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general description the max3380e/max3381e are +2.35v to +5.5v-pow-ered eia/tia-232 and v.28/v.24 communication inter- faces with low power requirements, high data-rate capabilities, and enhanced electrostatic discharge (esd) protection on both the ttl and rs-232 sides. the max3380e/max3381e have two receivers and two transmitters. all rs-232 inputs, outputs, and logic input pins are protected to ?5kv using iec 1000-4-2 air- gap discharge method and the human body model, and ?kv using iec 1000-4-2 contact discharge method. the proprietary low-dropout transmitter output stage enables true rs-232 performance from a +3.1v to +5.5v supply with a dual charge pump. the parts reduce the transmitter output levels to rs-232-compati- ble levels with no increase in supply current for sup- plies less than +3.1v and greater than +2.35v. the +2.35v to +5.5v operating range is fully compatible with lithium-ion (li+) batteries. the charge pump requires only four small 0.1? capacitors for operation. the max3380e/max3381e transceivers use maxim? revolutionary autoshutdown plus feature to auto- matically enter a 1a shutdown mode. these devices shut down the on-board power supply and drivers when they do not sense a valid signal transi- tion for 30 seconds on either the receiver or trans- mitter inputs. the max3380e is capable of transmitting data at rates of 460kbps while maintaining rs-232 output levels, and the max3381e operates at data rates up to 250kbps. the max3381e offers a slower slew rate for applications where noise and emi are issues. the max3380e/max3381e have a unique v l pin that allows interoperation in mixed-logic voltage systemsdown to +1.65v. both input and output logic levels are referenced to the v l pin. the max3380e/max3381e are available in a space-saving tssop package. applications cell phone data lump cablespda data lump cables gps receivers digital cameras features ? 15kv esd protection on all cmos and rs-232inputs and outputs (except invalid ) 15kv human body model15kv iec 1000-4-2 air-gap discharge 8kv iec 1000-4-2 contact discharge ? operates over entire li+ battery range ? low logic threshold down to +1.65v forcompatibility with cell phone logic supply voltages ? 1a low-power autoshutdown plus mode ? compatible with next-generation gsm data rates ? 20-pin tssop package max3380e/max3381e +2.35v to +5.5v, 1a, 2tx/2rx rs-232 transceivers with 15kv esd-protected i/o and logic pins ________________________________________________________________ maxim integrated products 1 19-2128; rev 0; 8/01 ordering information part temp. range pin-package max3380e cup 0 c to +70 c 20 tssop max3380eeup -40 c to +85 c 20 tssop max3381e cup 0 c to +70 c 20 tssop max3381eeup -40 c to +85 c 20 tssop pin configuration appears at end of data sheet. max3380e/ max3381e r2out r1out r2in gnd rs-232outputs ttl/cmos inputs t2in t1in c2- c2+ c1- c1+ r1in t2out t1out v- v+ v cc v l c1 0.1 f c2 0.1 f c5 0.1 f +3.3v rs-232inputs ttl/cmos outputs 5k 5k c30.1 f c40.1 f v l v l forceon forceoff typical operating circuit 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. autoshutdown plus is a trademark of maxim integrated products downloaded from: http:///
max3380e/max3381e +2.35v to +5.5v, 1a, 2tx/2rx rs-232 transceivers with 15kv esd-protected i/o and logic pins 2 _______________________________________________________________________________________ absolute maximum ratings electrical characteristics(v cc = +2.35v to +5.5v, v l = +1.65v to +5.5v. when v cc < +4.5v, c1 = c2 = c3 = c4 = 0.1?; when v cc +4.5v, c1 = 0.047?, c2 = c3 = c4 = 0.33?; t a = t min to t max , unless otherwise noted. typical values are at v cc = v l = +3.3v, 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. note 1: v+ and v- can have maximum magnitudes of +7v, but their absolute difference cannot exceed +13v. v cc to gnd ...........................................................-0.3v to +6.0v v l to gnd..............................................................-0.3v to +6.0v v+ to gnd .............................................................-0.3v to +7.0v v- to gnd ..............................................................+0.3v to -7.0v v+ + |v-| (note 1) .................................................................+13v input voltages t_in, forceon, forceoff to gnd ...............-0.3v to +6.0v r_in to gnd .....................................................................?5v output voltages t_out to gnd...............................................................?3.2v r_out, invalid to gnd ...........................-0.3v to (v l + 0.3v) short-circuit duration t_out to gnd........................continuous continuous power dissipation (t a = +70?) 20-pin tssop (derate 10.9mw/? over +70?) .........879mw operating temperature ranges max3380ecup/max3381ecup........................0? to +70? max3380eeup/max3381eeup .....................-40? to +85? junction temperature ......................................................+150? storage temperature range .............................-65? to +150? lead temperature (soldering, 10s) .................................+300? parameter symbol conditions min typ max units receivers idle, v t _ in = v cc or gnd, forceon = gnd, forceoff = v cc 10 supply current, autoshutdown plus i cc forceoff = gnd 1 10 ? supply current, normal operation i cc forceon = forceoff = v l , no load 0.3 1 ma logic inputs (t_in, forceon, forceoff ) v cc = +5.5v, v l = +5.5v 0.4 1.2 input logic threshold low v il v cc = +2.5v, v l = +1.65v 0.4 v v cc = +5.5v, v l = +5.5v v l ? 0.66 input logic threshold high v ih v cc = +2.5v, v l = +1.65v v l ? 0.66 v transmitter input hysteresis 0.5 v input leakage current 0.01 1 a receiver outputs (r_out) and invalid output voltage low i out = 500? 0.5 v output voltage high i out = -500? v l - 0.4 v l - 0.2 v receiver inputs (r_in) input voltage range -25 +25 v v l = +3.3v 0.6 1.2 input threshold low t a = +25 c v l = +5.0v 0.8 1.5 v v l = +3.3v 1.5 2.4 input threshold high t a = +25 c v l = +5.0v 1.8 2.4 v input hysteresis 0.3 v input resistance t a = +25? 3 5 7 k downloaded from: http:///
max3380e/max3381e +2.35v to +5.5v, 1a, 2tx/2rx rs-232 transceivers with 15kv esd-protected i/o and logic pins _______________________________________________________________________________________ 3 parameter symbol conditions min typ max units autoshutdown plus (forceon = gnd, forceoff = v l ) positive threshold 2.7 receiver input threshold toinvalid output high figure 3 negative threshold -2.7 v receiver input threshold toinvalid output low figure 3 -0.3 0.3 v receiver positive or negativethreshold to invalid high t invl v cc = +5.0v, figure 4 0.3 ? receiver positive or negativethreshold to invalid low t invh v cc = +5.0v, figure 4 30 s receiver or transmitter edge totransmitters enabled t wu v cc = +5.0v, figure 4 15 s receiver or transmitter edge totransmitters shutdown t au t os h d n v cc = +5.0v, figure 4 30 s transmitter outputs v cc mode switch point (v cc falling) t_out = 5.0v to 3.7v 2.95 3.1 3.25 v v cc mode switch point (v cc rising) t_out = 3.7v to 5.5v 3.3 3.5 3.7 v v cc mode switch point hysteresis 400 mv v c c = + 3.25v to + 5.5v , v c c fal l i ng 5 5.4 output voltage swing all transmitteroutputs loaded with 3k to ground v c c = + 2.5v to + 2.95v , v c c fal l i ng 3.7 v output resistance v cc = 0, transmitter output = 2.0v 300 10m output short-circuit current 60 ma output leakage current v out = 12v, transmitters disabled 25 ? esd protection human body model 15 iec 1000-4-2 air-gap discharge method 15 r_in, t_out, r_out, t_in,forceon, forceoff iec 1000-4-2 contact discharge method 8 kv electrical characteristics (continued)(v cc = +2.35v to +5.5v, v l = +1.65v to +5.5v. when v cc < +4.5v, c1 = c2 = c3 = c4 = 0.1?; when v cc +4.5v, c1 = 0.047?, c2 = c3 = c4 = 0.33?; t a = t min to t max , unless otherwise noted. typical values are at v cc = v l = +3.3v, t a = +25?.) downloaded from: http:///
-6 -2-4 20 64 8 0 1000 1500 500 2000 2500 3000 transmitter output voltage vs. load capacitance max3380e toc01 load capacitance (pf) transmitter output voltage (v) v out+ v out- v cc = +4.2v -6 -2-4 20 64 8 0 1000 1500 500 2000 2500 3000 transmitter output voltage vs. load capacitance max3380e toc02 load capacitance (pf) transmitter output voltage (v) v out+ v out- v cc = +2.5v 0 5 10 15 20 25 30 35 40 0 1000 500 1500 2000 2500 3000 max3380e slew rate vs. load capacitance max3380e toc03 load capacitance (pf) slew rate (v/ s) v cc = +4.2v v cc = +2.5v typical operating characteristics (v cc = v l = +4.2v, c1 = 0.22?, c2 = c3 = c4 = 1?, c5 = 0.1? parallel with 47?, r l = 3k , c l = 1000pf, data rate is 250kbps, t a = +25?, unless otherwise noted.) max3380e/max3381e +2.35v to +5.5v, 1a, 2tx/2rx rs-232 transceivers with 15kv esd-protected i/o and logic pins 4 _______________________________________________________________________________________ timing characteristics(v cc = +2.35v to +5.5v, v l = +1.65v to +5.5v. when v cc < +4.5v, c1 = c2 = c3 = c4 = 0.1?; when v cc +4.5v, c1 = 0.047?, c2 = c3 = c4 = 0.33?; t a = t min to t max , unless otherwise noted. typical values are at v cc = v l = +3.3v, t a = +25?.) parameter symbol conditions min typ max units max3381e 250 maximum data rate r l = 3k , c l = 1000pf, one transmitter switching max3380e 460 kbps t plh 0.15 receiver propagation delay t phl receiver input to receiver output, c l = 100pf 0.15 ? transmitter skew ? t phl - t plh ? (note 2) 200 ns receiver skew ? t phl - t plh ? 50 ns transition region slew rate(max3380e) v cc = +4.2v, -3.0v < t_out< +3.0v, r l = 3k , c l = 250pf to 1000pf, t a = +25 c 20 100 v/? transition region slew rate(max3381e) v cc = +4.2v, -3.0v < t_out< +3.0v, r l = 3k , c l = 150pf to 1000pf, t a = +25 c 63 0 v/? transition region slew rate(max3380e) v cc = +2.35v, -3.0v < t_out< +3.0v, r l = 3k , c l = 250pf to 1000pf, t a = +25 c 30 v/? transition region slew rate(max3381e) v cc = +2.35v, -3.0v < t_out< +3.0v, r l = 3k , c l = 250pf to 1000pf, t a = +25 c 10 v/? note 2: transmitter skew is measured at the transmitter zero crosspoint. downloaded from: http:///
max3380e/max3381e +2.35v to +5.5v, 1a, 2tx/2rx rs-232 transceivers with 15kv esd-protected i/o and logic pins _______________________________________________________________________________________ 5 6 7 8 9 10 11 12 13 14 0 1000 500 1500 2000 2500 3000 max3381e slew rate vs. load capacitance max3380e toc04 load capacitance (pf) slew rate (v/ s) v cc = +4.2v v cc = +2.5v 0 10 20 30 40 50 60 70 80 0 1000 500 1500 2000 2500 3000 supply current vs. load capacitance when transmitting data max3381e toc05 load capacitance (pf) supply current (ma) 460kbps 250kbps 20kbps 1 transmitter switching -6 -2-4 20 64 8 transmitter output voltage vs. supply voltage (v cc falling) max3380e toc06 supply voltage (v) transmitter output voltage (v) 2.5 3.5 4.5 5.5 v out+ v out- -6 -2-4 20 64 8 transmitter output voltage vs. supply voltage (v cc rising) max3380e toc07 supply voltage (v) transmitter output voltage (v) 2.5 3.5 4.5 5.5 v out+ v out- 0 5 10 15 20 25 2.5 3.5 4.5 5.5 supply current vs. supply voltage (v cc falling) max3380e toc08 supply voltage (v) supply current (ma) 1 transmitter switching 1 s/div t_in 5v/div t_out 5v/div max3380e toc09 max3380e datastream v cc = +4.2v 5v 05v 0 -5v v cc = v l = +2.5v 1 s/div t_in 5v/div t_out 5v/div max3380e toc10 max3380e datastream v cc = +2.5v 5v0 5v 0 -5v typical operating characteristics (continued) (v cc = v l = +4.2v, c1 = 0.22?, c2 = c3 = c4 = 1?, c5 = 0.1? parallel with 47?, r l = 3k , c l = 1000pf, data rate is 250kbps, t a = +25?, unless otherwise noted.) downloaded from: http:///
max3380e/max3381e +2.35v to +5.5v, 1a, 2tx/2rx rs-232 transceivers with 15kv esd-protected i/o and logic pins 6 _______________________________________________________________________________________ detailed description the max3380e/max3381e are rs-232 transceivers thatmaximize battery life by reducing current consumption at low battery levels. when the supply voltage is above +3.7v, the rs-232 outputs are at ?.5v, which is com- pliant with the rs-232 standard. as the supply voltage drops below the +3.1v set point, the rs-232 outputs change to ?.7v, which is compatible with the rs-232 standard. the outputs will remain at the compatible lev- els until the supply voltage rises above +3.5v, where they return to compliant levels. 400mv of hysteresis pro- tects against power-supply bounce that may cause numerous mode changes. most devices that use charge pumps to double and invert voltages consume higher current when the supply voltage is less than half of the required output voltage. this is due to the fact that the charge pump is constant- ly operating because the output voltage is below the regulation voltage. this requires more supply current because the output will never reach the regulation volt- age and switch off. the max3380e/max3381e reduce the output voltage requirement allowing the chargepump to operate with supply voltages down to +2.35v. dual-mode regulated charge-pump voltage converter the max3380e/max3381es?internal power supply is adual-mode regulated charge pump. the output regula- tion point depends on v cc and the direction in which v cc moves through the switchover region of +2.95v < v cc < +3.7v. for supply voltages above +3.7v, the charge pump willgenerate +5.5v at v+ and -5.5v at v-. the charge pumps operate in a discontinuous mode. if the output voltages are less than ?.5v, the charge pumps are enabled; if the output voltages exceed ?.5v, the charge pumps are disabled. for supply voltages below +2.95v, the charge pump will generate +4.0v at v+ and -4.0v at v-. the charge pumps operate in a discontinuous mode. each charge pump requires a flying capacitor (c1, c2) and a reservoir capacitor (c3, c4) to generate the v+ and v- supplies (see typical operating circuit ). pin description pin name function esd protected 1 c1+ positive terminal of voltage-doubler charge-pump capacitor 2 v+ +5.5v/+4.0v generated by the charge pump 3 c1- negative terminal of voltage-doubler charge-pump capacitor 4 c2+ positive terminal of inverting charge-pump capacitor 5 c2- negative terminal of inverting charge-pump capacitor 6 v- -5.5v/-4.0v generated by the charge pump 7 invalid invalid is asserted if any inputs of the receivers are in an invalid state; -0.3v < v r _ in < +0.3v 8, 9 t_in ttl/cmos transmitter inputs referenced to v l (t1in, t2in) ? 10, 11 r_out ttl/cmos receiver outputs referenced to v l (r2out, r1out) ? 12 forceon force-on input. drive high to override automatic circuitry keeping transmitters on( forceoff must be high) (table 1). ? 13 v l logic level supply. +1.65v to +5.5v, sets cmos logic thresholds and cmosoutputs. 14, 15 r_in rs-232 receiver inputs (r2in, r1in) ? 16, 17 t_out rs-232 transmitter outputs (t2out, t1out) ? 18 gnd ground 19 forceoff force-off input. drive low to shut down transmitters and on-board power supply.this overrides all automatic circuitry and forceon (table 1). ? 20 v cc +2.35v to +5.5v supply voltage downloaded from: http:///
max3380e/max3381e +2.35v to +5.5v, 1a, 2tx/2rx rs-232 transceivers with 15kv esd-protected i/o and logic pins _______________________________________________________________________________________ 7 voltage generation in the switchover region the max3380e/max3381e include a switchover circuitbetween rs-232-compliant and rs-232-compatible modes that has approximately 400mv of hysteresis around the switchover point. the hysteresis is shown in figure 1. this large hysteresis helps to avoid mode change under battery or power-supply bounce. under a decaying v cc , the charge pump will generate an output voltage of ?.5v with a v cc input range between +3.1v and +5.5v. when v cc drops below the switchover point of +3.1v, the charge pump switchesinto rs-232-compatible mode generating ?v. when v cc is rising, the charge pump will generate an output voltage of ?.0v, while v cc is between +2.5v and +3.5v. when v cc rises above the switchover volt- age of +3.5v, the charge pump switches to rs-232- compliant mode to generate an output voltage of ?.5v. rs-232 transmitters the transmitters are inverting level translators that con-vert cmos-logic levels to rs-232-compatible levels. the max3380e/max3381e will automatically reduce the rs-232-compliant levels from ?.5v to ?.7v when v cc falls below approximately +3.1v. the reduced lev- els are rs-232-compatible and reduce supply currentrequirements that help preserve the battery. built-in hysteresis of approximately 400mv for v cc ensures that the rs-232 output levels do not change if v cc is noisy or has a sudden current draw causing the supplyvoltage to drop slightly. the outputs will return to rs- 232-compliant levels (?.5v) when v cc rises above approximately +3.5v. the max3380e/max3381e transmitters guarantee a datarate of 460kbps/250kbps, respectively, with worst-case loads of 3k in parallel with 1000pf. transmitters can be paralleled to drive multiple receivers.when forceoff is driven to ground, the transmitters are disabled and the outputs go into high impedance;receivers remain active. when the autoshutdown plus circuitry senses that all receiver and transmitter inputs are inactive for more than 30s, the transmitters are dis- abled and the outputs go into a high-impedance state, and the receivers remain active. when the power is off, the max3380e/max3381e permit the outputs to be dri- ven up to ?2v. the transmitter inputs have a 400k active positive feedback resistor. they will retain a valid logic level ifthe driving signal is removed or goes high impedance. connect unused transmitter inputs to v cc or ground. rs-232 receivers the receivers convert rs-232 signals to logic levelsreferred to v l . both receivers are active in shutdown (table 1). autoshutdown plus mode the max3380e/max3381e achieve a 1? supply current with maxim? autoshutdown plus feature, which operates when forceoff is high and forceon is low. when these devices do not sense a valid signal transition onany receiver and transmitter input for 30s, the on-board charge pumps are shut down, reducing supply current to 1?. this occurs if the rs-232 cable is disconnected or if the connected peripheral transmitters are turned off, and if the uart driving the transmitter inputs is inactive. the system turns on again when a valid transition is applied to any rs-232 receiver or transmitter input. as a result, the system saves power without changes to the existing bios or operating system. figures 2a and 2b show valid and invalid rs-232 receiver voltage levels. invalid indicates the receiver input? condition, and is independent of the forceonand forceoff states. figure 2 and table 1 summa- rize the max3380e/max3381e? operating modes.forceon and forceoff override autoshutdown plus circuitry. when neither control is asserted, the icselects between these states automatically based on the last receiver or transmitter input edge received. by connecting forceon to invalid , the max3380e/ max3381e is shut down when no valid receiver level and no receiver or transmitter edge is detected for 30s, and wakes up when a receiver or transmitter edge is detect- ed (figure 2c). 20ms/div v cc 2v/div v+ 2v/div +4.5v +2.5v+5.8v +4.4v figure 1. v+ switchover for changing vcc downloaded from: http:///
max3380e/max3381e +2.35v to +5.5v, 1a, 2tx/2rx rs-232 transceivers with 15kv esd-protected i/o and logic pins 8 _______________________________________________________________________________________ +0.3v -0.3v invalid r_in invalid asserted if all receiver inputs are between +0.3v and -0.3v forat least 30 s. 30? timer r +2.7v -2.7v invalid r_in invalid deasserted if any receiver input has been between +2.7v and -2.7vfor less than 30 s. 0.3 s timer r figure 2a. i nvalid functional diagram, i nvalid low figure 2b. i nvalid functional diagram, i nvalid high table 1. autoshutdown plus truth table operation status forceon forceoff valid receiver level receiver or transmitter edge within 30s t_out r_out shutdown(forced off) x 0 x x high-z active normal operation (forced on) 1 1 x x active active normal operation (autoshutdown plus) 0 1 x yes active active shutdown (autoshutdown plus) 0 1 x no high-z active normal operation invalid 1 yes x active active normal operation invalid 1 x yes active active shutdown invalid 1 no no high-z active normal operation (autoshutdown) invalid invalid yes x active active shutdown (autoshutdown) invalid invalid no x high-z active x = don? care downloaded from: http:///
max3380e/max3381e +2.35v to +5.5v, 1a, 2tx/2rx rs-232 transceivers with 15kv esd-protected i/o and logic pins _______________________________________________________________________________________ 9 by connecting forceon and forceoff to invalid , the max3380e/max3381e are shut down when no validreceiver level is detected. v l logic supply input unlike other rs-232 interface devices where the receiv-er outputs swing between 0 and v cc , the max3380e/ max3381e feature a separate logic supply input (v l ) that sets v oh for the receiver and invalid outputs. v l also sets the threshold for the transmitter inputs,forceon and forceoff . this feature allows a great deal of flexibility in interfacing to many different types ofsystems with different logic levels. connect this input to +2.7v+0.3v 0 -0.3v-2.7v transmitters enabled, invalid high indeterminate autoshutdown, transmitters disabled, 1 a supply current invalid low indeterminate transmitters enabled, invalid high powerdown* autoshdn forceoff forceon * powerdown is only an internal signal. it controls the operational status of the transmitters and the power supplies. figure 2d. power-down logic autoshdn r_in t_in r s 30s timer edge detect edge detect forceoff forceon figure 2c. autoshutdown plus logic v l 0 v+ v- v cc 0 invalid output transmitter inputs receiver inputs } invalidregion transmitter outputs t autoshdn t wu t wu t invl t invh t autoshdn figure 4. autoshutdown plus/ invalid timing diagram figure 3. autoshutdown trip levels downloaded from: http:///
max3380e/max3381e the host logic supply (+1.65v to +5.5v). the v l input will draw a maximum current of 20? with receiver out-puts unloaded. 15kv esd protection maxim has developed state-of-the-art structures to pro- tect these pins against an esd of ?5kv without dam- age. the esd structures withstand high esd in all states: normal operation, shutdown, and power-down. after an esd event, maxim? ??version devices keep working without latch-up, whereas competing rs-232 products can latch and must be powered down to remove latch- up. esd protection can be tested in various ways. the transmitter and receiver outputs and receiver and logic inputs of this product family are characterized for protec- tion to the following limits: 15kv using the human body model 8kv using the contact discharge method speci- fied in iec 1000-4-2 15kv using iec 1000-4-2? air-gap discharge method esd test conditions esd performance depends on a variety of conditions.contact maxim for a reliability report that documents test setup, methodology, and 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 ics. the max3380e/max3381e help 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 is higher peak current in iec 1000-4-2, because series resistance is lower in the iec 1000-4-2 model. hence, the esd withstand voltages measured +2.35v to +5.5v, 1a, 2tx/2rx rs-232 transceivers with 15kv esd-protected i/o and logic pins 10 ______________________________________________________________________________________ charge-current limit resistor discharge resistance storagecapacitor c s 100pf r c 1m r d 1500 high- voltage dc source device under test figure 5a. human body esd test model 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 6a. iec 1000-4-2 esd test model 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 figure 5b. human body current waveform 100% 90% 60ns 10% tr = 0.7ns to 1ns i peak i 30ns t figure 6b. iec 1000-4-2 esd generator current waveform downloaded from: http:///
max3380e/max3381e +2.35v to +5.5v, 1a, 2tx/2rx rs-232 transceivers with 15kv esd-protected i/o and logic pins ______________________________________________________________________________________ 11 to iec 1000-4-2 are generally lower than that measuredusing the human body model. figure 6a shows the iec 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 test involves approaching the device with a charged probe. the contact discharge method con- nects the probe to the device before the probe is ener- gized. machine model the machine model for esd tests all pins using a 200pf storage capacitor and zero discharge resis- tance. its objective is to emulate the stress caused by contact that occurs with handling and assembly during manufacturing. all pins require this protection during manufacturing, not just rs-232 inputs and outputs. therefore, after pc board assembly, the machine model is less relevant to i/o ports. applications information capacitor selection the capacitor type used for c1?4 is not critical forproper operation. polarized or nonpolarized capacitors can be used. the charge pump requires 0.1? capaci- tors for +3.3v operation. for other supply voltages, see table 2 for required capacitor values. do not use val- ues smaller than those listed in table 2. increasing the capacitor values (e.g., by a factor of 2) reduces ripple on the transmitter outputs and slightly reduces power consumption. c2, c3, and c4 can be increased without changing c1? value. however, do not increase c1 without also increasing the values of c2, c3, c4, and c5 to maintain the proper ratios (c1 to the other capac- itors). when using the minimum required capacitor values, make sure the capacitor value does not degrade excessively with temperature. if in doubt, use capaci- tors with a large nominal value. the capacitor? equiva- lent series resistance (esr) usually rises at low temperatures and influences the amount of ripple on v+ and v-. power-supply decoupling in most circumstances, connect a 0.1? capacitor fromv cc to gnd. this capacitor is for noise reduction. if the max3380e/max3381e are used in a data cable appli-cation, add a 47? capacitor from v cc to ground. the 47? capacitor is used to ensure that the current need- ed during power-up is supplied to the device. in appli- cations that are sensitive to power-supply noise, decouple v cc to ground with a capacitor of the same value as charge-pump capacitor c1. connect bypasscapacitors as close to the ic as possible. transmitter outputs when recovering from shutdown figure 7 shows two transmitter outputs when exitingshutdown mode. as they become active, the two trans- mitter outputs are shown going to opposite rs-232 lev- els (one transmitter input is high, the other is low). each transmitter is loaded with 3k in parallel with 1000pf. the transmitter outputs display no ringing or undesir- able transients as they come out of shutdown. note that the transmitters are enabled only when the magnitude of v- exceeds approximately 3v. high data rates the max3380e/max3381e maintain the rs-232 ?.0vminimum transmitter output voltage even at high data rates. figure 8 shows a transmitter loopback test cir- cuit. figure 9 shows a loopback test result for the max3380e at 460kbps with true rs-232 output voltage levels (v cc = +4.2v). figure 10 shows the same test with rs-232-compatible levels (v cc = +2.5v). with data rates as high as 460kbps, the max3380e is com-patible with 2.5-generation gsm standards. v cc (v) c1, c5 (f) c2, c3, c4 (f) +2.35 to +3.6 0.1 0.1 +4.5 to +5.5 0.047 0.33 +2.35 to +5.5 0.22 1 table 2. minimum required capacitorvalues v cc = 3.3v, c1?4 = 0.1 f, c load = 1000pf 4 s/div 5v/div2v/div t2out t1out forceon = forceoff 5v 6v 6v 00 figure 7. transmitter outputs when recovering from shutdownor powering up downloaded from: http:///
max3380e/max3381e +2.35v to +5.5v, 1a, 2tx/2rx rs-232 transceivers with 15kv esd-protected i/o and logic pins 12 ______________________________________________________________________________________ for figure 9 and figure 10, a single transmitter was dri-ven at 460kbps, and all transmitters were loaded with an rs-232 receiver in parallel with 1000pf. data cable applications the max3380e/max3381es??5kv esd protection onboth the rs-232 i/os as well as the logic i/os makes them ideal candidates for data cable applications. a data cable is both an electrical connection and a level translator, allowing ultra-miniaturization of cell phones and other small portable devices. previous data cable approaches suffered from com- plexity due to the required protection circuits on both the logic side of the cable, as well as on the rs-232 connections. the example shown in figure 11 shows the ease of using the max3380e/max3381e in data cable applications. for best performance, keep the logic level lines short and use the rs-232 level lines to span any distance. v cc = v l = +2.5v, c1 = 0.1 f, c2 = c3 = c4 = 1 f, c load = 1000pf time (1 s/div) t1in 2v/div t1out 5v/div r1out 2v/div 05v 0 -5v 2v 0 2v figure 10. loopback test results at 460kbps (v cc = +2.5v) v cc = v l = +4.2v, c1 = 0.1 f, c2 = c3 = c4 = 1 f, c load = 1000pf 1 s/div t1in 5v/div t1out 5v/div r1out 5v/div 5v 0 5v0 -5v 5v 0 figure 9. loopback test results at 460kbps (v cc = +4.2v) max3380emax3381e 5k r_ in r_ out c2- c2+ c1- c1+ v- v+ v cc c4 c3 c1 c2 v cc forceoff t_ out t_ in gnd v cc forceon 1000pf c5 v l figure 8. loopback test circuit downloaded from: http:///
max3380e/max3381e +2.35v to +5.5v, 1a, 2tx/2rx rs-232 transceivers with 15kv esd-protected i/o and logic pins ______________________________________________________________________________________ 13 max3380e/ max3381e cell phone logic levels r2out r1out t2in t1in c1+c1- r2in r1in t2out t1out v+ v l v cc v- cts rx rts tx v batt 0.1 f 0.1 f peripherals rs-232 levels rts i/o rx cts tx invalid forceon forceoff c2+c2- 0.1 f 0.1 f 0.1 f 47 f figure 11. typical application circuit chip information transistor count: 1467process: bicmos 2019 18 17 16 15 14 13 12 3 4 5 6 7 8 v cc forceoff gndt1out c2+ c1- v+ c1+ top view t2outr1in r2in v l t1in invalid v- c2- 1211 9 10 forceonr1out r2out t2in max3380e/ max3381e tssop pin configuration downloaded from: http:///
max3380e/max3381e +2.35v to +5.5v, 1a, 2tx/2rx rs-232 transceivers with 15kv esd-protected i/o and logic pins 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. 14 ____________________maxim integrated products, 120 san gabriel drive, sunnyvale, ca 94086 408-737-7600 2001 maxim integrated products is a registered trademark of maxim integrated products. tssop4.40mm.eps package outline, tssop 4.40mm body 21-0066 1 1 i package information (continued) (the package drawing(s) in this data sheet may not reflect the most current specifications. for the latest package outline information, go to www.maxim-ic.com/packages .) downloaded from: http:///

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