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general description the max7391 replaces ceramic resonators, crystals, and supervisory functions for microcontrollers in 3.3v and 5v applications. the max7391 provides a clock source, reset, and power-fail functions. the programmable power-fail func- tion provides early warning of power failure and is con- figurable to detect either an external voltage or the v cc supply to the device. the clock output can be switched between normal and half-speed operation. this functionality allows the micro- controller to operate at reduced power and may be used to extend the time available to perform house- keeping tasks, such as writing data to flash during a power failure. connecting the power-fail output to the speed input reduces clock speed automatically during power-fail events. the max7391 clock output is factory programmed to a frequency in the 1mhz to 16mhz range. four standard frequencies are available. other frequencies are avail- able upon request. the maximum operating supply cur- rent is 5.5ma (typ) with a clock frequency of 12mhz. unlike typical crystal and ceramic resonator oscillator circuits, the max7391 is resistant to emi and vibration, and operates reliably at high temperatures. the high- output drive current and absence of high-impedance nodes make the oscillator invulnerable to dirty or humid operating conditions. the max7391 is available in an 8-pin ?ax package. the max7391 standard operating temperature range is from -40? to +125?. applications white goods automotive appliances and controls handheld products portable equipment microcontroller systems features ? robust microcontroller clock and supervisory functions in a single package ? integrated reset and power-fail functions ? speed select ? +2.7v to +5.5v operation ? factory-trimmed oscillator ? reset valid down to 1.1v supply voltage ? ?0ma clock-output drive current ? ?% total accuracy for -40? to +125? ? ?.75% total accurac for 0? to +85? ? 5.5ma operating current (12mhz version) ? -40? to +125? temperature range ? surface-mount package ? 1mhz to 16mhz factory preset frequency range max7391 speed-switching clock generator with power fail ________________________________________________________________ maxim integrated products 1 19-3981; rev 0; 1/06 for pricing, delivery, and ordering information, please contact maxim/dallas direct! at 1-888-629-4642, or visit maxim? website at www.maxim-ic.com. speed pfo gnd 1 2 8 7 clock rst/rst v cc n.c. pfi top view max 3 4 6 5 max7391 pin configuration ordering information part temp range pin-package pkg code max7391srff -40? to +125? 8 ?ax u8-1 note: ??is a placeholder for the reset output type. insert the symbol found in table 2 in the place of ?.???is a placeholder for the power-on reset (por) voltage. insert the symbol found in table 1 in the place of ?.??f?is a placeholder for the nominal output frequency. insert the symbol found in table 3 in the place of ?f.?for example, max7391cmtp describes a device with 4.38v reset level, open-collector rst output, and a clock output frequency of 8mhz. typical application circuit, functional diagram, and selector guide appear at end of data sheet. ?ax is a registered trademark of maxim integrated products, inc.
max7391 speed-switching clock generator with power fail 2 _______________________________________________________________________________________ absolute maximum ratings stresses beyond those listed under ?bsolute maximum ratings?may cause permanent damage to the device. these are stress rating s only, and functional operation of the device at these or any other conditions beyond those indicated in the operational sections of the specificatio ns is not implied. exposure to absolute maximum rating conditions for extended periods may affect device reliability. v cc to gnd ...........................................................-0.3v to +6.0v all other pins to gnd ................................-0.3v to (v cc + 0.3v) clock, rst /rst , pfo output current ..........................?0ma continuous power dissipation 8-pin ?ax (derate 4.5mw/? over t a = +70?)........362mw operating temperature range .........................-40? to +125? junction temperature ......................................................+150? storage temperature range .............................-65? to +150? lead temperature (soldering, 10s) .................................+300? electrical characteristics ( typical application circuit , v cc = +2.7v to +5.5v, t a = -40? to +125?, 1mhz to 16mhz output frequency range, typical values at v cc = +5.0v, t a = +25?, unless otherwise noted.) (note 1) parameter symbol conditions min typ max units power requirements operating supply voltage v cc 2.7 5.5 v valid rst/ rst supply voltage v ccr minimum supply voltage for valid rst/ rst output, t a = 0? to +85? 1.1 v f clock = 12mhz 5.5 operating supply current i cc f clock = 8mhz 4.5 ma logic input: speed input leakage current i leak input is high 0.5 ? logic-input high voltage v ih 0.7 x v cc v logic-input low voltage v il 0.3 x v cc v push-pull logic outputs: rst/ rst output high v oh i source = 1ma v cc - 1.5 v output low v ol i sink = 3ma 0.05 0.4 v open-drain logic outputs: rst , pfo output low v olo i sink = 3ma 0.05 0.4 v output: clock clock output high voltage v ohc i source = 5ma v cc - 0.3 v clock output low voltage v olc i sink = 5ma 0.3 v clock accuracy f clock table 3, v cc = +5.0v -4 +4 %
max7391 speed-switching clock generator with power fail _______________________________________________________________________________________ 3 electrical characteristics (continued) ( typical application circuit , v cc = +2.7v to +5.5v, t a = -40? to +125?, 1mhz to 16mhz output frequency range, typical values at v cc = +5.0v, t a = +25?, unless otherwise noted.) (note 1) parameter symbol conditions min typ max units clock frequency temperature coefficient v cc = +5.0v (note 2) 140 400 ppm/? clock frequency supply voltage coefficient t a = +25 c (note 2) 0.67 1 %/v clock duty cycle (note 2) 45 50 55 % clock output jitter observation for 20s using a 500mhz oscilloscope 310 ps rms output rise time t r c load = 10pf, 10% to 90% of full scale (note 2) 2.5 7.0 ns output fall time t f c load = 10pf, 90% to 10% of full scale (note 2) 2.5 7.5 ns internal power-on reset t a = +25? v th - 1.5% v th + 1.5% v th+ v cc rising, table 1 t a = -40? to +125? v th - 2.5% v th + 2.5% reset voltage v th- v cc falling 0.98 x v th+ v reset timeout period t rst figure 1 86 135 250 ? power fail power-fail select threshold v sel pfi input 0.65 x v cc 0.85 x v cc v v cc monitoring threshold (internal threshold) v ith v cc rising 4.06 4.38 4.60 v internal threshold hysteresis v ihyst v cc falling 1.0 2 4.0 %v ith pfi monitoring threshold (external threshold) v eth pfi rising 0.9 1.1 1.4 v external threshold hysteresis v ehyst pfi falling 1.0 3.5 8.0 %v eth note 1: all parameters are tested at t a = +25?. specifications over temperature are guaranteed by design. note 2: guaranteed by design. not production tested.
max7391 speed-switching clock generator with power fail 4 _______________________________________________________________________________________ typical operating characteristics ( typical application circuit , v cc = +5v, f clock = 16mhz, t a = +25?, unless otherwise noted.) frequency vs. supply voltage max7391 toc01 v cc (v) normalized frequency 4.85 4.20 3.55 0.990 1.000 1.010 1.020 0.980 2.90 5.50 normalized to v cc = 5v v th+ = 2.9v frequency vs. temperature max7391 toc02 temperature ( c) normalized frequency 110 95 80 65 50 35 20 5 -10 -25 0.990 1.000 1.010 1.020 1.030 1.040 0.980 -40 125 normalized to t a = +25 c duty cycle vs. supply voltage max7391 toc03 v cc (v) duty cycle (%) 4.85 4.20 3.55 49 50 51 52 48 2.90 5.50 v th+ = 2.9v duty cycle vs. temperature max7391 toc04 duty cycle (%) 49 50 51 52 48 temperature ( c) 110 95 80 65 50 35 20 5 -10 -25 -40 125 clock output waveform with c l = 10pf max7391 toc05 40ns/div clock 1v/div v cc = 3.3v clock output waveform with c l = 50pf max7391 toc06 40ns/div clock 1v/div v cc = 3.3v clock output waveform with c l = 100pf max7391 toc07 40ns/div clock 1v/div supply current vs. temperature max7391 toc08 i cc (ma) 2 3 4 5 1 temperature ( c) 110 95 80 65 50 35 20 5 -10 -25 -40 125 v cc = 5v v cc = 3.3v supply current vs. supply voltage max7391 toc09 v cc (v) i cc (ma) 4.85 4.20 3.55 2 3 4 5 1 2.90 5.50 v th+ = 2.9v
max7391 speed-switching clock generator with power fail _______________________________________________________________________________________ 5 clock settling time from start max7391 toc10 1 s/div clock 2v/div v cc 2v/div power-on reset behavior max7391 toc11 20 s/div clock 5v/div v cc 5v/div rst 5v/div pfo 5v/div maximum v cc transient duration vs. reset threshold overdrive max7391 toc12 reset threshold overdrive (mv) transient duration ( s) 900 800 700 600 500 400 300 200 10 100 1000 1 100 1000 reset occurs above this curve v cc falling from v th+ + 100mv rising threshold vs. temperature max7391 toc14 temperature ( c) v th+ (v) 110 95 80 65 50 35 20 5 -10 -25 2.82 2.84 2.86 2.88 2.90 2.80 -40 125 clock response to speed select input max7391 toc13 200ns/div speed 2v/div clock 2v/div typical operating characteristics (continued) ( typical application circuit , v cc = +5v, f clock = 16mhz, t a = +25?, unless otherwise noted.)
detailed description the max7391 replaces ceramic resonators, crystals, and supervisory functions for microcontrollers in 3.3v and 5v applications. the max7391 provides a clock source, reset, and power-fail functions. the power-fail output provides early warning of power failure. the power-fail threshold is configurable to detect either an external voltage or the v cc supply voltage to the device. the clock output can be switched between normal and half-speed operation. this functionality allows the microcontroller to operate at reduced power and may be used to extend the time available to perform house- keeping tasks, such as writing data to flash, during a power failure. connecting the power-fail output ( pfo ) to the speed input reduces clock speed automatically during power-fail events. the integrated reset provides the power-supply monitor- ing functions necessary to ensure correct microcontroller operation. the reset circuit has built-in power-supply transient immunity and provides both power-on reset and power-fail or brownout reset functionality. two stan- dard factory-trimmed reset levels are available. a power-fail function is provided for power-supply volt- age monitoring and can provide advance notice of an impending power failure. the power-fail input monitors external power-supply voltages through an external resistive divider. connect pfi to v cc to monitor v cc . clock output (clock) the push-pull clock output (clock) drives a ground- connected 1k ? load or a positive supply connected 500 ? load to within 300mv of either supply rail. clock remains stable over the full operating voltage range and does not generate short output cycles during either power-on or power-off. a typical startup characteristic is shown in the typical operating characteristics section. the clock output frequency is reduced by a factor of two by taking speed low. this functionality allows the microcontroller to operate at reduced power and may be used to extend the time available to perform house- keeping tasks, such as writing data to flash during power failure. reset the reset function drives the microcontroller reset input to prevent operation in the cases of the initial power-on setting, low power-supply voltages, and the failed watchdog operations. three reset output versions are available: push-pull rst, push-pull rst , and open-drain rst . the reset timeout period (t rst ) is nominally 135s. power-on reset (por) the internal power-on reset (por) circuit detects the power-supply voltage (v cc ) level at startup. the por circuit starts the oscillator when v cc exceeds the reset rising threshold level (v th+ ). the reset output remains asserted from the time v cc crosses the v th+ and con- tinues to be asserted for the reset timeout period (t rst ). upon completion of the reset timeout, the reset output is released. see figure 1. max7391 speed-switching clock generator with power fail 6 _______________________________________________________________________________________ pin name function 1 pfi power-fail input. pfi monitors the condition of either an external supplied voltage or v cc . see the power fail section for more details. 2v cc power input. connect v cc to the power supply. bypass v cc to gnd with a 0.1? capacitor. install the bypass capacitor as close to the device as possible. 3 n.c. no connection 4 gnd ground 5 pfo power-fail output. open-drain output asserts when the voltage being monitored drops below the power-fail threshold voltage. 6 speed clock-speed select input. connect speed high for the factory-trimmed clock output frequency. connect speed low to reduce the clock output frequency by half. 7 rst/ rst reset output. reset output is available in one of three configurations: push-pull rst, push-pull rst , or open-drain rst . the reset output occurs if any combination of the following conditions occurs: reset outp ut i s asser ted d ur i ng p ow er - up , and w henever v c c i s b el ow the r eset thr eshol d l evel ; for d evi ces w i th w d i, r eset outp ut asser ts w hen w d i d oes not r ecei ve a r i si ng or fal l i ng ed g e w i thi n the w atchd og ti m eout p er i od . 8 clock clock output pin description
max7391 speed-switching clock generator with power fail _______________________________________________________________________________________ 7 low-voltage lockout the reset output asserts whenever v cc drops below the reset falling threshold, v th- . the difference between the reset rising and falling threshold values is v th+ - (v th- ). the nominal hysteresis value is 2% of the reset rising threshold value. the reset detection circuitry provides filtering to prevent triggering on negative voltage spikes. see the typical operating characteristics for a plot of maximum transient duration without causing a reset pulse vs. reset comparator overdrive. figure 1 shows the reset output (rst/ rst ) behavior during power-up and brownout. power fail the power-fail function provides early warning of a power failure. the power-fail comparator detects the condition of either an external voltage or the v cc supply voltage. internal (v cc ) detection is configured by connecting pfi to v cc . the internal v cc rising threshold (v ith ) is set at 4.38v. the open-drain pfo asserts low if the v cc supply voltage drops below the v cc falling threshold value (v ihyst ). the v cc falling threshold is nominally 2% below the v cc rising threshold. external power-fail detection is selected when the applied voltage on pfi (v pfi ) is less than 0.65 x v cc (v sel minimum). when the voltage on pfi is more than 0.85 x v cc (v sel maximum), the device switches to internal monitoring. external power-fail detection is nor- mally used with a resistive divider from the supply being monitored. see the typical application circuit . for a 3.3v supply, the voltage on pfi needs to be set externally and less than 0.65 x v cc (v sel minimum). to set the voltage on pfi externally, choose r1 and r2 so that: see figure 1 for pfo behavior during power-up and brownout. v pfi = + r powersupply rr 2 21 5 4 3 2 1 clk t rst v th+ v ith v th- v ccr v ith - v ihyst rst pfo clock starts on internal por (v th+ , v cc rising). rst releases after the reset timeout period. v cc (v) pfo asserts as v cc drops below v th . clock frequency reduction shown is achieved by connecting speed to pfo. rst continues to assert until v ccr . rst asserts on reset falling voltage (v th- , v cc falling). clock stops. figure 1. rst/ rst and pfo behavior during power-up and brownout
max7391 speed-switching clock generator with power fail 8 _______________________________________________________________________________________ applications information interfacing to a microcontroller clock input the clock output is a push-pull, cmos logic output, which directly drives any microprocessor (?) or micro- controller (?) clock input. there are no impedance- matching issues when using the max7391. operate the max7391 and ? (or other clock input device) from the same supply voltage level. refer to the microcontroller data sheet for clock-input compatibility with external clock signals. table 3 lists clock output frequency. the max7391 requires no biasing components or load capacitance. when using the max7391 to retrofit a crystal oscillator, remove all biasing components from the oscillator input. power-supply considerations the max7391 operates with power-supply voltages in the 2.7v to 5.5v range. good power-supply decoupling is needed to maintain the power-supply rejection per- formance of the max7391. bypass v cc to gnd with a 0.1? surface-mount ceramic capacitor. mount the bypass capacitor as close to the device as possible. if possible, mount the max7391 close to the microcon- troller? decoupling capacitor so that additional decou- pling is not required. a larger-value bypass capacitor is recommended if the max7391 is to operate with a large capacitive load. use a bypass capacitor value of at least 1000 times that of the output load capacitance. output jitter the max7391? jitter performance is given in the electrical characteristics table as a peak-to-peak value obtained by observing the output of the device for 20s with a 500mhz oscilloscope. jitter measurements are approximately proportional to the period of the output frequency of the device. thus, a 4mhz part has approx- imately twice the jitter value of an 8mhz part. the jitter performance of all clock sources degrades in the presence of mechanical and electrical interference. the max7391 is immune to vibration, shock, and emi influences, and thus provides a considerably more robust clock source than crystal- or ceramic-resonator- based oscillator circuits. table 1. por voltage power-on reset voltage (v th ) r 4.38 m 3.96 j 3.44 n 3.34 p 3.13 q 2.89 s 2.82 v 2.5 x table 2. reset output type output type s push-pull rst a push-pull rst b open collector rst c table 3. clock output frequency clock frequency (f clock ) (mhz) ff 4rd 8tp 12 vb 16 wb note: contact factory for other frequencies. note: standard values are shown in bold. contact factory for other por voltages. note: standard values are shown in bold. contact factory for other output types. note: other versions with different features are available. refer to the max7387/max7388 and max7389/max7390 data sheets. selector guide part frequency range (mhz) reset function watchdog input (wdi) / watchdog output ( wdo ) power-fail input (pfi)/power-fail output (pfo) speed pin- package max7387 1 to 32 yes yes/yes yes/yes 10 ?ax max7388 1 to 32 yes yes/no no/yes 8 ?ax max7389 1 to 32 yes yes/yes 8 ?ax max7390 1 to 32 yes yes/no yes 8 ?ax max7391 1 to 32 yes yes/yes yes 8 ?ax
max7391 speed-switching clock generator with power fail _______________________________________________________________________________________ 9 max7391 reset timer rst/rst clock speed pfi pfo prescaler internal (v cc detection) oscillator v_th gnd power-on reset n functional diagram max7391 rst/rst v cc gnd pfo r1 power supply 5v r2 pfi speed clock int rst/rst c osc1 dc-dc typical application circuit chip information process: bicmos
max7391 speed-switching clock generator with power fail maxim cannot assume responsibility for use of any circuitry other than circuitry entirely embodied in a maxim product. no circu it patent licenses are implied. maxim reserves the right to change the circuitry and specifications without notice at any time. 10 ____________________maxim integrated products, 120 san gabriel drive, sunnyvale, ca 94086 408-737-7600 2006 maxim integrated products printed usa is a registered trademark of maxim integrated products, inc. package information (the package drawing(s) in this data sheet may not reflect the most current specifications. for the latest package outline info rmation, go to www.maxim-ic.com/packages .) 8lumaxd.eps package outline, 8l umax/usop 1 1 21-0036 j rev. document control no. approval proprietary information title: max 0.043 0.006 0.014 0.120 0.120 0.198 0.026 0.007 0.037 0.0207 bsc 0.0256 bsc a2 a1 c e b a l front view side view e h 0.60.1 0.60.1 ?0.500.1 1 top view d 8 a2 0.030 bottom view 1 6 s b l h e d e c 0 0.010 0.116 0.116 0.188 0.016 0.005 8 4x s inches - a1 a min 0.002 0.95 0.75 0.5250 bsc 0.25 0.36 2.95 3.05 2.95 3.05 4.78 0.41 0.65 bsc 5.03 0.66 6 0 0.13 0.18 max min millimeters - 1.10 0.05 0.15 dim
e nglish ? ???? ? ??? ? ??? what's ne w p roducts solutions de sign ap p note s sup p ort buy comp any me mbe rs max7391 part number table notes: see the max7391 quickview data sheet for further information on this product family or download the max7391 full data sheet (pdf, 280kb). 1. other options and links for purchasing parts are listed at: http://www.maxim-ic.com/sales . 2. didn't find what you need? ask our applications engineers. expert assistance in finding parts, usually within one business day. 3. part number suffixes: t or t&r = tape and reel; + = rohs/lead-free; # = rohs/lead-exempt. more: see full data sheet or part naming c onventions . 4. * some packages have variations, listed on the drawing. "pkgc ode/variation" tells which variation the product uses. 5. part number free sample buy direct package: type pins size drawing code/var * temp rohs/lead-free? materials analysis max7391c sac -40c to +125c rohs/lead-free: no max7391c mac -40c to +125c rohs/lead-free: no max7391c mwb-t -40c to +125c rohs/lead-free: no max7391c mvb umax;8 pin;3 x 3mm dwg: 21-0036j (pdf) use pkgcode/variation: u8-1 * -40c to +125c rohs/lead-free: no materials analysis max7391c mtp umax;8 pin;3 x 3mm dwg: 21-0036j (pdf) use pkgcode/variation: u8-1 * -40c to +125c rohs/lead-free: no materials analysis max7391c mrd umax;8 pin;3 x 3mm dwg: 21-0036j (pdf) use pkgcode/variation: u8-1 * -40c to +125c rohs/lead-free: no materials analysis max7391c mvb-t -40c to +125c rohs/lead-free: no
max7391c mtp-t -40c to +125c rohs/lead-free: no max7391c mrd-t -40c to +125c rohs/lead-free: no max7391c swb-t -40c to +125c rohs/lead-free: no max7391c svb-t -40c to +125c rohs/lead-free: no max7391c stp-t -40c to +125c rohs/lead-free: no max7391c srd-t -40c to +125c rohs/lead-free: no max7391c swb umax;8 pin;3 x 3mm dwg: 21-0036j (pdf) use pkgcode/variation: u8-1 * -40c to +125c rohs/lead-free: no materials analysis max7391c svb umax;8 pin;3 x 3mm dwg: 21-0036j (pdf) use pkgcode/variation: u8-1 * -40c to +125c rohs/lead-free: no materials analysis max7391c stp umax;8 pin;3 x 3mm dwg: 21-0036j (pdf) use pkgcode/variation: u8-1 * -40c to +125c rohs/lead-free: no materials analysis max7391c srd umax;8 pin;3 x 3mm dwg: 21-0036j (pdf) use pkgcode/variation: u8-1 * -40c to +125c rohs/lead-free: no materials analysis max7391c mwb umax;8 pin;3 x 3mm dwg: 21-0036j (pdf) use pkgcode/variation: u8-1 * -40c to +125c rohs/lead-free: no materials analysis didn't find what you need? c ontac t us: send us an email c opyright 2 0 0 7 by m axim i ntegrated p roduc ts , dallas semic onduc tor ? legal n otic es ? p rivac y p olic y

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