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1 ? fn6768.1 isl3241e, isl3243e qfn packaged, 15kv esd protected, +2.7v to +3.6v, 250kbps, rs-232 transmitters/receivers with separate logic supply pin the intersil isl324xe devices are 2.7v to 3.6v powered rs-232 transmitters/receivers which meet ela/tia-232 and v.28/v.24 specifications, even at v cc = 3.0v. additionally, they provide 15kv esd protection (iec61000-4-2 air gap and human body model) on transmitter outputs and receiver inputs (rs-232 pins). targeted applications are pos systems, and notebook and laptop computers where the low operational, and even lower standby, power consumption is critical. efficient on-chip charge pumps, coupled with manual and automatic power-down functions, reduce the standby supply current to a 0.5a trickle. tiny 5mmx5mm quad flat no-lead (qfn) packaging and the use of small, low value capacitors ensure board space savings as well. data rates greater than 250kbps are guaranteed at worst case load conditions. isl324xe are 3 driver, 5 receiver devices that, coupled with the 5x5 qfn package, provide the industry?s smallest, lowest power complete serial port. the 5x5 qfn requires 60% less board area than a 28 ld tssop, and is nearly 20% thinner. these devices also include a noninverting always-active receiver for ?wake-up? capability. the isl3243e features an automatic powerdown function that powers down the on-chip power supply and driver circuits. this occurs when an attached peripheral device is shut off or the rs-232 cable is removed, conserving system power automatically without changes to the hardware or operating system. it powers up again when a valid rs-232 voltage is applied to any receiver input. the isl324xe feature a v l pin that adjusts the logic pin (see ?pin descriptions? on page 2) output levels and input thresholds to values compatible with the v cc powering the external logic (e.g., a uart). table 1 summarizes the f eatures of the isl324xe. features ?v l pin for compatibility in mixed voltage systems adjusts logic output levels and input thresholds for compatibility with lower supply voltage logic ? parameters specified for 10% tolerance supplies and full industrial temp range ? pb-free small qfn (5mmx5mm) package is 60% smaller than a 28 lead tssop ? esd protection for rs-232 i/o pins to 15kv (iec61000) ? meets eia/tia-232 and v.28/v .24 specifications at 3v ? rs-232 compatible with v cc = 2.7v ? on-chip voltage converters require only four external 0.1f capacitors ? manual and automatic power-down features ? receiver hysteresis for improved noise immunity ? guaranteed minimum data rate . . . . . . . . . . . . . 250kbps ? low supply current in power-down state . . . . . . . . 0.5a ? pb-free (rohs compliant) applications ? any space constrained system requiring rs-232 ports - battery powered, hand-held, and portable equipment - pos systems and scanners - laptop computers, notebooks - gps receivers ? mixed voltage serial ports related literature ? technical brief tb363 ?guidelines for handling and processing moisture sensit ive surface mount devices ? ?technical brief tb379 ?thermal characterization of packages for ics? ? technical brief tb389 ?pcb land pattern design and surface mount guidelines for qfn packages? table 1. summary of features part number no. of tx. no. of rx. logic supply (v l ) pin? no. of monitor rx. (r outb ) data rate (kbps) rx. enable function? pb-free? manual power- down? automatic powerdown function? isl3241e 3 5 yes 2 250 yes yes yes no isl3243e 3 5 yes 1 250 no yes yes yes data sheet may 13, 2010 caution: these devices are sensitive to electrosta tic discharge; follow proper ic handling procedures. 1-888-intersil or 1-888-468-3774 | intersil (and design) is a registered trademark of intersil americas inc. copyright intersil americas inc. 2008, 2010. all rights reserved all other trademarks mentioned are the property of their respective owners.
2 fn6768.1 may 13, 2010 ordering information part number (note) part marking temp. range (c) package (pb-free) pkg. dwg. # isl3241eirz isl3241 eirz -40 to +85 32 ld 5x5 qfn l32.5x5b isl3241eirz-t* isl3241 eirz -40 to +85 32 ld 5x5 qfn (tape & reel) l32.5x5b isl3243eirz isl3243 eirz -40 to +85 32 ld 5x5 qfn l32.5x5b ISL3243EIRZ-T* isl3243 eirz -40 to +85 32 ld 5x5 qfn (tape & reel) l32.5x5b * please refer to tb347 for details on reel specifications. note: these intersil pb-free plastic packa ged products employ special pb-free material sets, molding compounds/die attach materi als, and 100% matte tin plate plus anneal (e3 termination fi nish, which is rohs compliant and compatible with both snpb and pb-free soldering operations). intersil pb-free products are msl classified at pb-free peak reflow temperatures that meet or exceed the pb-free requirements o f ipc/jedec j std-020 pinouts isl3241e (32 lead qfn) top view isl3243e (32 lead qfn) top view r1 in r2 in r3 in r4 in r5 in t1 out t2 out c1- en shdn r1 outb r2 outb r1 out r2 out t3 out t3 in t2 in t1 in r5 out r3 out r4 out v- c2- c2+ c1+ v+ gnd v cc nc 7 11 12 13 14 15 9 10 6 1 2 3 4 5 8 16 18 19 24 23 22 21 20 17 27 28 29 30 31 25 26 32 nc nc v l pd r1 in r2 in r3 in r4 in r5 in t1 out t2 out c1- forceon forceoff invalid r2 outb r1 out r2 out t3 out t3 in t2 in t1 in r5 out r3 out r4 out v- c2- c2+ c1+ v+ gnd v cc nc 7 11 12 13 14 15 9 10 6 1 2 3 4 5 8 16 18 19 24 23 22 21 20 17 27 28 29 30 31 25 26 32 nc nc v l pd pin descriptions pin function v cc system power supply input (2.7v to 3.6v). v l logic power supply. sets the v oh of all the logic outputs and the switch ing point of all logic inputs. keep v l greater than 1.6v (1.8v - 10%) and less than or equal to v cc . power up v l after v cc v+ internally generated positive trans mitter supply (typ ically +5.5v). v- internally generated negative transmi tter supply (typically -5.5v). gnd ground connection. this is also the potential of the thermal pad (pd). c1+ external capacitor (voltage doubl er) is connected to this lead. c1- external capacitor (voltage doubl er) is connected to this lead. c2+ external capacitor (voltage in verter) is connected to this lead. c2- external capacitor (voltage in verter) is connected to this lead. t in ttl/cmos compatible transmitter inputs. the v l voltage sets the input switching point. isl3241e, isl3243e
3 fn6768.1 may 13, 2010 t out 15kv esd protected , rs-232 level (nominally 5.5v) transmitter outputs. r in 15kv esd protected , rs-232 compatible receiver inputs. r out ttl/cmos level receiver outputs. swings between gnd and v l . r outb ttl/cmos level, noninverting, always enabled receiver outputs. swings between gnd and v l . invalid active low output that indicates if no valid rs-232 levels are present on any re ceiver input. swings between gnd and v l . forceoff active low to shut down transmitters and on-chip power supply. this overrides any automatic circuitry and forceon (see table 2). the v l voltage sets the input switching point. forceon active high input to override automatic powerdown ci rcuitry thereby keeping transmitters active. (forceoff must be high). the v l voltage sets the input switching point. en active low receiver enable control. the v l voltage sets the input switching point. shdn active low input to shut down transmitters and on-board power supply, to place device in low power mode. the v l voltage sets the input switching point. nc no connection pd exposed thermal pad. connect to gnd. pin descriptions (continued) pin function isl3241e, isl3243e
4 fn6768.1 may 13, 2010 typical operating circuits isl3241e isl3243e 26 v cc t1 out t2 out t3 out t1 in t2 in t3 in t 1 t 2 t 3 0.1 f + 0.1 f + 0.1 f 12 11 6 7 10 8 28 23 27 31 v+ v- c1+ c1- c2+ c2- + 0.1 f 29 30 r1 out r1 in 1 5k r2 out r2 in 2 17 5k r3 out r3 in 3 15 5k r4 out r4 in 4 14 5k r5 out r5 in r 5 5 13 5k 18 r2 outb c 1 c 2 + c 3 c 4 en shdn 22 gnd 21 +3.3v + 0.1 f 19 24 v cc ttl/cmos logic rs-232 levels rs-232 levels r1 outb 20 r 1 r 2 r 3 r 4 levels +1.8v + 0.1 f 25 v l 26 v cc t1 out t2 out t3 out t1 in t2 in t3 in t 1 t 2 t 3 0.1 f + 0.1 f + 0.1 f 12 11 6 7 10 8 28 23 27 31 v+ v- c1+ c1- c2+ c2- + 0.1 f 29 30 r1 out r1 in 1 5k r2 out r2 in 2 17 5k r3 out r3 in 3 15 5k r4 out r4 in 4 14 5k r5 out r5 in r 5 5 13 5k 18 r2 outb c 1 c 2 + c 3 c 4 forceon forceoff 22 gnd 21 +3.3v + 0.1 f 19 24 v cc ttl/cmos logic rs-232 levels rs-232 levels r 1 r 2 r 3 r 4 20 invalid to power control levels logic +1.8v + 0.1 f 25 v l isl3241e, isl3243e
5 fn6768.1 may 13, 2010 absolute maximum rati ngs thermal information v cc to ground. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . -0.3v to 6v v l to ground . . . . . . . . . . . . . . . . . . . . . . . . . -0.3v to (v cc + 0.3v) v+ to ground . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . -0.3v to 7v v- to ground. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . +0.3v to -7v v+ to v- . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 14v input voltages t in , forceoff , forceon, en , shdn . . . . . . . . . -0.3v to 6v r in . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 25v output voltages t out . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 13.2v r out , invalid . . . . . . . . . . . . . . . . . . . . . . . -0.3v to (v l + 0.3v) short circuit duration t out . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . continuous esd rating . . . . . . . . . . . . see ?esd performance? on page 7 thermal resistance (typical, notes 1, 2) ja (c/w) jc (c/w) 32 ld qfn package. . . . . . . . . . . . . . . 32 1.8 maximum junction temperature . . . . . . . . . . . . . . . . . . . . . +150 c maximum storage temperature range . . . . . . . . . -65 c to +150 c pb-free reflow profile . . . . . . . . . . . . . . . . . . . . . . . . see link below http://www.intersil.com/pbfree/pb-freereflow.asp operating conditions temperature range . . . . . . . . . . . . . . . . . . . . . . . . . . -40 c to 85 c caution: do not operate at or near the maximum ratings listed fo r extended periods of time. exposure to such conditions may adv ersely impact product reliability and result in failures not covered by warranty. notes: 1. ja is measured in free air with the component mounted on a high ef fective thermal conductivity te st board with ?direct attach? fe atures. see tech brief tb379 for details. 2. for jc , the ?case temp? location is the center of the exposed metal pad on the package underside. electrical specifications test conditions: v cc = 3v to 3.6v, v l = 1.8v 10%, c 1 to c 4 = 0.1f, unless otherwise specified. typicals are at t a = +25c, v cc = 3.3v, v l = 1.8v, unless otherwise specified parameter test conditions temp (c) min (note 3) typ max (note 3) units dc characteristics operating voltage range full 2.7 - 3.6 v supply current, automatic powerdown all r in open, forceon = gnd, forceoff = v l v l = v cc (isl3243e only) full - 0.5 3 a supply current, powerdown all r in open, forceoff = shdn = gnd, v l = v cc full - 0.5 3 a supply current, automatic powerdown disabled all outputs unloaded, forceon = forceoff = shdn = v l , v cc = v l = 3.0v 25 - 0.3 1.0 ma full - 0.3 1.5 ma logic and transmitter inputs; receiver and logic outputs input logic threshold low t in , forceon, forceoff , en , shdn full - - 0.5 v v l = v cc = 3v full - - 0.8 v input logic threshold high t in , forceon, forceoff , en , shdn full 1.25 - - v v l = v cc = 3.6v full 2.0 - - v input leakage current t in , forceon, forceoff , en , shdn full - 0.01 1.0 a output leakage current forceoff = gnd (isl3243e) or en = v l (isl3241e) full - 0.05 10 a output voltage low (see figure 21) i out = 250a, r out , r outb , invalid full - - 0.45 v i out = 1.6ma, v l = v cc , r out , r outb , invalid full - - 0.4 v output voltage high (see figure 21) i out = -250a, r out , r outb , invalid full v l - 0.25 v l - 0.1 - v i out = -1.0ma, v l = v cc , r out , r outb , invalid full v l - 0.6 v l - 0.1 - v automatic powerdown (isl3243e only, forceon = gnd, forceoff = v l ) receiver input thresholds to enable transmitters isl3243e powers up (see figure 10) full -2.7 - 2.7 v receiver input thresholds to disable transmitters isl3243e powers down (see figure 10) full -0.3 - 0.3 v receiver threshold to transmitters enabled delay (t wu ) 25 - 20 - s isl3241e, isl3243e
6 fn6768.1 may 13, 2010 receiver positive or negative threshold to invalid high delay (t invh ) 25 - 0.7 - s receiver positive or negative threshold to invalid low delay (t invl ) 25 - 20 - s receiver inputs input voltage range full -25 - 25 v input threshold low v cc 2.7v full - - 0.6 v v cc 3v full - - 0.8 v input threshold high full 2.0 1.5 - v input hysteresis 25 - 0.5 - v input resistance full357k transmitter outputs output voltage swing (v o ) all transmitter outputs loaded with 3k to ground full 5.0 5.4 - v v cc = 2.7v full 4.0 4.7 - v output resistance v cc = v l = v+ = v- = 0v, transmitter output = 2v full 300 10m - output short-circuit current full - 35 60 ma output leakage current v out = 12v, v cc = v l = 0v or 3v to 3.6v, automatic powerdown or forceoff = shdn = gnd full - - 25 a timing characteristics maximum data rate r l = 3k , c l = 1000pf, one transmitter switching full 250 400 - kbps r l = 3k , c l = 200pf, v cc = 3.15v, one transmitter switching full - 1.3 - mbps receiver propagation delay receiver input to receiver output, c l = 30pf, r in = 3v (see figure 2) t phl 25 - 0.23 0.55 s full - 0.26 0.6 s t plh 25 - 0.16 0.55 s full - 0.18 0.6 s receiver skew |t phl - t plh | 25 - 70 300 ns full - 80 350 ns transmitter propagation delay transmitter input to transmitter output, c l = 1000pf, r l = 3k (see figure 1) (note 4) t phl 25 - 0.7 1.5 s full - 0.8 1.7 s t plh 25 - 0.7 1.5 s full - 0.8 1.7 s transmitter skew |t phl - t plh | 25 - 20 500 ns full - 20 550 ns receiver output enable time from en or forceoff , v l = v cc , r l = 1k , c l = 15pf (see figure 3) 25 - 120 - ns receiver output disable time 25 - 200 - ns transmitter output enable time from powerdown from shdn or forceoff , r l = 3k , c l = 1000pf 25 - 20 - s transition region slew rate v cc = 3v to 3.6v, r l = 3k to 7k , measured from 3v to -3v or -3v to 3v c l = 150pf to 2500pf 25 4 12 30 v/s full 4 11 30 v/s c l = 150pf to 1000pf 25 6 18 30 v/s full 6 17 30 v/s electrical specifications test conditions: v cc = 3v to 3.6v, v l = 1.8v 10%, c 1 to c 4 = 0.1f, unless otherwise specified. typicals are at t a = +25c, v cc = 3.3v, v l = 1.8v, unless otherwise specified (continued) parameter test conditions temp (c) min (note 3) typ max (note 3) units isl3241e, isl3243e
7 fn6768.1 may 13, 2010 esd performance rs-232 pins (t out , r in ) human body model 25 - 15 - kv iec61000-4-2 contact discharge 25 - 8 - kv iec61000-4-2 air gap discharge 25 - 15 - kv all pins human body model 25 - 2 - kv machine model 25 - 200 - v notes: 3. parameters with min and/or max limits are 100% tested at +25 c, unless otherwise specified. temperature limits established by characterization and are not production tested. 4. transmitter propagation delays are measured at the transmitter output 0v crossing points. test circuits and waveforms figure 1a. test circuit figure 1b. measurement points figure 1. driver propagation delay and skew figure 2a. test circuit figure 2b. measurement points figure 2. receiver propagation delay and skew electrical specifications test conditions: v cc = 3v to 3.6v, v l = 1.8v 10%, c 1 to c 4 = 0.1f, unless otherwise specified. typicals are at t a = +25c, v cc = 3.3v, v l = 1.8v, unless otherwise specified (continued) parameter test conditions temp (c) min (note 3) typ max (note 3) units d shdn t in v l signal generator c l r l or forceoff t out t out v l 0v 1.5v 1.5v +v o -v o t phl t plh t in skew = |t phl - t plh | 0v 0v r en = gnd r in signal generator c l or forceoff = v l r out r out +3v -3v t phl 1.5v 1.5v v oh v ol 50% 50% t plh r in skew = |t phl - t plh | isl3241e, isl3243e
8 fn6768.1 may 13, 2010 detailed description the isl324xe operate from a single +2.7v to +3.6v supply, guarantee a 250kbps minimum data rate, require only four small external 0.1f capacitors, feature low power consumption, and meet all ela rs-232 and v.28 specifications even with v cc = 3.0v. the circuit is divided into three sections: the charge pump, the transmitters, and the receivers. charge-pump intersil?s new isl324xe devices utilize regulated on-chip dual charge pumps as voltage doublers, and voltage inverters to generate 5.5v transmitter supplies from a v cc supply as low as 3.0v. this allows them to maintain rs-232 compliant output levels over the 10% tolerance range of 3.3v powered systems. the effi cient on-chip power supplies require only four small, extern al 0.1f capacitors for the voltage doubler and inverter functions. the charge pumps operate discontinuously (i.e., they turn off as soon as the v+ and v- supplies are pumped up to the nominal values), resulting in signifi cant power savings. transmitters the transmitters are proprietary, low dropout, inverting drivers that translate logic inpu t levels to eia/tia-232 output levels. coupled with the on-chip 5.5v supplies, these transmitters deliver true rs-232 levels over a wide range of single supply system voltages. all transmitter outputs disable and assume a high impedance state when the device enters the power-down mode (see table 2). these outputs may be driven to 12v when disabled. the devices guarantee a 250kbps data rate for full load conditions (3k and 1000pf), v cc 3.0v, with one transmitter operating at full speed. under more typical conditions of v cc 3.3v, r l = 3k , and c l = 200pf, one transmitter easily operates at greater than 1mbps. the transmitter input switching threshold is set by the voltage applied to the v l pin, so tying v l to a voltage lower than v cc reduces the tx input v ih and v il to values compatible with logic ics (e.g., uarts and controllers) powered by the v l voltage (see figure 9 and table 3). transmitter inputs float if left unconnected (there are no pull-up resistors), and may cause supply current increases. connect unused inputs to gnd for the best performance. receivers all the isl324xe devices contain standard inverting receivers that three-state via the en or forceoff control lines. additionally, these products include noninverting ?monitor? receivers (denoted by the r outb label) that are always active, regardless of the state of any control lines. all the receivers convert rs-232 signals to cmos output levels, swinging between gnd and v l , and accept inputs up to 25v while presenting the required 3k to 7k input impedance (see figure 4) even if the power is off (v cc = 0v). the receivers? schmitt trigger input stage uses hysteresis to increase noise immunity and decrease errors due to slow input signal transitions. the isl3241e inverting receivers disable only when en is driven high. isl3243e receivers disable during forced (manual) powerdown, but not during automatic powerdown (see table 2). figure 3a. test circuit figure 3b. measurement points figure 3. receiver enable and disable times test circuits and waveforms (continued) parameter r in sw t phz and t pzh gnd gnd t plz and t pzl v cc v l r en r in v cc signal generator c l or forceoff r out v l gnd sw 1k or gnd v l forceon or shdn r out v l 0v 50% 50% v oh 0v 50% v oh - 0.3v t phz r out v l v ol 50% v ol + 0.3v t plz forceoff output high output low t pzl t pzh v l 0v 50% 50% en r xout gnd v rout v l 5k r xin -25v v rin +25v gnd v l figure 4. inverting receiver connections isl3241e, isl3243e
9 fn6768.1 may 13, 2010 isl324xe monitor receivers remain active even during manual powerdown, making them extremely useful for ring indicator monitoring. standard receivers driving powered down peripherals must be disabled to prevent current flow through the peripheral?s protection diodes (see figures 5 and 6). this renders them useless for wake up functions, but the corresponding monitor receiver can be dedicated to this task as shown in figure 6. low power operation these 3v devices require a nominal supply current of 0.3ma, even at v cc = 3.6v, during normal operation (not in power-down mode). this is considerably less than the 5ma to 11ma current required by comparable 5v rs-232 devices, allowing users to reduce system power simply by switching to this new family. power-down functionality the already low current requirement drops significantly when the device enters powerdown mode. in powerdown, supply current drops to less than 1a, because the on-chip charge pump turns off (v+ collapses to v cc , v- collapses to gnd), and the transmitter outputs three-state. inverting receiver outputs disable only in manual powerdown (isl3243e) or when en = v l (isl3241e); refer to table 2 for details. this micro-power mode makes the isl324xe ideal for battery powered and portable applications. table 2. power-down and enable logic truth table (note: ?h? = v l ) rs-232 signal present at receiver input? shdn or forceoff input forceon input en input transmitter outputs receiver outputs r outb outputs invalid output mode of operation isl3241e n/a l n/a l high-z active active n/a manual power-down n/a l n/a h high-z high-z active n/a m anual power-down w/rcvr. disabled n/a h n/a l active active active n/a normal operation n/a h n/a h active high-z active n/a norm al operation w/rcvr. disabled isl3243e no h h n.a. active active active l normal operation (auto powerdown disabled) yes h l n.a. active active active h normal operation (auto power-down enabled) no h l n.a. high-z active active l power-down due to auto power-down logic yes l x n.a. high-z high-z active h manual power-down no l x n.a. high-z high-z active l manual power-down figure 5. power drain through powered down peripheral old v cc powered gnd shdn = gnd v cc rx tx current v out = v cc flow rs-232 chip down uart v cc isl3241e, isl3243e
10 fn6768.1 may 13, 2010 software controlled (manual) powerdown the devices in this family provid e pins that allow the user to force the ic into the low power, standby state. on the isl3241e, the powerdown control is via a simple shutdown (shdn ) pin. driving this pin high enables normal operation, while driving it low forces the ic into it?s powerdown state. connect shdn to v l if the powerdown function isn?t needed. note that all the receiver outputs remain controlled by en during shutdown (see table 2). for the lowest power consumption during powerdown, the receivers should also be disabled by driving the en input high (see next section, and figures 5 and 6). the isl3243e utilizes a two pin approach where the forceon and forceoff inputs determine the ic?s mode. for always enabled operation, forceon and forceoff are both strapped high. to switch between active and powerdown modes, under logic or software control, only the forceoff input need be driven. the forceon state isn?t critical, as forceoff dominates over forceon. nevertheless, if strictly manual control over powerdown is desired, the user must strap forceon high to disable the automatic powerdown circuitry. isl3243e inverting (standard) receiver outputs also disable when the device is in manual powerdown, thereby eliminating the possible current path through a shutdown peripheral?s input protection diode (see figures 5 and 6). connecting forceoff and forceon together disables the automatic powerdown feature, enabling them to function as a manual shutdown input (see figure 7). with any of the above control schemes, the time required to exit powerdown, and resume transmission is only 20s. a mouse, or other application, may need more time to wake up from shutdown. if automatic power-down is being utilized, the rs-232 device will reenter power-down if valid receiver levels aren?t reestablished within 20s of the isl3243e powering up. figure 8 illustrates a circuit that keeps the isl3243e from initiating autom atic power-down for 100ms after powering up. this gives the slow-to-wake peripheral circuit time to reestablish valid rs-232 output levels. v l logic supply input note: power-up v cc before powering up the v l supply. the isl324xe feature a v l pin that powers the logic input and output pins. these pins interface with ?logic? devices such as uarts, asics, and controllers, and today most of these devices use power supplies significantly lower than 3.3v. thus, the logic device?s low v oh might not exceed the v ih of a 3.3v powered isl324xe logic input, or a 3.3v receiver output high level mi ght overdrive and damage the input diodes on an input of a 1.8v powered logic device, as shown in figure 9. connecting the v l pin to the power supply of the logic device (see figure 9) reduces the isl324xe?s logic input switching points, and limits the figure 6. disabled receivers prevent power drain isl324xe transition r x t x r2 outb r2 out t1 in forceoff = gnd v cc v ccl to r2 in t1 out v out = hi-z powered detector down uart wake-up logic or shdn = gnd, en = v l v l v cc v cci figure 7. connections for manual powerdown when no valid receiver signals are present pwr forceoff invalid cpu i/o forceon isl3243e mgt logic uart v cci v cc v ccl v l v cc figure 8. circuit to prevent auto powerdown for 100ms after forced powerup isl3243e forceoff forceon power master powerdown line 1m 0.1 f management unit isl3241e, isl3243e
11 fn6768.1 may 13, 2010 receiver output high voltage, to values compatible with the logic device?s i/o levels. tailoring the isl324xe?s logic pin input switching points and output levels to the supply voltage of the uart, asic, or controller eliminates the need for a level shifter/translator between the two ics. v l may range from 1.6v to v cc , and table 3 indicates the isl324xe?s typical v ih and v il levels for several v l values. note that the v l supply current increases significantly when v l exceeds v cc (see figure 20). if logic translation isn?t required, connect v l to v cc . invalid output (isl3243e only) the invalid output always indicates whether or not a valid rs-232 signal (see figure 10) is present at any of the receiver inputs (see table 2), giving the user an easy way to determine when the interface block should power down. invalid receiver levels occur whenever the driving peripheral?s outputs are shut off (powered down) or when the rs-232 interface cable is disco nnected. in the case of a disconnected interface cable where all the receiver inputs are floating (but pulled to gnd by the internal receiver pull down resistors), the invalid logic detects the invalid levels and drives the output low. the power management logic then uses this indicator to power-down the interface block. reconnecting the cable restores valid levels at the receiver inputs, invalid switches high, and the power management logic wakes up the interface block. invalid can also be used to indicate the dtr or ring indicator signal, as long as the other receiver inputs are floating, or driven to gnd (as in the case of a powered down driver). invalid switches low after invalid levels have persisted on all of the receiver inputs for more than 20s (see figure 11). invalid switches back high 1s after detecting a valid rs-232 level on a receiver input. invalid operates in all modes (forced or automatic power-down, or forced on), so it is also useful for systems employing manual power-down circuitry. when automatic pow erdown is utilized, invalid = 0 indicates that the isl3243e is in powerdown mode. automatic power-down (isl3243e only) even greater power savings is available by using the isl3243e which features an automatic power-down function. when no valid rs-232 voltages (see figure 11) are sensed on any receiver input for 20s, the charge pump and table 3. v ih and v il vs v l for v cc = 3.3v v l (v) v ih (v) v il (v) 1.6 0.85 0.8 1.8 0.95 0.9 2.5 1.25 1.2 figure 9. using v l pin to adjust logic levels gnd t xd rxd v ccl = +1.8v uart/processor gnd t in r out v cci = +3.3v rs-232 ic with no v oh 3v gnd t xd v ccl = +1.8v uart/processor gnd v l v cci = +3.3v isl324xe v oh 1.8v v ih 1v v oh 1.8v v ih 2v v oh 1.8v vl pin t in r out r xd input diode input diode figure 10. definition of valid rs-232 receiver levels 0.3v -0.3v -2.7v 2.7v invalid level - power-down occurs after 20 s valid rs-232 level - isl3243e is active valid rs-232 level - isl3243e is active indeterminate - powerdown may or indeterminate - powerdown may or may not occur may not occur receiver inputs transmitter outputs invalid output v+ v cc 0 v- v l 0 t invl t invh invalid region } figure 11. automatic powerdown and invalid timing diagrams autopwdn pwr up isl3241e, isl3243e
12 fn6768.1 may 13, 2010 transmitters power-down, ther eby reducing supply current to less than 1a. invalid receiver levels occur whenever the driving peripheral?s outputs are shut off (powered down) or when the rs-232 interface cable is disconnected. the isl3243e powers back up whenever it detects a valid rs-232 voltage level on any re ceiver input. this automatic power-down feature provides additional system power savings without changes to t he existing operating system. automatic power-down operates when the forceon input is low, and the forceoff input is high. tying forceon high disables automatic power-down, but manual power-down is always available via the overriding forceoff input. table 2 summarizes the automatic power-down functionality. the time to recover from automatic power-down mode is typically 20s. capacitor selection the charge pumps require 0.1f, or greater, capacitors for proper operation. increasing the capacitor values (by a factor of 2) reduces ripple on the transmitter outputs and slightly reduces power consumption. when using minimum required ca pacitor values, make sure that capacitor values do not degrade excessively with temperature. if in doubt, use capacitors with a larger nominal value. the capacitor?s equivalent series resistance (esr) usually rises at low temperatures and it influences the amount of ripple on v+ and v- . power supply decoupling in most circumstances a 0. 1f bypass capacitor is adequate. in applications that are particularly sensitive to power supply noise, decouple v cc and v l to ground with a capacitor of the same value as the charge-pump capacitor c 1 . connect the bypass capacitor as close as possible to the ic. transmitter outputs when exiting power-down figure 12 shows the response of two transmitter outputs when exiting powerdown mode. as they activate, the two transmitter outputs properly go to opposite rs-232 levels, with no glitching, ringing, nor undesirable transients. each transmitter is loaded with 3k in parallel with 1000pf. note that the transmitters enable only when the magnitude of v+ and v- exceeds approximately 3v. operation down to 2.7v isl324xe transmitter outputs meet rs-562 levels ( 3.7v), at the full data rate, with v cc as low as 2.7v. rs-562 levels typically ensure inter operability with rs-232 devices. high data rates the isl324xe maintain the rs-232 5v minimum transmitter output voltages even at high data rates. figure 13 details a transmitter loopback test circuit, and figure 14 illustrates the loopback test result at 120kbps. for this test, all transmitters were simultaneously driving rs-232 loads in parallel with 1000pf, at 120kbps. figure 15 shows the loopback results for a single transmitter driving 1000pf and an rs-232 load at 250kbps. the static transmitters were also loaded with an rs-232 receiver. figure 13. transmitter loopback test circuit time (20 s/div.) t1 t2 2v/div. 5v/div. v cc = +3.3v, v l = 1.8v forceoff figure 12. transmitter outputs when exiting powerdown c1 to c4 = 0.1 f isl324xe v l forceoff or shdn c 1 c 2 c 4 c 3 + + + + 1000pf v+ v- 5k t in r out c1+ c1- c2+ c2- r in t out + v cc 0.1 f v cc forceon v l + 0.1 f v l en isl3241e, isl3243e
13 fn6768.1 may 13, 2010 interconnection to 1.8v, and 2.5v logic standard 3.3v powered rs-232 devices interface well with 3v powered ttl compatible logic families (e.g., act and hct). the isl324xe v l supply pin allows interconnection to 1.8v or 2.5v logic. by connecting v l to the same supply (1.8v or 2.5v) powering the logic device, the isl324xe logic outputs will swing from gnd to the logic v cc . 15kv esd protection all pins on isl324xe devices include esd protection structures, but the rs-232 pins (transmitter outputs and receiver inputs) incorporate advanced structures which allow them to survive esd events up to 15kv. the rs-232 pins are particularly vulnerable to esd damage because they typically connect to an exposed port on the exterior of the finished product. simply touching the port pins, or connecting a cable, can cause an esd event that might destroy unprotected ics. these new esd structures protect the device whether or not it is powered up, protect without allowing any latchup mechanism to activate, and don?t interfere with rs-232 signals as large as 25v. human body model (hbm) testing as the name implies, this test method emulates the esd event delivered to an ic during human handling. the tester delivers the charge through a 1.5k current limiting resistor, making the test less severe than the iec61000 test which utilizes a 330 limiting resistor. the hbm method determines an ics ability to withstand the esd transients typically present during handling and manufacturing. due to the random nature of these events, each pin is tested with respect to all other pins. the rs-232 pins on ?e? family devices can withstand hbm esd events to 15kv. iec61000-4-2 testing the iec61000 test method applies to finished equipment, rather than to an individual ic. therefore, the pins most likely to suffer an esd event are t hose that are ex posed to the outside world (the rs-232 pins in this case), and the ic is tested in its typical application configuration (power applied) rather than testing each pin-to -pin combination. the lower current limiting resistor coupled with the larger charge storage capacitor yields a test that is much more severe than the hbm test. the extra esd protection built into this device?s rs-232 pins allows the design of equipment meeting level 4 criteria with out the need for additional board level protection on the rs-232 port. air-gap discharge test method for this test method, a charged probe tip moves toward the ic pin until the voltage arcs to it. the current waveform delivered to the ic pin depends on approach speed, humidity, temperature, etc., so it is difficult to obtain repeatable results. the ?e? device rs-232 pins withstand 15kv air-gap discharges. contact discharge test method during the contact discharge test, the probe contacts the tested pin before the probe tip is energized, thereby eliminating the variables associated with the air-gap discharge. the result is a more repeatable and predictable test, but equipment limits prevent testing devices at voltages higher than 8kv. all ?e? family devices survive 8kv contact discharges on the rs-232 pins. figure 14. loopback test at 120kbps figure 15. loopback test at 250kbps t1 in t1 out r1 out 4 s/div. v cc = +3.3v, v l = 1.8v 3v/div. c1 to c4 = 0.1 f 5v/div. 3v/div. t1 in t1 out r1 out 2 s/div. v cc = +3.3v, v l = 1.8v c1 to c4 = 0.1 f 3v/div. 5v/div. 3v/div. isl3241e, isl3243e
14 fn6768.1 may 13, 2010 typical performance curves v cc = 3.3v, v l = 1.8v, t a = +25c figure 16. transmitter output voltage vs load capacitance figure 17. slew rate vs load capacitance figure 18. supply current vs load capacitance when transmitting data figure 19. supply current vs supply voltage figure 20. v l supply current vs v l voltage figure 21. receiver output current vs receiver output voltage -6 -4 -2 0 2 4 6 1000 2000 3000 4000 5000 0 load capacitance (pf) transmitter output voltage (v) 1 transmitter at 250kbps +v out -v out other transmitters at 30kbps r l = 3k on all touts load capacitance (pf) slew rate (v/ s) 0 1000 2000 3000 4000 5000 5 10 15 20 25 +slew -slew r l = 3k 10 15 20 25 30 45 35 40 0 1000 2000 3000 4000 5000 load capacitance (pf) supply current (ma) 20kbps 250kbps 120kbps 1 transmitter switching other transmitters static r l = 3k on all touts supply current (ma) 0 0.5 1.0 1.5 0 1 2 3 4 supply voltage (v) 5 6 7 2.0 2.5 3.0 4.0 3.5 no load, v l = v cc all outputs static i l (na) v l (v) 01.01.52.0 0.5 0 10 20 30 50 40 2.5 3.5 4.0 3.0 no load all outputs static v cc = 3.3v v l v cc v l > v cc 0 1 2 3 4 5 0 0.5 1.0 1.5 2.0 2.5 3.0 receiver output voltage (v) receiver output current (ma) 3.3 6 7 8 9 10 v oh , v l = 2.5v v ol , v l = 2.5v v oh , v l = 1.8v v oh , v l = 1.6v v ol , v l = 1.8v v ol , v l = 1.6v v oh , v l = 3.3v v ol , v l = 3.3v isl3241e, isl3243e
15 all intersil u.s. products are manufactured, asse mbled and tested utilizing iso9000 quality systems. intersil corporation?s quality certifications ca n be viewed at www.intersil.com/design/quality intersil products are sold by description only. intersil corpor ation reserves the right to make changes in circuit design, soft ware and/or specifications at any time without notice. accordingly, the reader is cautioned to verify that data sheets are current before placing orders. information furnishe d by intersil is believed to be accurate and reliable. however, no responsibility is assumed by intersil or its subsidiaries for its use; nor for any infringements of paten ts or other rights of third parties which may result from its use. no license is granted by implication or otherwise under any patent or patent rights of intersil or its subsidiari es. for information regarding intersil corporation and its products, see www.intersil.com fn6768.1 may 13, 2010 die characteristics substrate and qfn thermal pad potential (powered up): gnd transistor count: 464 process: si gate bicmos isl3241e, isl3243e
16 fn6768.1 may 13, 2010 isl3241e, isl3243e package outline drawing l32.5x5b 32 lead quad flat no-lead plastic package rev 2, 11/07 located within the zone indicated. the pin #1 identifier may be unless otherwise specified, tolerance : decimal 0.05 tiebar shown (if present) is a non-functional feature. the configuration of the pin #1 identifier is optional, but must be between 0.15mm and 0.30mm from the terminal tip. dimension b applies to the metallized terminal and is measured dimensions in ( ) for reference only. dimensioning and tolerancing conform to amse y14.5m-1994. 6. either a mold or mark feature. 3. 5. 4. 2. dimensions are in millimeters. 1. notes: bottom view detail "x" side view typical recommended land pattern top view 5.00 a 5.00 b index area pin 1 6 (4x) 0.15 32x 0.40 0.10 4 a 32x 0.23 m 0.10 c b 16 9 4x 0.50 28x 3.5 6 pin #1 index area 3 .30 0 . 15 0 . 90 0.1 base plane see detail "x" seating plane 0.10 c c 0.08 c 0 . 2 ref c 0 . 05 max. 0 . 00 min. 5 ( 3. 30 ) ( 4. 80 typ ) ( 28x 0 . 5 ) (32x 0 . 23 ) ( 32x 0 . 60) + 0.07 - 0.05 17 25 24 8 1 32

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