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________________________________________________________________ maxim integrated products 1 general description the max3238e/max3248e transceivers use maxim? revolutionary autoshutdown plus feature to achieve 10na supply current. these devices shut down the on- board power supply and drivers when they do not sense a valid signal transition on either the receiver or transmit- ter inputs. this occurs if the rs-232 cable is disconnect- ed or if the transmitters of the connected peripheral are turned off. the devices turn on again when a valid transi- tion is applied to any rs-232 receiver or transmitter input. autoshutdown plus automatically achieves this power savings through its on-board circuitry, as no changes are required to the existing bios or operating system. all rs-232 inputs and outputs, as well as the logic i/o pins, have enhanced esd protection to ?5kv. the addi- tional esd protection on the logic i/o pins makes the max3238e/max3248e ideal for cell phone data cable applications because it eliminates the need for costly external transzorb or protection schemes. the max3238e/max3248e contain five drivers and three receivers and are 3v-powered eia/tia-232 and v.28/v.24 communication interfaces intended for cell phones, data cables, and modem applications. a proprietary, high-effi- ciency, dual charge-pump power supply and a low- dropout transmitter combine to deliver true rs-232 performance from a single +3.0v to +5.5v supply. a guaranteed data rate of 250kbps provides compatibility with popular software for communicating with personal computers. the max3238e and the max3248e differ only in their input logic thresholds. the max3238e has standard logic thresholds, while the max3248e has low-level logic thresholds of 0.6v to 1.2v, which are ideal for 1.8v sys- tems. the transmitter inputs, forceon, and forceoff have a 400k? active positive feedback resistor. once driven to a valid logic level, they will retain this level if the driving signal is removed or goes high impedance. unused transmitter and logic inputs may be left unconnected. the max3238e/max3248e can operate with supply voltages ranging from +3.0v to +5.5v. applications features enhanced esd protection on rs-232 i/o pins and all logic pins 15kv?uman body model 8kv?ec 1000-4-2 contact discharge 15kv?ec 1000-4-2 air-gap discharge guaranteed data rate: 250kbps 10na low-power shutdown with receivers active schmitt triggers on all inputs flow-through pinout meets eia/tia-232 specifications down to 3.0v guaranteed 6v/s slew rate low-level logic thresholds (max3248e) rs-232-compatible outputs to 2.7v max3238e/max3248e +3.0v to +5.5v, 10na, 250kbps rs-232 transceivers with 15kv esd-protected i/o and logic pins 28 27 26 25 24 23 22 21 20 19 18 17 16 15 1 2 3 4 5 6 7 8 9 10 11 12 13 14 c1+ v+ v cc c1- t1in t2in invalid t3in r1out r2out t4in r3out t5in r1outb forceoff forceon t5out r3in t4out r2in r1in t3out t2out t1out v- c2- gnd c2+ ssop top view max3238e max3248e ___________________pin configuration 19-1632; rev 1; 6/01 ordering information autoshutdown plus i s a trademark of maxim integrated products. transzorb is a trademark of general semiconductor industries, inc. ? c4; 4,r pg. cellular data cables modems battery-powered equipment peripherals data cradles printers typical operating circuit appears at end of data sheet. 28 ssop 28 ssop 28 ssop 28 ssop pin-package temp. range 0? to +70? -40? to +85? 0? to +70? -40? to +85? max3248eeai max3248ecai max3238eeai max3238ecai part 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.
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 specificatio ns is not implied. exposure to absolute maximum rating conditions for extended periods may affect device reliability. max3238e/max3248e +3.0v to +5.5v, 10na, 250kbps rs-232 transceivers with 15kv esd-protected i/o and logic pins 2 _______________________________________________________________________________________ absolute maximum ratings electrical characteristics (v cc = +3.0v to +5.5v, c1?4 = 0.1? (tested at 3.3v ?%), c1?4 = 0.22? (tested at 3.3v ?0%), c1 = 0.047?, and c2?4 = 0.33? (tested at 5.0v ?0%), t a = t min to t max , unless otherwise noted. typical values are at t a = +25?.) v cc ...........................................................................-0.3v to +6v v+ (note 1) ...............................................................-0.3v to +7v v- (note 1) ................................................................+0.3v to -7v v+ + |v-| (note 1) .................................................................+13v input voltages t_in, forceoff , forceon ..............................-0.3v to +6v r_in .................................................................................?5v output voltages t_out...........................................................................?3.2v r_out, invalid ....................................-0.3v to (v cc + 0.3v) short-circuit duration t_out (one at a time) ............................................continuous continuous power dissipation (t a = +70?) 28-pin ssop (derate 9.52mw/? above +70?) .........762mw operating temperature ranges max3238ecai/max3248ecai ...........................0? to +70? max3238eeai/max3248eeai .........................-40? to +85? storage temperature range ............................-65? to +150? lead temperature (soldering, 10s) ................................+300? note 1: v+ and v- can have a maximum magnitude of +7v, but their absolute difference can not exceed +13v. 1.10 1.2 1.15 1.6 0.95 1.2 max3248e forceon, forceoff, and t_in wake-up threshold; v cc = 5.0v forceon, forceoff, and t_in wake-up threshold; v cc = 3.3v t_in (active) forceon, forceoff, and t_in wake-up threshold; v cc = 5.0v forceon, forceoff, and t_in wake-up threshold; v cc = 3.3v t_in (active) forceon, forceoff, and t_in wake-up threshold; v cc = 5.0v forceon, forceoff, and t_in wake-up threshold; v cc = 3.3v t_in (active) forceon, forceoff, and t_in wake-up threshold; v cc = 5.0v forceon, forceoff, and t_in wake-up threshold; v cc = 3.3v t_in (active) parameter min typ max units input logic threshold low 0.8 1.20 v supply current, autoshutdown plus disabled 0.5 2.0 ma supply current, autoshutdown plus input logic threshold high 1.60 2.0 0.75 6 ? v 10 300 2.10 2.4 1.30 2.0 max3238e 0.6 0.7 0.8 1.45 0.6 1.0 0.6 0.85 0.8 1.00 max3248e supply current, shutdown 10 300 na conditions forceoff = gnd, r_in = gnd, t_in = v cc or gnd max3238e forceon = forceoff = v cc , no load receivers idle, t_in = v cc or gnd, forceon = gnd, forceoff = v cc r_in = forceon = gnd, forceoff = v cc, t_in = v cc or gnd na dc characteristics (v cc = +3.3v or +5.0v, t a = +25?) logic inputs and receiver outputs
max3238e/max3248e +3.0v to +5.5v, 10na, 250kbps rs-232 transceivers with 15kv esd-protected i/o and logic pins _______________________________________________________________________________________ 3 electrical characteristics (continued) (v cc = +3.0v to +5.5v, c1?4 = 0.1? (tested at 3.3v ?%), c1?4 = 0.22? (tested at 3.3v ?0%), c1 = 0.047?, and c2?4 = 0.33? (tested at 5.0v ?0%), t a = t min to t max , unless otherwise noted. typical values are at t a = +25?.) figure 4a figure 4a figure 4b v cc = 5v, figure 4b (note 3) v cc = 5v, figure 4b i out = 1.0ma i out = -1.0ma v cc = 5v, figure 4b v -0.3 0.3 receiver input threshold to invalid output low v 2.7 receiver input threshold to invalid output high s 15 30 60 receiver or transmitter edge to shutdown (t autoshdn ) ? 25 receiver or transmitter edge to transmitters enabled (t wu ) ? 60 receiver positive or negative threshold to invalid low (t invl ) v 0.4 invalid output voltage low v v cc - 0.6 invalid output voltage high ? 0.3 receiver positive or negative threshold to invalid high (t invh ) positive threshold negative threshold -2.7 v -25 25 i out = -1.0ma i out = 1.0ma input voltage range v cc = 3.3v receivers disabled t_in, forceon, forceoff (note 2) 0.6 1.0 conditions v cc = 5.0v v 0.8 1.4 input threshold low v cc = 3.3v 1.5 2.4 v cc = 5.0v v 2.0 2.4 input threshold high v 0.6 input hysteresis t a = +25? k? 357 input resistance v v cc -v cc - 0.6 0.1 output voltage high v 0.4 output voltage low ? ?.05 ?0 output leakage current ? 918 input leakage current units min typ max parameter all transmitter outputs loaded with 3k? to ground v ?.0 ?.4 output voltage swing v cc = 0, t out = ?v ? 300 50k output resistance v cc 3.6v ?5 ?0 v cc > 3.6v ma ?0 ?00 output short-circuit current iec 1000-4-2 air-gap discharge method ?5 iec 1000-4-2 contact discharge method ? human body model kv ?5 esd protection (r_in, t_in, r_out, t_out, forceon, forceoff, invalid, r_outb) receiver inputs autoshutdown (forceon = gnd, forceoff = v cc ) transmitter outputs esd protection
-6 -2 -4 2 0 4 6 -5 -3 1 -1 3 5 0 1000 1500 500 2000 2500 3000 transmitter output voltage vs. load capacitance max3238e toc01 load capacitance (pf) transmitter output voltage (v) v out- v out + for data rates up to 250kbps 1 transmitter 250kbps 4 transmitters 15.6kbps all transmitters loaded with 3k? + c l 0 4 2 8 6 10 12 0 1000 1500 500 2000 2500 3000 slew rate vs. load capacitance max3238e toc02 load capacitance (pf) slew rate (v/ s) sr+ sr- 1 transmitter 250kbps 4 transmitters 15.6kbps all transmitters loaded with 3k? + c l 50 20 10 0 0 1000500 2000 3000 supply current vs. load capacitance when transmitting data 30 max3238 toc-03 supply current (ma) load capacitance (pf) 1500 2500 40 250kbps 20kbps 120kbps 1 transmitter 20kbps, 120 kbps, 250kbps 4 transmitters 15.6kbps all transmitters loaded with 3k? + c l __________________________________________typical operating characteristics (v cc = +3.3v, 250kbps data rate, 0.1? capacitors, all transmitters loaded with 3k ?, t a = +25?, unless otherwise noted.) max3238e/max3248e +3.0v to +5.5v, 10na, 250kbps rs-232 transceivers with 15kv esd-protected i/o and logic pins 4 _______________________________________________________________________________________ electrical characteristics (continued) (v cc = +3.0v to +5.5v, c1?4 = 0.1? (tested at 3.3v ?%), c1?4 = 0.22? (tested at 3.3v ?0%), c1 = 0.047?, and c2?4 = 0.33? (tested at 5.0v ?0%), t a = t min to t max , unless otherwise noted. typical values are at t a = +25?.) note 2: the transmitter inputs have an active positive feedback resistor. the input current goes to zero when the inputs are at the supply rails. note 3: during autoshutdown only, a transmitter/receiver edge is defined as a transition through the transmitter/receiver input logic wake-up thresholds. conditions units min typ max parameter | t phl - t plh | 43 0 t phl r_in to r_out, c l = 150pf t plh c l = 150pf to 1000pf r l = 3k?, c l = 1000pf, one transmitter switching c l = 150pf to 2500pf 0.15 v cc = 3.3v, t a = +25?, r l = 3k? to 7k?, measured from +3v to -3v or -3v to +3v normal operation normal operation | t phl - t plh | ? 0.15 receiver propagation delay kbps 250 maximum data rate v/? 63 0 transition-region slew rate ? 2.6 receiver output enable time ? 2.4 receiver output disable time ns 50 ns 50 receiver skew transmitter skew timing characteristics
max3238e/max3248e +3.0v to +5.5v, 10na, 250kbps rs-232 transceivers with 15kv esd-protected i/o and logic pins _______________________________________________________________________________________ 5 typical operating characteristics (continued) (v cc = +3.3v, 250kbps data rate, 0.1? capacitors, all transmitters loaded with 3k ?, t a = +25?, unless otherwise noted.) ______________________________________________________________pin description output of the valid signal detector. a logic 1 indicates if a valid rs-232 level is present on receiver inputs. invalid 15 noninverting complementary receiver output. always active. r1outb 16 ttl/cmos transmitter inputs (t5in?1in). this pin has an active positive feedback resis- tor. once driven to a valid logic level, the pin retains that level if left unconnected until power is cycled. t_in 17, 19, 22, 23, 24 ttl/cmos receiver outputs (r3out?1out) r_out 18, 20, 21 negative terminal of voltage-doubler charge-pump capacitor c1- 25 rs-232 transmitter outputs (t1out?5out) t_out 5, 6, 7, 10, 12 rs-232 receiver inputs (r1in?3in) r_in 8, 9, 11 force-on input. drive high to override autoshutdown plus, keeping transmitters and receivers on (forceoff must be high) (table 1). this pin has an active positive feedback resistor. once driven to a valid logic level, the pin retains that level if left unconnected until power is cycled. forceon 13 force-off input. drive low to shut down transmitters, receivers (except r1outb), and on- board supply. this overrides autoshutdown plus and forceon (table 1). this pin has an active positive feedback resistor. once driven to a valid logic level, the pin retains that level if left unconnected until power is cycled. forceoff 14 -5.5v generated by the charge pump v- 4 negative terminal of inverting charge-pump capacitor c2- 3 pin ground gnd 2 positive terminal of inverting charge-pump capacitor c2+ 1 function name 26 v cc +3.0v to +5.5v supply voltage 27 v+ +5.5v generated by the charge pump 28 c1+ positive terminal of voltage-doubler charge-pump capacitor -6 -2 -4 2 0 4 6 -3 -5 1 -1 3 5 2.0 3.0 3.5 2.5 4.0 4.5 5.0 transmitter output voltage vs. supply voltage max3238e toc04 supply voltage (v) transmitter output voltage (v) v out- v out + 1 transmitter 250kbps 4 transmitters 15.6kbps all transmitters loaded with 3k? +1000pf 0 20 10 30 40 50 2.0 3.0 3.5 2.5 4.0 4.5 5.0 supply current vs. supply voltage max3238e toc05 supply voltage (v) supply current (ma) 1 transmitter 250kbps 4 transmitters 15.6kbps all transmitters loaded with 3k? +1000pf
max3238e/max3248e +3.0v to +5.5v, 10na, 250kbps rs-232 transceivers with 15kv esd-protected i/o and logic pins 6 _______________________________________________________________________________________ _______________detailed description dual charge-pump voltage converter the max3238e/max3248es?internal power supply consists of a regulated dual charge pump that provides output voltages of +5.5v (doubling charge pump) and -5.5v (inverting charge pump), regardless of the input voltage (v cc ) over the 3.0v to 5.5v range. the charge pumps operate in a discontinuous mode: if the output voltages are less than 5.5v, the charge pumps are enabled; if the output voltages exceed 5.5v, the charge pumps are disabled. each charge pump requires a fly- ing capacitor (c1, c2) and a reservoir capacitor (c3, c4) to generate the v+ and v- supplies. rs-232 transmitters the max3248e transmitters are inverting level translators that convert a logic low of 0.6v and logic high of 1.2v to 5.0v eia/tia-232 levels. the max3238e transmitters are inverting level translators that convert cmos-logic levels to 5.0v eia/tia-232 levels. the max3238e/max3248e transmitters both guarantee a 250kbps data rate with worst-case loads of 3k? in parallel with 1000pf, provid- ing compatibility with pc-to-pc communication software (such as laplink). transmitters can be paralleled to drive multiple receivers. figure 1 shows a complete sys- tem connection. laplink is a trademark of traveling software. when forceoff is driven to ground, the transmitters and receivers are disabled and the outputs go high impedance, except for r1outb. when the auto- shutdown plus circuitry 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, but the receivers remain active. when the power is off, the max3238e/max3248e per- mit the outputs to be driven up to ?2v. the transmitter inputs, forceon and forceoff, have a 400k ? active positive-feedback resistor. once driven to a valid logic level, they will retain this level if the driving signal is removed or goes high-impedance. unused transmitter inputs may be left unconnected. rs-232 receivers the receivers convert rs-232 signals to cmos-logic output levels. all receivers have inverting three-state outputs and are inactive in shutdown ( forceoff) (table 1). the ma x3238e/max3248e also feature an extra, always-active noninverting output, r1outb. this extra output monitors receiver activity while the other receivers are high impedance, allowing ring indicator to be monitored without forward biasing other devices connected to the receiver outputs. this is ideal for sys- tems where v cc is set to 0 in shutdown to accommo- date peripherals, such as uarts (figure 2). table 1. output control truth table forceon forceoff autoshutdown plus operation status t_out r_out r1outb x 0 x shutdown (forced off) high-z high-z active 1 1 x normal operation (forced on) active active active 0 1 <30s* normal operation (autoshutdown plus) active active active 0 1 >30s* shutdown (autoshutdown plus) high-z active active x = don? care *time since last receiver or transmitter input transition.
max3238e/max3248e +3.0v to +5.5v, 10na, 250kbps rs-232 transceivers with 15kv esd-protected i/o and logic pins _______________________________________________________________________________________ 7 autoshutdown plus mode a 10na supply current is achieved with maxim? autoshutdown plus feature, which operates when forceoff is low and forceon is high. when the max3238e/max3248e sense no valid signal transitions on all receiver and transmitter inputs for 30s, the on- board power supply and drivers are shut off, reducing supply current to 1?. if the receiver inputs are in the invalid range (-0.3v < r_in < +0.3v) and the transmit- ter inputs are at gnd or v cc , supply current is further reduced to 10na. this occurs if the rs-232 cable is disconnected or if the connected peripheral transmit- ters are turned off. 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 sys- tem. the invalid output is high when the receivers are active. since invalid indicates the receiver inputs condition, it can be used in any mode (figure 3). max3238e/ max3248e i/o chip with uart cpu rs-232 power management unit or keyboard controller forceoff forceon invalid t1 t2 t3 t4 t5 r1 r2 r3 figure 1. interface under control of pmu max3238e max3248e t1out r1outb tx 5k? uart v cc t1in three-stated logic transition detector r1in protection diode r1out forceoff = gnd v cc to p rx previous rs-232 tx uart shdn = gnd v cc v cc gnd rx 5k? a) older rs-232: powered-down uart draws current from active receiver output in shutdown. b) new max3238e/max3248e: in shutdown, r1outb is used to monitor external devices and r1out is three stated, eliminating a current path through the uart's protection diode. gnd protection diode i i figure 2. max3238e/max3248e detect rs-232 activity when the uart and interface are shut down.
max3238e/max3248e +3.0v to +5.5v, 10na, 250kbps rs-232 transceivers with 15kv esd-protected i/o and logic pins 8 _______________________________________________________________________________________ tables 1 and 2 and figure 3 summarize the max3238e/ max2348es?operating modes. forceon and force- off override the automatic circuitry and force the transceiver into its normal operating state or into its low- power standby state. when neither control is asserted, the ic enters autoshutdown plus mode and selects between these states automatically, based on the last receiver or transmitter input edge received. when shut down, the devices?charge pumps turn off, v+ decays to v cc, v- decays to ground, and the trans- mitter outputs are disabled (high impedance). the time required to recover from shutdown is typically 25 s (figure 4b). software-controlled shutdown if direct software control is desired, use invalid to indicate dtr or ring indicator signal. tie forceoff and forceon together to bypass the autoshutdown plus feature so the line acts like a shdn input. esd protection as with all maxim devices, esd protection structures are incorporated to protect against electrostatic dis- charges (esds) encountered during handling and assembly. the max3238e/max3248e rs-232 transmit- ters and receivers, as well as the i/o have extra protec- tion against static electricity found in normal operation. maxim? engineers developed state-of-the-art struc- tures to protect these pins against esd of ?5kv with- out damage. after an esd event, the max3238e/ max3248e keep working without latchup. esd protection can be tested in various ways. the pins are characterized for protection to ?5kv and ?kv (see electrical characteristics). esd test 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 figure 5b 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- table 2. invalid truth table +0.3v -0.3v invalid r_in invalid asserted if all receiver inputs are between +0.3v and -0.3v for at least 60s. 60? timer r +2.7v -2.7v invalid r_in invalid deasserted if any receiver input has been between +2.7v and -2.7v for less than 60s. 60? timer r autoshdn r_in t_in r s 30s timer edge detect edge detect forceoff forceon figure 3a. invalid functional diagram, invalid low figure 3b. invalid functional diagram, invalid high figure 3c. autoshutdown plus logic powerdown* autoshdn forceoff forceon * power down is only an internal signal. it controls the operational status of the transmitters and the power supplies. figure 3d. power-down logic l no h yes invalid output rs-232 signal present at any receiver input
max3238e/max3248e +3.0v to +5.5v, 10na, 250kbps rs-232 transceivers with 15kv esd-protected i/o and logic pins _______________________________________________________________________________________ 9 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 and per- formance of finished equipment; it does not specifically refer to integrated circuits. the max3238e/max3248e help you design equipment that meets level 4 (the high- est level) of iec 1000-4-2, without additional esd pro- tection 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 esd test model (figure 6a), the esd withstand voltage measured to this standard is generally lower than that measured using the human body model. 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 connects the probe to the device before the probe is energized. machine model the machine model for esd testing uses a 200pf stor- age capacitor and zero-discharge resistance. its objec- tive is to mimic the stress caused by contact that occurs with handling and assembly during manufactur- ing. of course, all pins (not just rs-232 inputs and out- puts) require this protection during manufacturing. receiver input levels -2.7v -0.3v +2.7v +0.3v 0v indeterminate invalid high invalid low invalid high indeterminate figure 4a. receiver positive/negative thresholds for invalid v cc 0 v+ v- v cc 0 invalid output *all receivers/transmitters inactive **any one receiver/transmitter becomes active forceon = gnd, forceoff = v cc transmitter inputs voltage receiver inputs voltage transmitter outputs voltage t autoshdn invalid region *** t wu t wu i nvl t autoshdn figure 4b. autoshutdown plus and invalid timing diagram
max3238e/max3248e 10 ______________________________________________________________________________________ therefore, the machine model is less relevant to the i/o ports than the human body model and iec 1000-4-2. applications information capacitor selection the capacitor type used for c1?4 is not critical for proper 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 3 for required capacitor values. do not use val- ues smaller than those listed in table 3. 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 c bypass to maintain the proper ratios (c1 to the other capacitors). power-supply decoupling in most applications, decouple v cc to ground with a 0.1? capacitor. further increasing this capacitor value reduces power-supply ripple and enhances noise mar- gin. connect the bypass capacitor as close to the ic as possible. charge-current limit resistor discharge resistance storage capacitor 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 figure 5a. human body esd test model 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 6a. iec 1000-4-2 esd test model figure 5b. human body model 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 +3.0v to +5.5v, 10na, 250kbps rs-232 transceivers with 15kv esd-protected i/o and logic pins v cc (v) c2, c3, c4 (f) 3.0 to 3.6 0.22 c1, c bypass (f) 0.22 4.5 to 5.5 0.33 3.0 to 5.5 1 0.047 0.22 table 3. required minimum capacitance values 3.15 to 3.6 0.1 0.1
max3238e/max3248e ______________________________________________________________________________________ 11 transmitter outputs when recovering from shutdown figure 7 shows two transmitter outputs when recovering from shutdown mode. as they become active, the out- puts are shown going to opposite rs-232 levels (one transmitter input is high, the other is low). each trans- mitter is loaded with 3k? in parallel with 2500pf. the transmitter outputs display no ringing or undesirable 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 max3238e/max3248e maintain the rs-232 ?.0v minimum transmitter output voltage even at high data rates. figure 8 shows a transmitter loopback test cir- cuit. figure 9 shows a loopback test result at 120kbps, v cc = 3.3v, c1?4 = 0.1f, c load = 1000pf 2s/div t1in t1out r1out +5v 0 0 0 +5v +5v -5v figure 10. loopback test result at 250kbps v cc = 3.3v, c1c4 = 0.1f, c load = 1000pf 2s/div t1in t1out r1out 0 0 0 +5v +5v +5v -5v figure 9. loopback test result at 120kbps 4s/div 5v/div 2v/div t2out t1out forceon = forceoff v cc = 3.3v, c1c4 = 0.1f, r load = 3k?, c load = 2500pf figure 7. transmitter outputs when recovering from shutdown or powering up max3238e max3248e 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 *c3 can be returned to v cc or gnd. forceon 1000pf figure 8. loopback test circuit +3.0v to +5.5v, 10na, 250kbps rs-232 transceivers with 15kv esd-protected i/o and logic pins
max3238e/max3248e figure 11. data cable application example 12 ______________________________________________________________________________________ max3238e max3248e sub- miniature connector 15kv esd protection 15kv esd protection t1in t1out t2in t2out t3in t3out t4in t4out t5in 5 6 7 10 r2in 9 r3in 11 12 1 2 3 4 5 9 8 7 6 t5out 8 r1in 24 23 22 19 c1+ c2+ c2- c1- v+ v- v cc c2 0.1f c4 0.1f 28 1 3 4 c3 0.1f c5 0.1f c1 0.1f 25 27 26 tvs 17 r1out21 r2out20 r3out18 r1outb16 13 14 15 forceon forceoff invalid gnd dcd dsr rd rts td cts dtr ri 2 + control +3.0v to +5.5v, 10na, 250kbps rs-232 transceivers with 15kv esd-protected i/o and logic pins
max3238e/max3248e +3.0v to +5.5v, 10na, 250kbps rs-232 transceivers with 15kv esd-protected i/o and logic pins ______________________________________________________________________________________ 13 max3238e max3248e rs-232 outputs logic inputs rs-232 inputs logic outputs *c3 may be returned to either v cc or gnd. forceoff invalid autoshutdown plus forceon t1in t1out t2in t2out t3in t3out t4in t4out t5in 5 6 7 10 12 t5out 15 24 23 22 19 c1+ v cc v+ c1- c2+ v- c2- 27 26 4 28 0.1f 0.1f 0.1f 1f +3.3v 25 1 3 17 r1outb16 r1out 8 r1in 21 r2out 9 r2in 20 r3out 11 5k? 5k? 5k? gnd 2 r3in 18 14 13 t1 t2 t3 t4 t5 r1 r2 r3 0.1f* typical operating circuit ___________________chip information transistor count: 2110 and figure 10 shows the same test at 250kbps. for figure 9, all transmitters were driven simultaneously at 120kbps into rs-232 loads in parallel with 1000pf. for figure 10, a single transmitter was driven at 250kbps, and all transmitters were loaded with an rs-232 receiv- er in parallel with 1000pf. data cable applications the max3238e/max3248es??5kv esd protection on both 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 10 shows the ease of using the max3238e/max3248e in data cable applications. the max3238e/max3248es?five-transmitter and three- receiver configuration is optimized for a data communi- cation equipment (dce) application, allowing full hard- ware handshaking. the 9-pin rs-232 connector is configured for direct attachment to a pc? serial port. r1outb is also connected to the subminiature con- nector. this allows the remote system to shut down until the pc asserts the ready to send (rts) signal. r1outb stays active when the max3238e/max3248e is shut down (forceoff = gnd).
max3238e/max3248e +3.0v to +5.5v, 10na, 250kbps rs-232 transceivers with 15kv esd-protected i/o and logic pins ________________________________________________________package information ssop.eps 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. 14 ____________________maxim integrated products, 120 san gabriel drive, sunnyvale, ca 94086 408-737-7600 ? 2001 maxim integrated products printed usa is a registered trademark of maxim integrated products.

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