ANALOG DEVICES INC ANALOG DEVICES HEE D MM 0416800 0029700 8 MANA T~7T5 -4%5 -O5 +5 V Powered CMOS RS-232 Drivers/Receivers AD230-AD241 FEATURES APPLICATIONS Computers Peripherals Modems Printers Instruments Single 5 V Power Supply Meets All RS-232-C and V.28 Specifications Multiple Drivers and Receivers On-Board DC-DC Converters +9 V Output Swing with +5 V Supply Low Power CMOS: 5 mA Operation Low Power Shutdown <1 pA 3-State TTL/CMOS Receiver Outputs +30 V Receiver Input Levels Plug-in Replacement for MAX230-241 GENERAL DESCRIPTION The AD230 family of 5 V only, RS-232 line drivers/receivers provides a variety of configurations to fit most communication needs, especially in applications where +12 V is not available, The AD230, AD235, AD236 and AD241 feature a low power shutdown mode which reduces power dissipation to less than 5 pW making them ideally suited for battery powered equip- ment. The AD233 and AD235 do not require any external com- ponents and are particularly useful in applications where printed circuit board space is critical. AD232 TYPICAL OPERATING CIRCUIT +5V INPUT 10pF 6.3 tour 6.3V +18V TO ~10V VOLTAGE INVERTER aw 11 TTLICMOS: BS-232 INPUTS T2 Rlour RL Trucos 2 OUTPUTS eure R2 AD232 SINTERAAL SER PULL Gated RESIS A BT BY eT All members. of the AD230 family, except the AD231 and the AD239, include two internal charge pump voltage converters which allow operation from a single +5 V supply. These con- verters convert the +5 V input power to the 10 V required for RS-232 output levels. The AD231 and AD239 are designed to operate from +5 V and +12 V supplies, An internal +12 V to ~12 V charge pump voltage converter generates the 12 V supply. In order to minimize the package count in all applications, a wide selection of driver/receiver contbinations is available (see table below). SELECTION TABLE No. of | No. of Low Power | TTL Part Power RS-232 | RS-232 External Shutdown Three-State | No. of Number | Supply Voltage | Drivers | Receivers Capacitors | (SD) EN Pins AD230 | +5V 5 0 4 Yes No 20 AD231 +5 V&+4+7.5V | 2 2 2 No No 14 to 13,2V AD232 +5 V 2 2 4 No No 16 AD233 +5V 2 2 None No No 20 AD234 | +5 V 4 0 4 No No 16 AD235 +5 V 5 5 None Yes Yes 24 AD236 | +5 V 4 3 4 Yes Yes 24 AD237 +5V 5 3 4 No No 24 AD238 +5V 4 4 4 No No 24 AD239 t5V&+12V | 3 5 2 No Yes 24 AD241 +5 V 4 5 4 Yes Yes 28 COMMUNICATIONS PRODUCTS 4-29ANALOG DEVICES INC AD230-AD241SPECIFICATIONS 4eE D MM 0815800 0029701 T MANA Woo = +5 V 10% (AD231, AD232, AD234, AD236, AD236, AD239, AD241); Vog = +5 V + 5% (AD233, AD235); V+ = 7.5 V to 13.2 V (AD231) & V+ = 12 + 10% (AD23y); All Specifications Tyjq to Tax unless otherwise noted.) : T-75~45-05 Parameter Min | Typ | Max | Units | Test Conditions/Comments Output Voltage Swing +5 +9 Volts All Transmitter Outputs Loaded with 3 kQ to Ground Veco Power Supply Current 4 10 mA No Load, T, = 25C 0.4 1 mA AD231, AD239 V+ Power Supply Current 5 10 mA No Load, V+ = 12 V AD231 & AD239 Only Shutdown Supply Current 1 10 pA Ta = +25C, Vsp = +5 V Input Logic Threshold Low, Vixy, 0.8 Vv Ti EN, SD Input Logic Threshold High, Vins 2.0 Vv Tw; EN, SD Logic Pullup Current 15 200 pA Tw =0V RS-232 Input Voltage Range 30 +30 Vv RS-232 Input Threshold Low 0.8 1,2 Vv Vee = 5 V, Ta = +25C RS-232 Input Threshold High 1.7 2.4 Vv Veo = 5 V; Ta = +25C RS-232 Input Hysteresis 0.2 0.5 1.0 Vv Veo = 5 V RS-232 Input Resistance 3 5 7 ko Vee = 5V, Ta = +25C TTL/CMOS Output Voltage Low, Vor 0.4 v Iour = 1.6 mA (AD231-AD233, Toyz = 3.2 mA) TTL/CMOS Output Voltage High, Vo;; | 3.5 Vv Tour = 1.0 mA TTL/CMOS Output Leakage Current 0.05 | +10 pA EN = Voc, 0 V = Rour = Veo Output Enable Time (Tg) 400 ns AD235, AD236, AD239, AD241 (Figure 25. C, = 150 pF) Output Disable Time (Tpis) 250 ns AD235, AD236, AD239, AD241 (Figure 25. Ry, = 1k) Propagation Delay 0.5 ps RS-232 to TTL Instantaneous Slew Rate! 30 Vins C, = 10 pF, Ry = 3-7 kO, Ty = +25C Transition Region Slew Rate 3 Vins R, = 3 kQ, C,, = 2500 pF Measured from +3 V to -3 Vor -3 Vto +3 V Output Resistance 300 a Veo = V+ = V- = 0V, Vour = +2 V RS-232 Output Short Circuit Current +10 mA NOTE "Sample tested to ensure compliance. Specifications subject to change without notice. ABSOLUTE MAXIMUM RATINGS* Power Dissipation (T, = 25C unless otherwise noted) Cerdip (Derate 9.5 mW/C above +70C) .......675 mW Vee ss seeae os beens . 0.3 V to +6V Plastic DIP (Derate 7 mW/C above +70C) .....375 mW Vt cee eeae beeen sees Veo ~0, 3V)to +13 V SOIC (Derate 7 mW/C above +70C) .........375 mW rrr we teen e ener eae +0.3 V to -13 V Operating Temperature Range Input Voltages Commercial (J Version)... 0.06. .00e 000+. 0 to +70C TIN cece eee eee Cece ee -0.3 V to (Veg +0.3 V) Industrial (A Version).............. . 40C to +85C Rin cece eens Detect ee eee e ene ... 30V Extended (S Version) .........5 eee 755C to +125C Output Voltages Storage Temperature Range ..... tae aes 65C to +150C Rot scenes saeco ee (Vt, +0.3 V) to (V-, -0.3 V) Lead Temperature (Soldering, 10 secs)... .. 2.0%. $300C sees beeen e eee ee 703 V to Veg +03. V) *This is a stress rating only and functional operation of the device at these or Short Circuit Duration . any other conditions above those indicated in the operation sections of this Tour ++sre: Perea cee rears ferns - Continuous specification is not implied. Exposure to absolute maximum rating conditions for extended periods of time may affect reliability. CAUTION ESD (electrostatic discharge) sensitive device. The digital control inputs are diode protected; however, permanent damage may occur on unconnected devices subject to high energy electro- static fields. Unused devices must be stored in conductive foam or shunts. The protective foam should be discharged to the destination socket before devices are removed. i aad RTS ad iia [lel 4-30 COMMUNICATIONS PRODUCTS REV.AANALOG DEVICES INC 4eE D MM 04164800 0029702 1 MANA ORDERING GUIDE T-75-45-05 Temperature Package Temperature Package Temperature Package Model Range Option* | Model Range Option* | Model Range Option* AD230 AD231 AD232 AD230JN | 0C to +70C N-20 AD231JN_ | 0C to +70C N-14 AD232JN | 0C to +70C N-16 AD230JR | 0C to +70C R-20 AD231JR | 0C to +70C R-16 AD232JR_ | 0C to +70C R-16 AD230AN | 40C to +85C | N-20 AD231AN | 40C to +85C | N-14 AD232AN | 40C to +85C | N-16 AD230AR | 40C to +85C | R-20 AD231AR |} 40C to +85C' | R-16 AD232AR | 40C to +85C | R-16 AD230AQ | 40C to +85C | Q-20 AD231AQ | 40C to +85C | Q-14 AD232AQ | 40C to +85C | Q-16 AD2318Q | -55C to +125C Q-14 AD232SQ | 55C to +125C | Q-16 AD233 AD234 AD235 AD233JN | 0C to +70C N-20 AD234JN_ | 0C to +70C N-16 AD235JN | 0C to +70C N-24A AD233AN | 40C to +85C | N-20 AD234JR | 0C to +70C R-16 AD235AN | 40C to +85C. | N-24A AD234AN | 40C to +85C | N-16 AD235AQ | -40C to +85C | D-24 AD234AR | 40C to +85C | R-16 AD234AQ | ~40C to +85C | Q-16 AD2348Q | 55C to +125C | O-16 AD236 AD237 AD238 AD236JN_ | 0C to +70C N-24 AD237JN | 0C to +70C N-24 AD238JN | 0C to +70C N-24 AD236JR | 0C to +70C R-24 AD237JR_ | 0C to +70C R-24 AD238JR | 0C to +70C R-24 AD236AN | 40C to +85C | N-24 AD237AN | 40C to +85C | N-24 AD238AN | 40C to +85C | N-24 AD236AR | 40C to +85C | R-24 AD237AR | 40C to +85C. | R-24 AD238AR | 40C to +85C | R-24 AD236AQ | 40C to +85C | Q-24 AD237AQ | 40C to 85C | Q-24 AD238AQ | -40C to +85C Q-24 AD236SQ_ | 55C to +125C Q-24 AD238SQ_ | 55C to +125C | Q-24 AD239 AD241 AD239JN_ | 0C to +70C N-24 AD241JR_ | OC to +70C R-28 AD239JR_ | 0C to +70C R-24 AD241AR | 40C to +85C | R-28 AD239AN | 40C to +85C | N-24 AD239AR | 40C to +85C | R-24 AD239AQ | ~40C to +85C | Q-24 AD239SQ | 55C to +125C | Q-24 ; *N = Plastic DIP; Q = Cerdip; R = Small Outline IC (SOIC). For outline information see Package Information section, +5V INPUT 10pF 63V 4.7pF +5V ro +10V TT 6.3V T3 our Gy e ao] T4 our 4.7uF | #10V To -10v V 10uF Tour [2] 9] TS iy 16V _ VOLTAGE INVERTER Tv Tour [3] ia] NC Tas TI Tour Tam [a] 7] so Thy [5 | AD230 6] T5 our Tain 12 Tour TOP VIEW GND [] (Not to Scale) 15] T4in TL iCMOS | 4, 3 RS-232 Vee [7 a] T3 iy INPUTS* 1 our F OUTPUTS t+ [a] 13] V- Tay Tour v+ [2] 2] c2- c1- [fo i] c2+ TS. Tour NC = NO CONNECT Nc 8D Figure 1, AD230 DIP/SOIC Pin Configuration REV. A INTERNAL 400G{ PULL-UP RESISTOR ON EACH TTL/CAOS INPUT Figure 2, AD230 Typical Operating Circuit COMMUNICATIONS PRODUCTS 4~31ANALOG DEVICES INC W2E D MM 08164800 0029703 3 MBANA AD230-AD241 1-7-4808 DIP WY cis [fe 14] vs +5V INPUT e1- [2] fi3] Vee 8 1N914 OR EQUIVALENT v- [3] 12] GND 4 Vee 14 - a AD231 5 ac-|* +2V 10 -12v vat +7.5V TO 13.2V T2our | 4 TOP VIEW 411] Toyr 4.7p VOLTAGE CONVERTER \_ (Not te Scale) ev Tay yo a7uF Ray, [5 HO] Rtn T+ R2our [6 9 | Rtour Th, 2 "u in v1 * Tour T2m [7] ra] Tw TTLicmos RS-232 INPUTS* ; 4 OUTPUTS SOIC Tae ts>0 * Tour C+ Gi] . 6] V+ Rlour. 8 of 40 a Ri . TTLicMos RS-232 c 2] 15] Vee OUTPUTS 6 5 INPUTS** v- [3] Ha] Gn R2guy oe Ry Tour [4]| AD231 | [13] Ttour TOP VIEW AD231 R2w [5] | ot to Scale) fa] Rtn GND R2 our [| i] Rlour +? Taw [7 0] Thuy INTERNAL Skil PULUDOWN RESISTOR ON GACH R&ase NEUT. NC 8 9} NC . : : ae [e| 2] Figure 4. AD231 Typical Operating Circuit NC = NO CONNECT Figure 3. AD231 DIP & SOIC Pin Configurations +5V INPUT 1OnF G 1 6av | tone 1 = (146 + 6.3V Ci+ ce wr a7pr tl 5V TO 10V c+ [fife 6] Vee 6.3V T__3]ct- volTaGe ooUBLER V+ 2 v+ [2 15] GND tro-G]* stovto -10v, Vy 2] 5] yi 4 2_VOLTAGE INVERTER Te 4-13 14 5k C- (3) apago fia] Tan , > C2+ [a] TOP VIEW 13] Riw Thy Te 4 > Tour (Not to Scale) TTIL/cmMos RS-232 c2- [5] 12] Rtour INPUTS* 0 , OUTPUTS v- [6 Ha] Ts Tay fae Tour T2our [7] 0] T2iy 12 13 Ry, [8 [3] Four Rlour 2G] , Pliw TTLICMOS RS-292 OUTPUTS 9 3 INPUTS** Figure , AD232 DIP/SOIC Pin Configuration R2our R2 4 R2iy AD232 QND 15_L, INTERNAL 400k22 PULL-UP RESISTOR ON EACH TTL/CMOS INPUT **(NTERNAL 5ki2 PULL-DOWN RESISTOR ON EACH AS-232 INPUT Figure 6. AD232 Typical Operating Circuit . 4-32 COMMUNICATIONS PRODUCTS REV. AANALOG DEVICES INC 42E D MM 0416800 O0e9704 s MANA AD230-AD241 | fy +5V INPUT | Tay Li}e 20] R2our | Tiw [2] 19] R2qy Rl our [3 3] Tour Thin Tlour _ TTL/CMOS RS-232 Rw [4 fz] v INPUTS* OUTPUTS Tour [5] _AD233_ fig] ca T2 yy Tour TOP VIEW GND [ (Not to Seale) hs] C2+ Vee [7] 14] Ve Rlour Rin TTL/CMOS RS-232 c1+ [a] 3] c1- OUTPUTS INPUTS** GNO [| 2} V- R2our R2iy DO NOT MAKE c2- f10 1] C2+ CONNECTIONS r0{ THESE PINS , INTERNAL Figure 7, AD233 DIP Pin Configuration 10V POWER gure 233 DIP 9 SUPPLY INTERNAL +10V POWER SUPPLY "INTERNAL 400k92 PULL-UP RESISTOR ON EACH TTL/CMOS INPUT **INTERNAL 5k{2 PULL-DOWN RESISTOR ON EACH RS-232 INPUT Figure 8, AD233 Typical Operating Circuit b +5V INPUT aa 10pF 7 % OSV me too Vee TOS 4.7uF 9 +5V TO +10V vale Tour i rg] T3 our 6.3V C__3}c1~voLTAGE pouaLeR 2 +279] 2+ +10 To -10V I] 4.74F 10 10pF Tour [2] H5} T4our iy 2_VOLTAGE INVERTER Tv T2y 13 14 = DT apesg fl v1. 4 1 on Tw [4] top view fia] T3,y " = our GND fe (Not to Scale) 3] v- T2y > Vec [s] | c2- TTLICMOS RS-232 pb [p> (NPUTS* OUTPUTS Ctl+ 17 10) C2 [| to] * T3y 3 {> 6. T3our [> 3 vs [8 fa] ct- Figure 9. AD234 DIP/SOIC Pin Configuration T4yy it AD234 GND 5 INTERNAL 400ki2 PULL-UP RESISTOR ON EACH TTL/CMOS INPUT Figure 10. AD234 Typical Operating Circuit REV. A COMMUNICATIONS PRODUCTS 4-33ANALOG DEVICES INC AD230-AD241 a > o a IEME ele TE eile leis Tour T2our R2iy R2 our T2in Ti Rlour Rin GND Vee T3 ouT Tlouy 42E D MM 0416800 0029705 7 MMANA T-75-45-05 C4 a Tour [3 Rin Gy Rlour iG Taw GND [3] Vee [9 Cl+ fro) Ve i G7 Bi c1- [2] +5V INPUT 12 Vee / \ Thuy 8 {ide 3 Tour VY a] Faw Taw 2 hae jp tour 23] Fou 15 2 RS-232 a] 180 GUEST > Pur + Bibra 2t] SD ai oe Te mt Tour AD235 [i] T8our Two 22 [> 8s ean TOP VIEW AD238 < 18] Ran / S (Not to Scale) | Rlour 3 al 10 Ry 7] Pour 16] T4iy R2oure s Hose 5 Fs 5] 131m TrLicMos 23 m3 24 na AS-232 OUTPUTS | Pour Mee INPUTS E* Fa] Abou 13] RSq Pagur uw 25 18 Rhy . . . . RSour# a RS Le Roe Figure 11. AD238 DIP Pin Configuration \ 20 21 EN <- SD GND i SINTERNAL Soft BULLOGWN RESISTGA ON EACH RGSS INPUT Figure 12, AD235 Typical Operating Circuit +5V INPUT TT 47yr t ere Vee al , . 14 ~~ 24] 14 83V C_t2le1- vorraak pouBLERY* our amet ta] 2", #10v TO -10v__ V- a 1OuF 23] Ry iw ~ cg VOLTAGE INVERTER Telev ( = \ 22] R2our Thy Z [> 2 Tour 6 3 Tin T2 T2our ale aes > BBs AD236[t9] Tay n,-2 [> 1 nies TOP VIEW ur (Not to Seale) 18} 73.4 AD236 h7] R3 Tain 18 4 7 24. T4our out \ LL ? 6] R s \ ts] Sui Rleur s Ai 4 Rin TrLicmos 22 < 23 . 4] c2- OUTPUTS ] Four Az - Raw FINPuTS* 13 3] C2+ Alour 7 A3 4.16 Ay 20 1 2 a 2 Figure 13. AD236 DIP/SOIC Pin Configuration EN No ~* so 8 4-34 COMMUNICATIONS PRODUCTS *INTEANAL 4006i1 PULL-UP RESISTOR ON EACH TTLICMOS INPUT *INTEANAL Skil PULL-OOWN RESISTOR ON EACH AS-232 INPUT Figure 14, AD236 Typical Operating Circuit REV. AANALOG DEVICES INC WEE D MM 08164600 0029706 9 MANA AD230-AD241 T3 our Tour T2our Rly Rlour T2my AD237 TOP VIEW (Not to Scale) ea Fal | Fa] | ral ral il ral Fal ra] T4 our R2iy R2 our T5in TS our Tay T3iy R3our R3in v- C2- a ae ' n REEPIPEIPIEELFIRIE 3] C2+ Figure 18, AD237 DIP/SOIC Pin Configuration op ae TTL/CMOS JJ T3ing INPUTS* TTL/GMOS | po 6V INPUT 1OpF 9 6.3V TO+i0V +#10VTO -10v V 10pF VOLTAGE INVERTER = ,16v \ TI Tout T2our |_AS-232 Tour F guTPUTS Taour TSaur / Rly |_ RS-232 Fw FP iInpuTs* Ray 7 INTERNAL 400kit PULL-UP RESISTOR ON EACH TYL/CMOS INPUT *INTERNAL SkSt PULL-DOWN RESISTOR ON EACH AS-232 INPUT Figure 16. AD237 Typical Operating Circuit T2our C4 ov Tout [2] R2iy [3] R2 our [a] Tw [5] Rlour [6] AD238 TOP VIEW Atw [7 ano [2 | Vee [2 C1+ [to] V+ [fr] ct fia] (Not to Scale) za] T3 our 23] R3in 23] R3our 24] T4y 20] T4our 9] T3iy 3] T2in 7] R4 our He] Ray 14] c2- 3] C2+ Figure 17, AD238 DIP/SOIC Pin Configuration REV. A OUTPUTS 4.7nF 63V 4.7pF 16V ( Tas Tis Trucmos | INPUTS Tis Thy \ / Rlour R2uur Tricmos _ | ouTPuTS R3our R4our' \ +5V INPUT +10V TO -16V VOLTAGE INVERTER 1 |_AS-232 OUTPUTS |_ AS-232 INPUTS** INTERNAL 40CkS? PULL-UP RESISTOR ON EACH TIL/CMOS INPUT SINTERNAL Skit PULL-OOWN RESISTOR ON EACH AS-232 INFUT Figure 18. A0238 Typical Operating Circuit COMMUNICATIONS PRODUCTS 4-35 T-75-45-05ANALOG DEVICES INC | AD230-AD241 Rlour oy Rly [Z| eno [3 | Vee [a] V+ [5] C+ [e oy i RS [3] R5 our [ro] R4our [11] Ray [12] AD239 TOP VIEW (Not to Scale) 24] Thing 23] T2y 22] R2our 21] R2iy 20] T2our 19] Tour Ha] Row 7] F3our 16] 13, 5] NC ia] ew 3] T3 our NC= NO CONNECT Figure 19. AD239 DIP/SOIC Pin Configuration 42E D MM 0416400 0029707 O MANA T-75-45-05 +12V510% +5V INPUT 1N914 OR v EQUIVALENT #12V TO =12V VOLTAGE INVERTER 100025% + 4.7pF 16 10yF Tetev \ Mout ( T TILICMOS | 12 RS-232 INPUTS* Tour F outputs \ T3isg T3our (tour 7 5 At Rn TTLICMOS : OUTPLTS R38 mien Rois NC INTERNAL 400k12 PULL-UP RESISTOR ON EACH TILICMOS INPUT *INTERNAL Sk{) PULL-OOWN RESISTOR ON EACH AS-232 INPUT Figure 20. AD239 Typical Operating Circuit Tour [7] Tour [2] T2our (3 Rly [a] R2our [5 T2in [6] Thy 7 Rlour [8] Btn [2] Go [ro] Vee [i] cts [i2| V+ fis] c1- [14] AD241 TOP VIEW (Not to Scale) 28) T4 oun 27] Rl 26] Rout fas] sp 24] EN 23] Ray 23] R4 our [21] Ty 20] T3iy 9] RS our 18] Sy 7] v- he] c2- 5] C2+ Figure 21, AD241 SOIC Pin Configuration 4-36 COMMUNICATIONS PRODUCTS +5V INPUT 2 fy ta +S Veo lal 1 Tlet- vocrace pousten * = ageroe ML voittenetter |e Sit" N\ 2 z r nu 4 . = 3s z j a \a7 \e/ \G7 w # i Trucmos _| L. RS-232 INPUTS 20 OUTPUTS 21 Tay 8 - Pour 7 e SL AD241 YX rs 2 = z / A r Bg TTL/CMOS _| 26]. 27 |_ AS-232 oututs | "ourt ad TFB INPUTS* Pour 22 256 2 Sour 9 set 18 es RS 7 EN 23 28 sp Sno Lio INTERNAL 400h5) PULL-UP RESISTOR ON EACH TTL/CMOS INFUT **INTERNAL Skit PULL-OOWN RESISTOR ON EACH RS-232 INFUT. Figure 22. AD241 Typical Operating Circuit REV. AANALOG DEVICES INC 4eE D mM 0416800 0029708 2 MANA AD230-AD241 V+ yv- GND C+ Cc- Cl+ cl- C2+ C2- Tin Rin Rour EN 8D PIN FUNCTION DESCRIPTION T-75-45-05 Mnemonic Function ; Veo Power Supply Input 5 V + 10% (AD231, AD232, AD234, AD236, AD238, AD239, AD241), 5 V+ 5% (AD233, AD235). Internally generated positive supply (+10 V nominal) on all parts except AD231 and AD239. AD231 requires external 7.5 V to 13,2 V supply; AD239 requires external 10.8 V to 13.2 V supply. Internally generated negative supply (~10 V nominal), Ground pin. Must be connected to 0 V. (AD231 and AD239 only). External capacitor (+ terminal) is connected to this pin. (AD231 and AD239 only). External capacitor ( terminal) is connected to this pin. (AD230, AD232, AD234, AD236, AD237, AD238, AD241) External capacitor (+ terminal) is connected to this pin. (AD233) The capacitor is connected internally and no external connection to this pin is required. (AD230, AD232, AD234, AD236, AD237, AD238, AD24}) External capacitor ( terminal) is connected to this pin, (AD233) The capacitor is connected internally and no external connection. to: this pin is required. (AD230, AD232, AD234, AD236, AD237, AD238, AD241) External capacitor (+ terminal) is connected to this pin. (AD233) Internal capacitor connections, Pins 11 and 15 must be connected together. (AD230, AD232, AD234, AD236, AD237, AD238, AD241) External capacitor ( terminal) is connected to this pin. (AD233) Internal capacitor connections, Pins 10 and 16 must be connected together. Transmitter (Driver) Inputs. These inputs accept TTL/CMOS levels. An internal 400 kQ. pull-up resistor to Veg is connected on each input. Transmitter (Driver) Outputs. These are RS-232 levels (typically +10 V). Receiver Inputs. These inputs accept RS-232 signal levels. An internal 5 kO pull-down resistor to GND is connected on each input. Receiver Outputs. These are TTL/CMOS levels. Enable Input (AD235, AD236, AD239, AD241), This is an active low input which is used to enable the receiver outputs. With EN = 0 V, the receiver outputs are enabled. With EN = 5 V, the outputs are placed in a high impedance state. This facility is useful for connecting to microprocessor systems. Shutdown Input. (AD230, AD235, AD236, AD241). With SD = 5 V, the charge pump is disabled, the receiver outputs are placed in a high impedance state and the driver outputs are turned off. The supply current reduces to <5 pA making these parts ideally suited for battery operation. No Connect. No connections are required to this pin, COMMUNICATIONS PRODUCTS 4~37ANALOG DEVICES INC AD230-AD241 GENERAL INFORMATION The AD230-AD241 family of RS-232 drivers/receivers are de- signed to solve interface problems by meeting the RS-232-C specifications while using a single digital +5 V supply. The RS- 232-C standard requires transmitters which will deliver +5 V minimum on the transmission channel and receivers which can accept signal levels down to 3 V. The AD230-AD241 meet these requirements by integrating step up voltage converters and level shifting transmitters and receivers onto the same chip. CMOS technology is used to keep the power dissipation to an absolute minimum. A comprehensive range of transmitter/ receiver combinations is available to cover most communications needs, The AD230, AD235, AD236 and AD241 are particularly useful in battery powered systems as they feature a low power shut- down mode which reduces power dissipation to less than 5 pW. The AD233 and AD235 are designed for applications where space saving is important as the charge pump capacitors are molded into the package. The AD231 and AD239 include only a negative charge pump converter and are intended for applications where a positive 12 V is available. To facilitate sharing a common line or for connection to a mi- croprocessor data bus the AD235, AD236, AD239 and AD241 feature an enable (EN) function. When disabled, the receiver outputs are placed in a high impedance state. CIRCUIT DESCRIPTION The internal circuitry in the AD230-AD241 consists of three main sections. These are: (a) A charge pump voltage converter (b) RS-232 to TTL/CMOS receivers (c) TTL/CMOS to RS-232 transmitters Charge Pump DC-DC Voltage Converter The charge pump voltage converter consists of an oscillator and a switching matrix. The converter generates a +10 V supply from the input 5 V level. This is done in two stages using a switched capacitor technique as illustrated in Figures 23 and 24. First, the 5 V input supply is doubled to 10 V using capacitor Cl as the charge storage element. The 10 V level is then in- verted to generate 10 V using C2 as the storage lement. INTERNAL , OSCILLATOR Figure 23. Charge-Pump Voltage Doubler 4-38 COMMUNICATIONS PRODUCTS 4eE D MM 04616800 0029705 4 MBANA si $3 Ve T=75-45-05 0-010 7 ofo-r_-0 GND. FROM t VOLTAGE DOUBLER 52 c2 $4 T a GNO OOo ) V-=- (V+) INTERNAL OSCILLATOR . Figure 24, Charge-Pump Voltage Inverter Capacitors C3 and C4 are used to reduce the output ripple. Their values are not critical and can be reduced if higher levels of ripple are acceptable. The charge pump capacitors Cl and C2 may also be reduced at the expense of higher output impedance on the V+ and V supplies. The V+ and V supplies may also be used to power external circuitry if the current requirements are small, Transmitter (Driver) Section The drivers convert TTL/CMOS input levels into RS-232-C out- put levels, With Veg = +5 V and driving a typical RS-232-C load, the output voltage swing is +9. V. Even under worst case conditions the drivers are guaranteed to meet the 5: V RS-232-C minimum requirement. The input threshold levels are both TTL and CMOS compatible with the switching threshold set at Voq/4. With a nominal Veo = 5 V the switching threshold is 1.25 V typical. Unused inputs may be left uriconnected, as an internal 400 kO pull-up resistor pulls them high forcing the outputs into a low state. As required by the RS-232-C standard, the slew rate is limited to less than 30 V/ps without the need for an external slew limit- ing capacitor and the output impedance in the power-off state is greater than 300 0. Receiver Section The receivers are inverting level shifters which accept RS-232-C input levels (+5 V to 15 V) and translate them into 5 V TTL/ CMOS levels. The inputs have internal 5 kQ pull-down resistors to ground and are also protected against overvoltages of up to +30 V. The guaranteed switching thresholds are 0.8 V minimum and 2.4 V maximum which are well within the +3 V RS-232 requirement. The low level threshold is deliberately positive as it ensures that an unconnected input will be interpreted as a low level, The receivers have Schmitt trigger inputs with a hysteresis level of 0,5 V. This ensures error-free reception for both noisy inputs and for inputs with slow transition times. Shutdown (SD) The AD230, AD235, AD236 and AD241 feature a control input which may be used to disable the part and reduce the power consumption to less than 5 .W. This is very useful in battery operated systems. With SD = 5 V, the charge pump is disabled, the receiver outputs are placed in a high impedance state and the driver outputs are turned off. REV. AANALOG DEVICES INC 4eE D MM 08164800 0029710 O MANA AD230-AD241 Enable Input The AD235, AD236, AD239 and AD241 feature an enable in- put (EN), It is used to enable the receiver outputs, With EN = 0 V the outputs are enabled. With EN = 5 V the outputs are placed in a high impedance state. This function allows the outputs to be connected directly to a microprocessor data bus. It can also be used to allow receivers from different devices to share a common data line. The timing diagram for the enable function is shown in Figure 25. av EN V ov ! t t J ' ' Tay Tos 5 < aoe el ae t Rour DATA VALID { Voit 0.1V Figure 26. Enable Timing APPLICATION HINTS Protection for Shorts to +15 V Supplies The driver outputs are internally protected against shorting to ground, to other driver outputs, to V+ or to V. In practice, these are the highest voltages likely to be encountered in an ap- plication. If the possibility exists for shorting to 15 V, then it is recommended that external protection be provided. This may be done by connecting a series 220 2 resistor on each transmit- ter output, 2202 Ty NWA Tour pp 2200 T2 > [>> anne T2 our AD230-AD241 Figure 26. Protection for Shorts to #15 V Over-Voltage Protection for AD231, AD239 The AD231 and AD239 require an external +12 V supply as they do not contain an internal V+ generator. It is important that this supply be switched on before the 5 V; Voc supply. REV. A If there is a possibility that the Vec supply will be switched on first, or if the 12 V supply may be inadvertently shorted to ground, then it is recommended that a diode (1N914 or equiva- lent) be connected in series with the 12 V input. This will not affect normal operation but it ensures that under fault condi- tions, the device will be protected. T~75-45-05 +5V +#12V 1N914 Ve Veo AD231 & AD239 Y 7 Figure 27. Diode Protection Scheme for AD231 and AD239 High Baud Rate Operation The RS-232-C standard requires that For Data and Timing interchange Circuits, the time for the signal to pass through the tran- sition region shall not exceed one millisecond or four percent of the nominal duration of the signal element on that interchange circuit, whichever is the lesser. With the maximum transtnission rate of 19.2 kbaud, this translates into a minimum slew rate of 3 Vis. The typical slew rate of the AD230-AD241 is 3 V/us under maximum loading conditions and therefore meets the standard. The V.28 standard is more stringent and requires a transition time which will not exceed three percent of the nominal signal duration. This translates into a slew rate of 4 Vi/us at the maxi- mum 19.2 kbaud rate. In practice, less than ideal slew rates will have negligible affect on the data transmission. The result is that the valid mark/space duration is slightly shorter than the opti- mum because the signal spends more time in the transition re- gion. The valid duration remains more than adequate for error- free reception even at maximum transmission rates and under worst case load conditions. Driving Long Cables In accordance with the RS-232-C standard, long cables are per- missible provided that the total load capacitance does not exceed 2500 pF. For longer cables which do exceed this, then it is pos- sible to trade off baud rate vs. cable length, Large load capaci- tances cause a reduction in slew rate, and hence the maximum transmission baud rate is decreased. The AD230-AD241 are designed so that the slew rate reduction with increasing load capacitance is minimized. For the receivers, it is important that a high level of noise im- munity be inbuilt so that slow rise and fall times do not cause multiple output transitions as the signal passes slowly through the transition region. The AD230-AD241 have 0.5 V of hystere- sis to. guard against this. This ensures that, even in noisy envi- ronments, error-free reception can be achieved, COMMUNICATIONS PRODUCTS 4-39