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for free samples & the latest literature: http://www.maxim-ic.com, or phone 1-800-998-8800. for small orders, phone 1-800-835-8769. general description the max221e is a +5v powered, single transmit/receive rs-232 and v.28 communications interface with automatic shutdown/wake-up features and high data rate capabilities. the max221e features enhanced electrostatic discharge (esd) protection. both the transmitter output and receiver input are protected to ?5kv using the iec 1000-4-2 air- gap discharge method, to ?kv using the iec 1000-4-2 contact discharge method, and to ?5kv using the human body model. the max221e achieves a low 1? supply current with maxim? revolutionary autoshutdown feature. autoshutdown saves power without changes to the existing bios or operating system by entering low- power shutdown mode when the rs-232 cable is dis- connected or when the transmitter of the connected peripheral is off. the max221e wakes up and drives the invalid pin high when an active rs-232 cable is con- nected, signaling the host that a peripheral is connectedto the communications port. the max221e is available in a 16-pin ssop package as well as a 16-pin tssop that uses 50% less board space than a 16-pin so. applications maintenance/diagnostic portsindustrial systems telecommunications set-top boxes features ? single rs-232 transceiver in a small 16-pin tssop ? esd protection for rs-232 i/o pins 15kvhuman body model8kviec 1000-4-2, contact discharge 15kviec 1000-4-2, air-gap discharge ? latchup free ? 1a supply current ? autoshutdown saves power without changesto bios ? guaranteed 250kbps data rate max221e ?5kv esd-protected, +5v, 1?, single rs-232 transceiver with autoshutdown ________________________________________________________________ maxim integrated products 1 1615 14 13 12 11 10 9 12 34 5 6 7 8 en forceoff v cc gndtout forceon tin invalid rout top view max221e tssop/ssop c1+ v+ c2- c1- c2+ v- rin max221e forceon en 12 1 rout 9 forceoff 16 invalid 10 gnd 14 tin 11 c2- 6 c2+ 5 c1- 4 c1+ 2 rin 8 tout 13 v- 7 v+ 3 v cc v cc c40.1 f c30.1 f 15 c1 0.1 f c2 0.1 f c bypass 0.1 f +5v to power-management unit capacitors may bepolarized or unpolarized. 5k typical operating circuit 19-1527; rev 0; 8/99 part max221ecuemax221ecae max221eeue 40? to +85? 0? to +70? 0? to +70? temp. range pin-package 16 tssop16 ssop 16 tssop pin configuration ordering information autoshutdown is a trademark of maxim integrated products. max221eeae 40? to +85? 16 ssop downloaded from: http:///
max221e ?5kv esd-protected, +5v, 1?, single rs-232 transceiver with autoshutdown 2 _______________________________________________________________________________________ absolute maximum ratings electrical characteristics(v cc = +5v ?0%, c1?4 = 0.1?, t a = t min to t max , unless otherwise noted. typical values are at t a = +25?.) stresses beyond those listed under ?bsolute maximum ratings?may cause permanent damage to the device. these are stress ratings only, and functional operation 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. v cc ..........................................................................-0.3v to +6v v+ ...............................................................(v cc - 0.3v) to +14v v- ...........................................................................-14v to +0.3v input voltages tin ............................................................-0.3v to (v+ + 0.3v) rin ...................................................................................?0v forceon, forceoff , en ..................-0.3v to (v cc + 0.3v) output voltages tout ................................................(v- - 0.3v) to (v+ + 0.3v) rout, invalid ......................................-0.3v to (v cc + 0.3v) short-circuit duration, tout .....................................continuous continuous power dissipation (t a = +70?) 16-pin tssop (derated 6.7mw/? above +70?) .......533mw 16-pin ssop (derated 7.1mw/? above +70?) .........571mw operating temperature range max221ec_ _. ....................................................0? to +70? max221ee_ _ ..................................................-40? to +85? maximum junction temperature .................................... +150? storage temperature range ........................... -65? to +150? lead temperature (soldering, 10sec) ............................ +300? figure 3 figure 3 no load, t a = +25? figure 3 i source = 1.0ma i sink = 1.6ma conditions i cc = 1?, figure 3 rout; i sink = 3.2ma figure 3 tin, en , forceoff , forceon t a = +25?, figure 1 en = v cc , 0 rout v cc tin = 0 to v cc rout; i source = 1.0ma ? 30 t invl receiver positive or negativethreshold to invalid low ? 1 t invh receiver positive or negativethreshold to invalid high ? 250 t wu receiver threshold totransmitter enabled v v cc - 0.6 invalid output voltage high v 0.4 invalid output voltage low v -0.3 0.3 receiver input threshold,transmitter disabled -2.7 positive threshold v 2.7 receiver input threshold, transmitter enabled ? ?.05 ?0 negative threshold output leakage current v 3.5 v oh output voltage high ma 51 0 i cc v cc supply current units min typ max symbol parameter v 0.4 v ol output voltage low v 0.8 v il input threshold low ? 11 0 i shdn shutdown supply current ? 11 0 i as autoshutdown supply current ? ? input leakage current en , forceoff , tin v 2.4 v ih input threshold high dc characteristics logic inputs autoshutdown downloaded from: http:///
max221e ?5kv esd-protected, +5v, 1?, single rs-232 transceiver with autoshutdown _______________________________________________________________________________________ 3 timing characteristics(v cc = +5v ?0%, c1?4 = 0.1?, t a = t min to t max , unless otherwise noted. typical values are at t a = +25?.) electrical characteristics (continued)(v cc = +5v ?0%, c1?4 = 0.1?, t a = t min to t max , unless otherwise noted. typical values are at t a = +25?.) note 1: transmitter skew is measured at the transmitter zero crosspoints. r l = 3k to 7k , c l = 50pf to 1000pf, v cc = 4.5v conditions kbps 250 maximum data rate units min typ max symbol parameter t a = +25?, v cc = 5v, r l = 3k to 7k , c l = 500pf to 1000pf, measured from -3v to +3v or +3v to -3v (note 1) normal operation normal operation c l = 150pf v/? 363 0 transition-region slew rate ns 50 |t phl t plh | receiver skew ns 200 |t phl t plh | transmitter skew ns 200 receiver output disable time ns 300 receiver output enable time ms 0.15 t phl, t plh receiver propagation delay conditions units min typ max symbol parameter v cc = v+ = v- = 0, v out = ?v driver loaded with 3k to ground t a = +25?, v cc = 5v v cc = 5v, no hysteresis in shutdown t a = +25?, v cc = 5v t a = +25?, v cc = 5v ma ?0 ?0 output short-circuit current 300 output resistance v ? ? output voltage swing k 357 input resistance v 0.5 input hysteresis v 1.7 2.4 input threshold high v 0.8 1.2 input threshold low v -25 25 input voltage range iec 1000-4-2 air-gap discharge kv ?5 rin, tout iec 1000-4-2 contact discharge ? human body model ?5 receiver input transmitter output esd protection downloaded from: http:///
max221e ?5kv esd-protected, +5v, 1?, single rs-232 transceiver with autoshutdown 4 _______________________________________________________________________________________ 0 10 20 30 40 50 0 1000 2000 3000 4000 5000 slew rate vs. load capacitance max221etoc02 load capacitance (pf) slew rate (v/ s) +slew -slew name function 1 en receiver enable control. drive low for normal operation. drive high to force the receiver output(rout) into a high-impedance state. 2 c1+ positive terminal of the voltage doubler charge-pump capacitor pin 3 v+ positive voltage generated by the charge pump 4 c1- negative terminal of the voltage doubler charge-pump capacitor 8 rin rs-232 receiver input, ?5kv esd protected 7 v- negative voltage generated by the charge pump 6 c2- negative terminal of the inverting charge-pump capacitor 5 c2+ positive terminal of the inverting charge-pump capacitor 13 tout rs-232 transmitter output, ?5kv esd protected 12 forceon drive high to override automatic circuitry, keeping transmitter and charge pump on. forceoff must be high (table 1). 11 tin ttl/cmos transmitter input 10 invalid output of the invalid signal detector. invalid is pulled low if no valid rs-232 level is present on the receiver input. 9 rout ttl/cmos receiver output pin description 14 gnd ground 15 v cc +4.5v to +5.5v supply voltage 16 forceoff force-off input, active low. drive low to shut down transmitter, receiver, and on-board chargepump. this overrides all automatic circuitry and forceon (table 1). -10 -6-8 -2-4 20 4 86 10 0 1000 2000 3000 4000 5000 transmitter output voltage vs. load capacitance max221etoc01 load capacitance (pf) transmitter output voltage (v) 250kbps 250kbps 120kbps 20kbps 20kbps 120kbps 0 10 20 30 40 50 0 1000 2000 3000 4000 5000 operating supply current vs. load capacitance max221etoc03 load capacitance (pf) supply current (ma) 250kbps 20kbps 120kbps typical operating characteristics (v cc = +5v, 250kbps data rate, 0.1? capacitors, transmitter loaded with 3k and c l , t a = +25?, unless otherwise noted.) downloaded from: http:///
max221e ?5kv esd-protected, +5v, 1?, single rs-232 transceiver with autoshutdown _______________________________________________________________________________________ 5 _______________detailed description dual charge-pump voltage converter the max221e? internal power supply consists of adual charge pump that provides a positive output volt- age (doubling charge pump) and negative output volt- age (inverting charge pump) from a single +5v supply. the charge pumps operate in continuous mode. each charge pump requires a flying capacitor (c1, c2) and a reservoir capacitor (c3, c4) to generate the v+ and v- supplies. rs-232 transmitter the transmitter is an inverting level translator that con-verts cmos-logic levels to 5.0v eia/tia-232 levels. it guarantees a 250kbps data rate with worst-case loads of 3k in parallel with 1000pf. when forceoff is driven to ground, or when the autoshutdown circuitry senses invalid voltage levels onthe receiver input, the transmitter is disabled and the output is forced into a high-impedance state. the trans- mitter input does not have a pull-up resistor. rs-232 receiver the max221e? receiver converts rs-232 signals tocmos-logic output levels. the receiver has an inverting three-state output and can be active or inactive. in shutdown ( forceoff = low) or in autoshutdown, the receiver is active (table 1). drive en high to place the receiver in a high-impedance state. the receiver ishigh-impedance when the max221e is in shutdown ( forceoff = low). the max221e? invalid output is pulled low when there is no valid rs-232 signal level detected on thereceiver input. invalid is functional in any mode (figures 2 and 3). autoshutdown the max221e achieves 1? supply current withmaxim? autoshutdown feature, which operates when forceon is low and forceoff is high. when the device senses no valid signal levels on the receiverinput for 30?, the on-board charge pump and driver are shut off, reducing supply current to 1?. this occurs if the rs-232 cable is disconnected or the con- nected peripheral transmitter is turned off. the max221e turns on again when a valid level is applied to the rs-232 receiver input. as a result, the system saves power without changes to the existing bios or operating system. table 1 and figure 2c summarize the max221e operat- ing modes. forceon and forceoff override autoshutdown. when neither control is asserted, thedevice selects between these states automatically, based on the receiver input level. figures 2a, 2b, and 3a depict valid and invalid rs-232 receiver levels. figure 3 shows the input levels and timing diagram for autoshutdown operation. a device or another system with autoshutdown con- nected to the max221e may need time to wake up. figure 4 shows a circuit that forces the transmitter on for 100ms, allowing enough time for the other system to realize that the max221e is awake. if the other system transmits valid rs-232 signals within that time, the rs-232 ports on both systems remain enabled. when shut down, the device? charge pumps turn off, v+ is pulled to v cc , v- is pulled to ground, and the transmitter output is high impedance. the time requiredto exit shutdown is typically 100? (figure 3b). max221e forceon en 12 1 rout i shdn 9 forceoff 16 invalid 10 gnd 14 tin 11 c2- 6 c2+ 5 c1- 4 c1+ 2 rin 8 tout 13 v- 7 v+ 3 v cc c40.1 f 15 c1 0.1 f c2 0.1 f c bypass 0.1 f +5v to power-management unit 5k 3k c30.1 f figure 1. shutdown current test circuit downloaded from: http:///
max221e ?5kv esd-protected, +5v, 1?, single rs-232 transceiver with autoshutdown 6 _______________________________________________________________________________________ 1 no shutdown(autoshutdown) high-z 1 high-z 0 1 1 1 operation status x 0 valid receiver en x shutdown(forced off) x normal operation(forced on) x 0 yes normal operation(autoshutdown) no yes 0 0 high-z active active high-z tout active high-z active 0 forceoff 1 0 1 1 1 1 high-z high-z active active rout high-z active active x forceon 1 x 1 0 0 0 rs-232 signal present at receiver input invalid output yes high no low table 1. output control truth table table 2. invalid truth table figure 2c. autoshutdown logic +0.3v -0.3v invalid to max221epower supply and transmitter rin * transmitter is disabled, reducing supply current to 1 a if receiver input is between +0.3v and -0.3v for at least 30 s. 30? counter r +2.7v -2.7v invalid to max221epower supply rin * transmitter is enabled if: receiver input is greater than +2.7v or less than -2.7v. receiver input has been between +0.3v and -0.3v for less than 30 s. 30? counter r forceoff power down invalid forceon invalid is an internally generated signal used byautoshutdown logic and appears as an output. power down is only an internal signal. it controls theoperational status of the transmitter and power supplies. figure 2b. transmitter enabled using autoshutdown figure 2a. entering 1? supply mode via autoshutdown x = don? care downloaded from: http:///
software-controlled shutdown for direct software control, use invalid to indicate a dtr or ring indicator signal. connect forceoff and forceon together to disable autoshutdown so theline acts like a shdn input. ?5kv esd protection as with all maxim devices, esd-protection structuresare incorporated on all pins to protect against electro- static discharges encountered during handling and assembly. the driver output and receiver input of the max221e have extra protection against static electrici- ty. maxim? engineers have developed state-of-the-art structures to protect these pins against esd of ?5kv without damage. the esd structures withstand high esd in all states: normal operation, shutdown, and powered down. after an esd event, maxim? e versions keep working without latchup, whereas competing rs-232 products can latch and must be powered down to remove latchup. esd protection can be tested in various ways; the trans- mitter output and receiver input of the max221e are characterized for protection to the following limits: 1) ?5kv using the human body model 2) ?kv using the contact-discharge method specified in iec 1000-4-2 3) ?5kv using iec 1000-4-2? air-gap method esd test conditions esd performance depends on a variety of conditions.contact maxim for a reliability report that documents test setup, test methodology, and test results. human body model figure 5a shows the human body model, and figure5b shows the current waveform it generates when dis- charged into a low impedance. this model consists of a 100pf capacitor charged to the esd voltage of inter- est, which is then discharged into the test device through a 1.5k resistor. iec 1000-4-2 the iec 1000-4-2 standard covers esd testing andperformance of finished equipment; it does not specifi- cally refer to integrated circuits. the max221e helps you design equipment that meets level 4 (the highest level) of iec 1000-4-2, without the need for additional esd-protection components. the major difference between tests done using the human body model and iec 1000-4-2 (figure 6) is higher peak current in the iec 1000-4-2 because series resistance is lower in the iec 1000-4-2 model. hence, max221e ?5kv esd-protected, +5v, 1?, single rs-232 transceiver with autoshutdown _______________________________________________________________________________________ 7 figure 3. autoshutdown trip levels transmitter enabled, invalid high receiver input level autoshutdown, transmitter disabled, 1 a supply current, invalid low transmitter enabled, invalid high -2.7v -0.3v +2.7v+0.3v 0 indeterminateindeterminate v- v cc 0 v+ 0 v cc t invl t wu invalid region receiver input voltage (v) invalid output (v) t invh a)b) forceon master shdn line 0.1? 1m forceoff max221e power- management unit figure 4. autoshutdown with initial turn-on to wake up a mouse or another system downloaded from: http:///
the esd that withstands voltage measured to iec 1000-4-2 is generally lower than that measured using the human body model. figure 6a shows the ieee 1000-4- 2 model and figure 6b shows the current waveform for the ?kv iec 1000-4-2 level 4 esd contact-discharge test. the air-gap method involves approaching the device with a charged probe. the contact-discharge method connects the probe to the device before the probe is energized. machine model the machine model for esd tests all pins, using a200pf storage capacitor and zero discharge resis- tance. its objective is to emulate the stress caused not only by rs-232 inputs and outputs, but also by contact that occurs due to handling and assembling during manufacturing. therefore, after pc board assembly, the machine model is less relevant to i/o ports. max221e ?5kv esd-protected, +5v, 1?, single rs-232 transceiver with autoshutdown 8 _______________________________________________________________________________________ charge-current limit resistor discharge resistance storagecapacitor c s 100pf r c 1m r d 1500 high- voltage dc source device under test i p 100% 90% 36.8% t rl time t dl current waveform peak-to-peak ringing(not drawn to scale) i r 10% 0 0 amperes t r = 0.7ns to 1ns 30ns 60ns t 100% 90%10% i peak i charge-current limit resistor discharge resistance storagecapacitor c s 150pf r c 50m to 100m r d 330 high- voltage dc source device under test figure 5a. human body esd test model figure 6a. iec 1000-4-2 esd test model figure 6b. iec 1000-4-2 esd generator current waveform figure 5b. human body model current waveform downloaded from: http:///
max221e ?5kv esd-protected, +5v, 1?, single rs-232 transceiver with autoshutdown _______________________________________________________________________________________ 9 __________applications information using i i n n v v a a l l i i d d invalid indicates when an rs-232 signal is present at the receiver input, and therefore when the port is in use.invalid can be used in alternative shutdown control schemes where it relieves the processor from constantlypolling the part for activity. capacitor selection the capacitor type used for c1?4 is not critical forproper operation; either polarized or nonpolarized capacitors are acceptable. if polarized capacitors are used, connect polarity as shown in the typical operating circuit . the charge pump requires 0.1? capacitors. increasing the capacitor values (e.g., by afactor of 2) reduces ripple on the transmitter output, and slightly reduces power consumption. c2, c3, and c4 can be increased without changing c1? value. however, do not increase c1? value without also increasing the values of c2, c3, and c4 to maintain the proper ratios (c1 to the other capacitors). when using the minimum 0.1? capacitors, make sure the capacitance does not degrade excessively with temperature. if in doubt, use capacitors with a larger nominal value. the capacitor? equivalent series resis-tance (esr) usually rises at low temperatures and influ- ences the amount of ripple on v+ and v-. power-supply decoupling in most circumstances, a 0.1? v cc bypass capacitor is adequate. in applications that are sensitive to power-supply noise, use a capacitor of the same value as the charge-pump capacitor c1. connect bypass capaci- tors as close to the ic as possible. transmitter output when exiting shutdown figure 7 shows the transmitter output when exitingshutdown mode. the transmitter is loaded with 3k in parallel with 1000pf. the transmitter output displays noringing or undesirable transients as the max221e comes out of shutdown. high data rates the max221e maintains the rs-232 ?.0v minimumtransmitter output voltage even at high data rates. figure 8 shows a transmitter loopback test circuit. figure 9 shows the loopback test result at 120kbps, and figure 10 shows the same test at 250kbps. 5v/div forceon = forceofftout 5v/div 50 s/div tin = v cc tin = gnd figure 7. transmitter output when exiting shutdown or powering up max221e 5k rin routen c2- c2+ c1- c1+ v- v+ v cc c4 c3 c1 c2 0.1 f +5v forceoff tout tin gnd v cc 1000pf 0v forceon invalid figure 8. loopback test circuit downloaded from: http:///
max221e ?5kv esd-protected, +5v, 1?, single rs-232 transceiver with autoshutdown 10 ______________________________________________________________________________________ 2 s/div 5v/div5v/div 5v/div tintout rout figure 9. loopback test result at 120kbps 2 s/div 5v/div5v/div 5v/div tintout rout figure 10. loopback test result at 250kbps ___________________chip information transistor count: 157 downloaded from: http:///
max221e ?5kv esd-protected, +5v, 1?, single rs-232 transceiver with autoshutdown ______________________________________________________________________________________ 11 tssop.eps package information downloaded from: http:///
max221e ?5kv esd-protected, +5v, 1?, single rs-232 transceiver with autoshutdown 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. 12 ____________________maxim integrated products, 120 san gabriel drive, sunnyvale, ca 94086 408-737-7600 1999 maxim integrated products printed usa is a registered trademark of maxim integrated products. 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. 12 ____________________maxim integrated products, 120 san gabriel drive, sunnyvale, ca 94086 408-737-7600 1999 maxim integrated products printed usa is a registered trademark of maxim integrated products. 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. 12 ____________________maxim integrated products, 120 san gabriel drive, sunnyvale, ca 94086 408-737-7600 1999 maxim integrated products printed usa is a registered trademark of maxim integrated products. package information (continued) ssop.eps downloaded from: http:///

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