________________ge ne ra l de sc ript ion the max212 rs-232 transceiver is intended for 3v-po w- ered eia/tia-232e and v.28/v.24 communication inter - faces where 3 drivers and 5 receivers are needed wi th minimum power consumption. the operating voltage range extends from 3.6v down to 3.0v while still ma in- taining true rs-232 and eia/tia-562 voltage levels. a 1a typical shutdown mode reduces power con- sumption, extending battery life in portable syste ms. while shut down, all receivers can remain active or can be disabled under logic control. this enables a sy stem incorporating the cmos max212 to be in low-power shutdown mode and monitor incoming rs-232 activity. a guaranteed data rate of 120kbps provides compati- bility with popular software for communicating with per- sonal computers. three-state drivers on all receiver outputs are pro vided so that multiple receivers, generally of different inter- face standards, can be wire-ored at the uart. the max212 is available in both small-outline (so) and shrink-small-outline (ssop) packages. the ssop package occupies less than half of the board area required by the equivalent so package. ________________________applic a t ions computers notebooks/palmtops/subnotebooks printers peripherals instruments ____________________________fe a t ure s superior to bipolar:? operates from single +3.0v to +3.6v supply ? 24-pin ssop or wide so packages ? meets all eia/tia-232e & eia/tia-562specifications ? 3ma max supply current (unloaded) ? 1a low-power shutdown mode ? all receivers active during low-power shutdown ? mouse compatible at 3.0v ? low-cost, surface-mount external components ? 120kbps guaranteed data ratelaplink?compatible ? three-state receiver outputs ? evaluation kit available ? flow-through pinout m ax 2 1 2 +3 v-pow e re d, low -pow e r, true rs-2 3 2 tra nsc e ive r ________________________________________________________________ maxim integrated products 1 ca ll t oll fre e 1 -8 0 0 -9 9 8 -8 8 0 0 for fre e sa m ple s or lit e ra t ure . part temp. range pin-package max212cwg 0c to +70c 24 wide so max212cag 0c to +70c 24 ssop max212c/d 0c to +70c dice* MAX212EAG -40c to +85c 24 ssop max212ewg -40c to +85c 24 wide so ev kit temp. range board type max212evkit-ssop 0c to +70c surface mount 19-0162; rev 2; 2/94 ?laplink is a registered trademark of traveling sof tware. _______________orde ring i nform a t ion * dice are tested at t a = +25c only. ___________t ypic a l ope ra t ing circ uit max212 t1 in v cc sd +3.3v
dc-dc converter en t1 out ln lp v- v+ gnd 1 214 23 t1 shutdown 11 3 4 17 t2 in t2 out t2 12 16 t3 in t3 out t3 13 15 r1 out r1 in 62 2 r2 out r2 in r2 72 1 r3 out r3 in 82 0 r3 r4 out r4 in 91 9 r4 r5 out r5 in 10 18 r5 5 24 enable r1 evaluation kit information included downloaded from: http:///
m ax 2 1 2 +3 v-pow e re d, low -pow e r, true rs-2 3 2 tra nsc e ive r 2 _______________________________________________________________________________________ absolute maximum ratings electrical characteristics (v cc = 3.0v to 3.6v, t a = t min to t max , unless otherwise noted.) stresses beyond those listed under absolute maximu m ratings may cause permanent damage to the device . these are stress ratings only, and functional operation of the device at these or any other condi tions beyond those indicated in the operational sec tions of the specifications is not implied. exposur e to absolute maximum rating conditions for extended per iods may affect device reliability. parameter min typ max units input logic threshold low v cc / 3 v 11 5 a shutdown supply current 11 5 a input logic threshold high 2v cc / 3 v input current high 1 a input current low 1 a hysteresis 0.3 v operating voltage range 3.0 3.6 v v cc supply current 1.5 3.0 ma logic output voltage low 0.25 v logic output voltage high v cc - 0.5 v logic output leakage current 10 a -25 +25 v eia/tia-232e input hysteresis 0.7 v eia/tia-232e input resistance 357 k 5.0 5.5 v output resistance 300 28 100 ma conditions i out = 1.0ma t_ in , en, C s d; v cc = 3.0v to 3.6v i out = -1.0ma C s d = gnd, en = v cc , r_ in = gnd or v cc C s d = en = gnd, r_ in = gnd or v cc t_ in , en, C s d; v cc = 3.0v to 3.6v t_ in , en, C s d; v in = v cc en = gnd, 0v < r_ out < v cc t_ in , en, C s d, v in = gnd t_ in ; v cc = 3.3v -15v < v in < 15v meets or exceeds eia/tia-232e specifications all transmitters loaded 3k to gnd v cc = v- = v+ = 0v, -2v < t_ out < 2v no load, v cc = 3.3v supply voltages v cc ................................................... ..................-0.3v to +4.6v v+ ................................................. ...........(v cc - 0.3v) to +7.4v v- ................................................. .......................-7.4v to +2.0v ln ................................................. .............-0.3v to (v+ + 1.0v) lp................................................. ......(v- - 1.0v) to (v+ + 0.3v) input voltages t_ in , C s d, en .............................................. -0.3v to (v+ + 0.3v) r_ in ................................................... ................................25v output voltages t_ out ................................................... .............................15v r_ out ................................................... .....-0.3v to (v+ + 0.3v) short-circuit duration, t_ out .....................................continuous continuous power dissipation (t a = +70c) wide so (derate 11.76mw/c above +70c)............ ...941mw ssop (derate 8.00mw/c above +70c) ................ .....640mw lead temperature (soldering, 10sec) ................ .............+300c shutdown supply current with receivers active eia/tia-232e input voltage operating range eia/tia-232e input voltage threshold low 0.4 v eia/tia-232e input voltage threshold high 2.8 v output voltage swing (v high , v low ) eia/tia-232e short-circuit current dc characteristics logic eia/tia-232e receivers eia/tia-232e transmitters downloaded from: http:///
m ax 2 1 2 +3 v-pow e re d, low -pow e r, true rs-2 3 2 tra nsc e ive r _______________________________________________________________________________________ 3 timing characteristics (v cc = 3.0v to 3.6v, t a = t min to t max , unless otherwise noted.) parameter min typ max units transmitter output disable time 600 ns 250 s receiver output enable time 70 200 ns receiver output disable time 420 700 ns conditions includes power-supply start-up receiver propagation delay 300 700 ns 150pf load 800 2000 transmitter propagation delay 800 2000 ns 2500pf ?? 3k load 300 700 symbol t plhr t phlt t plht t dt t phlr t et t er t dr transmitter output enable time 4.0 10 30 v/s r l = 3k to 7k , c l = 50pf to 2500pf, measured from +3v to -3v or -3v to +3v transition-region slew rate __________________________________________typic a l o pe ra t ing cha ra c t e rist ic s (v cc = 3.3v, t a = +25c, unless otherwise noted.) 0204060 data rate (kbps) supply power (mw) 60 80 120 140 180 160 supply power vs.
data rate 100 212 gr4 2500pf 1000pf 2500pf 80 all transmitters
loaded w/ 3k w and
stated capacitance 120 100 1000pf 3 transmitters
at data rate 3 transmitters,
1 at data rate,
1 low, 1 high 0 50 100 150 data rate (kbps) output voltage (v) -6 -4 0 2 6 4 transm itter output voltage vs.
data rate 212 gr5 5000pf
4000pf
2500pf
1000pf 200 250 -2 4000pf
2500pf
1000pf 5000pf all transmitters
loaded simultaneously
w/ specified capacitance and 3k w data rate 120 250 kbps 1000pf ?? 3k load on each transmitter, 150pf load on each receiver downloaded from: http:///
m ax 2 1 2 +3 v-pow e re d, low -pow e r, true rs-2 3 2 tra nsc e ive r 4 _______________________________________________________________________________________ ____________________________typic a l ope ra t ing cha ra c t e rist ic s (c ont inue d) (v cc = 3.3v, t a = +25c, unless otherwise noted.) 500 1500 2500 3500 load capacitance (pf) slew rate (v/ m s) 6 7 9 10 12 11 slew rate vs.
load capacitance 212 gr6 4500
8 rising edge all transmitters
loaded simultaneously
w/ specified capacitance and 3k w 13 14 falling edge name function ln lp v cc supply voltage input, 3.0v to 3.6v 1 2 C s d en r1 out - r5 out receiver outputs, swing gnd to v cc t1 in -t3 in transmitter inputs 3 4 5 transmitter outputs r5 in -r1 in receiver inputs 6-10 11-13 15-17 18-22 _____________________pin de sc ript ion pin t3 out - t1 out v+ positive supply generated on-board 23 gnd ground 24 v- 14 inductor/diode connection point inductor/diode connection point shutdown control. connect to v cc for normal operation. connect to gnd to shut down the power supply and to disable the drivers. receiver status is not changed by this control. receiver enable control. connect to v cc for normal operation. connect to gnd to force the receiver outputs into a high-z state. negative supply generated on-board _______________de t a ile d de sc ript ion the max212 line driver/receiver is intended for 3v- powered eia/tia-232e and v.28/v.24 communications interfaces where 3 drivers and 5 receivers are required. the operating voltage range extends from 3.6v down to 3.0v while still maintaining true rs-2 32 and eia/tia-562 transmitter output voltage levels. the circuit comprises three sections: power supply , transmitters, and receivers. the power-supply sec- tion converts the supplied 3v to about 6.5v, to pr o- vide the voltages necessary for the drivers to meet true rs-232 levels. external components are small and inexpensive. the transmitters and receivers are guaranteed to op er- ate at data rates of 120kbps. a shutdown mode reduces current to 1a to extend battery life in portable systems. while shut down, all receivers can remain active or can be disabled unde r logic control. this enables a system incorporating the max212 to be in low-power shutdown mode and still monitor incoming rs-232 activity. three-state drivers on all receiver outputs are pro vided so that multiple receivers, generally of different inter- face standards, can be wire-ored at the uart. 2.5 3.0 3.5 4.0 supply voltage (v) supply power (mw) 80 100 120 140 180 160 supply power vs.
supply voltage 4.5 212 gr2 120kbps all transmitters
at specified data rates
w/ 2500pf and 3k w loads 64kbps 20kbps 0 1000 2000 3000 load capacitance (pf) supply current (ma) 20 30 40 50 70 60 supply current vs.
load capacitance 5000 212 gr3 120kbps 64kbps 20kbps 4000 80 all transmitters
at specified capacitance and
data rates w/ 3k w loads downloaded from: http:///
m ax 2 1 2 +3 v-pow e re d, low -pow e r, true rs-2 3 2 tra nsc e ive r _______________________________________________________________________________________ 5 sw it c h-m ode pow e r supply the switch-mode power supply uses a single inductor with two inexpensive diodes and two capacitors to generate 6.5v from the 3.0v to 3.6v input. figure 1 shows the complete circuit for the power supply. use a 15 m h inductor with a saturation current rating of at least 350ma and under 1 w resistance. sample surface- mount inductors are available from maxim. use 1n605 0 diodes or equivalent. surface-mount equivalents for the 1n6050 include the motorola mmbd6050lt1, p hilips pmbd6050, and allegro (formerly sprague) tmpd6050lt . for c1 and c2, use ceramic capacitors with values n o less than indicated in figure 1. these capacitors d eter- mine the ripple on v+ and v-, but not the absolute volt- ages. bypass v cc to gnd with at least 0.33 m f close to the max212. increase this to 4.7 m f if there are no other v cc supply bypass components less than 6 inches (15cm) away from the max212. component suppliers are listed in table 1. rs-2 3 2 drive rs all three drivers are identical and deliver eia/tia -232e and eia/tia-562 output voltage levels when v cc is between 3.0v and 3.6v. disable the drivers by taki ng the C s d pin to gnd. the transmitter outputs are forced into a high-impedance state when C s d is grounded. rs-2 3 2 re c e ive rs all five receivers are identical and accept eia/tia-232e and eia/tia-562 input signals. the cmo s receiver outputs swing rail-to-rail (0v to v cc ). when en is high, the receivers are active regardless of C s ds status. when en is low, the receivers outputs are put into a high-impedance state. this allows two rs-232 ports (or two parts of different types) to be wire-ored at th e uart. max212 t1 in v cc sd +3.3v +3.3v to 6.5v
dc-dc converter en t1 out ln lp v- v+ gnd l
15 m h d1
1n6050 1 214 23 t1 c2
0.33 m f c1
0.68 m f c3
0.33 m f d2
1n6050 shutdown 11 3 4 17 t2 in t2 out t2 12 16 t3 in t3 out t3 13 15 r1 out r1 in 62 2 r2 out r2 in r2 72 1 r3 out r3 in 82 0 r3 r4 out r4 in 91 9 r4 r5 out r5 in 10 18 r5 5 24 enable r1 figure 1. typical application circuit table 1. suggested component suppliers manufacturer part number phone number fax number allegro tmpd6050lt usa (508) 853-5049 motorola mmbd6050lt1 usa (408) 991-7420 murata lqh4n150k-ta philips pmbd6050 usa (401) 762-3800 usa (401) 767-4493 sumida cd43150 usa (708) 956-0666 japan (03) 3607-5111 tdk nlc453232t-150k usa (708) 803-6296 japan (03) 3278-5358 usa (508) 853-5000 usa (408) 749-0510 usa (404) 831-9172 japan (075) 951-9111 usa (404) 436-3030 japan (075) 955-6526 usa (708) 956-0702 japan (03) 3607-5428 usa (708) 803-6100 japan (03) 3278-5111 downloaded from: http:///
m ax 2 1 2 +3 v-pow e re d, low -pow e r, true rs-2 3 2 tra nsc e ive r 6 _______________________________________________________________________________________ ope ra t ing m ode s C s d and en determine the operation of the max212 as follows: shut dow n v+ and v- are disabled and the transmitters are put into a high-impedance state when C s d is taken to logic low. receiver operation is not affected, but power consu mp- tion is dramatically reduced while in shutdown mode . supply current is minimized when the receiver input s are static in any of three states: floating (ground), less than gnd, or greater than v cc . this will be true for all static rs-232 conditions. the presence of ac signals on re ceiv- er inputs will increase v cc current in shutdown. from a low-power system perspective, powering-up wi th non-critical or unused sections of circuitry shut d own or deselected is generally recommended. activating the se sections only when required saves power and reduces power-up current surges. powering-up the max212 in shutdown mode (holding the shutdown pin, C s d, low until v cc > 2.7v), helps to achieve this. driving t he m ax 2 1 2 from 5 v logic the max212 can interface with 5v logic while it ope rates from a 3v supply, however a 200k series resistor between C s d and the +5v logic signal is required (see figure 2 ). this protects the max212 by preventing C s d from sinking current while v+ is powering up. also, the uart must not be permitted to send a logic high to the max212s e n or transmitter input pins until C s d is high (not shut down). m ouse drive a bilit y the max212 has been specifically designed to power serial mice while operating from low-voltage power supplies. it has been tested with samples of ten ma jor mouse models from six manufacturers, including the leading three, logitech (5 models), mouse systems, and microsoft. the max212 successfully drove all se ri- al mice and met their respective current and voltag e requirements (figure 1). figure 3 shows the transmitter output voltages unde r increasing load current. the max212s switching reg u- lator ensures the transmitters will supply at least 5v during worst-case load conditions. ei a/t i a-2 3 2 e a nd 5 6 2 st a nda rds most of the power drawn by rs-232 circuits is con- sumed because the eia/tia-232e standard demands that at least 5v be delivered by the transmitters to impedances that can be as low as 3k . for applica- C s d en receiver outputs driver outputs l l high-z high-z off minimum l h enabled high-z off minimum h l high-z enabled on normal h h enabled enabled on normal supply current part no. of transmitters/ receivers data rate (kbps) features max212 3.0 to 3.6 3/5 5 250 true rs-232 from +3v max560 3.0 to 3.6 4/5 2 120 2 receivers active in shutdown max561 3.0 to 3.6 4/5 0 120 pin compatible with max241 max562 2.7 to 5.25 3/5 5 250 wide supply range power-supply voltage (v) no. of receivers active in shutdown ____________________________+3 v pow e re d rs-2 3 2 tra ns c e ive rs from m a x im dc-dc converter max212 t_ in sd +3.3v dc-dc converter r_ out r_ in t x x3 r x x5 en t_ out ln lp v- gnd +5v
logic
signals 200k v+ figure 2. connecting to +5v logic downloaded from: http:///
m ax 2 1 2 +3 v-pow e re d, low -pow e r, true rs-2 3 2 tra nsc e ive r _______________________________________________________________________________________ 7 tions where power consumption is especially critica l, the eia/tia-562 standard provides an alternative. eia/tia-562 transmitter output voltage levels need only reach 3.7v, and because they need only drive the same 3k receiver loads specified by rs-232, total power consumption is considerably reduced. since t he eia/tia-232e and eia/tia-562 receiver input voltage thresholds are the same, interoperability between t he two standards is guaranteed and devices from both stan- dards will communicate with each other successfully . maxims max560 and max561 are eia/tia-562 trans- ceivers that operate on a single supply from 3.0v t o 3.6v, and the max562 transceiver operates from 2.7v to 5.25v while producing eia/tia-562 levels. ______________________eva lua t ion k it the max212 evaluation kit (ev kit) is a fully assem - bled and tested, surface-mount demonstration board that provides quick and easy evaluation of the max212. the max212 ev kit is intended for 3.3v 300mv-pow- ered eia/tia-232e and v.28/v.24 communications interfaces where 3 drivers and 5 receivers are need ed with minimum power consumption. a logic or pin-selectable shutdown mode reduces current to 1a. while shut down, all receivers can remain active or can be disabled under logic contro l via the en input. figure 4. max212 evaluation kit 1
2
3
4 load current per transmitter (ma) transmitter output voltage (v) -6 -4 -2 0 2 6 4 transm itter output voltage vs.
load current per transm itter
5
6 212 gr1 t1 out and t2 out t3 out t1 in and t2 in = gnd,
t3 in = v cc = 3.0v,
t3 out , t2 out , t1 out
all loaded
simultaneously figure 3. mouse emulation circuit current downloaded from: http:///
maxim cannot assume responsibility for use of any c ircuitry other than circuitry entirely embodied in a maxim product. no circuit patent licenses are implied. maxim reserves the right to change the cir cuitry and specifications without notice at any tim e. 8 ___________________m a x im i nt e gra t e d produc t s, 1 2 0 s a n ga brie l drive , sunnyva le , ca 9 4 0 8 6 (4 0 8 ) 7 3 7 -7 6 0 0 ? 1993 maxim integrated products printed usa is a reg istered trademark of maxim integrated products. m ax 2 1 2 +3 v-pow e re d, low -pow e r, true rs-2 3 2 tra nsc e ive r ___________________chip topogra phy sd v cc r1 out v cc lp gnd v+ t1 in 0. 15"
(3. 81mm) 0. 1"
(2. 54mm) v- gnd ln en r2 out r3 out r4 out r5 out t2 in t3 in t3 out t2 out t1 out r1 in r2 in r3 in r4 in r5 in transistor count: 1382 ; substrate connected to v+. 24 23 22 21 20 19 18 17 1 2 3 4 5 6 7 8 gnd v+ r1 in r2 in sd v cc lp ln top view r3 in r4 in r5 in t1 out r3 out r2 out r1 out en 16 15 14 13 9 10 11 12 t2 out t3 out v- t3 in t2 in t1 in r5 out r4 out ssop/wide so max212 _________________pin configura t ion downloaded from: http:///
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