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max34406 quad current-sense amplifier with overcurrent threshold comparators _________________________________________________________________ maxim integrated products 1 general description the max34406 is a quad, high-side, unidirectional, cur - rent-sense amplifier that offers precision accuracy. it provides analog outputs for each of the four amplifiers that can be routed to an external adc, and contains four overcurrent comparators with a fixed 1.0v threshold. all four comparators are logically ored, and the result can be delayed/filtered with an external capacitor before it is fed to a latched common shutdown open-drain output pin. applications network switches/routersbase stations servers smart grid network systems industrial controls features s four precision current-sense amplifiers s fixed gains of 25v/v, 50v/v, 100v/v, and 200v/v s less than 600v of input offset s less than 0.6% of gain error (t/f/h) or 0.8% of gain error (w) s wide 2.0v to 28v common mode range s analog voltage outputs for each amplifier s independent overcurrent comparators with fixed 1.0v threshold s low power consumption s -40 n c to +85 n c temperature range s small 24-pin tqfn (4mm x 4mm) package block diagram 19-5930; rev 1; 1/12 ordering information appears at end of data sheet. for related parts and recommended products to use with this part, refer to: www.maxim-ic.com/max34406.related evaluation kit available amplifier 4 v dd ena cdly ocx gnd outx inx+ inx- shtdn amplifier 3 amplifier 2 amplifier 1 max34406 p n n n r1 4 r out r1 6v clamp or 5a or por 1.0v reference clrd ck latch threshold = v dd x 50% q 4 4 4 for pricing, delivery, and ordering information, please contact maxim direct at 1-888-629-4642, or visit maxim?s website at www.maxim-ic.com. downloaded from: http:///
_________________________________________________________________ maxim integrated products 2 max34406 quad current-sense amplifier with overcurrent threshold comparators voltage range on inx+ and inx- relative to gnd ................................................. -0.3v to +30v voltage range on v dd relative to gnd ................. -0.3v to +6v voltage range on remaining pins relative to gnd .................................... -0.3v to (v dd + 0.3v) continuous power dissipation (t a = +70 n c) tqfn (derate 27.8mw/ n c above +70 n c)...............2222.2mw out1, out2, out3, out4 short circuit to gnd .... continuous operating junction temperature range ........... -40 n c to +85 n c storage temperature range ............................ -55 n c to +125 n c lead temperature (soldering, 10s) ................................ +300 n c soldering temperature (reflow) ...................................... +260 n c absolute maximum ratingsstresses beyond those listed under ?absolute maximum ratings? may cause permanent damage to the device. these are stress ratings only, and functional opera - tion of the device at these or any other conditions beyond those indicated in the operational sections of the specifications is not implied. exposure to absolute maximum rating conditions for extended periods may affect device reliability. electrical characteristics (v inx+ = v inx- = 12v, v sense = 0v, t a = -40 n c to +85 n c, unless otherwise noted. typical values are t a = +25 n c) (note 1) parameter symbol conditions min typ max units v dd operating range v dd 2.7 5.5 v v dd supply current i dd (note 2) 200 f a common-mode input range v cm guaranteed by cmrr 2.0 28 v common-mode rejection ratio cmrr v inx+ > 2.0v at t a = +25 n c 86 120 db input offset voltage v os (note 3) q 100 q 600 f v gain (0.5v < v outx < 1.5v) g max34406t 25 v/v max34406f 50 max34406h 100 max34406w 200 gain error ge max34406t/f/h (note 4) q 0.6 % max34406w q 0.8 outx output resistance r outx max34406t/f/h (note 5) 10 k max34406w 20 outx low voltage v ol max34406t 15 mv max34406f 30 max34406h 60 max34406w 120 bandwidth bw max34406t v outx = 2.0v (note 5) 125 khz max34406f 60 max34406h 30 max34406w 15 ena input logic-high v ih v dd x 0.7 v dd + 0.3 v ena input logic-low v il v gnd - 0.3 v dd x 0.3 v ena input leakage q 1 f a output logic-low (shtdn, ocx) v ol i ol = 2ma 0.3 v downloaded from: http:///
_________________________________________________________________ maxim integrated products 3 max34406 quad current-sense amplifier with overcurrent threshold comparators note 1: all devices are 100% production tested at t a = +25 n c. all temperature limits are guaranteed by design. note 2: v out1 , v out2 , v out3 , v out4 = 0v. all open-drain outputs left disconnected. note 3: v os is extrapolated from measurements for the gain-error test. note 4: gain error is calculated by applying two values of v sense and calculating the error of the slope vs. the ideal: gain = 100, v sense is 5mv and 15mv. note 5: the device is stable for any external capacitance value. electrical characteristics ( continued) (v inx+ = v inx- = 12v, v sense = 0v, t a = -40 n c to +85 n c, unless otherwise noted. typical values are t a = +25 n c) (note 1)x typical operating characteristics (v inx+ = v inx- = 12v, t a = +25c, unless otherwise noted.) parameter symbol conditions min typ max units output leakage (shtdn, ocx) i o q 1 f a comparator threshold v th 0.98 1.00 1.02 v comparator offset v cos q 5 mv comparator hysteresis v hys 20 mv comparator propagation delay t d overdrive = q 50mv, output load = 2ma 3 f s shtdn delay t dly v dd = 3.3v, c cdly = 10nf 3.3 ms v dd = 3.3v, c cdly = 22nf 7.3 v dd = 3.3v, c cdly = 33nf 11 v dd = 5.0v, c cdly = 10nf 5 v dd = 5.0v, c cdly = 22nf 11 v dd = 5.0v, c cdly = 33nf 16 +25c input offset max34406 toc01 offset (v) % of population (%) 100 50 -50 0 -100 -150 2 4 6 8 10 12 14 16 18 20 0 -200 150 +25c gain error max34406 toc02 gain error (%) % of population (%) 0.35 0.30 0.25 0.20 0.15 0.10 0.05 0 -0.05 -0.10 5 10 15 20 25 0 -0.15 0.40 v ol vs. i ol max34406 toc03 current in (ma) voltage (mv) 1.8 1.6 0.4 0.6 0.8 1.2 1.0 1.4 20 40 60 80 100 120 140 160 0 0.2 2.0 shtdn oc1 downloaded from: http:///
_________________________________________________________________ maxim integrated products 4 max34406 quad current-sense amplifier with overcurrent threshold comparators typical operating characteristics (continued) ((v inx+ = v inx- = 12v, t a = +25c, unless otherwise noted.) shtdn delay vs. temperature max34406 toc12 temperature (c) shtdn delay (ms) 60 35 -15 10 0.5 1.0 1.5 2.0 3.02.5 3.5 4.0 0 -45 85 c cdly = 10nf comparator threshold vs. temperature max34406 toc11 temperature (c) threshold (v) 60 35 10 -15 0.96 0.97 0.98 0.99 1.00 1.01 1.02 1.03 1.04 1.050.95 -40 85 large-signal pulse response (gain = 100) max34406 toc10 20s/div 25mv5mv 2.5v 0.5v v sense v outx small-signal pulse response (gain = 100) max34406 toc09 20s/div 10mv5mv 1.0v 0.5v v sense v outx small-signal gain vs. frequency (gain = 100) max34406 toc08 frequency (khz) gain (db) 100 10 5 10 15 20 25 30 35 40 45 50 0 1 1000 gain error vs. temperature max34406 toc07 temperature (c) gain error (%) 60 35 10 -15 0.1 0.2 0.3 0.4 0.5 0 -40 85 gain error vs. common-mode voltage max34406 toc06 common-mode voltage (v) gain error (%) 25 20 15 10 5 0 0.1 0.2 0.3 0.4 0.5 -0.1 03 0 input offset vs. temperature max34406 toc05 temperature (c) input offset (v) 60 35 10 -15 -50 -40 -30 -20 -10 0 -60 -40 85 input offset vs. common-mode voltage max34406 toc04 common-mode voltage (v) input offset (v) 25 20 15 10 5 -20 -10 0 10 20 30 -30 03 0 downloaded from: http:///
_________________________________________________________________ maxim integrated products 5 max34406 quad current-sense amplifier with overcurrent threshold comparators pin configuration pin description pin name function 1 in1+ external sense resistor power-side connection for amplifier 1. bias at this pin also provides the supply voltage for amplifier 1. this pin can be left open circuit if not needed. 2 in1- external sense resistor load-side connection for amplifier 1 3 out1 output voltage from amplifier 1 proportional to v sense . this output is clamped at 6v. 4 out2 output voltage from amplifier 2 proportional to v sense . this output is clamped at 6v. 5 in2- external sense resistor load-side connection for amplifier 2 6 in2+ external sense resistor power-side connection for amplifier 2. bias at this pin also provides the supply voltage for amplifier 2. this pin can be left open circuit if not needed. 7, 8, 23 n.c. no connection. not internally connected. 9 oc1 overcurrent threshold comparator associated with amplifier 1. open-drain output. this output transitions to high impedance during an overcurrent event. 10 oc2 overcurrent threshold comparator associated with amplifier 2. open-drain output. this output transitions to high impedance during an overcurrent event. 11 oc3 overcurrent threshold comparator associated with amplifier 3. open-drain output. this output transitions to high impedance during an overcurrent event. 12 oc4 overcurrent threshold comparator associated with amplifier 4. open-drain output. this output transitions to high impedance during an overcurrent event. 13 in3+ external sense resistor power-side connection for amplifier 3. bias at this pin also provides the supply voltage for amplifier 3. this pin can be left open circuit if not needed. 2324 22 21 87 9 in1- out2 in2- in2+ 10 in1+ in4-out3 in3- in4+in3+ 12 cdly 45 6 17 18 16 14 13 n.c. ep gnd oc2oc1 n.c. n.c. out1 out4 3 15 shtdn 20 11 oc3 ena 19 12 oc4 v dd tqfn (4mm x 4mm) top view + max34406 downloaded from: http:///
_________________________________________________________________ maxim integrated products 6 max34406 quad current-sense amplifier with overcurrent threshold comparators pin description (continued) pin name function 14 in3- external sense resistor load-side connection for amplifier 3 15 out3 output voltage from amplifier 3 proportional to v sense . this output is clamped at 6v. 16 out4 output voltage from amplifier 4 proportional to v sense . this output is clamped at 6v. 17 in4- external sense resistor load-side connection for amplifier 4 18 in4+ external sense resistor power-side connection for amplifier 4. bias at this pin also provides the supply voltage for amplifier 4. this pin can be left open circuit if not needed. 19 v dd supply voltage for reference, comparators, and logic. a +2.7v to +5.5v supply. this pin should be decoupled to gnd with a 100nf ceramic capacitor. 20 ena shtdn enable input. cmos digital input. connect to gnd to clear the latch and unconditionally deassert (force low) the shtdn output. connect to v dd to enable normal latch operation of the shtdn output. ena should be toggled low once v dd reaches nominal operating voltage. 21 shtdn shutdown output. open-drain output. this output transitions to high impedance when any of the four overcurrent comparator outputs (oc1 to oc4) are asserted (high impedance) as long as the ena pin is high. toggling the ena pin allows shtdn to reset to logic-low. 22 cdly shutdown delay capacitor. a capacitor (c cdly ) from this pin to gnd delays the transition of the shtdn pin. the delay time can be calculated by the following formula: t dly = c cdly x (v dd /10 f a). the capacitor connected to cdly is discharged when ena is low and upon v dd being applied (i.e., at power- on reset), and also any time all ocx outputs are low (i.e., inactive). if the shutdown delay is not required, this pin can be left unconnected. 24 gnd ground reference ? ep exposed pad. connect to ground or leave unconnected. downloaded from: http:///
_________________________________________________________________ maxim integrated products 7 max34406 quad current-sense amplifier with overcurrent threshold comparators typical application circuit max34406 v dd v dd v dd c ena shtdn oc1 oc2 oc3 oc4 out1 adcinputs out2out3 cdly out4 v dd r pu r pu c cdly gnd v 1 r sense1 in1+ in1- v 2 r sense2 in2+ in2- v 3 r sense3 in3+ in3- v 4 r sense4 in4+ in4- downloaded from: http:///
_________________________________________________________________ maxim integrated products 8 max34406 quad current-sense amplifier with overcurrent threshold comparators detailed description the max34406 quad-channel, unidirectional, high-side, current-sense amplifier features a 2.0v to 28v input common-mode range. this feature allows the monitoring of current out of a voltage supply as low as 2.0v. the device monitors current through a current-sense resistor and amplifies the voltage across that resistor. current-sense amplifier output voltages (out1 to out4) are compared to a fixed 1.0v reference; if v outx exceeds 1.0v, the corresponding overcurrent warning output (oc1 to oc4) is asserted. if the enable input (ena) is logic-high, shtdn asserts when any of the four overcurrent outputs go logic-high. assertion of shtdn on overcurrent can be delayed and/or filtered by attaching an external capacitor to cdly. once shtdn is latched high impedance, it remains so until ena is toggled. the unidirectional current-sense amplifiers used in each channel of the device have a well established history. for each channel, an op amp is used to force the current through an internal gain resistor at in+, which has a value of r1, such that its voltage drop equals the voltage drop across an external sense resistor, r sense . there is an internal resistor at in- with the same value as r1 to mini - mize offset voltage. the current through r1 is sourced by a high-voltage p-channel fet. its source current is the same as its drain current, which flows through a second gain resistor, r outx . this produces an output voltage, v outx , whose magnitude is i load x r sense x r outx /r1. the gain accuracy is based on the matching of the two gain resistors, r1 and r outx ( table 1 ). total gain = 25v/v for the max34406t, 50v/v for the max34406f, 100v/v for the max34406h, and 200v/v for the max34406w. the output is protected from input overdrive by use of a 6v clamp-protection circuit. applications information choosing the sense resistor choose r sense based on the criteria detailed in the fol - lowing sections. voltage loss a high r sense value causes the power-source voltage to drop due to ir loss. for minimal voltage loss, use the lowest r sense value. outx swing vs. v inx+ and v sense the device is unique because the supply voltage for the current-sense amplifier in each channel is the input common-mode voltage for that channel (the average voltage at inx+ and inx-). there are no separate supply voltage pins for the current-sense amplifiers. therefore, the outx voltage swing for a given channel is limited by the minimum voltage at in+ for that channel. v outx(max) = v inx+(min) - v sense(max) - v oh and outx sense load v (max) r g i (max) = v sense full scale should be less than v outx /gain at the minimum inx+ voltage. for best performance with a 3.6v supply voltage, select r sense to provide approximately 120mv (gain of 25v/v), 60mv (gain of 50v/v), 30mv (gain of 100v/v), or 15mv (gain of 200v/v) of sense voltage for the full-scale current in each application. these can be increased by use of a higher minimum input voltage. accuracy in the linear region (v outx < v outx(max) ), there are two components to accuracy: input offset voltage (v os ) and gain error (ge). for all variants of the device, v os = p 600 f v (max); gain error is 0.6% (max) for the max34406t/f/h or 0.8% (max) for the max34406w. use the linear equation to calculate total error: os sense v error (%) ge 100 v ?? = ?? ?? where ge is gain error, v sense is the voltage across the sense resistor r sense , and v os is offset voltage. a high r sense value allows lower currents to be measured more accurately because offsets are less significant when the sense voltage is larger. table 1. internal gain setting resistors (typical values) gain (v/v) r1 ( i ) r outx (k i ) 200 100 20 100 100 10 50 200 10 25 400 10 downloaded from: http:///
_________________________________________________________________ maxim integrated products 9 max34406 quad current-sense amplifier with overcurrent threshold comparators efficiency and power dissipation at high current levels, the i 2 r losses in r sense can be significant. take this into consideration when choosing the resistor value and its power dissipation (wattage) rating. also, the sense resistor?s value might drift if it is allowed to heat up excessively. the precision v os of the device allows the use of small sense resistors to reduce power dissipation and reduce hot spots. kelvin connections because of the high currents that flow through r sense , take care to eliminate parasitic trace resistance from causing errors in the sense voltage. either use a four- terminal current-sense resistor or use kelvin (force and sense) pcb layout techniques. minimizing trace resistance pcb trace resistance from r sense to the inx+ inputs contributes to gain error in the current-sense amplifiers. care should be taken to minimize this resistance (shown as r trc in figure 1 ). total gain including error caused by trace resistance can be calculated as follows: outx trc r g r1 r = + for example, assume a gain of 100v/v, as in the max34406h. from table 1 , r1 = 100 i and r outx = 10k i . then every 10m i of pcb trace resistance adds -0.01% gain error. optional output filter capacitor when designing a system that uses a sample-and-hold stage in the adc, the sampling capacitor momentarily loads outx and causes a drop in the output voltage. if sampling time is very short (less than a microsecond), consider using a ceramic capacitor across outx and gnd to hold v outx constant during sampling. this also decreases the small-signal bandwidth of the current-sense amplifier and reduces noise at outx. input filters some applications of current-sense amplifiers need to measure currents accurately even in the presence of both differential and common-mode ripple, as well as a wide variety of input transient conditions. for example, high-frequency ripple at the output of a switching buck or boost regulator results in a common-mode voltage at the device?s inputs. alternatively, the fast load-current tran - sients, when measuring at the input of a switching buck or boost regulator, can cause high-frequency differential sense voltages to occur at the device?s inputs, although the signal of interest is the average dc value. such high- frequency differential sense voltages can result in a volt - age offset at the device output.the device allows a method of filtering to help improve performance in the presence of input common-mode voltage and input differential voltage transients. figure 2 shows a differential input filter.the capacitor c in between inx+ and inx- along with the resistor r in between the sense resistor and inx- helps filter against input differential voltages and prevents them from reaching the device. the corner frequency of this filter is determined by the choice of r in , c in , and the value of the input resistance at inx- (r1). see table 1 for r1 values at the different gain options.the value of r in should be chosen to minimize its effect on the input offset voltage due to the bias current at inx-. figure 1. input trace resistance figure 2. differential input filter r sense inx+ gnd inx- outx r trc max34406 load r sense c in inx+ gnd inx- outx r in max34406 load downloaded from: http:///
________________________________________________________________ maxim integrated products 10 max34406 quad current-sense amplifier with overcurrent threshold comparators r in x i bias contributes to the input voltage offset. i bias is typically 0.2 f a. placing r in at the inx- input voltage does not affect the gain error of the device because the gain is given by the ratio between r outx and r1 at inx+. bidirectional application some systems can require a precise bidirectional cur - rent-sense amplifier to accurately monitor currents. measurement of the two separate outputs with respect to gnd yields an accurate measure of the bidirectional currents ( figure 3 ). choosing the delay capacitor the shtdn output asserts upon overcurrent detection on any of the 4 channels. oc1 to oc4 are logically ored together; shtdn latches the output after some delay. shtdn latch delay is determined by the following equation: t dly = c cdly (v dd 10a) example c cdly and t dly pairs are given in the electrical characteristics table. figure 3. bidirectional application ordering information + denotes a lead(pb)-free/rohs-compliant package. t = tape and reel.* future product?contact factory for availability. ** ep = exposed pad. package information for the latest package outline information and land patterns (footprints), go to www.maxim-ic.com/packages . note that a ?+?, ?#?, or ?-? in the package code indicates rohs status only. package drawings may show a different suffix character, but the drawing pertains to the package regardless of rohs status. package type package code outline no. land pattern no. 24 tqfn-ep t2444+4 21-0139 90-0022 part gain (v/v) temp range pin-package max34406tetg+* 25 -40 n c to +85 n c 24 tqfn-ep** max34406tetg+t* 25 -40 n c to +85 n c 24 tqfn-ep** max34406fetg+* 50 -40 n c to +85 n c 24 tqfn-ep** max34406fetg+t* 50 -40 n c to +85 n c 24 tqfn-ep** max34406hetg+ 100 -40 n c to +85 n c 24 tqfn-ep** max34406hetg+t 100 -40 n c to +85 n c 24 tqfn-ep** MAX34406WETG+* 200 -40 n c to +85 n c 24 tqfn-ep** MAX34406WETG+t* 200 -40 n c to +85 n c 24 tqfn-ep** in2+ out1 in2- gnd in1+ in1- r sense i load out2 max34406 c adcinputs v dd = 3.3v downloaded from: http:///
maxim cannot assume responsibility for use of any circuitry other than circuitry entirely embodied in a maxim product. no circuit patent licenses are implied. maxim reserves the right to change the circuitry and specifications without notice at any time. the parametric values (min and max limits) shown in the electrical characteristics table are guaranteed. other parametric values quoted in this data sheet are provided for guidance. maxim integrated products, 120 san gabriel drive, sunnyvale, ca 94086 408-737-7600 11 ? 2012 maxim integrated products maxim is a registered trademark of maxim integrated products, inc. max34406 quad current-sense amplifier with overcurrent threshold comparators revision history revision number revision date description pages changed 0 6/11 initial release ? 1 1/12 removed the requirement for the bleed resistor on cdly; added the function to discharge the cdly capacitor when all four ocx outputs are low ( block diagram , electrical characteristics table t dly specification, pin description , typical application circuit , and choosing the delay capacitor section) 1, 3, 6, 7, 10 downloaded from: http:///

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