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| ? 2013 microchip technology inc. ds25165a-page 1 MCP6421 features: ? low quiescent current: - 4.4 a/amplifier (typical) ? low input offset voltage: - 1.0 mv (maximum) ? enhanced emi protection: - electromagnetic interference rejection ratio (emirr) at 1.8 ghz: 97 db ? supply voltage range: 1.8v to 5.5v ? gain bandwidth product: 90 khz (typical) ? rail-to-rail input/output ? slew rate: 0.05 v/s (typical) ? unity gain stable ? no phase reversal ? small packages: - singles in sc70-5, sot-23-5 ? extended temperature range: - -40c to +125c applications: ? portable medical instrument ? safety monitoring ? battery powered system ? remote sensing ? supply current sensing ? analog active filter design aids: ? spice macro models ?filterlab ? software ? microchip advanced part selector (maps) ? analog demonstration and evaluation boards ? application notes description: the microchip technology inc. MCP6421 family of operational amplifiers operate with a single supply voltage as low as 1.8v, while drawing low quiescent current per amplifier (5.5 a, maximum). this family also has low input offset voltage (1.0 mv, maximum) and rail-to-rail input and output operation. in addition, the MCP6421 family is unity gain stable and has a gain bandwidth product of 90 khz (typical). this combination of features supports battery-powered and portable applications. the MCP6421 family has enhanced emi protection to minimize any electromagnetic interference from external sources, such as power lines, radio stations, and mobile communications, etc. this feature makes it well suited for emi sensitive applications. the MCP6421 family is offered in single (MCP6421) packages. all devices are designed using an advanced cmos process and fully specified in extended temperature range from -40c to +125c. package types typical application 5 4 1 2 3 v dd v in ? v in + v ss v out MCP6421 sc70-5, sot-23-5 v dd r 2 + - v out MCP6421 r 1 r 3 100k r 5 100k 1k 1k r-r r+r v a v b v dd + - v dd + - MCP6421 MCP6421 r+r r-r v dd a a v out v a v b ? ?? 10k ? 100 ? ------------- ? = 4.4 a, 90 khz op amp
MCP6421 ds25165a-page 2 ? 2013 microchip technology inc. notes: ? 2013 microchip technology inc. ds25165a-page 3 MCP6421 1.0 electrical characteristics 1.1 absolute maximum ratings ? v dd ? v ss ............................................................................................................................... .......................................................... 6.5v current at analog input pins (v in + , v in - ) .............................................................................................................................. ......... 2 ma analog inputs (v in + , v in - ) ?? ............................................................................................................................v ss ? 1.0v to v dd + 1.0v all other inputs and outputs .................................................................................................. .........................v ss ? 0.3v to v dd + 0.3v difference input voltage ...................................................................................................... ..................................................|v dd ? v ss | output short-circuit current .................................................................................................. ............................................... continuous current at input pins .......................................................................................................... ............................................................ 2 ma current at output and supply pins ............................................................................................. ................................................ 30 ma storage temperature ............................................................................................................ ......................................... -65c to +150c maximum junction temperature (t j ).............................................................................................................................. ............. +150c esd protection on all pins (hbm; mm) ??????????????????????????????????????????????????????????????? ??????????????????????????????????????????????????????????????? ??????????????? ? 4kv; 400v ? notice: stresses above those listed under ?absolute maximum ratings? may cause permanent damage to the device. this is a stress rating only and functional operation of the device at those or any other conditions above those indicated in the operational listings of this specification is not implied. exposure to maximum rating conditions for extended peri- ods may affect device reliability. ?? see section 4.1.2 ?input voltage limits? . 1.2 specifications table 1-1: dc electrical specifications electrical characteristics : unless otherwise indicated, t a = +25c, v dd = +1.8v to +5.5v, v ss = gnd, v cm = v dd /2, v out =v dd /2, v l =v dd /2, r l = 100 k ? to v l and c l = 30 pf (refer to figure 1-1 ). parameters sym min typ max units conditions input offset input offset voltage v os -1.0 ? 1.0 mv v dd = 3.0v; v cm =v dd / 4 input offset drift with temperature ? v os / ? t a ?3.0?v/ct a = -40c to +125c, v cm = v ss power supply rejection ratio psrr 75 90 ? db v cm = v ss input bias current and impedance input bias current i b ?150pa ?20?pat a = +85c ?800?pat a = +125c input offset current i os ?1?pa common mode input impedance z cm ?10 13 ||12 ? ? ||pf differential input impedance z diff ?10 13 ||12 ? ?? |pf common mode common mode input voltage range v cmr v ss -0.3 ? v dd +0.3 v common mode rejection ratio cmrr 75 90 ? db v dd = 5.5v v cm = -0.3v to 5.8v 70 85 ? db v dd = 1.8v v cm = -0.3v to 2.1v MCP6421 ds25165a-page 4 ? 2013 microchip technology inc. open-loop gain dc open-loop gain (large signal) a ol 95 115 ? db 0.3 < v out < (v dd -0.3v) v cm = v ss v dd = 5.5v output high-level output voltage v oh 1.796 1.799 ? v v dd = 1.8v 5.495 5.499 ? v v dd = 5.5v low-level output voltage v ol ? 0.001 0.004 v v dd = 1.8v ? 0.001 0.005 v v dd = 5.5v output short-circuit current i sc ?6?mav dd = 1.8v ?22?mav dd = 5.5v power supply supply voltage v dd 1.8 ? 5.5 v quiescent current per amplifier i q ?4.45.5ai o = 0, v cm = v dd /4 table 1-1: dc electrical specifications (continued) electrical characteristics : unless otherwise indicated, t a = +25c, v dd = +1.8v to +5.5v, v ss = gnd, v cm = v dd /2, v out =v dd /2, v l =v dd /2, r l = 100 k ? to v l and c l = 30 pf (refer to figure 1-1 ). parameters sym min typ max units conditions table 1-2: ac electri cal specifications electrical characteristics : unless otherwise indicated, t a = +25c, v dd = +1.8v to +5.5v, v ss = gnd, v cm = v dd /2, v out =v dd /2, v l =v dd /2, r l = 100 k ? to v l and c l = 30 pf (refer to figure 1-1 ). parameters sym min typ max units conditions ac response gain bandwidth product gbwp ? 90 ? khz phase margin pm ? 55 ? g = +1 v/v slew rate sr ? 0.05 ? v/s noise input noise voltage e ni ? 15 ? vp-p f = 0.1 hz to 10 hz input noise voltage density e ni ?95?nv/ ? hz f = 1 khz ?90?nv/ ? hz f = 10 khz input noise current density i ni ?0.6?fa/ ? hz f = 1 khz electromagnetic interference rejection ratio emirr ? 77 ? db v in = 100 mv pk , 400 mhz ?92? v in = 100 mv pk , 900 mhz ?97? v in = 100 mv pk , 1800 mhz ?99? v in = 100 mv pk , 2400 mhz ? 2013 microchip technology inc. ds25165a-page 5 MCP6421 1.3 test circuits the circuit used for most dc and ac tests is shown in figure 1-1 . this circuit can independently set v cm and v out (see equation 1-1 ). note that v cm is not the circuit?s common mode voltage ((v p +v m )/2), and that v ost includes v os plus the effects (on the input offset error, v ost ) of the temperature, cmrr, psrr and a ol . equation 1-1: figure 1-1: ac and dc test circuit for most specifications. table 1: temperature specifications electrical characteristics: unless otherwise indicated, v dd = +1.8v to +5.5v and v ss = gnd. parameters sym min typ max units conditions temperature ranges operating temperature range t a -40 ? +125 c note 1 storage temperature range t a -65 ? +150 c thermal package resistances thermal resistance, 5l-sc70 ? ja ? 331 ? c/w thermal resistance, 5l-sot-23 ? ja ?220.7?c/w note 1: the internal junction temperature (t j ) must not exceed the absolute maximum specification of +150c. g dm r f r g ? = v cm v p v dd 2 ? + ?? 2 ? = v out v dd 2 ? ?? v p v m ? ?? v ost 1g dm + ?? ++ = where: g dm = differential mode gain (v/v) v cm = op amp?s common mode input voltage (v) v ost = op amp?s total input offset voltage (mv) v ost v in? v in+ ? = v dd r g r f v out v m c b2 c l r l v l c b1 100 k ? 100 k ? r g r f v dd /2 v p 100 k ? 100 k ? 30 pf 100 k ? 1f 100 nf v in? v in+ c f 6.8 pf c f 6.8 pf MCP6421 MCP6421 ds25165a-page 6 ? 2013 microchip technology inc. notes: ? 2013 microchip technology inc. ds25165a-page 7 MCP6421 2.0 typical performance curves note: unless otherwise indicated, t a = +25c, v dd = +1.8v to +5.5v, v ss = gnd, v cm = v dd /2, v out =v dd /2, v l =v dd /2, r l = 100 k ? to v l and c l = 30 pf. figure 2-1: input offset voltage. figure 2-2: input offset voltage drift. figure 2-3: input offset voltage vs. common mode input voltage. figure 2-4: input offset voltage vs. common mode input voltage. figure 2-5: input offset voltage vs. output voltage. figure 2-6: input offset voltage vs. power supply voltage. note: the graphs and tables provided following this note are a statistical summary based on a limited number of samples and are provided for informational purposes only. the performance characteristics listed herein are not tested or guaranteed. in some graphs or tables, the data presented may be outside the specified operating range (e.g., outside specified power supply range) and therefore outside the warranted range. 12% 16% 20% 24% 28% 32% 36% 40% 44% 48% e ntage of occurences 1253samples v dd = 3.0v v cm = v dd /4 0% 4% 8% -1000 -800 -600 -400 -200 0 200 400 600 800 1000 perc e input offset voltage (v) 4% 6% 8% 10% 12% n tage of occurances 1253 samples v dd = 3.0v v cm = v dd /4 t a = -40c to +125c 0% 2% 4% -20 -18 -16 -14 -12 -10 -8 -6 -4 -2 0 2 4 6 8 10 12 14 16 18 20 perce n input offset voltage drift (v/c) -400 -200 0 200 400 600 800 1000 t offset voltage (v) t a = +125c t a = +85c t a = +25c t a = -40c -1000 -800 -600 -0.3 0.0 0.3 0.6 0.9 1.2 1.5 1.8 2.1 inpu t common mode input voltage (v) v dd = 1.8v representative part -400 -200 0 200 400 600 800 1000 t offset voltage (v) t a = +125c t a = +85c t a = +25c t a = -40c v =55v -1000 -800 -600 -0.5 0.0 0.5 1.0 1.5 2.0 2.5 3.0 3.5 4.0 4.5 5.0 5.5 6.0 inpu t common mode input voltage (v) v dd =5 . 5v representative part -400 -200 0 200 400 600 800 1000 t offset voltage (v) v dd = 1.8v representative part v dd = 5.5v -1000 -800 -600 00.511.522.533.544.555.5 inpu t output voltage (v) -200 0 200 400 600 800 1000 offset voltage (v) t a = +125c representative part -1000 -800 -600 -400 00.511.522.533.544.555.566.5 input o power supply voltage (v) t a 125 c t a = +85c t a = +25c t a = -40c MCP6421 ds25165a-page 8 ? 2013 microchip technology inc. note: unless otherwise indicated, t a = +25c, v dd = +1.8v to +5.5v, v ss = gnd, v cm = v dd /2, v out =v dd /2, v l =v dd /2, r l = 100 k ? to v l and c l = 30 pf. figure 2-7: input noise voltage density vs. common mode input voltage. figure 2-8: input noise voltage density vs. frequency. figure 2-9: cmrr, psrr vs. frequency. figure 2-10: cmrr, psrr vs. ambient temperature. figure 2-11: input bias, offset current vs. ambient temperature. figure 2-12: input bias current vs. common mode input voltage. 30 40 50 60 70 80 90 o ise voltage density (nv/hz) 0 10 20 30 -0.5 0 0.5 1 1.5 2 2.5 3 3.5 4 4.5 5 5.5 6 input n o common mode input voltage (v) f = 10 khz v dd = 5.5 v 100 1,000 10,000 o ise voltage density (nv/hz) 10 100 1.e-1 1.e+0 1.e+1 1.e+2 1.e+3 1.e+4 1.e+5 input n o frequency (hz) 0.1 1 10 100 1k 10k 100k 50 60 70 80 90 100 r r, psrr (db) cmrr psrr+ psrr- representative part 20 30 40 10 100 1000 10000 100000 cm r frequency (hz) 10 100 1k 10k 100k 80 90 100 110 120 130 140 m rr, psrr (db) psrr 50 60 70 80 -50 -25 0 25 50 75 100 125 c m ambient temperature (c) cmrr @ v dd = 5.5v @ v dd = 1.8v 1 10 100 1000 as and offset currents (a) in p ut bias current v dd = 5.5v 1p 1n 100p 10p 0.01 0.1 25 35 45 55 65 75 85 95 105 115 125 input bi ambient temperature (c) input offset current 0.1p 0.01p 300 400 500 600 700 800 900 1000 b ias current (pa) t a = +125c t a = +85c -100 0 100 200 00.511.522.533.544.555.5 input b common mode input voltage (v) v dd = 5.5 v t a = +25c ? 2013 microchip technology inc. ds25165a-page 9 MCP6421 note: unless otherwise indicated, t a = +25c, v dd = +1.8v to +5.5v, v ss = gnd, v cm = v dd /2, v out =v dd /2, v l =v dd /2, r l = 100 k ? to v l and c l = 30 pf. figure 2-13: quiescent current vs. ambient temperature. figure 2-14: quiescent current vs. power supply voltage. figure 2-15: quiescent current vs. common mode input voltage. figure 2-16: quiescent current vs. common mode input voltage. figure 2-17: open-loop gain, phase vs. frequency. figure 2-18: dc open-loop gain vs. ambient temperature. 2 3 4 5 6 uiescent current (a/amplifier) v dd = 5.5v v dd = 1.8v 0 1 -50 -25 0 25 50 75 100 125 q ambient temperature (c) 2 3 4 5 6 q uiescent current (a/amplifier) t a = +125c t a = +85c t 25 c 0 1 00.511.522.533.544.555.56 q power supply voltage (v) t a = + 25 c t a = -40c 2 3 4 5 6 u iescent current a/amplifier) 0 1 2 -0.5 -0.2 0.1 0.4 0.7 1.0 1.3 1.6 1.9 2.2 2.5 o u ( common mode input voltage (v) v dd = 1.8v g = +1 v/v 2 3 4 5 6 u iescent current (a/amplifier) 0 1 2 -0.5 0.0 0.5 1.0 1.5 2.0 2.5 3.0 3.5 4.0 4.5 5.0 5.5 o u common mode input voltage (v) v dd = 5.5v g = +1 v/v -120 -90 -60 -30 0 40 60 80 100 120 n -loop phase () n -loop gain (db) open-loop gain open-loop phase -210 -180 -150 -20 0 20 1.0e-02 1.0e-01 1.0e+00 1.0e+01 1.0e+02 1.0e+03 1.0e+04 1.0e+05 ope n ope n frequency (hz) 0.01 0.1 1 10 100 1k 10k 100k 100 110 120 130 140 open-loop gain (db) v dd = 5.5v v dd = 1.8v 80 90 -50 -25 0 25 50 75 100 125 dc ambient temperature (c) MCP6421 ds25165a-page 10 ? 2013 microchip technology inc. note: unless otherwise indicated, t a = +25c, v dd = +1.8v to +5.5v, v ss = gnd, v cm = v dd /2, v out =v dd /2, v l =v dd /2, r l = 100 k ? to v l and c l = 30 pf. figure 2-19: dc open-loop gain vs. output voltage headroom. figure 2-20: gain bandwidth product, phase margin vs. ambient temperature. figure 2-21: gain bandwidth product, phase margin vs. ambient temperature. figure 2-22: output short circuit current vs. power supply voltage. figure 2-23: output voltage swing vs. frequency. figure 2-24: output voltage headroom vs. output current. 90 100 110 120 130 140 150 - open loop gain (db) v dd = 5.5v v dd = 1.8v 70 80 0.00 0.05 0.10 0.15 0.20 0.25 0.30 dc - output voltage headroom (v) v dd -v oh or v ol -v ss 60 80 100 120 140 160 180 60.0 70.0 80.0 90.0 100.0 b andwidth product (mhz) gain bandwidth product h ase margin () 0 20 40 60 30.0 40.0 50.0 -50 -25 0 25 50 75 100 125 gain b ambient temperature (c) v dd = 12v v dd = 12v v dd = 12v v dd = 12v v dd = 12v v dd = 12v v dd = 12v phase margin v dd = 5.5v p h 60 80 100 120 140 160 180 60.0 70.0 80.0 90.0 100.0 b andwidth product (mhz) gain bandwidth product ase margin () 0 20 40 60 30.0 40.0 50.0 -50 -25 0 25 50 75 100 125 gain b ambient temperature (c) phase margin v dd = 1.8v ph 20 -10 0 10 20 30 40 t short circuit current (ma) isc+@ t a = +125c t a = +85c t a = +25c t a = -40c isc-@ t a = +125c t 85 c -40 -30 - 20 0 0.5 1 1.5 2 2.5 3 3.5 4 4.5 5 5.5 outpu power supply voltage (v) t a = + 85 c t a = +25c t a = -40c 1 10 t voltage swing (v p-p ) v dd = 1.8v v dd = 5.5v 0.1 1000 10000 100000 outpu t frequency (hz) 1k 10k 100k 10 100 1000 v oltage headroom (mv) v dd -v oh v ol -v ss v dd = 1.8v 0.1 1 0.001 0.01 0.1 1 10 100 output v output current (ma) ? 2013 microchip technology inc. ds25165a-page 11 MCP6421 note: unless otherwise indicated, t a = +25c, v dd = +1.8v to +5.5v, v ss = gnd, v cm = v dd /2, v out =v dd /2, v l =v dd /2, r l = 100 k ? to v l and c l = 30 pf. figure 2-25: output voltage headroom vs. output current. figure 2-26: output voltage headroom vs. ambient temperature. figure 2-27: output voltage headroom vs. ambient temperature. figure 2-28: slew rate vs. ambient temperature. figure 2-29: small signal non-inverting pulse response. figure 2-30: small signal inverting pulse response. 10 100 1000 v oltage headroom (mv) v dd -v oh v ol -v ss v dd = 5.5v 0.1 1 0.01 0.1 1 10 100 output v output current (ma) 0.3 0.4 0.5 0.6 0.7 0.8 0.9 v oltage headroom (mv) v dd -v oh v ol -v ss 0 0.1 0.2 -50 -25 0 25 50 75 100 125 output v ambient temperature (c) v dd = 1.8v 0.4 0.6 0.8 1 1.2 v oltage headroom (mv) v dd -v oh v ol -v ss 0 0.2 -50 -25 0 25 50 75 100 125 output v ambient temperature (c) v dd = 5.5v 0.03 0.04 0.05 0.06 0.07 0.08 0.09 s lew rate (v/s) falling edge, v dd = 5.5v rising edge, v dd = 5.5v falling edge, v dd = 1.8v ri i ed v 18v 0.00 0.01 0.02 -50 -25 0 25 50 75 100 125 s ambient temperature (c) ri s i ng ed ge, v dd = 1 . 8v t voltage (20 mv/div) v =55v outpu t time (25 s/div) v dd =5 . 5v g = +1 v/v t voltage (20 mv/div) v dd = 5.5 v g = -1 v/v outpu time (25 s/div) MCP6421 ds25165a-page 12 ? 2013 microchip technology inc. figure 2-31: large signal non-inverting pulse response. figure 2-32: large signal inverting pulse response. figure 2-33: the MCP6421 device shows no phase reversal. figure 2-34: closed loop output impedance vs. frequency. figure 2-35: measured input current vs. input voltage (below v ss ). figure 2-36: emirr vs. frequency. 2 3 4 5 6 u tput voltage (v) v =55v 0 1 2 o u time (0.1 ms/div) v dd =5 . 5v g = +1 v/v 2 3 4 5 6 o utput voltage (v) v dd = 5.5 v g = -1 v/v 0 1 2 o time (0.1 ms/div) 2 3 4 5 6 output voltages (v) v out v in -1 0 1 input, time (1 ms/div) v dd = 5.5v g = +2v/v 100 1000 10000 s ed loop output m pedance ( ) g n : 101 v/v 11 v/v 1 10 1.0e+00 1.0e+01 1.0e+02 1.0e+03 1.0e+04 1.0e+05 clo s i m frequency (hz) 11 v/v 1 v/v 1 10 100 1k 10k 100k -i in (a) 100 10 1 100n -1.0 -0.9 -0.8 -0.7 -0.6 -0.5 -0.4 -0.3 -0.2 -0.1 0.0 v in (v) 10n 1n t a = +125c t a = +85c t a = +25c t a = -40c 0 10 20 30 40 50 60 70 80 90 100 110 120 emirr (db) frequency (hz) 100k 1m 10m 100m 1g 10g v in = 100 mv pk v dd = 5.5v ? 2013 microchip technology inc. ds25165a-page 13 MCP6421 note: unless otherwise indicated, t a = +25c, v dd = +1.8v to +5.5v, v ss = gnd, v cm = v dd /2, v out =v dd /2, v l =v dd /2, r l = 100 k ? to v l and c l = 30 pf. figure 2-37: emirr vs. rf input peak- to-peak voltage. 0 20 40 60 80 100 120 -45 -40 -35 -30 -25 -20 -15 -10 -5 0 5 10 emirr (db) rf input voltage (v pk ) emirr @ 2400 mhz @ 1800 mhz @ 900 mhz @ 400 mhz MCP6421 ds25165a-page 14 ? 2013 microchip technology inc. notes: ? 2013 microchip technology inc. ds25165a-page 15 MCP6421 3.0 pin descriptions descriptions of the pins are listed in table 3-1 . 3.1 analog output (v out ) the output pin is a low-impedance voltage source. 3.2 analog inputs (v in +, v in -) the non-inverting and inverting inputs are high- impedance cmos inputs with low bias currents. 3.3 power supply pins (v ss , v dd ) the positive power supply (v dd ) is 1.8v to 5.5v higher than the negative power supply (v ss ). for normal operation, the other pins are at voltages between v ss and v dd . typically, these parts are used in a single (positive) supply configuration. in this case, v ss is connected to ground and v dd is connected to the supply. v dd will need bypass capacitors. table 3-1: pin function table MCP6421 symbol description sc70-5, sot-23-5 1v out analog output 2v ss negative power supply 3v in + non-inverting input 4v in ? inverting input 5v dd positive power supply MCP6421 ds25165a-page 16 ? 2013 microchip technology inc. notes: ? 2013 microchip technology inc. ds25165a-page 17 MCP6421 4.0 application information the MCP6421 op amp is manufactured using microchip?s state-of-the-art cmos process. this op amp is unity gain stable and suitable for a wide range of general purpose applications. 4.1 rail-to-rail input 4.1.1 phase reversal the MCP6421 op amp is designed to prevent phase reversal, when the input pins exceed the supply voltages. figure 2-33 shows the input voltage exceeding the supply voltage with no phase reversal. 4.1.2 input voltage limits in order to prevent damage and/or improper operation of the amplifier, the circuit must limit the voltages at the input pins (see section 1.1, absolute maximum ratings ? ). the electrostatic discharge (esd) protection on the inputs can be depicted as shown in figure 4-1 . this structure was chosen to protect the input transistors against many, but not all, over-voltage conditions, and to minimize the input bias current (i b ). figure 4-1: simplified analog input esd structures. the input esd diodes clamp the inputs when they try to go more than one diode drop below v ss . they also clamp any voltages that go well above v dd ; their breakdown voltage is high enough to allow normal operation, but not low enough to protect against slow over-voltage (beyond v dd ) events. very fast esd events that meet the spec are limited so that damage does not occur. in some applications, it may be necessary to prevent excessive voltages from reaching the op amp inputs; figure 4-2 shows one approach to protecting these inputs. figure 4-2: protecting the analog inputs. a significant amount of current can flow out of the inputs when the common mode voltage (v cm ) is below ground (v ss ); see figure 2-35 . 4.1.3 input current limits in order to prevent damage and/or improper operation of the amplifier, the circuit must limit the currents into the input pins (see section 1.1, absolute maximum ratings ? ). figure 4-3 shows one approach to protecting these inputs. the resistors r 1 and r 2 limit the possible currents in or out of the input pins (and the esd diodes, d 1 and d 2 ). the diode currents will go through either v dd or v ss . figure 4-3: protecting the analog inputs. bond pad bond pad bond pad v dd v in + v ss input stage bond pad v in ? v 1 v dd d 1 v 2 d 2 MCP6421 v out v 1 r 1 v dd d 1 min(r 1 ,r 2 )> v ss ?min(v 1 , v 2 ) 2ma v 2 r 2 d 2 MCP6421 v out min(r 1 ,r 2 )> max(v 1 ,v 2 )?v dd 2ma MCP6421 ds25165a-page 18 ? 2013 microchip technology inc. 4.1.4 normal operation the input stage of the MCP6421 op amp uses two differential input stages in parallel. one operates at a low common mode input voltage (v cm ), while the other operates at a high v cm . with this topology, the device operates with a v cm up to 300 mv above v dd and 300 mv below v ss . the input offset voltage is measured at v cm =v ss ? 0.3v and v dd + 0.3v, to ensure proper operation. the transition between the input stages occurs when v cm is near v dd ?0.6v (see figures 2-3 and 2-4 ). for the best distortion performance and gain linearity, with non-inverting gains, avoid this region of operation. 4.2 rail-to-rail output the output voltage range of the MCP6421 op amp is 0.001v (typical) and 5.499v (typical) when r l =100k ? is connected to v dd /2 and v dd =5.5v. refer to figures 2-24 and 2-26 for more information. 4.3 capacitive loads driving large capacitive loads can cause stability problems for voltage feedback op amps. as the load capacitance increases, the feedback loop?s phase margin decreases, and the closed-loop bandwidth is reduced. this produces gain peaking in the frequency response, with overshoot and ringing in the step response. while a unity-gain buffer (g = +1 v/v) is the most sensitive to the capacitive loads, all gains show the same general behavior. when driving large capacitive loads with the MCP6421 op amp (e.g., > 60 pf when g = +1 v/v), a small series resistor at the output (r iso in figure 4-5 ) improves the feedback loop?s phase margin (stability) by making the output load resistive at higher frequencies. the bandwidth will be generally lower than the bandwidth with no capacitance load. figure 4-4: output resistor, r iso stabilizes large capacitive loads. figure 4-5 gives the recommended r iso values for the different capacitive loads and gains. the x-axis is the normalized load capacitance (c l /g n ), where g n is the circuit's noise gain. for non-inverting gains, g n and the signal gain are equal. for inverting gains, g n is 1+|signal gain| (e.g., -1 v/v gives g n = +2 v/v). figure 4-5: recommended r iso values for capacitive loads. after selecting r iso for your circuit, double-check the resulting frequency response peaking and step response overshoot. modify r iso ?s value until the response is reasonable. bench evaluation and simulations with the MCP6421 spice macro model are very helpful. 4.4 supply bypass the MCP6421 op amp?s power supply pin (v dd for single-supply) should have a local bypass capacitor (i.e., 0.01 f to 0.1 f) within 2 mm for good high frequency performance. it can use a bulk capacitor (i.e., 1 f or larger) within 100 mm to provide large, slow currents. this bulk capacitor can be shared with other analog parts. 4.5 pcb surface leakage in applications where low input bias current is critical, printed circuit board (pcb) surface leakage effects need to be considered. surface leakage is caused by humidity, dust or other contamination on the board. under low humidity conditions, a typical resistance between nearby traces is 10 12 ? . a 5v difference would cause 5 pa of current to flow, which is greater than the MCP6421 op amp?s bias current at +25c (1 pa, typical). v in r iso v out c l ? + MCP6421 100 1000 10000 100000 o mmended r iso ( ) g n : 1 v/v 2 v/v 5 v/v v dd = 5.5 v r l = 100 k 1 10 1.e-11 1.e-10 1.e-09 1.e-08 1.e-07 rec o normalized load capacitance; c l /g n (f) 10p 100p 1n 10n 0.1 ? 2013 microchip technology inc. ds25165a-page 19 MCP6421 the easiest way to reduce surface leakage is to use a guard ring around sensitive pins (or traces). the guard ring is biased at the same voltage as the sensitive pin. an example of this type of layout is shown in figure 4-6 . figure 4-6: example guard ring layout for inverting gain. 1. non-inverting gain and unity-gain buffer: a) connect the non-inverting pin (v in +) to the input with a wire that does not touch the pcb surface. b) connect the guard ring to the inverting input pin (v in ?). this biases the guard ring to the common mode input voltage. 2. inverting gain and transimpedance gain amplifiers (convert current to voltage, such as photo detectors): a) connect the guard ring to the non-inverting input pin (v in +). this biases the guard ring to the same reference voltage as the op amp (e.g., v dd /2 or ground). b) connect the inverting pin (v in ?) to the input with a wire that does not touch the pcb surface. 4.6 electromagnetic interference rejection ratio (emirr) definitions the electromagnetic interference (emi) is the distur- bance that affects an electrical circuit due to either elec- tromagnetic induction or electromagnetic radiation emitted from an external source. the parameter which describes the emi robustness of an op amp is the electromagnetic interference rejection ratio (emirr). it quantitatively describes the effect that an rf interfering signal has on op amp performance. internal passive filters make emirr better compared with older parts. this means that, with good pcb layout techniques, your emc performance should be better. emirr is defined as : equation 4-1: 4.7 application circuits 4.7.1 co gas sensor a co gas detector is a device which detects the presence of carbon monoxide gas level. usually this is battery powered and transmits audible and visible warnings. the sensor responds to co gas by reducing its resistance proportionaly to the amount of co present in the air exposed to the internal element. on the sensor module, this variable is part of a voltage divider formed by the internal element and potentiometer r 1 . the output of this voltage divider is fed into the non- inverting inputs of the MCP6421 op amp. the device is configured as a buffer with unity gain and is used to provide a non-loaded test point for sensor sensitivity. because this sensor can be corrupted by parasitic elec- tromagnetic signals, the MCP6421 op amp can be used for conditioning this sensor. in figure 4-7 , the variable resistor is used to calibrate the sensor in different environments. . figure 4-7: co gas sensor circuit. guard ring v in ?v in + v ss emirr db ?? 20 v rf ? v os ------------- ?? ?? log ? = where: v rf = peak amplitude of rf interfering signal (v pk ) ? v os = input offset voltage shift (v) v dd + - v out MCP6421 r 1 v ref v dd MCP6421 ds25165a-page 20 ? 2013 microchip technology inc. 4.7.2 pressure sensor amplifier the MCP6421 op amp is well suited for conditioning sensor signals in battery-powered applications. many sensors are configured as wheatstone bridges. strain gauges and pressure sensors are two common exam- ples. figure 4-8 shows a strain gauge amplifier, using the MCP6421 enhanced emi protection device. the difference amplifier with emi robustness op amp is used to amplify the signal from the wheatstone bridge. the two op amps, configured as buffers and connected at outputs of pressure sensors, prevents resistive loading of the bridge by resistor r1 and r2. resistors r 1 ,r 2 and r 3, r 5 need to be chosen with very low tolerance to match the cmrr. figure 4-8: pressure sensor amplifier. 4.7.3 battery current sensing the MCP6421 op amp?s common mode input range, which goes 0.3v beyond both supply rails, supports their use in high-side and low-side battery current sensing applications. the low quiescent current helps prolong battery life, and the rail-to-rail output supports detection of low currents. figure 4-9 shows a high side battery current sensor circuit. the 10 ? resistor is sized to minimize power losses. the battery current (i dd ) through the 10 ? resistor causes its top terminal to be more negative than the bottom terminal. this keeps the common mode input voltage of the op amp below v dd , which is within its allowed range. the output of the op amp will also be below v dd , within its maximum output voltage swing specification. figure 4-9: battery current sensing. v dd r 2 + - v out MCP6421 r 1 r 3 100k r 5 100k 1k 1k r-r r+r v a v b v dd + - v dd + - MCP6421 MCP6421 r+r r-r v dd strain gauge v out v a v b ? ?? 10k ? 100 ? ------------- ? = v dd i dd 100 k ? 1m ? 1.8v v out high-side battery current sensor 10 ? to 5.5v i dd v dd v out ? 10 v/v ?? 10 ? ?? ? ----------------------------------------- - = MCP6421 v dd v ss ? 2013 microchip technology inc. ds25165a-page 21 MCP6421 5.0 design aids microchip provides the basic design tools needed for the MCP6421 op amp. 5.1 spice macro model the latest spice macro model for the MCP6421 op amp is available on the microchip web site at www.microchip.com . the model was written and tested in the official orcad (cadence ? ) owned pspice ? . for the other simulators, translation may be required. the model covers a wide aspect of the op amp's electrical specifications. not only does the model cover voltage, current and resistance of the op amp, but it also covers the temperature and the noise effects on the behavior of the op amp. the model has not been verified outside of the specification range listed in the op amp data sheet. the model behaviors under these conditions cannot ensure it will match the actual op amp performance. moreover, the model is intended to be an initial design tool. bench testing is a very important part of any design and cannot be replaced with simulations. also, simulation results using this macro model need to be validated by comparing them to the data sheet specifications and characteristic curves. 5.2 filterlab ? software microchip?s filterlab software is an innovative software tool that simplifies analog active filter design using op amps. available at no cost from the microchip web site at www.microchip.com/filterlab , the filterlab design tool provides full schematic diagrams of the filter circuit with component values. it also outputs the filter circuit in spice format, which can be used with the macro model to simulate the actual filter performance. 5.3 microchip advanced part selector (maps) maps is a software tool that helps semiconductor professionals efficiently identify the microchip devices that fit a particular design requirement. available at no cost from the microchip website at www.microchip.com/ maps , the maps is an overall selection tool for microchip?s product portfolio that includes analog, memory, mcus and dscs. using this tool, you can define a filter to sort features for a parametric search of devices and export side-by-side technical comparison reports. helpful links are also provided for data sheets, purchase and sampling of microchip parts. 5.4 analog demonstration and evaluation boards microchip offers a broad spectrum of analog demonstration and evaluation boards that are designed to help you achieve faster time to market. for a complete listing of these boards and their corresponding user?s guides and technical information, visit the microchip web site at www.microchip.com/ analogtools . some boards that are especially useful are: ? mcp6xxx amplifier evaluation board 1 ? mcp6xxx amplifier evaluation board 2 ? mcp6xxx amplifier evaluation board 3 ? mcp6xxx amplifier evaluation board 4 ? active filter demo board kit ? 5/6-pin sot-23 evaluation board, p/n vsupev2 5.5 application notes the following microchip analog design note and application notes are available on the microchip web site at www.microchip.com/appnotes , and are recommended as supplemental reference resources. ? adn003 ? ?select the right operational amplifier for your filtering circuits?, ds21821 ? an722 ? ?operational amplifier topologies and dc specifications?, ds00722 ? an723 ? ?operational amplifier ac specifications and applications?, ds00723 ? an884 ? ?driving capacitive loads with op amps?, ds00884 ? an990 ? ?analog sensor conditioning circuits ? an overview?, ds00990 ? an1177 ? ?op amp precision design: dc errors?, ds01177 ? an1228 ? ?op amp precision design: random noise?, ds01228 ? an1297 ? ?microchip?s op amp spice macro models?, ds01297 ? an1332: ?current sensing circuit concepts and fundamentals?? ds01332 ? an1494: ?using mcp6491 op amps for photode- tection applications?? ds01494 these application notes and others are listed in the design guide: ? ?signal chain design guide?, ds21825 MCP6421 ds25165a-page 22 ? 2013 microchip technology inc. notes: ? 2013 microchip technology inc. ds25165a-page 23 MCP6421 6.0 packaging information 6.1 package marking information example: legend: xx...x customer-specific information y year code (last digit of calendar year) yy year code (last 2 digits of calendar year) ww week code (week of january 1 is week ?01?) nnn alphanumeric traceability code pb-free jedec designator for matte tin (sn) * this package is pb-free. the pb-free jedec designator ( ) can be found on the outer packaging for this package. note : in the event the full microchip part number cannot be marked on one line, it will be carried over to the next line, thus limiting the number of available characters for customer-specific information. 3 e 3 e example: 5-lead sot-23 5-lead sc70 ds25 xxnn 3h25 MCP6421 ds25165a-page 24 ? 2013 microchip technology inc. !" ! #$! !% # $ !% # $ #&! ! !# "' ( )*+ ) # & #, $ --# $## . # #$ # / ! - 0 # 1 / % # #! # ## +22--- 2 / 3# 44" " 4 # 5 56 7 5$ 8 %1 5 ( 1# 9()* 6, : # ; < !!1 / / ; < # ! %% < 6, =!# " ; !!1 / =!# " ( ( ( 6, 4# ; ( . #4# 4 9 4 ! / ; < 9 4 !=!# 8 ( < d b 1 2 3 e1 e 4 5 ee c l a1 aa2 - *9 ) ? 2013 microchip technology inc. ds25165a-page 25 MCP6421 . # #$ # / ! - 0 # 1 / % # #! # ## +22--- 2 / 5-lead plastic small outline transistor (lt) [sc70] MCP6421 ds25165a-page 26 ? 2013 microchip technology inc. !" ! #$! !% # $ !% # $ #&! ! !# "' ( )*+ ) # & #, $ --# $## . # #$ # / ! - 0 # 1 / % # #! # ## +22--- 2 / 3# 44" " 4 # 5 56 7 5$ 8 %1 5 ( 4 !1# ()* 6$# !4 !1# )* 6, : # < ( !!1 / / ; < # ! %% < ( 6, =!# " < !!1 / =!# " < ; 6, 4# < . #4# 4 < 9 . # # 4 ( < ; . # > < > 4 ! / ; < 9 4 !=!# 8 < ( n b e e1 d 1 2 3 e e1 a a1 a2 c l l1 - * ) ? 2013 microchip technology inc. ds25165a-page 27 MCP6421 \ note: for the most current package drawings, please see the microchip packaging specification located at http://www.microchip.com/packaging MCP6421 ds25165a-page 28 ? 2013 microchip technology inc. notes: ? 2013 microchip technology inc. ds25165a-page 29 MCP6421 appendix a: revision history revision a (march 2013) ? original release of this document. MCP6421 ds25165a-page 30 ? 2013 microchip technology inc. notes: ? 2013 microchip technology inc. ds25165a-page 31 MCP6421 product identification system to order or obtain information, e. g., on pricing or delivery, refer to the factory or the listed sales office . device: MCP6421t: single op amp (tape and reel) (sc70, sot-23) temperature range: e = -40c to +125c (extended) package: lty = plastic package (sc70), 5-lead ot = plastic small outline transistor (sot-23), 5-lead part no. -x /xx package temperature range device t tape and reel examples: a) MCP6421t-e/lty: tape and reel, extended temperature, 5ld sc-70 package b) MCP6421t-e/ot: tape and reel, extended temperature, 5ld sot-23 package MCP6421 ds25165a-page 32 ? 2013 microchip technology inc. notes: ? 2013 microchip technology inc. ds25165a-page 33 information contained in this publication regarding device applications and the like is provided only for your convenience and may be superseded by updates. it is your responsibility to ensure that your application meets with your specifications. microchip makes no representations or warranties of any kind whether express or implied, written or oral, statutory or otherwise, related to the information, including but not limited to its condition, quality, performance, merchantability or fitness for purpose . microchip disclaims all liability arising from this information and its use. use of microchip devices in life support and/or safety applications is entirely at the buyer?s risk, and the buyer agrees to defend, indemnify and hold harmless microchip from any and all damages, claims, suits, or expenses resulting from such use. no licenses are conveyed, implicitly or otherwise, under any microchip intellectual property rights. trademarks the microchip name and logo, the microchip logo, dspic, flashflex, k ee l oq , k ee l oq logo, mplab, pic, picmicro, picstart, pic 32 logo, rfpic, sst, sst logo, superflash and uni/o are registered trademarks of microchip technology incorporated in the u.s.a. and other countries. filterlab, hampshire, hi-tech c, linear active thermistor, mtp, seeval and the embedded control solutions company are registered trademarks of microchip technology incorporated in the u.s.a. silicon storage technology is a registered trademark of microchip technology inc. in other countries. analog-for-the-digital age, app lication maestro, bodycom, chipkit, chipkit logo, codeguard, dspicdem, dspicdem.net, dspicworks, dsspeak, ecan, economonitor, fansense, hi-tide, in-circuit serial programming, icsp, mindi, miwi, mpasm, mpf, mplab certified logo, mplib, mplink, mtouch, omniscient code generation, picc, picc-18, picdem, picdem.net, pickit, pictail, real ice, rflab, select mode, sqi, serial quad i/o, total endurance, tsharc, uniwindriver, wiperlock, zena and z-scale are trademarks of microchip technology incorporated in the u.s.a. and other countries. sqtp is a service mark of microchip technology incorporated in the u.s.a. gestic and ulpp are registered trademarks of microchip technology germany ii gmbh & co. & kg, a subsidiary of microchip technology inc., in other countries. all other trademarks mentioned herein are property of their respective companies. ? 2013, microchip technology incorporated, printed in the u.s.a., all rights reserved. printed on recycled paper. isbn: 978-1-62077-046-7 note the following details of the code protection feature on microchip devices: ? microchip products meet the specification cont ained in their particular microchip data sheet. ? microchip believes that its family of products is one of the most secure families of its kind on the market today, when used i n the intended manner and under normal conditions. ? there are dishonest and possibly illegal methods used to breach the code protection feature. all of these methods, to our knowledge, require using the microchip produc ts in a manner outside the operating specif ications contained in microchip?s data sheets. most likely, the person doing so is engaged in theft of intellectual property. ? microchip is willing to work with the customer who is concerned about the integrity of their code. ? neither microchip nor any other semiconduc tor manufacturer can guarantee the security of their code. code protection does not mean that we are guaranteeing the product as ?unbreakable.? code protection is constantly evolving. we at microchip are co mmitted to continuously improvin g the code protection features of our products. attempts to break microchip?s code protection feature may be a violation of the digital millennium copyright act. if such acts allow unauthorized access to your software or other copyrighted work, you may have a right to sue for relief under that act. microchip received iso/ts-16949:2009 certification for its worldwide headquarters, design and wafer fabrication facilities in chandler and tempe, arizona; gresham, oregon and design centers in california and india. the company?s quality system processes and procedures are for its pic ? mcus and dspic ? dscs, k ee l oq ? code hopping devices, serial eeproms, microperipherals, nonvolatile memory and analog products. in addition, microchip?s quality system for the design and manufacture of development systems is iso 9001:2000 certified. quality management s ystem certified by dnv == iso/ts 16949 == ds25165a-page 34 ? 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