oe $ temp erature average v iout ?i p (a) vr oe $ temp erature vr oe $ temp erature decreasing v iout (v) i p (min) i p (max) full scale
fully integrated, hall effect-based linear current sensor ic with 2.1 kvrms isolation and a low-resistance current conductor ACS712 10 allegro microsystems, inc. 115 northeast cutoff worcester, massachusetts 01615-0036 u.s.a. 1.508.853.5000; www.allegromicro.com power on time versus external filter capacitance 0 20 40 60 80 100 120 140 160 180 200 01020304050 c f (nf) c f (nf) t po ( s) i p = 5 a i p = 0 a noise versus external filter capacitance 1 1000 10 100 10000 0.01 0.1 1 10 100 1000 noise (p-p) (ma) noise vs. filter cap 400 350 300 250 200 150 100 50 0 050 25 75 100 125 150 t r ( s) c f (nf) rise time versus external filter capacitance rise time versus external filter capacitance 0 200 400 600 800 1000 1200 0 100 200 300 400 500 t r ( s) c f (nf) expanded in chart at right } definitions of dynamic response characteristics primary current transducer output 90 10 0 i (%) rise time, t r t rise time (t r ). the time interval between a) when the device reaches 10% of its full scale value, and b) when it reaches 90% of its full scale value. the rise time to a step response is used to derive the bandwidth of the device, in which ?(?3 db) = 0.35 / t r . both t r and t response are detrimentally affected by eddy current losses observed in the conductive ic ground plane. excitation signal output (mv) 15 a step response t a =25c c f (nf) t r ( s) 0 6.6 1 7.7 4.7 17.4 10 32.1 22 68.2 47 88.2 100 291.3 220 623.0 470 1120.0 power-on time (t po ). when the supply is ramped to its operat- ing voltage, the device requires a finite time to power its internal components before responding to an input magnetic field. power-on time, t po , is defined as the time it takes for the output voltage to settle within 10% of its steady state value under an applied magnetic field, after the power supply has reached its minimum specified operating voltage, v cc (min), as shown in the chart at right.
fully integrated, hall effect-based linear current sensor ic with 2.1 kvrms isolation and a low-resistance current conductor ACS712 11 allegro microsystems, inc. 115 northeast cutoff worcester, massachusetts 01615-0036 u.s.a. 1.508.853.5000; www.allegromicro.com chopper stabilization is an innovative circuit technique that is used to minimize the offset voltage of a hall element and an asso- ciated on-chip amplifier. allegro patented a chopper stabiliza- tion technique that nearly eliminates hall ic output drift induced by temperature or package stress effects. this offset reduction technique is based on a signal modulation-demodulation process. modulation is used to separate the undesired dc offset signal from the magnetically induced signal in the frequency domain. then, using a low-pass filter, the modulated dc offset is sup- pressed while the magnetically induced signal passes through the filter. as a result of this chopper stabilization approach, the output voltage from the hall ic is desensitized to the effects of temperature and mechanical stress. this technique produces devices that have an extremely stable electrical offset voltage, are immune to thermal stress, and have precise recoverability after temperature cycling. this technique is made possible through the use of a bicmos process that allows the use of low-offset and low-noise amplifiers in combination with high-density logic integration and sample and hold circuits. chopper stabilization technique amp regulator clock/logic hall element sample and hold low-pass filter concept of chopper stabilization technique
fully integrated, hall effect-based linear current sensor ic with 2.1 kvrms isolation and a low-resistance current conductor ACS712 12 allegro microsystems, inc. 115 northeast cutoff worcester, massachusetts 01615-0036 u.s.a. 1.508.853.5000; www.allegromicro.com + C ip+ ip+ ipC ipC i p 7 5 5 8 +5 v u1 lmv7235 viout v out gnd 6 2 4 4 1 1 2 3 3 filter vcc ACS712 d1 1n914 r2 100 k r1 33 k r pu 100 k fault c byp 0.1 f c f 1 nf + C ip+ ip+ ipC ipC 7 5 8 +5 v u1 lt1178 q1 2n7002 viout v out v peak v reset gnd 6 2 4 1 3 d1 1n914 vcc ACS712 r4 10 k r1 1 m r2 33 k r f 10 k r3 330 k c byp 0.1 f c1 0.1 f c out 0.1 f c f 1 nf c2 0.1 f filter i p ip+ ip+ ipC ipC i p 7 5 8 +5 v d1 1n4448w viout v out gnd 6 2 4 1 3 filter vcc ACS712 r1 10 k c byp 0.1 f r f 2 k c f 1 nf c1 a-to-d converter typical applications application 5. 10 a overcurrent fault latch. fault threshold set by r1 and r2. this circuit latches an overcurrent fault and holds it until the 5 v rail is powered down. application 2. peak detecting circuit application 4. rectified output. 3.3 v scaling and rectification application for a-to-d converters. replaces current transformer solutions with simpler acs circuit. c1 is a function of the load resistance and filtering desired. r1 can be omitted if the full range is desired. + C ip+ ip+ ipC ipC i p 7 5 5 8 +5 v lm321 viout v out gnd 6 2 4 1 1 4 2 3 3 filter vcc ACS712 r2 100 k r1 100 k r3 3.3 k c byp 0.1 f c f 0.01 f c1 1000 pf r f 1 k application 3. this configuration increases gain to 610 mv/a (tested using the ACS712elc-05a).
fully integrated, hall effect-based linear current sensor ic with 2.1 kvrms isolation and a low-resistance current conductor ACS712 13 allegro microsystems, inc. 115 northeast cutoff worcester, massachusetts 01615-0036 u.s.a. 1.508.853.5000; www.allegromicro.com improving sensing system accuracy using the filter pin in low-frequency sensing applications, it is often advantageous to add a simple rc filter to the output of the device. such a low- pass filter improves the signal-to-noise ratio, and therefore the resolution, of the device output signal. however, the addition of an rc filter to the output of a sensor ic can result in undesirable device output attenuation ? even for dc signals. signal attenuation, ? v at t , is a result of the resistive divider effect between the resistance of the external filter, r f (see application 6), and the input impedance and resistance of the customer interface circuit, r intfc . the transfer function of this resistive divider is given by: even if r f and r intfc are designed to match, the two individual resistance values will most likely drift by different amounts over temperature. therefore, signal attenuation will vary as a function of temperature. note that, in many cases, the input impedance, r intfc , of a typical analog-to-digital converter (adc) can be as low as 10 k . the ACS712 contains an internal resistor, a filter pin connec- tion to the printed circuit board, and an internal buffer amplifier. with this circuit architecture, users can implement a simple rc filter via the addition of a capacitor, c f (see application 7) from the filter pin to ground. the buffer amplifier inside of the ACS712 (located after the internal resistor and filter pin connection) eliminates the attenuation caused by the resistive divider effect described in the equation for ? v at t . therefore, the ACS712 device is ideal for use in high-accuracy applications that cannot afford the signal attenuation associated with the use of an external rc low-pass filter. = ? v at t r intfc r f + r intfc v iout ? ? ? ? ? ? ? . application 6. when a low pass filter is constructed externally to a standard hall effect device, a resistive divider may exist between the filter resistor, r f, and the resistance of the customer interface circuit, r intfc . this resistive divider will cause excessive attenuation, as given by the transfer function for ? v att . application 7. using the filter pin provided on the ACS712 eliminates the attenuation effects of the resistor divider between r f and r intfc , shown in appli- cation 6. application interface circuit resistive divider r intfc low pass filter r f amp out vcc +5 v pin 8 pin 7 viout pin 6 n.c. input gnd pin 5 filter dynamic offset cancellation ip+ ip+ 0.1 m f pin 1 pin 2 ip? ip? pin 3 pin 4 gain temperature coefficient offset voltage regulator trim control to all subcircuits input vcc pin 8 pin 7 viout gnd pin 5 filter pin 6 dynamic offset cancellation ip+ pin 1 ip+ pin 2 ip? pin 3 ip? pin 4 sense trim signal recovery sense temperature coefficient trim 0 ampere offset adjust hall current drive +5 v application interface circuit buffer amplifier and resistor r intfc allegro ACS712 allegro acs706 c f 1 nf c f 1 nf
fully integrated, hall effect-based linear current sensor ic with 2.1 kvrms isolation and a low-resistance current conductor ACS712 14 allegro microsystems, inc. 115 northeast cutoff worcester, massachusetts 01615-0036 u.s.a. 1.508.853.5000; www.allegromicro.com package lc, 8-pin soic copyright ?2006-2010, allegro microsystems, inc. the products described herein are protected by u.s. patents: 5,621,319; 7,598,601; and patent pending. allegro microsystems, inc. reserves the right to make, from time to time, such de par tures from the detail spec i fi ca tions as may be required to per- mit improvements in the per for mance, 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?s products are not to be used in life support devices or systems, if a failure of an allegro product can reasonably be expected to cause the failure of that life support device or system, or to affect the safety or effectiveness of that device or system. the in for ma tion in clud ed herein is believed to be ac cu rate and reliable. how ev er, allegro microsystems, inc. assumes no re spon si bil i ty for its use; nor for any in fringe ment of patents or other rights of third parties which may result from its use. for the latest version of this document, visit our website: www.allegromicro.com c seating plane 1.27 bsc gauge plane seating plane a terminal #1 mark area b reference land pattern layout (reference ipc7351 soic127p600x175-8m); all pads a minimum of 0.20 mm from all adjacent pads; adjust as necessary to meet application process requirements and pcb layout tolerances b d c 2 1 8 branding scale and appearance at supplier discretion c seating plane c 0.10 8x 0.25 bsc 1.04 ref 1.75 max for reference only; not for tooling use (reference ms-012aa) dimensions in millimeters dimensions exclusive of mold flash, gate burrs, and dambar protrusions exact case and lead configuration at supplier discretion within limits shown 4.90 0.10 3.90 0.10 6.00 0.20 0.51 0.31 0.25 0.10 0.25 0.17 1.27 0.40 8 0 n = device part number p = package designator t = device temperature range a = amperage l = lot number belly brand = country of origin nnnnnnn lllll 1 ppt-aaa a standard branding reference view 2 1 8 pcb layout reference view c 0.65 1.27 5.60 1.75 branded face

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