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? 2015-2016 microchip technology inc. ds20005474c-page 1 mcp1501 features ? maximum temperature coefficient: 50 ppm/c from -40c to +125c ? initial accuracy: 0.1% ? operating temperature range: -40 to +125c ? low typical operating current: 140 a ? line regulation: 50 ppm/v maximum ? load regulation: 40 ppm/ma maximum ? 8 voltage variants available: - 1.024v - 1.250v - 1.800v - 2.048v - 2.500v - 3.000v - 3.300v - 4.096v ? output noise (10 hz to 10 khz): < 0.1 v p-p applications ? precision data acquisition systems ? high-resolution data converters ? medical equipment applications ? industrial controls ? battery-powered devices introduction the mcp1501 is a buffered voltage reference capable of sinking and sourcing 20 ma of current. the voltage reference is a low-drift bandgap-based reference. the bandgap uses chopper-based amplifiers, effectively reducing the drift to zero. the mcp1501 is available in the following packages: ? 6-lead sot-23 ? 8-lead soic ? 8-lead 2mmx2mm wdfn package types 4 1 2 3 6 v dd shdn out gnd gnd 5 gnd mcp1501 6-lead sot-23 feedback gnd v dd nc shdn out mcp1501 8-lead soic gnd gnd mcp1501 2x2 wdfn* shdn gnd gnd out gnd 1 2 3 4 8 7 6 5 gnd feedback v dd ep 9 *includes exposed thermal pad (ep). see ta b l e 3 - 1 8 7 6 5 1 2 3 4 high-precision buffered voltage reference
mcp1501 ds20005474c-page 2 ? 2015-2016 microchip technology inc. block diagram shutdown circuitry out feedback shdn gnd v dd ? 2015-2016 microchip technology inc. ds20005474c-page 3 mcp1501 1.0 electrical characteristics absolute maximum ratings (?) v dd ............................................................................................................................... ..............................................5.5v maximum current into v dd pin ........................................................................................................................... .... 30 ma clamp current, i k (v pin < 0 or v pin > v dd )........................................................................................................... 20 ma maximum output current sunk by output pin ............... ....................................................................... ................30 ma maximum output current sourced by output pin ................................................................................... ..............30 ma (hbm:cdm:mm)................................................................................................................... ............. (2 kv:1.5 kv:200v) ? notice : stresses above those listed under ?absolute ma ximum 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 operation listings of th is specification is not implied. exposure above maximum rating conditions for extended periods may affect device reliability. table 1-1: dc characteristics electrical characteristics: unless otherwise specified, v dd(min) ?? v dd ? 5.5v at -40 ? c ? t a ? +125 ? c. characteristic sym. min. typ. max. units conditions supply voltage v dd 1.65 ? 5.5 v mcp1501-10 v dd 1.7 ? 5.5 v mcp1501-12 v dd 2.0 ? 5.5 v mcp1501-18 v dd 2.25 ? 5.5 v mcp1501-20 v dd 2.70 ? 5.5 v mcp1501-25 v dd 3.2 ? 5.5 v mcp1501-30 v dd 3.5 ? 5.5 v mcp1501-33 v dd 4.3 ? 5.5 v mcp1501-40 power-on-reset release voltage v por ?1.45 ? v power-on-reset rearm voltage ??0.8?v output voltage mcp1501-10 v out 1.0232 1.024 1.0248 v mcp1501-12 1.2490 1.250 1.2510 v mcp1501-18 1.7985 1.800 1.8015 v mcp1501-20 2.0460 2.048 2.0500 v mcp1501-25 2.4980 2.500 2.5020 v mcp1501-30 2.9975 3.000 3.0025 v mcp1501-33 3.2975 3.300 3.3025 v mcp1501-40 4.0925 4.096 4.0995 v temperature coefficient mcp1501-xx t c ? 10 50 ppm/ ? c line regulation ? v out / ? v in ? ? 50 ppm/v load regulation ? v out / ? i out ? ? 40 ppm ? sink 70 ppm ? source ppm/ma -5 ma < i load <+5ma dropout voltage v do ? ? 200 mv -5 ma < i load <+2ma power supply rejection ratio psrr 94 db 1.024v option, v in =5.5v, 1khz at 100mv p-p mcp1501 ds20005474c-page 4 ? 2015-2016 microchip technology inc. shutdown v il 1.35 v in =5.5v v ih 3.80 output voltage hysteresis ? v out_hyst 300 v refer to section 1.1.10 ?output voltage hysteresis? for additional details on testing conditions. output noise mcp1501-10 e n ?0.1 ? v p-p 0.1 hz to 10 hz, t a =+25 ? c ? 5 ? 10 hz to 10 khz, t a =+25 ? c mcp1501-20 e n ?0.1 ? v p-p 0.1 hz to 10 hz, t a =+25 ? c ? 10 ? 10 hz to 10 khz, t a =+25 ? c mcp1501-40 e n ?0.1 ? v p-p 0.1 hz to 10 hz, t a =+25 ? c ? 20 ? 10 hz to 10 khz, t a =+25 ? c maximum load current i load ?20 ? mat a =+25c 2.048v option supply current i dd ? 140 550 a no load ? ? 350 no load, t a = +25c shutdown current mcp1501-10 i shdn 205 na t a =+25c mcp1501-20 185 mcp1501-40 185 table 1-1: dc characteristics (continued) electrical characteristics: unless otherwise specified, v dd(min) ?? v dd ? 5.5v at -40 ? c ? t a ? +125 ? c. characteristic sym. min. typ. max. units conditions table 1-2: temperature specifications electrical specifications: unless otherwise indicated, all parameters apply at av dd, dv dd = 2.7 to 3.6v. parameters sym. min. typ. max. units conditions temperature ranges operating temperature range t a -40 ? +125 c storage temperature range t a -65 ? +150 c thermal package resistance thermal resistance for sot-23-6 ? ja ? +190.5 ? c/w thermal resistance for soic-8 ? ja ? +149.5 ? c/w thermal resistance for dfn-8 ? ja ? +141.3 ? c/w ? 2015-2016 microchip technology inc. ds20005474c-page 5 mcp1501 1.1 terminology 1.1.1 output voltage output voltage is the reference voltage that is available on the out pin. 1.1.2 input voltage the input voltage (v in ) is the range of voltage that can be applied to the v dd pin and still have the device produce the designated outp ut voltage on the out pin. 1.1.3 temperature coefficient (tc out ) the output temperature coeffi cient or voltage drift is a measure of how much the output voltage will vary from its initial value with changes in ambient temperature. the value specified in the el ectrical specifications is measured as shown in equation 1-1 . equation 1-1: tc output calculation 1.1.4 dropout voltage the dropout voltage is defined as the voltage difference between v dd and v out under load. equation 1-2 is used to calculate the dropout voltage. equation 1-2: 1.1.5 line regulation an ideal voltage reference will maintain a constant out- put voltage regardless of any changes to the input volt- age. however, when real devices are considered, a small error may be measured on the output when an input voltage change occurs. line regulation is defined as the change in output volt- age ( ? v out ) as a function of a change in input voltage ( ? v in ), and expressed as a percentage, as shown in equation 1-3 . equation 1-3: line regulation may also be expressed as %/v or in ppm/v, as shown in equation 1-4 and equation 1-5 , respectively. equation 1-4: equation 1-5: as an example, if the mcp 1501-20 is implemented in a design and a 2 v change in output voltage is mea- sured from a 250 mv change on the input, then the error in percent, ppm, percent/volt, and ppm/volt, as shown in equation 1-6 ? equation 1-9 . equation 1-6: equation 1-7: equation 1-8: equation 1-9: tc out out max out min ? ? t out nom ? -------------------------------------------------------- 10 6 ppm/ ? c ? = where: out max = maximum output voltage over the temperature range out min = minimum output voltage over the temperature range out nom = average output voltage over the temperature range ? t = temperature range over which the data was collected v do v in v out | i out cons t tan = ? = ? v out ? v in -------------------- 100% ? % line regulation = ? v out ? v out nom ?? --------------------------------------- ?? ?? ?? ? v in --------------------------------------------- 100% ? % v ---- - line regulation = ? v out ? v out nom ?? --------------------------------------- ?? ?? ?? ? v in --------------------------------------------- 10 6 ? ppm v ---------- - line regulation = ? v out ? v in -------------------- 100% ? ?? ?? ?? 2 ? v 250 mv ------------------ 100% ? ?? ?? ? .0008% = ? v out ? v in -------------------- 10 6 ? ?? ?? ?? 2 ? v 250 mv ------------------ 10 6 ? ?? ?? ? 8 ppm = ? v out ? v in -------------------- 100% ? 2 ? v 2.048v ----------------- ?? ?? 250 mv ---------------------- - ?? ?? ?? ?? ?? 100% ? 0.000390625 % v ---- - = = ? v out ? v in -------------------- 10 6 ? 2 ? v 2.048v ----------------- ?? ?? 250 mv ---------------------- - ?? ?? ?? ?? ?? 10 6 ? 3.90625 ppm v ----------- - = = mcp1501 ds20005474c-page 6 ? 2015-2016 microchip technology inc. 1.1.6 load regulation an ideal voltage reference will maintain the specified output voltage regardless of the load's current demand. however, real devices experi ence a small error voltage that deviates from the specified output voltage when a load is present. load regulation is defined as the voltage difference when under no load (v out @ i out|0 ) and under maxi- mum load (v out @ i out|max ), and is expressed as a percentage, as shown in equation 1-10 . equation 1-10: similar to line regulation, load regulation may also be expressed as %/ma or in ppm/ma as shown in equation 1-11 and equation 1-12 , respectively. equation 1-11: equation 1-12: as an example, if the mcp 1501-20 is implemented in a design and a 10 v change in output voltage is mea- sured from a 2 ma change on the input, then the error in percent, ppm, percent/volt, ppm/volt, as shown in equation 1-13 ? equation 1-16 . equation 1-13: equation 1-14: equation 1-15: equation 1-16: v out @ i out|0 v out @ i out|max ? v out @ i out|max -------------------------------------------------------------------------------------------------------------- 100% ? % load regulation = ? v out ? v out nom ?? --------------------------------------- ?? ?? ?? ? i out --------------------------------------------- 100% ? % ma ------- - line regulation = ? v out ? v out nom ?? --------------------------------------- ?? ?? ?? ? i out --------------------------------------------- 10 6 ? ppm ma ---------- - load regulation = 2.048v 2.04799v ? 2.04799v ---------------------------------------------- - 100% . = ? 0004882% 2.048v 2.04799v ? 2.04799v ---------------------------------------------- - 10 6 2.048v 2.04799v ? 2.04799v ---------------------------------------------- - 10 6 ? ?? ?? = ? 4.882 ppm = ? v out v out nom ?? ----------------------------------- - ?? ?? ?? ? i out ----------------------------------------- - 100% ? 10 ? v 2.048v ----------------- ?? ?? 2 ma ---------------------- - ?? ?? ?? ?? ?? 100% ? 0.2441 % ma ------- - = = ? v out v out max ?? ---------------------------------- - ?? ?? ?? ? i out ---------------------------------------- - 10 6 ? 10 ? v 2.048v ----------------- ?? ?? 2 ma ---------------------- - ?? ?? ?? ?? ?? 10 6 ? 0.2441 ppm m a ---------- - = = ? 2015-2016 microchip technology inc. ds20005474c-page 7 mcp1501 1.1.7 input current the input current (operating cu rrent) is the current that sinks from v in to gnd without a load current on the output pin. this current is affected by temperature, input voltage, output volt age, and the load current. 1.1.8 power supply rejection ratio power supply rejection ratio (psrr) is a measure of the change in output voltage ( ? v out ) relative to the change in input voltage ( ? v in ) over frequency. 1.1.9 long-term drift the long-term output stability is measured by exposing the devices to an ambient temperature of +125c, as shown in figure 2-18 while configured in the circuit shown in figure 1-1 . in this test, all electrical specifica- tions of the devices are measured periodically at +25c. figure 1-1: long-term drift test circuit. 1.1.10 output vo ltage hysteresis the output voltage hysteresis is a measure of the out- put voltage error after the powered devices are cycled over the entire operating temperature range. the amount of hysteresis can be quantified by measuring the change in the +25c output voltage after tempera- ture excursions from +25c to +125c to +25c, and also from +25c to -40c to +25c. v in gnd gnd gnd gnd gnd fb v out power signal in mcp1501 ds20005474c-page 8 ? 2015-2016 microchip technology inc. notes: ? 2015-2016 microchip technology inc. ds20005474c-page 9 mcp1501 2.0 typical operating curves note: unless otherwise specified, maximum values are: v dd(min) ?? v dd ? 5.5v at -40 ? c ? t a ? +125 ? c. figure 2-1: v out vs. temperature, no load, 4.096v option. figure 2-2: v out vs. temperature, no load, 2.048v option. figure 2-3: v out vs. temperature, no load, 1.024v option. figure 2-4: load regulation vs. temperature, i load 5ma sink. figure 2-5: load regulation vs. temperature, i load 5ma source. figure 2-6: i dd vs. temperature, all options. note: the graphs and tables provided following this note ar e a statistical summary ba sed 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 pres ented may be outside the specified operating range (e.g., outside specified power suppl y range) and therefore outs ide the warranted range. 4.092 4.093 4.094 4.095 4.096 4.097 4.098 -40 5 25 85 125 vout (v) temperature ( c) 2.046 2.0465 2.047 2.0475 2.048 2.0485 -40 5 25 85 125 vout (v) temperature ( c) 1.023 1.0232 1.0234 1.0236 1.0238 1.024 1.0242 1.0244 -40 5 25 85 125 vout (v) temperature ( c) 0 5 10 15 20 25 30 35 40 -40 25 125 load reg (ppm/ma) temperature ( c) 1.024v 1.25v 1.8v 2.048v 2.5v 3v 3.3v 4.096v 0 5 10 15 20 25 30 35 40 -40 25 125 load reg (ppm/ma) temperature ( c) 1.024v 1.25v 1.8v 2.048v 2.5v 3v 3.3v 4.096v 150 175 200 225 250 275 300 -40 5 25 85 125 i dd (a) temperature ( c) v 2 8 7 = 4.096v v 2 8 7 = 2.048v v 2 8 7 = 1.024v mcp1501 ds20005474c-page 10 ? 2015-2016 microchip technology inc. figure 2-7: i dd vs. temperature for v out , 50 units, no load, 4.096v option. figure 2-8: i dd vs. temperature for v out , 50 units, no load, 1.024v option. figure 2-9: i dd vs. v dd , v out = 4.096v, 50 units, no load. figure 2-10: i dd vs. v dd , v out = 1.024v, 50 units, no load. figure 2-11: line regulation vs. temperature. figure 2-12: noise vs. frequency, no load, t a = +25c. 0 50 100 150 200 250 300 350 400 450 -40 5 25 85 125 i dd (a) temperature ( c) average +3 sigma -3 sigma 0 50 100 150 200 250 300 -40 5 25 85 125 i dd (a) temperature ( c) average +3 sigma -3 sigma 0 50 100 150 200 250 300 350 4.3 4.45 4.6 4.75 4.9 5.05 5.2 5.5 i dd (a) v dd (v) average +3 sigma -3 sigma 100 120 140 160 180 200 220 240 260 1.65 2 2.25 2.5 2.75 3 3.25 3.5 3.75 4 4.25 4.5 4.75 5 5.25 5.5 i dd (a) v dd (v) average -3 sigma +3 sigma 0 0.5 1 1.5 2 2.5 3 3.5 4 4.5 5 -40 -25 -10 5 20 35 50 65 80 95 110 125 line reg (ppm/v) temperature ( c) v 2 8 7 = 1.8v v 2 8 7 = 3.0v v 2 8 7 = 1.024v v 2 8 7 = 2.048v v 2 8 7 = 3.3v v 2 8 7 = 1.25v v 2 8 7 = 2.5v v 2 8 7 = 4.096v 0.1 1 10 100 1000 10000 0.01 1 100 10000 1000000 noise nv/sqrt hz frequency v 2 8 7 = 1.024v, v ' ' = 1.65v v 2 8 7 = 1.024v, v ' ' = 5.5v v 2 8 7 = 4.096v, v ' ' = 4.3v v 2 8 7 = 4.096v, v ' ' = 5.5v ? 2015-2016 microchip technology inc. ds20005474c-page 11 mcp1501 figure 2-13: psrr vs. frequency, no load, t a = +25c. figure 2-14: psrr vs. frequency, 1 k ? load, t a = +25c. figure 2-15: dropout voltage vs. load, t a = +25c, 2.048v option. figure 2-16: tempco distribution, no load, t a = +25c, v dd = 2.7v, 50 units. figure 2-17: tempco distribution, no load, t a = +25c, v dd = 5.5v, 50 units. figure 2-18: v out drift vs. time, t a = +25c, no load, 800 units. 0 20 40 60 80 100 120 1 10 100 1000 10000 100000 psrr (db) frequency (hz) v 2 8 7 = 1.024, v , 1 = 1.65v v 2 8 7 = 1.024v, v , 1 = 5.5v v 2 8 7 = 4.096v, v , 1 = 4.3v v 2 8 7 = 4.096v, v , 1 = 5.5v 0 20 40 60 80 100 120 1 10 100 1000 10000 100000 psrr (db) frequency (hz) v 2 8 7 = 1.024v, v , 1 = 1.65v v 2 8 7 = 1.024v, v , 1 = 5.5v v 2 8 7 = 4.096v, v , 1 = 4.3v v 2 8 7 = 4.096v, v , 1 = 5.5v 0 20 40 60 80 100 120 140 160 -5 -2 0 2 5 dropout voltage (mv) load (ma) 0 0.02 0.04 0.06 0.08 0.1 0.12 0.14 0.16 0.18 1 3 5 7 9 111315171921232527 29 percentage of total units temperature coefficient (ppm/ & ) 0 0.02 0.04 0.06 0.08 0.1 0.12 0.14 0.16 13579111315171921232527 29 percentage of total units temperature coefficient (ppm/ & ) -0.6 -0.4 -0.2 0 0.2 0.4 0.6 0.8 1 1.2 0 48 1008 vout drift (mv) time (hrs) average +3 sigma -3 sigma mcp1501 ds20005474c-page 12 ? 2015-2016 microchip technology inc. figure 2-19: v out vs. load, t a = +25c, 2.048v option. figure 2-20: v out at v ddmin , v dd = 2.7v, 800 units, 2.5v option, no load. figure 2-21: v out distribution at v ddmax , v dd = 5.5v, 800 units, 2.5v option, no load. figure 2-22: noise vs. time, vdd = 5.5v, t a = +25c, 2.048v option, no load, 2 v/div, 100 ms/div. figure 2-23: turn on transient, v dd = 5/5v, v in = 2.048v option, no load. figure 2-24: line transient, v dd = 5.5v, v in = 500 mv pp @ 5v dc , 2.048v option, no load. 2.0475 2.0476 2.0477 2.0478 2.0479 2.048 2.0481 2.0482 2.0483 2.0484 2.0485 -30 -20 -10 0 10 20 30 v out (v) load (ma) 0.00 0.05 0.10 0.15 0.20 0.25 0.30 0.35 0.40 0.45 2.495111 2.4956108 2.4961106 2.4966104 2.4971102 2.49761 2.4981098 2.4986096 2.4991094 2.4996092 2.500109 2.5006088 2.5011086 2.5016084 2.5021082 2.502608 2.5031078 2.5036076 2.5041074 2.5046072 2.505107 2.5056068 2.5061066 2.5066064 2.5071062 2.507606 2.5081058 2.5086056 2.5091054 2.5096052 2.510105 percentage of total units v out qc +25c qc -40c qc +125c 0.00 0.05 0.10 0.15 0.20 0.25 0.30 0.35 0.40 0.45 2.495111 2.4956108 2.4961106 2.4966104 2.4971102 2.49761 2.4981098 2.4986096 2.4991094 2.4996092 2.500109 2.5006088 2.5011086 2.5016084 2.5021082 2.502608 2.5031078 2.5036076 2.5041074 2.5046072 2.505107 2.5056068 2.5061066 2.5066064 2.5071062 2.507606 2.5081058 2.5086056 2.5091054 2.5096052 2.510105 percentage of total units v out qc +25c qc -40c qc +125c conditions: v out 2v/div 500 s/div v in 2v/div 500 s/div conditions: v in 1v/div 5 ms/div v out 10 mv 5 ms/div /div ? 2015-2016 microchip technology inc. ds20005474c-page 13 mcp1501 figure 2-25: load transient, v dd = 5.5, v in = 2.5, 2.048v option. figure 2-26: r iso vs. c load , 4.096v option unloaded. figure 2-27: r iso vs. c load , 4.096v option loaded. i out 10 ma/div v out 500 mv/div 200 s/div 1.e-12 10.e-12 100.e-12 1.e-9 10.e-9 100.e-9 1.e-6 10.e-6 100.e-6 1.e-3 04590 135 capacitive load (f) phase margin ( ) r , 6 2 = 1 r , 6 2 = 10 r , 6 2 = 100 r , 6 2 = 1k 1.e-12 10.e-12 100.e-12 1.e-9 10.e-9 100.e-9 1.e-6 10.e-6 100.e-6 1.e-3 0 45 90 135 capacitive load (f) phase margin ( ) r iso = 1 ? r iso = 10 ? r iso = 100 ? r iso = 1k ? mcp1501 ds20005474c-page 14 ? 2015-2016 microchip technology inc. notes: ? 2015-2016 microchip technology inc. ds20005474c-page 15 mcp1501 3.0 pin function table the pin functions are described in ta b l e 3 - 1 . 3.1 buffered v ref output (out) this is the buffered refe rence output. on the wdfn and soic package, this should be connected to the feedback pin at the device. the output driver is tristated when in shutdown. 3.2 buffered v ref feedback (feedback) this is the buffer amplifier feedback pin. on the wdfn and soic package, this should be connected to the out pin at the device. this connection is internal on the sot-23 package. note t hat if there is routing impedance or ir-drop between the out and feedback pins, it is the feedback pin which accu- rately holds the output voltage. this can be used in an application to remove ir-drop effects on output voltage caused by the printed circuit board (pcb) or interconnect resistance with a high-current load. 3.3 system ground (gnd) this is the power supply return and should be connected to system ground. 3.4 shutdown pin (shdn ) this is a digital input that will place the device in shutdown. this pin is active low. 3.5 power supply input (v dd ) this power pin also serves as the input voltage for the voltage reference. refer to the electrical tables to determine minimum voltage, based on the device. 3.6 exposed thermal pad (ep) not internally connected, but recommend grounding. table 3-1: pin function table sot-23 soic 2 x 2 wdfn symbol function 18 8 outbuffered v ref output ? 7 7 feedback buffered v ref feedback 2,3,5 2,4,5,6 2,4,5,6 gnd system ground 4 3 3 shdn shutdown pin active low 61 1 v dd power supply input ? ? 9 ep exposed thermal pad mcp1501 ds20005474c-page 16 ? 2015-2016 microchip technology inc. notes: ? 2015-2016 microchip technology inc. ds20005474c-page 17 mcp1501 4.0 theory of operation the mcp1501 is a buffered voltage reference that is capable of operating over a wide input supply range while providing a stable output across the input supply range. the fundamental building block (see block dia- gram ) of the mcp1501 is an internal bandgap refer- ence circuit. as with all bandgap circuits, the internal reference sums together two voltages having an oppo- site temperature coefficient which allows a voltage ref- erence that is practically independent from temperature. the bandgap of the mcp1501 is based on a second order temperature coefficient (tc) compensated band- gap circuit that allows the mcp1501 to achieve high ini- tial accuracy and low temperature coefficient operation across supply and ambient temperature. the bandgap curvature compensation is determined during device characterization and is trimmed for optimal accuracy. the mcp1501 also includes a chopper-based amplifier architecture that ensures excellent low-noise opera- tion, further reduces temperature dependent offsets that would otherwise increas e the temperature coeffi- cient of the mcp1501, and significantly improves long-term drift performance. additional circuitry is included to eliminate the chopping frequency from the output of the device. after the bandgap voltage is compensated, it is ampli- fied, buffered, and provided to the output drive circuit which has excellent performance when sinking or sourcing load currents (5 ma). mcp1501 ds20005474c-page 18 ? 2015-2016 microchip technology inc. notes: ? 2015-2016 microchip technology inc. ds20005474c-page 19 mcp1501 5.0 application circuits 5.1 application tips 5.1.1 basic application circuit figure 5-1 illustrates a basic circ uit configuration of the mcp1501. figure 5-1: basic circuit configuration. an output capacitor is not required for stability of the voltage reference, but may be optionally added to pro- vide noise filtering or act as a charge-reservoir for switching loads, e.g., su ccessive approximation regis- ter (sar) analog-to-digital converter (adc). as shown, the input voltage is connected to the device at the v in input, with an optional 2.2 f ceramic capacitor. this capacitor would be required if the input voltage has excessive noise. a 2.2 f capacitor would reject input voltage noise at approximately 1 to 2 mhz. noise below this frequency will be amply rejected by the input voltage rejection of the voltage reference. noise at fre- quencies above 2 mhz will be beyond the bandwidth of the voltage reference and, consequently, not transmit- ted from the input pin through the device to the output. if the noise at the output of these voltage references is too high for the particular applic ation, it can be easily fil- tered with an external rc filter and op-amp buffer (see figure 5-2 ). figure 5-2: output noise-reducing filter. v dd shdn gnd 1 2 3 4 5 8 7 6 soic-8/dfn-8 gnd ) ( ( ' % $ & |