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1 ? fn8038.5 isl4238e, ISL4244E, isl4245e qfn packaged, 15kv esd protected, +2.7v to +5.5v, 10nanoamp, 250kbps/ 1mbps, rs-232 transceivers with enhanced automatic power-down the intersil isl4238e, ISL4244E and isl4245e devices are 2.7v to 5.5v 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 pdas, palmtops, 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 enhanced automatic power-down functions, reduce the standby supply current to a 10na 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 (isl4238e/ISL4244E)/1mbps (isl4245e) are guaranteed at worst case load conditions. the isl424xe are 3 driver, 5 re ceiver (dte) devices that, coupled with the qfn package, provide the industry?s smallest, lowest power comple te serial port suitable for pdas, and laptop or notebook computers. the 32 ld 5x5 qfn requires 60% less board area than a 28 lead tssop, and is nearly 20% thinner. the devices also include a noninverting always-active receiver for ?wake-up? capability. the isl4238e is a 5 driver, 3 receiver device optimized for dce applications with full hardware handshaking. it also includes a noninverting always-active receiver for ring indicator monitoring. transmitter and logic inputs include active feedback resistors that retain the input state once driven to a valid logic level. these devices feature an enhanced automatic power-down function which powers down the on-chip power-supply and driver circuits. this occurs when all receiver and transmitter inputs detect no signal transitions for a period of 30s. these devices power back-up, automati cally, whenever they sense a transition on any transmitter or receiver input. table 1 summarizes the f eatures of the isl4238e, ISL4244E, isl4245, while application note an9863 summarizes the features of each device comprising the 3v rs-232 family. features ? parameters fully specified for 10% tolerance supplies and full industrial temp range ? available in small qfn (5mm x 5mm) package which is 60% smaller than a 28 lead tssop ? esd protection for rs-232 i/o pins to 15kv (iec61000) ? dte (ISL4244E/45e) and dce (isl4238e) versions ? lowest supply current in powe r-down . . . . . . . . . . .10na ? active feedback resistors on t x and logic inputs (isl4238e) ? flow through pinouts ? manual and enhanced automatic power-down features ? guaranteed minimum data rate 250kbps (isl4238e/ISL4244E) / 1mbps (isl4245e) ? latch-up free ? on-chip charge pumps require only four external 0.1f capacitors ? wide power supply range . . . . . . single +2.7v to +5.5v ? meets eia/tia-232 and v.28/v .24 specifications at 3v ? rs-232 compatible with v cc = 2.7v ? pb-free available (rohs compliant) applications ? any space constrained system requiring rs-232 ports - battery powered, hand-held, and portable equipment - laptop computers, notebooks - pdas and palmtops, data cables - cellular/mobile phones, digital cameras, gps receivers 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? 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. 2004, 2008, 2010. all rights reserved all other trademarks mentioned are the property of their respective owners.
2 fn8038.5 may 13, 2010 table 1. summary of features part number no. of tx. no. of rx. config. qfn pkg. no. of monitor rx. (r outb ) data rate (kbps) rx. enable function? manual power- down? enhanced automatic power- down function? isl4238e 5 3 dce 5x5 1 250 no yes yes ISL4244E 3 5 dte 5x5 1 250 no yes yes isl4245e 3 5 dte 5x5 1 1000 no yes yes ordering information part number part marking temp. range (c) package pkg. dwg. # isl4238eir isl 4238eir -40 to +85 32 ld 5x5 qfn l32.5x5b isl4238eirz (note) isl4238 eirz -40 to +85 32 ld 5x5 qfn (pb-free) l32.5x5b isl4238eir-t* isl 4238eir -40 to +85 32 ld 5x5 qfn tape & reel l32.5x5b isl4238eirz-t* (note) isl4238 eirz -40 to +85 32 ld 5x5 qfn tape & reel, (pb-free) l32.5x5b ISL4244Eir isl 4244eir -40 to +85 32 ld 5x5 qfn l32.5x5b ISL4244Eirz (note) isl4244 eirz -40 to +85 32 ld 5x5 qfn (pb-free) l32.5x5b ISL4244Eir-t* isl 4244eir -40 to +85 32 ld 5x5 qfn tape & reel l32.5x5b ISL4244Eirz-t* (note) isl4244 eirz -40 to +85 32 ld 5x5 qfn tape & reel, (pb-free) l32.5x5b isl4245eir isl 4245eir -40 to +85 32 ld 5x5 qfn l32.5x5b isl4245eirz (note) isl4245 eirz -40 to +85 32 ld 5x5 qfn (pb-free) l32.5x5b isl4245eir-t* isl 4245eir -40 to +85 32 ld 5x5 qfn tape & reel l32.5x5b isl4245eirz-t* (note) isl4245 eirz -40 to +85 32 ld 5x5 qfn tape & reel, (pb-free) l32.5x5b *please refer to tb347 for detai ls on reel specifications. note: these intersil pb-free plastic pack aged 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 temper atures that meet or exceed the pb-free requirements of ipc/jed ec j std-020. isl4238e, ISL4244E, isl4245e
3 fn8038.5 may 13, 2010 pinouts isl4238e (32 ld qfn) top view ISL4244E, isl4245e (32 ld qfn) top view pin descriptions pin function v cc system power supply input (2.7v to 5.5v). v+ internally generated positive transmitter supply (+5.5v). v- internally generated negative transmitter supply (-5.5v). gnd ground connection. this is also the potential of the thermal pad (pd). c1+ external capacitor (voltage doubler) is connected to this lead. c1- external capacitor (voltage doubl er) is connected to this lead. c2+ external capacitor (voltage inverter) is connected to this lead. c2- external capacitor (voltage inverter) is connected to this lead. t in ttl/cmos compatible transmitter inputs. (note) 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. r outb ttl/cmos level, noninverting, always enabled receiver outputs. invalid active low output that indicates if no valid rs-232 levels are present on any receiver input. forceoff active low to shut down transmitters and on-chip power supply. this overrides any automatic ci rcuitry and forceon (see table 2) . forceon active high input to override automatic power-down circuitry thereby keeping trans mitters active. (forceoff must be high). nc no connection pd exposed thermal pad. connect to gnd. note: isl4238e input pins incorporat e positive feedback resistors. once the input is driven to a valid logic level, the feedback resistor maintains that logic level until v cc is removed. unused transmitter input s may be left unconnected by the user. t1 out t2 out t3 out r1 in r2 in t4 out r3 in t1 in t2 in t3 in r1 out r2 out t4 in r3 out t5 out forceon forceoff invalid nc t5 in r1 outb c2- gnd c2+ c1+ v+ c1- v cc nc v- nc 1 2 3 4 5 6 7 8 24 23 22 21 20 19 18 17 32 31 30 29 28 27 26 25 9 10111213141516 nc 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 nc nc nc 1 2 3 4 5 6 7 8 24 23 22 21 20 19 18 17 32 31 30 29 28 27 26 25 9 10111213141516 pd isl4238e, ISL4244E, isl4245e
4 fn8038.5 may 13, 2010 typical operating circuits isl4238e 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 23 22 1 2 21 3 28 24 27 32 v+ v- c1+ c1- c2+ c2- + 0.1 f 29 31 r1 out r1 in 4 5k r2 out r2 in 5 19 5k r3 out r3 in 7 17 5k 20 r1 outb c 1 c 2 + c 3 c 4 forceon forceoff gnd 11 +3.3v + 0.1 f 14 30 v cc ttl/cmos logic rs-232 levels rs-232 levels r 1 r 2 r 3 12 invalid to power control levels logic t4 out t5 out t4 in t5 in t 4 t 5 18 6 15 8 10 note: for v cc = 3.15v (3.3v -5%), use c 1 to c 4 = 0.1f or greater. for v cc = 3.0v (3.3v -10%), use c 1 to c 4 = 0.22f or greater. (note) (note) isl4238e, ISL4244E, isl4245e
5 fn8038.5 may 13, 2010 ISL4244E, isl4245e typical operating circuits (continued) 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 levels rs-232 levels rs-232 levels r 1 r 2 r 3 r 4 20 invalid to power control logic isl4238e, ISL4244E, isl4245e
6 fn8038.5 may 13, 2010 absolute maximum rati ngs thermal information v cc to ground. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . -0.3v to 6v v+ to ground . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . -0.3v to 7v v- to ground. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . +0.3v to -7v v+ to v- . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 14v input voltages t in , forceoff , forceon. . . . . . . . . . . . . . . . . . . -0.3v to 6v r in . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 25v output voltages t out . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 13.2v r out , invalid . . . . . . . . . . . . . . . . . . . . . . . . -0.3v to v cc +0.3v short circuit duration t out . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . continuous esd rating . . . . . . . . . . . . see ?esd performance? on page 8 thermal resistance (typical, notes 1, 2) ja (c /w) jc (c /w) 32 ld qfn package. . . . . . . . . . . . . . . 32 3.0 moisture sensitivity (see technical brief tb363) qfn package. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . level 1 maximum storage temperature range . . . . . . . . . .-65c to +150c pb-free reflow profile. . . . . . . . . . . . . . . . . . . . . . . . .see link below http://www.intersil.com/pbfree/pb-freereflow.asp operating conditions temperature range isl42xxeir . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .-40c to +85c 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. note: 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, and tech brief tb389. 2. for jc , the ?case temp? location is the center of the exposed metal pad on the package underside. electrical specifications test conditions: isl4238e v cc = 3.15v to 5.5v, c 1 to c 4 = 0.1f; v cc = 3v, c 1 to c 4 = 0.22f; isl424xe v cc = 3v to 5.5v, c 1 to c 4 = 0.1f; unless otherwise specified. typicals are at t a = +25c parameter test conditions temp (c) min (note 7) typ max (note 7) units dc characteristics operating voltage range full 2.7 - 5.5 v supply current, automatic power- down all r in open, forceon = gnd, forceoff = v cc 25 - 3 300 na full 50 300 na supply current, power-down all r in open, forceoff = gnd 25 - 3 300 na full 50 300 na supply current, automatic power-down disabled all outputs unloaded, forceon = forceoff = v cc , v cc = 3.0v 25 - 0.3 1.0 ma full 0.3 1.5 ma logic and transmitter inputs and receiver outputs input logic threshold low t in , forceon, forceoff full - - 0.8 v input logic threshold high t in , forceon, forceoff , v cc = 3.6v full 2.0 - - v transmitter input hysteresis 25 - 0.5 - v input leakage current t in , forceon, forceoff (isl4238e, note 3) full - 0.01 1.0 a output leakage current forceoff = gnd full - 0.05 10 a output voltage low i out = 1.6ma full - - 0.4 v output voltage high i out = -1.0ma full v cc - 0.6 v cc - 0.1 - v receiver inputs input voltage range full -25 - 25 v input threshold low v cc = 3.0v full - 1.0 0.6 v input threshold high v cc = 3.6v full 2.4 1.5 - v input hysteresis 25 - 0.5 - v input resistance full 3 5 7 k transmitter outputs output voltage swing all transmitter outputs loaded with 3k to ground full 5.0 5.4 - v output resistance v cc = 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 = 0v or 3v to 5.5v, automatic power-down or forceoff = gnd full - - 25 a isl4238e, ISL4244E, isl4245e
7 fn8038.5 may 13, 2010 enhanced automatic power-down (forceon = gnd, forceoff = v cc ) receiver input thresholds to invalid high (see figure 6) full -2.7 - 2.7 v receiver input thresholds to invalid low (see figure 6) full -0.3 - 0.3 v invalid , output voltage low i out = 1.6ma full - - 0.4 v invalid , output voltage high i out = -1.0ma full v cc - 0.6 - - v receiver positive or negative threshold to invalid high delay (t invh ) 25 - 0.5 1 s full - 0.9 1.5 s receiver positive or negative threshold to invalid low delay (t invl ) isl4238e 25 - 60 100 s full 100 150 s receiver positive or negative threshold to invalid low delay (t invl ) ISL4244E/isl42445e 25 - 30 50 s full 40 60 s receiver or transmitter edge to transmitters enabled delay (t wu ) (note 4) full - 20 100 s receiver or transmitter edge to transmitters disabled delay (t autopwdn ) (note 4) full 15 30 60 sec timing characteristics maximum data rate isl4238e/4244e r l =3k , c l = 1000pf, one transmitter switching full 250 500 - kbps maximum data rate isl4245e r l = 3k , one transmitter switching c l = 1000pf full 250 900 - kbps v cc = 3v to 4.5v, c l = 250pf full 1000 2000 - kbps v cc = 4.5v to 5.5v, c l = 1000pf full 1000 1500 - kbps receiver propagation delay receiver input to receiver output, c l = 150pf t phl 25 - 0.15 0.3 s full - 0.2 0.35 s t plh 25 - 0.3 0.5 s full - 0.35 0.55 s receiver skew t phl - t plh , c l = 150pf 25 - 120 250 ns full - 150 300 ns transmitter propagation delay isl4238e/44e transmitter input to transmitter output, c l = 1000pf, r l = 3k t phl 25 - 0.75 1 s full - 0.85 1.1 s t plh 25 - 0.8 1 s full - 0.9 1.1 s transmitter skew isl4238e/44e t phl - t plh (see note 6), r l = 3k , c l = 1000pf 25 - 50 200 ns full - 100 250 ns transmitter propagation delay isl4245e transmitter input to transmitter output, c l = 1000pf, r l = 3k t phl 25 - 0.4 0.8 s full - 0.5 0.8 s t plh 25 - 0.35 0.7 s full - 0.4 0.7 s transmitter skew isl4245e t phl - t plh (see note 5), r l = 3k , c l = 1000pf 25 - 50 200 ns full - 60 250 ns receiver output enable time normal operation, r l = 1k to 0.5v cc , c l = 15pf 25 - 200 350 ns full - 200 400 ns electrical specifications test conditions: isl4238e v cc = 3.15v to 5.5v, c 1 to c 4 = 0.1f; v cc = 3v, c 1 to c 4 = 0.22f; isl424xe v cc = 3v to 5.5v, c 1 to c 4 = 0.1f; unless otherwise specified. typicals are at t a = +25c parameter test conditions temp (c) min (note 7) typ max (note 7) units isl4238e, ISL4244E, isl4245e
8 fn8038.5 may 13, 2010 detailed description these interface ics operate from a single +2.7v to +5.5v supply, guarantee a 250kbps (isl4238e/ISL4244E)/1mbps (isl4245e) minimum data rate, require only four small external 0.1f capacitors, fe ature low power consumption, and meet all ela rs-232c and v.28 specifications. the circuit is divided into three sections: the charge pump, the transmitters, and the receivers. charge-pump intersil?s new rs-232 family utilizes 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 these devices 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 ttl/cm os inputs 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. 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 isl4238e/ISL4244E 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 = 250pf, one transmitter easily operates at 1mbps. the isl4245e guarantees a 1mbps data rate for full load conditions (3k and 250pf), 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 = 250pf, one transmitter easily operates at 1.4mbps. transmitter inputs on the isl424xe float if left unconnected, and may cause i cc increases. connect unused inputs to receiver output disable time normal operation, r l = 1k to 0.5v cc , c l = 15pf 25 - 350 500 ns full - 400 600 ns transmitter output enable time isl4238e/ISL4244E/isl4245e normal operation, r l = 3k , c l = 1000pf 25 - 25 40 s full - 35 50 s transmitter output disable time isl4238e/ISL4244E/isl4245e normal operation, r l = 3k , c l = 1000pf 25 - 2.5 4 s full - 2.7 4 s transition region slew rate isl4238e/ISL4244E v cc = 3v to 3.6v, r l =3k to 7k , measured from 3v to -3v or -3v to 3v c l = 150pf to 1000pf 25 6 11 30 v/s full 6 10 30 v/s c l = 150pf to 2500pf 25 4 9 30 v/s full 4 8 30 v/s transition region slew rate isl4245e v cc = 3v to 3.6v, r l = 3k to 7k , measured from 3v to -3v or -3v to 3v, c l = 150pf to 1000pf 25 24 40 150 v/s full 24 35 150 v/s esd performance rs-232 pins (t out , r in ) human body model 25 - 15 - kv iec61000-4-2 air gap discharge 25 - 15 - kv iec61000-4-2 contact discharge 25 - 8 - kv all other pins human body model 25 - 3 - kv notes: 3. isl4238e inputs utilize a positive feedback resistor. the input current is negligible when the input is at either supply rail . 4. an ?edge? is defined as a transition through the transmitter or receiver input thresholds. 5. skew is measured at the receiver input switching points (1.4v). 6. skew is measured at the tr ansmitter zero crossing points. 7. 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. electrical specifications test conditions: isl4238e v cc = 3.15v to 5.5v, c 1 to c 4 = 0.1f; v cc = 3v, c 1 to c 4 = 0.22f; isl424xe v cc = 3v to 5.5v, c 1 to c 4 = 0.1f; unless otherwise specified. typicals are at t a = +25c parameter test conditions temp (c) min (note 7) typ max (note 7) units isl4238e, ISL4244E, isl4245e
9 fn8038.5 may 13, 2010 gnd for the best performance. isl4238e transmitter inputs incorporate an active positive feedback resistor that maintains the last input state in the absence of a forcing signal, so unused transmitter inputs may be left unconnected. receivers isl4238e, ISL4244E, isl4245 devices contain standard inverting receivers which can tristate via the forceoff control line. additionally, they include a noninverting (monitor) receiver (denoted by the r outb label) that is always active, regardless of the state of any control lines. both receiver types convert rs-232 signals to cmos output levels and accept inputs up to 25v while presenting the required 3k to 7k input impedance (see figure 1) 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 isl4238e, ISL4244E, isl4245 inverting receivers disable during forced (manual) power-down, but not during automatic power-down (see table 2). conversely, the monitor receiver remains active even during manual power- down making it 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 2 and 3). this renders them useless for wake up functions, but the corresponding monitor receiver can be dedicated to this task as shown in figure 3. low power operation these 3v devices require a nominal supply current of 0.3ma, even at v cc = 5.5v, during normal operation (not in power-down mode). this is c onsiderably 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. table 2. power-down logic truth table rcvr or xmtr edge within 30 sec? forceoff input forceon input transmitter outputs receiver outputs r outb outputs rs-232 level present at receiver input? invalid output mode of operation no h h active active active no l n ormal operation (enhanced auto power-down disabled) no h h active active active yes h yes h l active active active no l n ormal operation (enhanced auto power-down enabled) yes h l active active active yes h no h l high-z active active no l power-down due to enhanced auto power-down logic no h l high-z active active yes h x l x high-z high-z active no l manual power-down x l x high-z high-z active yes h invalid driving forceon and forceoff (emulates automatic power-down) x note 8 note 8 active active active yes h normal operation x note 8 note 8 high-z high-z active no l forced auto power-down note: 8. input is connected to invalid output. r xout gnd v rout v cc 5k r xin -25v v rin +25v gnd v cc figure 1. inverting receiver connections figure 2. power drain through powered down peripheral old v cc powered gnd shdn = gnd v cc rx tx v cc current v out = v cc flow rs-232 chip down uart isl4238e, ISL4244E, isl4245e
10 fn8038.5 may 13, 2010 power-down functionality the already low current requirement drops significantly when the device enters power-down mode. in power-down, supply current drops to 10na, because the on-chip charge pump turns off (v+ collapses to v cc , v- collapses to gnd), and the transmitter outputs tristate. inverting receiver outputs disable only in manual power-down; refer to table 2 for details. this micro-power mode makes these devices ideal for battery powered and portable applications. software controlled (manual) power-down these devices allow the user to force the ic into the low power, standby state, and utilize 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 power-down 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 power-down is desired, the user must strap forceon high to disable the enhanced automatic power-down circuitry. isl4238e, ISL4244E, isl4245 inverting (standard) receiver outputs also disable when the device is in manual power- down, thereby eliminating the possible current path through a shutdown peripheral?s input protection diode (see figures 2 and 3). connecting forceoff and forceon together disables the enhanced automatic power-d own feature, enabling them to function as a manual shutdown input (see figure 4). with any of the previous mentioned control schemes, the time required to exit power-down, and resume transmission is only 100s. when using both manual and en hanced automatic power- down (forceon = 0), the isl4238e, ISL4244E, isl4245 won?t power up from manual power-down until both forceoff and forceon are driven high, or until a transition occurs on a receiver or transmitter input. figure 5 illustrates a circuit for ensuring that the isl4238e, ISL4244E, isl4245 powers up as soon as forceoff switches high. the rising edge of the master power-down signal forces the device to power up, and the isl4238e, ISL4244E, isl4245 returns to enhanced automatic power- down mode an rc time constant after this rising edge. the time constant isn?t critic al, because the isl4238e, ISL4244E, isl4245 remains powered up for 30s after the forceon falling edge, even if there are no signal transitions. this gives slow-to- wake systems (e.g., a mouse) plenty of time to start transmitting, and as long as it starts transmitting within 30s both systems remain enabled. invalid output the invalid output always indicates (see table 2) whether or not 30s have elapsed with invalid rs-232 signals (see figures 6 and 9) persisting on all of the receiver inputs, 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 disconnected. in the case of a disconnected interface cable where all the receiver inputs are figure 3. disabled receivers prevent power drain isl4238e transition r x t x r outb r out t1 in forceoff = gnd v cc v cc to r in t1 out v out = hi-z powered detector down uart wake-up logic ISL4244E isl4245 figure 4. connections for manual power-down when no valid receiver signals are present pwr forceoff invalid cpu i/o forceon isl4238e mgt logic uart ISL4244E isl4245 figure 5. circuit to ensure immediate power up when exiting forced power-down forceoff forceon power master power-down line 1m 0.1 f management unit isl4238e, ISL4244E, isl4245 isl4238e, ISL4244E, isl4245e
11 fn8038.5 may 13, 2010 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 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.= enhanced automatic power-down even greater power savings is available by using these devices which feature an enhanced automatic power-down function. when the enhanced power-down logic determines that no transitions have occurred on any of the transmitter nor receiver inputs for 30 seconds, the charge pump and transmitters power-down, thereby reducing supply current to 10na . the isl4238e, ISL4244E, isl4245 automatically powers back up whenever it detects a transition on one of these inputs. this automatic power-down feature provides additional system power savings without changes to the existing operating system. enhanced 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 enhanced automatic power-down functionality. figure 7 illustrates the enhanced power-down control logic. note that once the isl4238e, ISL4244E, isl4245 enters power-down (manually or autom atically), the 30 second timer remains timed out (s et), keeping the isl4238e, ISL4244E, isl4245 powered down until forceon transitions high, or until a transition occurs on a receiver or transmitter input. the invalid output signal switches low to indicate that invalid levels have persisted on all of the receiver inputs for more than 30s (see figure 9), but this has no direct effect on the state of the isl4238e, ISL4244E, isl4245 (see the next sections for methods of utilizing invalid to power down the device). the time to recover from automatic power-down mode is typically 100s. emulating standard automatic power-down if enhanced automatic power-down isn?t desired, the user can implement the standard automa tic power-down feature (mimics the function on the isl4243e) by connecting the invalid output to the forceon and forceoff inputs, as shown in figure 8. after 30s of invalid receiver levels, invalid switches low and drives the isl4238e, ISL4244E, isl4245 into a forced power-down condition. invalid switches high as soon as a receiver input senses a valid rs-232 level, forcing the isl4238e, ISL4244E, isl4245 to power on. see the ?invalid driving forceon and forceoff ? section of table 2 for an operational summary. this operational mode is perfect for handheld devices that communicate with another computer via a detachable cable. detaching the cable allows the internal receiver pull-down resistors to pull the inputs to gnd (an invalid rs-232 level), causing the 30s timer to time-out and drive the ic into power-down. reconnecting the cable restores valid levels, causing the ic to power back up. figure 6. definition of valid rs-232 receiver levels 0.3v -0.3v -2.7v 2.7v invalid level - invalid = 0 valid rs-232 level - invalid = 1 valid rs-232 level - invalid = 1 indeterminate indeterminate figure 7. enhanced automatic power-down logic 30sec timer s r forceoff autopwdn forceon r_in t_in edge detect edge detect figure 8. connections for automatic power-down when no valid receiver signals are present forceoff invalid cpu i/o forceon isl4238e uart ISL4244E isl4245 isl4238e, ISL4244E, isl4245e
12 fn8038.5 may 13, 2010 hybrid automatic power-down options for devices which communicate only through a detachable cable, connecting invalid to forceoff (with forceon = 0) may be a desirable configuration. while the cable is attached invalid and forceoff remain high, so the enhanced automatic power-down logic powers down the rs- 232 device whenever there is 30 seconds of inactivity on the receiver and transmitter inputs. detaching the cable allows the receiver inputs to drop to an invalid level (gnd), so invalid switches low and forces the rs -232 device to power down. the isl4238e, ISL4244E, isl4245 remains powered down until the cable is reconnected (invalid = forceoff = 1) and a transition occurs on a receiver or transmitter input (see figure 7). for immediate power up when the cable is reattached, connect forceon to forceoff through a network similar to that shown in figure 5. capacitor selection the isl4238e charge pumps require 0.1 f, or greater, capacitors for 3.3v (5% tolerance) operation. for other supply voltages refer to table 3 for capacitor values. do not use values smaller than those listed in table 3. the ISL4244E/45e charge pumps require 0.1 f capacitors for proper operation. increasing the capacitor values (by a factor of 2) reduces ripple on the transmitter outputs and slightly reduces power consumption. c 2 , c 3 , and c 4 can be increased without increasing c 1 ?s value, however, do not increase c 1 without also increasing c 2 , c 3 , and c 4 to maintain the proper ratios (c 1 to the other capacitors). when using minimum required capacitor values, make sure that capacitor values do not degrade excessively with temperature. if in doubt, use ca pacitors with a larger nominal value. the capacitor?s equivalent series resistance (esr) usually rises at low temperat ures 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 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 10 shows the response of two transmitter outputs when exiting power-down 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 2500pf. note that the transmitters enable only when the magnitude of the supplies exceed approximately 3v. operation down to 2.7v isl4238e, ISL4244E, isl4245 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 interoperability with rs-232 devices. table 3. required capacitor values (isl4238e) v cc (v) c 1 (f) c 2 , c 3 , c 4 (f) 3.0 to 3.6 (3.3v 10%) 0.22 0.22 3.15 to 3.6 (3.3v 5%) 0.1 0.1 4.5 to 5.5 0.047 0.33 3.0 to 5.5 0.22 1 receiver inputs transmitter outputs invalid output v+ v cc 0 v- t invl t invh figure 9. enhanced automatic power-down and invalid timing diagrams output transmitter inputs t wu t autopwdn t autopwdn t wu invalid region } isl4238e, ISL4244E, isl4245e
13 fn8038.5 may 13, 2010 mouse driveability the isl424xe are specifically designed to power a serial mouse while operating from low voltage supplies. figure 11 shows the transmitter output voltages under increasing load current. the on-chip switching regulator ensures the transmitters will supply at least 5v during worst case conditions (15ma for parallel ed v+ transmitters, 7.3ma for single v- transmitter). high data rates the isl4238e, ISL4244E, isl4245 maintain the rs-232 5v minimum transmitter output voltages even at high data rates. figure 12 details a transmitter loopback test circuit, and figure 13 illustrates the isl4238e/ISL4244E loopback test result at 120kbps. for this test, all transmitters were simultaneously driving rs-232 loads in parallel with 1000pf, at 120kbps. figure 14 shows the isl4238e/ISL4244E loopback results for a single transmitter driving 1000pf and an rs-232 load at 250kbps. figure 15 illustrates the isl4245e loopback test result at 250kbps. for this test, all transmitters were simultaneously driving rs-232 loads in parallel with 1000pf, at 250kbps. figure 16 shows the isl4245e loopback results for a single transmitter driving 250pf and an rs-232 load at 1mbps. the static transmitters were also loaded with an rs-232 receiver. time (20 s/div) t1 t2 2v/div 5v/div v cc = +3.3v forceoff figure 10. transmitter outputs when exiting power-down c1 to c4 = 0.1 f figure 11. transmitter output voltage vs load current (per transmitter, i.e., double current axis for total v out+ current) transmitter output voltage (v) load current per transmitter (ma) 0246810 -6 -4 -2 0 2 4 6 -5 -3 -1 1 3 5 13579 v out + v out - v cc v out + v out - t1 t2 t3 v cc = 3.0v isl424xe figure 12. transmitter loopback test circuit figure 13. isl4238e/ISL4244E loopback test at 120kbps figure 14. isl4238e/ISL4244E loopback test at 250kbps (c l = 1000pf) isl4238e v cc c 1 c 2 c 4 c 3 + + + + c l v+ v- 5k t in r out c1+ c1- c2+ c2- r in t out + v cc 0.1 f v cc forceoff forceon ISL4244E isl4245 t1 in t1 out r1 out 5 s/div v cc = +3.3v 5v/div. c1 to c4 = 0.1 f t1 in t1 out r1 out 2 s/div. v cc = +3.3v 5v/div. c1 - c4 = 0.1 f isl4238e, ISL4244E, isl4245e
14 fn8038.5 may 13, 2010 interconnection with 3v and 5v logic the isl4238e, ISL4244E, isl4245 directly interface with 5v cmos and ttl logic families. nevertheless, with the isl4238e, ISL4244E, isl4245 at 3.3v, and the logic supply at 5v, ac, hc, and cd4000 outputs can drive isl4238e, ISL4244E, isl4245 inputs, but isl4238e, ISL4244E, isl4245 outputs do not reach the minimum v ih for these logic families. see table 4 for more information. 15kv esd protection all pins on isl4238e, ISL4244E, isl4245 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 finis hed product. simply touching the port pins, or connecting a cable, can cause an esd event that might destroy unprot ected ics. these new esd structures protect the device whet her 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 15. isl4245e loopback test at 250kbps figure 16. isl4245e loopback test at 1mbps (c l = 250pf) table 4. logic family compatibility with various supply voltages system power-supply voltage (v) v cc supply voltage (v) compatibility 3.3 3.3 compatible with all cmos families. 5 5 compatible with all ttl and cmos logic families. 5 3.3 compatible with act and hct cmos, and with ttl. isl4238e, ISL4244E, isl4245 outputs are incompatible with ac, hc, and cd4000 cmos inputs. t1 in t1 out r1 out 2 s/div. 5v/div. v cc = +3.3v c1 - c4 = 0.1 f t1 in t1 out r1 out 0.5 s/div. 5v/div. v cc = +3.3v c1 - c4 = 0.1 f isl4238e, ISL4244E, isl4245e
15 fn8038.5 may 13, 2010 typical performance curves v cc = 3.3v, t a = +25c figure 17. isl4238e transmitter output voltage vs load capacitance figure 18. ISL4244E transmitter output voltage vs load capacitance figure 19. isl4245e transmitter output voltage vs load capacitance figure 20. isl4238e supply current vs load capacitance when transmitting data figure 21. ISL4244E supply current vs load capacitance when transmitting data figure 22. isl4245e supply current vs load capacitance when transmitting data -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 -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 -6 -4 -2 0 2 4 6 1000 2000 3000 4000 5000 0 load capacitance (pf) transmitter output voltage (v) 1 transmitter at 1mbps v out + v out - other transmitters at 30kbps 20 25 30 35 40 55 45 50 0 1000 2000 3000 4000 5000 load capacitance (pf) supply current (ma) 20kbps 250kbps 120kbps 1 transmitter at indicated rate 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 at indicated rate 10 20 30 40 50 80 60 70 0 1000 2000 3000 4000 5000 load capacitance (pf) supply current (ma) 120kbps 1mbps 250kbps 90 1 transmitter at indicated rate isl4238e, ISL4244E, isl4245e
16 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 fn8038.5 may 13, 2010 figure 23. isl4238e/ISL4244E slew rate vs load capacitance figure 24. isl4245e slew rate vs load capacitance figure 25. supply current vs supply voltage die characteristics substrate and qfn thermal pad potential (powered up): gnd transistor count isl4238e: 1235 ISL4244E: 1109 isl4245e: 1109 process si gate bicmos typical performance curves v cc = 3.3v, t a = +25c (continued) load capacitance (pf) slew rate (v/ s) 0 1000 2000 3000 4000 5000 5 10 15 20 25 +slew -slew load capacitance (pf) slew rate (v/ s) 0 1000 2000 3000 4000 5000 0 10 30 50 110 -slew +slew 70 90 supply current (ma) 2.5 3.0 3.5 4.0 4.5 5.0 5.5 6.0 0 0.5 1.0 1.5 2.0 supply voltage (v) 2.5 3.0 3.5 no load all outputs static isl4238e, ISL4244E, isl4245e
17 fn8038.5 may 13, 2010 isl4238e, ISL4244E, isl4245e 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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