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general description the max13234e?ax13237e are +3v to +5.5v pow- ered eia/tia-232 and v.28/v.24 communications inter- faces with high data-rate capabilities (up to 3mbps), a flexible logic voltage interface, and enhanced electro- static discharge (esd) protection. all receiver inputs and transmitter outputs are protected to ?5kv iec 61000?-2 air gap discharge, ?kv iec 61000-4-2 contact discharge, and ?5kv human body model. the max13234e/max13235e have two receivers and two transmitters, while the max13236e/max13237e have a single receiver and transmitter. the transmitters have a low-dropout transmitter output stage, delivering true rs-232 performance from a +3v to +5.5v supply based on a dual charge pump. the charge pump requires only four small 0.1? capacitors for operation from a +3.3v supply. all devices achieve a 1? supply current using maxim? autoshutdown plus feature. these devices automati- cally enter a low-power shutdown mode when the rs-232 cable is disconnected or the devices driving the transmitter and receiver inputs are inactive for more than 30s. the max13234e?ax13237e are available in space- saving tqfn and tssop packages and operate over the -40? to +85? extended temperature range. applications features ? data rate up to 3mbps ? low-voltage logic interface ? +3v to +5.5v supply voltage ? autoshutdown plus ? 1 a shutdown current max13234e?ax13237e 3mbps rs-232 transceivers with low-voltage interface ________________________________________________________________ maxim integrated products 1 ordering information/selector guide 19-4343; rev 0; 10/08 for pricing, delivery, and ordering information, please contact maxim direct at 1-888-629-4642, or visit maxim? website at www.maxim-ic.com. evaluation kit available part drivers/ receivers maximum data rate temp range pin-package max13234e eup+ 2 x 2 250kbps -40? to +85? 20 tssop MAX13234EETP+ 2 x 2 250kbps -40? to +85? 20 tqfn-ep* max13235e eup+ 2 x 2 3mbps -40? to +85? 20 tssop max13235eetp+ 2 x 2 3mbps -40? to +85? 20 tqfn-ep* max13236e ete+ 1 x 1 250kbps -40? to +85? 16 tqfn-ep* max13237e ete+ 1 x 1 3mbps -40? to +85? 16 tqfn-ep* telematics gps systems industrial systems portable devices wireless modules pos systems communication systems data cables autoshutdown plus is a registered trademark of maxim integrated products, inc. functional diagrams continued at end of data sheet. + denotes a lead-free/rohs-compliant package. * ep = exposed pad. functional diagrams logic-level transla tion t2in t1in r1out r2out forceoff forceon ready c1+ c1- c2+ c2- v l v cc 1.62v to v cc 3.0v to 5.5v v+ v- c bypass2 gnd rs-232 outputs rs-232 inputs ttl/cmos outputs ttl/cmos inputs t1out t2out r1in r2in max13234e max13235e 5k ? 5k ? c4 c3 c1 c2 c bypass1
max13234e?ax13237e 3mbps rs-232 transceivers with low-voltage interface 2 _______________________________________________________________________________________ absolute maximum ratings electrical characteristics (v cc = +3v to +5.5v, v l = +1.62v to v cc , t a = -40? to +85?, c1?4 = 0.1?, v cc = v l , tested at 3.3v ?0%. typical values are at t a = +25?.) (note 2) 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. note 1: package thermal resistances were obtained using the method described in jedec specification jesd51-7, using a four- layer board. for detailed information on package thermal considerations, refer to www.maxim-ic.com/thermal-tutorial . (all voltages referenced to gnd.) v cc ...................................................................... -0.3v to +6.0v v l ......................................................................... -0.3v to +6.0v v+ ........................................................................ -0.3v to +7.0v v- ......................................................................... +0.3v to -7.0v (v+) + |(v-)| ..................................................................... +13.0v t_in, forceoff , forceon ..................... -0.3v to (v l + 0.3v) r_in ................................................................................... ?5v t_out.............................................................................. ?3.2v r_out, ready ........................................... -0.3v to (v l + 0.3v) short-circuit duration t_out to gnd ......................................................... continuous continuous power dissipation (t a = +70?) 16-pin tqfn (derate 20.8mw/? above +70?) ..... 1666mw 20-pn tssop (derate 10.9mw/? above +70?) ...... 879mw 20-pin tqfn (derate 21.3mw/? above +70?) ..... 1702mw junction-to-case thermal resistance ( jc ) (note 1) 16-pin tqfn ................................................................. 2?/w 20-pin tssop ............................................................. 20?/w 20-pin tqfn ................................................................. 2?/w junction-to-ambient thermal resistance ( ja ) (note 1) 16-pin tqfn ............................................................... 30?/w 20-pin tssop ............................................................. 73?/w 20-pin tqfn ............................................................... 29?/w operating temperature range max1323x operating temperature range .... -40? to +85? max1323x operating temperature range .. -40? to +105? storage temperature range ........................... -65? to +160? lead temperature (soldering, 10s) .................................+300 c parameter symbol conditions min typ max units supply voltage v cc 3 5.5 v logic supply voltage v l 1.62 v cc v forceoff = forceon = v l , no loads 0.3 1 ma v l = 0v 1 10 v cc supply current i cc autoshutdown plus, forceoff = v l , forceon = gnd, all r_in idle, all t_in idle. 110 ? v cc shutdown current i ccsh forceoff = gnd 1 10 a v l supply current i l v cc = +5.5v 1 10 a v l shutdown current i lsh forceoff = gnd 1 10 a logic inputs (t_in, forceon, forceoff , referred to v l ) input threshold low v il tested at room temperature only 1/3 x v l v input threshold high v ih tested at room temperature only 2/3 x v l v input hysteresis 60 mv input leakage current ?.01 ? ? receiver outputs (ready) output-voltage low v ol i out = 0.8ma 0.4 v output-voltage high v oh i out = -0.5ma v l - 0.6 v l - 0.1 v
max13234e?ax13237e 3mbps rs-232 transceivers with low-voltage interface _______________________________________________________________________________________ 3 electrical characteristics (continued) (v cc = +3v to +5.5v, v l = +1.62v to v cc , t a = -40? to +85?, c1?4 = 0.1?, v cc = v l , tested at 3.3v ?0%. typical values are at t a = +25?.) (note 2) parameter symbol conditions min typ max units receiver inputs input-voltage range - 25 +25 v v cc = +3.3v 0.6 1.2 input threshold low v il t a = +25? v cc = +5v 0.8 1.5 v v cc = +3.3v 1.5 2.4 input threshold high v ih t a = +25? v cc = +5v 1.8 2.4 v input hysteresis 0.5 v input resistance 357k ? transmitter outputs output-voltage swing all transmitter outputs loaded with 3k ? to gnd ? ?.4 v output resistance v cc = v+ = v- = 0v, transmitter outputs = ?v 300 10m ? output short-circuit current -60 +60 ma output leakage current v cc = 0v or +3v to +5.5v, v out = ?2v, transmitters disabled -25 +25 ? autoshutdown plus (forceon = gnd, forceoff = v l ) positive threshold, figure 1 2.7 v receiver input threshold valid level negative threshold, figure 1 -2.7 v receiver input threshold invalid level figure 1 -0.3 +0.3 v receiver or transmitter edge-to- transmitters enabled t wu v l = 5v, figure 1 (note 3) 100 ? receiver or transmitter edge-to- transmitters shutdown t autoshdn v l = 5v, figure 1 (note 3) 15 30 60 s timing characteristics (max13234e/max13236e) maximum data rate r l = 3k ? , c l = 1000pf, one transmitter switching 250 kbps receiver propagation delay t rphl , t rplh c l = 150pf, figures 2, 3 0.15 ? transmitter skew |t tphl - t tplh | figures 4, 5 (note 4) 100 ns receiver skew |t rphl - t rplh | figures 2, 3 50 ns
max13234e?ax13237e 3mbps rs-232 transceivers with low-voltage interface 4 _______________________________________________________________________________________ electrical characteristics (continued) (v cc = +3v to +5.5v, v l = +1.62v to v cc , t a = -40? to +85?, c1?4 = 0.1?, v cc = v l , tested at 3.3v ?0%. typical values are at t a = +25?.) (note 2) parameter symbol conditions min typ max units transition-region slew rate v cc = +3.3v, t a = +25?, r l = 3k ? to 7k ? , measured from +3v to -3v or -3v to +3v, one transmitter switching, c l = 150pf to 1000pf 6 30 v/? timing characteristics (max13235e/max13237e) r l = 3k ? , c l = 250pf, one transmitter switching 1 maximum data rate r l = 3k ? , c l = 150pf, one transmitter switching 3 mbps receiver propagation delay t rphl , t rplh c l = 150pf, figures 2, 3 0.15 ? transmitter skew |t tphl t tplh | figures 4, 5 (note 4) 25 ns receiver skew |t rphl t rplh | figures 2, 3 50 ns transition-region slew rate v cc = +3.3v, t a = +25?, r l = 3k ? to 7k ? , measured from t _out = +3v to -3v or -3v to +3v, one transmitter switching, c l = 150pf to 1000pf 24 150 v/? esd protection human body model ?5 iec 61000-4-2 air discharge ?5 r_in, t_out to gnd iec 61000-4-2 contact discharge ? kv note 2 : all devices are 100% production tested at t a = +85?. all temperature limits are guaranteed by design. note 3 : a transmitter/receiver edge is defined as a transition through the transmitter/receiver input-logic thresholds. note 4 : transmitter skew is measured at the transmitter zero cross points.
max13234e?ax13237e 3mbps rs-232 transceivers with low-voltage interface _______________________________________________________________________________________ 5 test circuits/timing diagram 0 v+ v- v+ v- v cc 0 ready transmitter inputs receiver inputs transmitter outputs v cc t autoshdn t wu t wu t autoshdn figure 1. autoshutdown plus, and ready timing diagram c l t_out r_out r_in t_in figure 2. receiver test circuit
max13234e?ax13237e 3mbps rs-232 transceivers with low-voltage interface 6 _______________________________________________________________________________________ test circuits/timing diagram (continued) 0 t tphl 0 v o -v o t_in t_out -3v 3v t f 0 t tplh 3v -3v t r sr f = 6/t f sr r = 6/t r v l /2 v l /2 v l t r , t f 10ns figure 5. transmitter propagation delay c l t_out t_in r l v o figure 4. transmitter test circuit v oh v ol r_in r_out 1.3v t rphl 1.7v t rplh t r , t f 10ns v l /2 v l /2 figure 3. receiver propagation delay
max13234e?ax13237e 3mbps rs-232 transceivers with low-voltage interface _______________________________________________________________________________________ 7 typical operating characteristics (v cc = v l = 3.3v, t a = +25?, unless otherwise noted.) transmitter output voltage vs. load capacitance max13234e toc01 load capacitance (pf) output voltage (v) 500 2000 1000 1500 -4 -2 0 2 4 6 -6 0 2500 max13234e/max13236e r l = 3k ? t1 at 250kbps v+ v- transmitter output voltage vs. load capacitance max13234e toc02 load capacitance (pf) output voltage (v) 100 250 150 200 -4 -2 0 2 4 6 -6 50 300 max13235e/max13237e r l = 3k ? t1 at 3mbps v+ v- slew rate vs. load capacitance max13234e toc03 load capacitance (pf) slew rate (v/ s) 500 2000 1000 1500 6 7 8 10 5 9 11 12 4 0 2500 max13234e/max13236e r l = 3k ? sr+ sr- slew rate vs. load capacitance max13234e toc04 load capacitance (pf) slew rate (v/ s) 100 250 150 200 50 55 60 70 45 65 75 40 50 300 max13235e/max13237e r l = 3k ? sr+ sr- v cc supply current vs. load capacitance max13234e toc05 load capacitance (pf) supply current (ma) 500 2000 1000 1500 10 15 25 5 20 30 0 0 2500 max13234e r l = 3k ? t1 at 250kbps t2 at 15.6kbps v cc supply current vs. load capacitance max13234e toc06 load capacitance (pf) supply current (ma) 100 250 150 200 15 20 30 35 10 25 40 5 50 300 max13235e r l = 3k ? t1 at 3mbps t2 at 187.5kbps transmitter skew vs. load capacitance max13234e toc07 load capacitance (pf) transmitter skew (ns) 500 2000 1000 1500 30 50 90 110 130 10 70 150 -10 0 2500 max13234e/max13236e r l = 3k ? 1 transmitter operating at 250kbps transmitter skew vs. load capacitance max13234e toc08 load capacitance (pf) transmitter skew (ns) 150 200 100 3 4 6 7 8 2 1 5 9 0 50 250 max13235e/max13237e r l = 3k ? 1 transmitter operating at 3mbps ready turn-on time vs. temperature max13234e toc09 temperature ( c) ready turn-on time ( s) -15 60 10 35 50 60 70 80 90 100 40 -40 85
max13234e?ax13237e 3mbps rs-232 transceivers with low-voltage interface 8 _______________________________________________________________________________________ ready turn-off time vs. temperature max13234e toc10 temperature ( c) ready turn-off time ( s) -15 60 10 35 0.6 0.8 1.0 1.6 1.8 0.2 0.4 1.2 1.4 2.0 0 -40 85 supply current vs. data rate max13234e toc11 data rate (kbps) supply current (ma) 0.1 1 0.01 10 15 25 30 5 20 35 0 0.001 10 max13235e 1 transmitter operating r l = 3k ? , c l = 150pf logic-input threshold vs. v l max13234e toc12 v l (v) logic-input threshold (v) 3.5 4.5 2.5 1.5 1.7 2.1 2.3 1.3 0.9 1.1 0.7 1.9 2.5 0.5 1.5 5.5 v cc = 5.5v v ih v il transmitter output voltage vs. supply voltage max13234e toc13 supply coltage (v) output voltage (v) 3.5 4.5 4.0 5.0 -4 -2 2 4 6 -6 0 8 -8 3.0 5.5 max13235e/max13237e r l = 3k ? , c l = 150pf 1 transmitter operating at 1mbps v+ v- transmitter output voltage vs. load current max13234e toc14 load current (ma) output voltage (v) 26 4 -4 -2 2 4 6 -6 0 8 -8 08 1 transmitter operating, dc v+ v- typical operating characteristics (continued) (v cc = v l = 3.3v, t a = +25?, unless otherwise noted.)
max13234e?ax13237e 3mbps rs-232 transceivers with low-voltage interface _______________________________________________________________________________________ 9 pin descriptions pin max13234e/ max13235e max13236e/ max13237e tssop tqfn-ep tqfn-ep name function 1 19 14 ready ready to transmit output, active-high. ready is enabled high when v- goes below -4v and the device is ready to transmit. 2 1 16 c1+ positive terminal of the voltage doubler charge-pump capacitor 3 20 15 v+ +5.5v generated by the charge pump 4 2 1 c1- negative terminal of the voltage doubler charge-pump capacitor 5 3 2 c2+ positive terminal of the inverting charge-pump capacitor 6 4 3 c2- negative terminal of the inverting charge-pump capacitor 7 5 4 v- -5.5v generated by the charge pump 8 6 t2out rs-232 transmitter output 2 5 rin rs-232 receiver input 9 7 r2in rs-232 receiver input 2 6 rout cmos receiver output. v l referred logic. 10 8 r2out cmos receiver output 2. v l referred logic. 11 9 7 v l logic-level supply. all cmos inputs and outputs are related to this supply. 8 tin cmos transmitter input. v l referred logic. 12 10 t2in cmos transmitter input 2. v l referred logic. 13 11 t1in cmos transmitter input 1. v l referred logic. 14 12 9 forceon forceon input, active-high. v l referenced logic. drive forceon high to override automatic circuitry keeping transmitters on ( forceoff must be high). see table 1. 15 13 r1out cmos receiver output 1. v l referred logic. 10 tout rs-232 transmitter output 16 14 r1in rs-232 receiver input 1 17 15 t1out rs-232 transmitter output 1 18 16 11 gnd ground 19 17 12 v cc +3v to +5.5v supply voltage 20 18 13 forceoff forceoff input, active-low. v l referenced logic. drive forceoff low to shut down transmitters and on-board charge pumps. all receiver and transmitter outputs are tri- stated. this overrides all automatic circuitry and forceon (table 1). ep exposed pad. connect ep to gnd or leave unconnected.
max13234e?ax13237e 3mbps rs-232 transceivers with low-voltage interface 10 ______________________________________________________________________________________ detailed description vl logic supply input the max13234e?ax13237e feature a separate logic supply input (v l ) that sets the receiver? output level (v oh ), and sets the transmitter? input thresholds (v il , v ih ). this feature allows flexibility in interfacing to uarts or communication controllers that have different logic levels. connect this input to the host logic supply (1.62v v l v cc ). dual charge-pump voltage converter the internal power supply consists of a regulated dual charge pump that provides output voltages of +5.5v and -5.5v (inverting charge pump), over the +3.0v to +5.5v range. the charge pump operates in discontinu- ous mode: if the output voltages are less than +5.5v, the charge pump is enabled; if the output voltages exceed +5.5v, the charge-pump is disabled. the charge pumps require flying capacitors (c1, c2) and reservoir capacitors (c3, c4) to generate the v+ and v- supplies. the ready output is low when the charge pumps are disabled in shutdown mode. the ready signal asserts high when v- goes below -4v. rs-232 transmitters the transmitters are inverting level translators that con- vert cmos-logic levels to ?.0v eia/tia-232 levels. the max13234e/max13236e guarantee a 250kbps data rate with worst-case loads of 3k ? in parallel with 1000pf. the max13235e/max13237e guarantee a 1mbps data rate with worst-case loads of 3k ? in paral- lel with 250pf, and a 3mbps data rate with worst-case loads of 3k ? in parallel with 150pf. transmitters can be paralleled to drive multiple receivers. when forceoff is driven to ground or when the autoshutdown plus cir- cuitry senses that all receiver and transmitter inputs are inactive for more than 30s, the transmitters are disabled and the outputs go into a high-impedance state. when powered off or shut down, the outputs can be driven to ?2v. the transmitter inputs do not have pullup resis- tors. connect unused inputs to gnd or v l . rs-232 receivers the receivers convert rs-232 signals to cmos-logic output levels. the max13234e?ax13237e have inverting outputs that are active when in shutdown ( forceoff = gnd) (table 1). autoshutdown plus mode drive forceoff high and forceon low to invoke autoshutdown plus mode. when these devices do not sense a valid signal transition on any receiver and transmitter input for 30s, the onboard charge pumps are shut down, reducing supply current to 1?. this occurs if the rs-232 cable is disconnected or if the devices driving the transmitter and receiver inputs are inactive for more than 30s. the max13234e?ax13237e turn on again when a valid transition is applied to any rs-232 receiver or transmit- ter input. as a result, the system saves power without requiring any control. figure 6 and table 1 summarize the max13234e max13237e operating modes. the forceon and forceoff inputs override autoshutdown plus circuit- ry. when neither control is asserted, the ic selects between these states automatically based on the last receiver or transmitter input edge received. hardware-controlled shutdown drive forceoff low to place the max13234e max13237e into shutdown mode. forceon master shdn line 0.1 f1m ? forceoff max13234e max13235e max13236e max13237e power- management unit figure 7. autoshutdown plus initial turn-on to wake up a mouse or another system
max13234e?ax13237e 3mbps rs-232 transceivers with low-voltage interface ______________________________________________________________________________________ 11 table 1. transceiver mode control forceoff forceon r_in or t_in edge within 30s t_out r_out transceiver status 0 x x high-impedance active shutdown (forced off) 1 1 x active active normal operation (forced on) 1 0 yes active active normal operation in autoshutdown plus 1 0 no high-impedance active shutdown in autoshutdown plus x = don? care. r_in t_in r s 30s timer edge detect edge detect forceoff forceon powerdown* autoshdn forceoff forceon * powerdown is only an internal signal. it controls the operational status of the transmitters and the power supplies. figure 6. autoshutdown plus and shutdown logic
max13234e?ax13237e 3mbps rs-232 transceivers with low-voltage interface 12 ______________________________________________________________________________________ charge-current limit resistor discharge resistance storage capacitor c s 100pf r c 1m ? r d 1500 ? high- voltage dc source device under test figure 8a. human body 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 8b. human body current waveform charge-current limit resistor discharge resistance storage capacitor c s 150pf r c 50m ? to 100m ? r d 330 ? high- voltage dc source device under test figure 9a. iec61000-4-2 esd test model t r = 0.7ns to 1ns 30ns 60ns t 100% 90% 10% i peak i figure 9b. iec61000-4-2 esd generator current waveform ?5kv esd protection esd-protection structures are incorporated on all pins to protect against electrostatic discharges encountered during handling and assembly. the driver outputs and receiver inputs of the max13234e?ax13237e have extra protection against static electricity. maxim? engi- neers have developed state-of-the-art structures to pro- tect 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. esd protection can be tested in various ways; the transmitter outputs and receiver inputs of this prod- uct family are characterized for protection to the follow- ing limits: 1) ?5v using the human body model 2) ?5kv using iec 61000-4-2 air-gap method 3) ?kv using iec 61000-4-2 contact-discharge 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 8a shows the human body model and figure 8b 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 61000-4-2 the iec 61000-4-2 standard covers esd testing and performance of finished equipment; it does not specifi- cally refer to integrated circuits. the max13234e max13237e helps design equipment that meets level 4 (the highest level) of iec 61000-4-2, without the need for additional esd-protection components. the major difference between tests done using the human body model and iec 61000-4-2 is higher peak current in iec 61000-4-2, because series resistance is lower in the iec 61000-4-2 model. hence, the esd withstand volt- age measured to iec 61000-4-2 is generally lower than that measured using the human body model. figure 9a shows the iec 61000-4-2 model and figure 9b shows the current waveform for the 8kv, iec 61000-4-2, level 4, esd contact-discharge method. 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. applications information capacitor selection the capacitor type used for c1?4 is not critical for proper operation; polarized or non-polarized capacitors can be used. the charge pump requires 0.1? capaci- tors for v cc = +3.3v operation. for other supply volt- ages, see table 2 for required capacitor values. do not use values 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, c bypass1 , and c bypass2 to maintain the proper ratios (c1 to the other capacitors). when using the minimum required capacitor values, make sure the capacitor value does not degrade excessively with temperature. if in doubt, use capacitors with a larger nominal value. the capacitor? equivalent series resistance (esr), usually rises at low temperatures influencing the amount of ripple on v+ and v-. power-supply decoupling in most circumstances, a 0.1? v cc bypass capacitor and a 1? v l bypass capacitor are adequate. in appli- cations that are sensitive to power-supply noise, use capacitors of the same value as charge-pump capaci- tor c1. connect bypass capacitors as close to the ic as possible. transmitter outputs when exiting shutdown figure 10 shows two transmitter outputs when exiting shutdown 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. max13234e?ax13237e 3mbps rs-232 transceivers with low-voltage interface ______________________________________________________________________________________ 13 v cc (v) c1, c bypass2 (?) c bypass1 (?) c2, c3, c4 (?) 3.0 to 3.6 0.22 0.22 0.22 3.15 to 3.6 0.1 0.1 0.1 4.5 to 5.5 0.047 1 0.33 3.0 to 5.5 0.22 1 1 table 2. required minimum capacitance values 5 f figure 10. transmitter outputs when exiting shutdown or powering up
max13234e?ax13237e 3mbps rs-232 transceivers with low-voltage interface 14 ______________________________________________________________________________________ 2 figure 12. loopback test results at 120kbps 100ns/div t1in t1out r1out 3.3v/div 5v/div 3.3v/div v cc = 3.3v figure 13. loopback test results at 3mbps t_in r_out forceon forceoff c1+ c1- c2+ c2- *c3 can be returned to v cc or gnd. v l v cc 1.62v to v cc v cc v+ v- c bypass2 gnd t_out r_in max13236e max13237e 5k ? c4 1000pf c3* c1 c2 c bypass1 v cc figure 11. loopback test circuit chip information process: bicmos high data rates the max13234e?ax13237e maintain the rs-232 ?v minimum transmitter output voltage even at high data rates. figure 11 shows a transmitter loopback test cir- cuit. figure 12 shows a loopback test result at 120kbps, and figure 13 shows the same test at 3mbps. in figure 12, all transmitters were driven simultaneously at 120kbps into rs-232 loads in parallel with 1000pf. in figure 13, a single transmitter was driven at 3mbps, and all transmitters were loaded with an rs-232 receiv- er in parallel with 150pf.
max13234e?ax13237e 3mbps rs-232 transceivers with low-voltage interface ______________________________________________________________________________________ 15 pin configurations max13236e max13237e *ep *exposed pad. connect ep to gnd. top view 1 12 2 11 3 10 4 9 forceon tout gnd v cc v- c2- c2+ c1- rin rout v l tin 5 6 7 8 16 15 14 13 c1+ v+ ready forceoff tqfn + max13234e max13235e t1out gnd v cc forceoff 17 18 19 20 4 3 2 1 c1- r1in 16 5 c2+ v+ c1+ ready tssop + t2in t1in forceon r1out 12 13 14 15 9 8 7 6 r2in v l 11 10 r2out t2out v- c2- max13234e max13235e *ep *exposed pad. connect ep to gnd. top view top view 2 14 3 13 4 12 5 11 t1in forceon r1out r1in v- c2- c2+ c1- 1 15 t1out c1+ r2in r2out v l t2in 7 8 9 10 19 18 17 16 ready t2out 6 20 v+ forceoff v cc gnd tqfn + functional diagrams (continued) logic-l evel transla tion t_in r_out forceoff forceon ready c1+ c1- c2+ c2- v l v cc 1.62v to v cc 3.0v to 5.5v v+ v- c bypass2 gnd rs-232 output rs-232 input ttl/cmos output ttl/cmos input t_out r_in max13236e max13237e 5k ? c4 c3 c1 c2 c bypass1
max13234e?ax13237e 3mbps rs-232 transceivers with low-voltage interface 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. 16 ____________________maxim integrated products, 120 san gabriel drive, sunnyvale, ca 94086 408-737-7600 2008 maxim integrated products is a registered trademark of maxim integrated products, inc. package type package code document no. 20 tssop u20-2 21-0066 20 tqfn-ep* t2055-5 21-0140 16 tqfn-ep* t1655-2 21-0140 package information for the latest package outline information and land patterns, go to www.maxim-ic.com/packages . * ep = exposed pad.

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