View ACS712_3415828.PDF datasheet online --- IC-ON-LINE

Datasheet File OCR Text:

approximate scale 1:1 application 1. the ACS712 outputs an analog signal, v out . that varies linearly with the uni- or bi-directional ac or dc primary sensed 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, automotive, commercial, and communications systems. the device package allows for easy implementation by the customer. typical applications include motor control, load detection and management, switched-mode power supplies, and overcurrent fault protection. the device consists of a precise, low-offset, linear hall sensor 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 is sensed by the integrated hall ic and converted 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 sensing. the internal resistance of this conductive path is 1.2 m typical, providing low power ACS712-ds, rev.1 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 ? 50 khz bandwidth ? total output error 1.5% at t a = 25c, and 4% at ?40c to 85c ? small footprint, low-profile soic8 package ? 1.2 m internal conductor resistance ? 2.1 kv rms 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 with 2.1 kvrms voltage isolation and a low-resistance current conductor continued on the next page? package: 8 pin soic (suffix lc) typical application 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
fully integrated, hall effect-based linear current sensor with 2.1 kvrms voltage isolation and a low-resistance current conductor ACS712 2 allegro microsystems, inc. 115 northeast cutoff, box 15036 worcester, massachusetts 01615-0036 (508) 853-5000 www.allegromicro.com selection guide part number packing* t op (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. loss. the thickness of the copper conductor allows survival of the device at up to 5 overcurrent conditions. the terminals of the conductive path are electrically isolated from the sensor leads (pins 5 through 8). this allows the ACS712 current sensor 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) 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 output current source i iout(source) 3ma output current sink i iout(sink) 10 ma overcurrent transient tolerance i p 100 total pulses, 250 ms duration each, applied at a rate of 1 pulse every 100 seconds. 60 a maximum transient sensed current i r (max) junction temperature, t j < t j (max) 60 a nominal operating ambient temperature t a range e ?40 to 85 oc maximum junction t j (max) 165 oc storage temperature t stg ?65 to 170 oc tv america certificate number: u8v 06 05 54214 010 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 with 2.1 kvrms voltage isolation and a low-resistance current conductor ACS712 3 allegro microsystems, inc. 115 northeast cutoff, box 15036 worcester, massachusetts 01615-0036 (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 sensed; fused internally 3 and 4 ip? terminals for current being sensed; 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 with 2.1 kvrms voltage isolation and a low-resistance current conductor ACS712 4 allegro microsystems, inc. 115 northeast cutoff, box 15036 worcester, massachusetts 01615-0036 (508) 853-5000 www.allegromicro.com common operating characteristics 1 over full range of t op , 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 6 8 11 ma output zener clamp voltage v z i cc = 11 ma, t a = 25c 6 8.3 ? v output resistance r iout i iout = 1.2 ma, t a =25c ? 1 2 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 rms isolation voltage v isorms pins 1-4 and 5-8; 60 hz, 1 minute, t a =25c 2100 ? ? v dc isolation voltage v isodc pins 1-4 and 5-8; 1 minute, t a =25c ? 5000 ? v propagation time t prop i p = i p (max), t a = 25c, c out = open ? 3 ? s response time t response i p = i p (max), t a = 25c, c out = open ? 7 ? s 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 50 ? ? khz nonlinearity e lin over full range of i p ? 1 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 magnetic offset error v errom i p = 0 a, after excursion of 5 a ? 0 ? mv clamping voltage v ch typ. ?110 v cc 0.9375 typ. +110 mv v cl typ. ?110 v cc 0.0625 typ. +110 mv 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 op , 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 op 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 with 2.1 kvrms voltage isolation and a low-resistance current conductor ACS712 5 allegro microsystems, inc. 115 northeast cutoff, box 15036 worcester, massachusetts 01615-0036 (508) 853-5000 www.allegromicro.com x05a performance characteristics t op = ?40c to 85c 1 , 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 2 sens ta over full range of i p, t a = 25c ? 185 ? mv/a sens top over full range of i p 178 ? 193 mv/a noise v noise(pp) peak-to-peak, t a = 25c, 185 mv/a programmed sensitivity, c f = 4.7 nf, c out = open, 20 khz bandwidth ?45 ?mv peak-to-peak, t a = 25c, 185 mv/a programmed sensitivity, c f = 47 nf, c out = open, 2 khz bandwidth ?20 ?mv peak-to-peak, t a = 25c, 185 mv/a programmed sensitivity, c f = 1 nf, c out = open, 50 khz bandwidth ?75 ?mv electrical offset voltage v oe i p = 0 a ?40 ? 40 mv total output error 3 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 op , provided that the maximum junction temperature, t j(max) , is not exceeded. 2 at ?40c sensitivity may shift as much 9% outside of the datasheet limits. 3 percentage of i p , with i p = 5 a. output filtered. x20a performance characteristics t op = ?40c to 85c 1 , 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 2 sens ta over full range of i p, t a = 25c ? 100 ? mv/a sens top over full range of i p 97 ? 103 mv/a noise v noise(pp) peak-to-peak, t a = 25c, 100 mv/a programmed sensitivity, c f = 4.7 nf, c out = open, 20 khz bandwidth ?24 ?mv peak-to-peak, t a = 25c, 100 mv/a programmed sensitivity, c f = 47 nf, c out = open, 2 khz bandwidth ?10 ?mv peak-to-peak, t a = 25c, 100 mv/a programmed sensitivity, c f = 1 nf, c out = open, 50 khz bandwidth ?40 ?mv electrical offset voltage v oe i p = 0 a ?30 ? 30 mv total output error 3 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 op , provided that the maximum junction temperature, t j (max), is not exceeded. 2 at ?40c sensitivity may shift as much 9% outside of the datasheet limits. 3 percentage of i p , with i p = 20 a. output filtered. x30a performance characteristics t op = ?40c to 85c 1 , 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 2 sens ta over full range of i p , t a = 25c ? 66 ? mv/a sens top over full range of i p 64 ? 68 mv/a noise v noise(pp) peak-to-peak, t a = 25c, 66 mv/a programmed sensitivity, c f = 4.7 nf, c out = open, 20 khz bandwidth ?20 ?mv peak-to-peak, t a = 25c, 66 mv/a programmed sensitivity, c f = 47 nf, c out = open, 2 khz bandwidth ?7 ?mv peak-to-peak, t a = 25c, 66 mv/a programmed sensitivity, c f = 1 nf, c out = open, 50 khz bandwidth ?35 ?mv electrical offset voltage v oe i p = 0 a ?30 ? 30 mv total output error 3 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 op , provided that the maximum junction temperature, t j (max), is not exceeded. 2 at ?40c sensitivity may shift as much 9% outside of the datasheet limits. 3 percentage of i p , with i p = 30 a. output filtered.
fully integrated, hall effect-based linear current sensor with 2.1 kvrms voltage isolation and a low-resistance current conductor ACS712 6 allegro microsystems, inc. 115 northeast cutoff, box 15036 worcester, massachusetts 01615-0036 (508) 853-5000 www.allegromicro.com characteristic performance i p = 5 a, sens = 185 mv/a unless otherwise specified 6.0 6.5 7.0 7.5 8.0 8.5 9.0 9.5 10.0 -50 0 50 100 150 200 t a (c) t a (c) mean i cc (ma) v errom (mv) v iout (v) 8.5 8.7 8.9 9.1 9.3 9.5 9.7 9.9 10.1 10.3 10.5 4.5 4.6 4.7 4.8 4.9 5 5.1 5.2 5.3 5.4 5.5 v cc (v) i cc (ma) e lin (%) t a (c) -50 0 50 100 150 200 0 0.25 0.50 0.75 1.00 1.25 1.50 1.75 2.00 -50 0 50 100 150 200 0 0.2 0.4 0.6 0.8 1.0 1.2 1.4 1.6 1.8 2.0 t a (c) mean e tot (%) -15.0 -10.0 -5.0 0.0 5.0 10.0 15.0 -50 0 50 100 150 200 0 0.5 1.0 1.5 2.0 2.5 3.0 3.5 4.0 4.5 -10-8-6-4-20246810 ip (a) ip (a) 176.0 178.0 180.0 182.0 184.0 186.0 188.0 -10 -8 -6 -4 -2 0 2 4 6 8 10 sens (mv/a) -40 25 85 150 t a (c) -40 25 85 t a (c) mean supply current versus ambient temperature v cc = 5 v supply current versus supply voltage magnetic offset versus ambient temperature nonlinearity versus ambient temperature i p = 10 a mean total output error versus ambient temperature i p = 10 a output voltage versus sensed current sensitivity versus sensed current
fully integrated, hall effect-based linear current sensor with 2.1 kvrms voltage isolation and a low-resistance current conductor ACS712 7 allegro microsystems, inc. 115 northeast cutoff, box 15036 worcester, massachusetts 01615-0036 (508) 853-5000 www.allegromicro.com -50 0 50 100 150 200 t a (c) t a (c) mean i cc (ma) v errom (mv) v iout (v) 8.5 8.7 8.9 9.1 9.3 9.5 9.7 9.9 10.1 10.3 10.5 4.5 4.6 4.7 4.8 4.9 5 5.1 5.2 5.3 5.4 5.5 v cc (v) i cc (ma) e lin (%) t a (c) -50 0 50 100 150 200 0 0.20 0.40 0.60 0.80 1.00 -50 0 50 100 150 200 0 0.2 0.4 0.6 0.8 1.0 1.2 1.4 1.6 1.8 2.0 t a (c) mean e tot (%) -5.0 -3.0 -2.0 -4.0 -1.0 0.0 1.0 2.0 3.0 4.0 5.0 -50 0 50 100 150 200 0 0.5 1.0 1.5 2.0 2.5 3.0 3.5 4.0 4.5 -30 -20 -10 0 10 20 30 -30 -20 -10 0 10 20 30 ip (a) ip (a) 50.0 55.0 60.0 65.0 70.0 75.0 sens (mv/a) -40 25 85 150 t a (c) -40 25 85 t a (c) 6.0 6.5 7.0 7.5 8.0 8.5 9.0 9.5 10.0 mean supply current versus ambient temperature v cc = 5 v supply current versus supply voltage magnetic offset current versus ambient temperature nonlinearity versus ambient temperature mean total output error versus ambient temperature output voltage versus sensed current sensitivity versus sensed current characteristic performance i p = 30 a, sens = 66 mv/a unless otherwise specified
fully integrated, hall effect-based linear current sensor with 2.1 kvrms voltage isolation and a low-resistance current conductor ACS712 8 allegro microsystems, inc. 115 northeast cutoff, box 15036 worcester, massachusetts 01615-0036 (508) 853-5000 www.allegromicro.com sensitivity (sens). the change in sensor 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 sensor varies in direct proportion to the primary current through its full-scale amplitude. nonlinearity in the output can be attributed 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 sensed current approximates full-scale i p . symmetry (e sym ). the degree to which the absolute voltage output from the sensor 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 sensor 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 ouput 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 of sensing zero current flow at 25c, without the effects of temperature. ? 0 a over temperature. accuracy of sensing zero current flow including temperature effects. ? full-scale current at 25c. accuracy of sensing the full-scale current at 25c, without the effects of temperature. ? full-scale current over temperature. accuracy of sensing 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 sensed 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 with 2.1 kvrms voltage isolation and a low-resistance current conductor ACS712 9 allegro microsystems, inc. 115 northeast cutoff, box 15036 worcester, massachusetts 01615-0036 (508) 853-5000 www.allegromicro.com rise time versus external filter capacitance 0 200 400 600 800 1000 1200 0 100 200 300 400 500 t r ( s) 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) c f (nf) expanded in chart at right rise time versus external filter capacitance 0 150 200 250 300 350 400 0 50 75 100 125 150 t r ( s) 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 definitions of dynamic response characteristics propagation delay (t prop ). the time required for the sensor output to reflect a change in the primary current signal. propaga- tion delay is attributed to inductive loading within the linear ic package, as well as in the inductive loop formed by the primary conductor geometry. propagation delay can be considered as a fixed time offset and may be compensated. primary current transducer output 90 0 i (%) propagation time, t prop t primary current transducer output 90 0 i (%) response time, t response t primary current transducer output 90 10 0 i (%) rise time, t r t rise time (t r ). the time interval between a) when the sensor 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 current sensor, 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. response time (t response ). the time interval between a) when the primary current signal reaches 90% of its final value, and b) when the sensor reaches 90% of its output corresponding to the applied current. 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
fully integrated, hall effect-based linear current sensor with 2.1 kvrms voltage isolation and a low-resistance current conductor ACS712 10 allegro microsystems, inc. 115 northeast cutoff, box 15036 worcester, massachusetts 01615-0036 (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 suppressed 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 tempera- ture 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 + 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 with 2.1 kvrms voltage isolation and a low-resistance current conductor ACS712 11 allegro microsystems, inc. 115 northeast cutoff, box 15036 worcester, massachusetts 01615-0036 (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 sensor. such a low- pass filter improves the signal-to-noise ratio, and therefore the resolution, of the sensor output signal. however, the addition of an rc filter to the output of a sensor ic can result in undesirable sensor 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 with 2.1 kvrms voltage isolation and a low-resistance current conductor ACS712 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 de par tures from the detail spec i fi ca tions as may be required to permit 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. 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. copyright ?2006, allegro microsystems, inc. 0.25 0.10 .010 .004 1.75 1.35 .069 .053 0.51 0.31 .020 .012 4.00 3.80 .157 .150 0.25 0.17 .010 .007 8o 0o 1.27 0.40 .050 .016 5.00 4.80 .197 .189 c seating plane a b 8x 0.25 [.010] m c a b 6.20 5.80 .244 .228 c 0.10 [.004] 8x 0.25 [.010] m b m 1.27 .050 0.25 .010 2 1 8 gauge plane seating plane preliminary dimensions, for reference only dimensions in millimeters u.s. customary dimensions (in.) in brackets, for reference only (reference jedec ms-012 aa) dimensions exclusive of mold flash, gate burrs, and dambar protrusions exact case and lead configuration at supplier discretion within limits shown a terminal #1 mark area a package lc, 8-pin soic ACS712t r lc ppp yywwa acs allegro current sensor 712 device family number t indicator of 100% matte tin leadframe plating r operating ambient temperature range code lc package type designator ppp primary sensed current yy date code: calendar year (last two digits) ww date code: calendar week a date code: shift code ACS712t r lc ppp l...l yyww acs allegro current sensor 712 device family number t indicator of 100% matte tin leadframe plating r operating ambient temperature range code lc package type designator ppp primary sensed current l...l lot code yy date code: calendar year (last two digits) ww date code: calendar week package branding two alternative patterns are used text 1 text 2 text 3 1 2 3 4 8 7 6 5 for the latest version of this document, go to our website at: www.allegromicro.com

▲Up To Search▲

Price & Availability of ACS712

	To Download ACS712 Datasheet File
If you can't view the Datasheet, Please click here to try to view without PDF Reader .