a FEATURES RS-232 and RS-422 on One Chip Single +5 V Supply 0.1 mF Capacitors Short Circuit Protection Excellent Noise Immunity Low Power BiCMOS Technology High Speed, Low Skew RS-422 Operation –408C to +858C Operations APPLICATIONS DTE-DCE Interface Packet Switching Local Area Networks Data Concentration Data Multiplexers Integrated Services Digital Network (ISDN) GENERAL DESCRIPTION The AD7306 line driver/receiver is a 5 V monolithic product which provides an interface between TTL signal levels and dual standard EIA RS-232/RS-422 signal levels. The part contains two RS-232 drivers, one RS-422 driver, one RS-232 receiver, and one receiver path which can be configured either as RS-232 or as RS-422. An internal charge pump voltage converter facilitates operation from a single +5 V power supply. The internal charge pump generates ± 10 V levels allowing RS-232 output levels to be developed without the need for external bipolar power supplies. A highly efficient charge pump design allows operation using non polarized, miniature 0.1 µF capacitors. This gives a considerable saving in printed circuit board space over conventional products which can use up to 10 µF capacitors. The charge pump output voltages may also be used to power external circuitry which requires dual supplies. +5 V Powered RS-232/RS-422 Transceiver AD7306 FUNCTIONAL BLOCK DIAGRAM V+ 1 24 V– C1+ 2 23 C2– C1– 3 22 C2+ R2 IN 4 21 R2 OUT T1OUT 5 20 T1IN T2OUT 6 19 T2IN VCC 7 18 GND 17 R1 OUT AD7306 SOIC TOP VIEW (Not to Scale) R1 IN (B) 8 R1 IN /R1 IN (A) 9 16 T3IN T3OUT (B) 10 15 232/422 SEL T3OUT (A) 11 14 GND NC 12 13 NC NC = NO CONNECT The RS-232 channels are suitable for communications rates up to 100 kHz and the RS-422 channels are suitable for high speed communications up to 5 MHz. The RS-422 transmitter complementary outputs are closely matched and feature low timing skew between the complementary outputs. This is often an essential requirement to meet tight system timing specifications. All inputs feature ESD protection, all driver outputs feature high source and sink current capability and are internally protected against short circuits on the outputs. An epitaxial layer is used to guard against latch-up. The part is available in a 24-lead SOIC and 24-pin plastic DIP package. REV. B Information furnished by Analog Devices is believed to be accurate and reliable. However, no responsibility is assumed by Analog Devices for its use, nor for any infringements of patents 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 Analog Devices. One Technology Way, P.O. Box 9106, Norwood, MA 02062-9106, U.S.A. Tel: 617/329-4700 Fax: 617/326-8703 AD7306–SPECIFICATIONS (VT CC MAX Parameter RS-232 DRIVER TTL Input Logic Low, VINL TTL Input Logic High, VINH Input Logic Current RS-232 High Level Output Voltage RS-232 Low Level Output Voltage Output Short Circuit Current Slew Rate Output Resistance (Powered Down) RS-232 RECEIVER Input Voltage Range RS-232 Input Threshold Low RS-232 Input Threshold High RS-232 Input Hysteresis RS-232 Input Resistance TTL Output Voltage Low, VOL TTL Output Voltage High, VOH RS-422 DRIVER TTL Input Logic Low, VINL TTL Input Logic High, VINH Logic Input Current Differential Output Voltage = +5 V 6 5%, C1 = C2 = C3 = C4 = 0.1 mF. All specifications TMIN to unless otherwise noted.) Min Typ 2.0 5.0 –5.0 ±5 8 300 –15 0.8 0.1 3 3.5 0.1 7.3 –6.5 ± 12 20 4 10M Max Units Test Conditions/Comments 0.8 V V µA V V mA V/µs V/µs Ω VIN = 0 V to VCC RL = 3 kΩ RL = 3 kΩ VOUT = 0 V, TA = 0°C to +70°C CL = 50 pF, RL = 3 kΩ CL = 2500 pF, RL = 3 kΩ VCC = 0 V, VOUT = ± 3 V V V V V kΩ V V IOUT = +4 mA IOUT = –4 mA ± 10 30 +15 1.3 1.7 0.4 5 0.2 4.8 2.4 1.0 7 0.4 0.8 2.0 0.1 ± 10 5.0 2 Common-Mode Output Voltage ∆|VOUT| for Complementary O/P States Output Short Circuit Current RS-422 RECEIVER Common-Mode Voltage Range Differential Input Threshold Voltage Input Voltage Hysteresis Input Resistance TTL Output Voltage Low, VOL TTL Output Voltage High, VOH 232/422 SEL Input Input Logic Low, VINL Input Logic High, VINH Logic Input Current 35 3 0.2 150 –0.2 ±7 +0.2 3 3.5 70 5 0.2 4.8 7 0.4 0.8 V V µA V V V V mA VIN = 0 V to VCC VCC = 5 V, RL Diff = ∞; Figure 3 RL Diff = 100 Ω; Figure 3 RL Diff = 100 Ω 0 V ≤ VCMR ≤ +7 V V V mV kΩ V V Typical RS-422 Input Voltage <5 V IOUT = +4.0 mA IOUT = –4.0 mA VIN = 0 V to VCC VCM = 0 V 0.1 ± 10 V V µA POWER SUPPLY CURRENT ICC 10 15 mA Outputs Unloaded CHARGE PUMP VOLTAGE GENERATOR V+ Output Voltage 9 V V– Output Voltage –9 V Generator Rise Time 200 µs RS-232 Output Unloaded; See Typical Performance Curves RS-232 Outputs Unloaded; See Typical Performance Curves 2.0 Specifications subject to change without notice. –2– REV. B AD7306 TIMING SPECIFICATIONS (VCC = +5 V 6 5%, C1 = C2 = C3 = C4 = 0.1 mF. All specifications TMIN to TMAX unless otherwise noted.) Parameter RS-422 Driver Propagation Delay Input to Output TPLH, TPHL RS-422 O/P to O/P TSKEW Driver Rise/Fall Time TR, TF RS-422 Receiver Propagation Delay Input to Output TPLH, TPHL RS-232/RS-422 Enable RS-232 Disable to RS-422 Enable TEN1 RS-422 Disable to RS-232 Enable TEN2 Transmission Rate (RS-422) RS-232 Receiver Propagation Delay Input to Output Transmission Rate (RS-232) Typ Max Units Test Conditions/Comments 35 2 15 100 10 40 ns ns ns RL Diff = 100 Ω. CL1 = CL2 = 100 pF, Figures 2 & 4 RL Diff = 100 Ω. CL1 = CL2 = 100 pF, Figures 2 & 4 RL Diff = 100 Ω. CL1 = CL2 = 100 pF, Figures 2 & 4 70 200 ns CL = 15 pF. Figure 5 70 70 5 200 200 ns ns MHz Figure 6 Figure 6 1000 100 20 ns kHz kHz CL = 50 pF CL = 2.5 nF Short Circuit Duration TOUT . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Continuous Power Dissipation Small Outline . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 650 mW DIP . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 650 mW Operating Temperature Range Commercial (J Version) . . . . . . . . . . . . . . . . . 0°C to +70°C Industrial (A Version) . . . . . . . . . . . . . . . . –40°C to +85°C Storage Temperature Range . . . . . . . . . . . . –65°C to +150°C Lead Temperature (Soldering, 10 secs) . . . . . . . . . . . +300°C ABSOLUTE MAXIMUM RATINGS* (TA = +25°C unless otherwise noted) VCC . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . +7 V V+ . . . . . . . . . . . . . . . . . . . . . . . . . . . (VCC –0.3 V) to +13.2 V V– . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . +0.3 V to –13.2 V Inputs T1IN, T2IN . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . V– to V+ T3IN . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . –0.3 V to V+ R1IN A/B, R2IN . . . . . . . . . . . . . . . . . . . . . . . –25 V to +25 V 232/422 SEL . . . . . . . . . . . . . . . . . . . . . . . . . . –0.3 V to V+ Outputs T1OUT, T2OUT . . . . . . . . . . . . . . . . . . . . . . . –15 V to +15 V T3OUT(A), (B) . . . . . . . . . . . . . . . . . . . . . . . –0.3 V to +7 V R1OUT, R2OUT . . . . . . . . . . . . . . . . –0.3 V to (VCC + 0.3 V) *Stresses above those listed under “Absolute Maximum Ratings” may cause permanent damage to the device. This is a stress rating only and functional operation of the device at these or any other conditions above those listed in the operational sections of this specification is not implied. Exposure to absolute maximum ratings for extended periods of time may affect device reliability. CAUTION ESD (electrostatic discharge) sensitive device. Electrostatic charges as high as 4000 V readily accumulate on the human body and test equipment and can discharge without detection. Although the AD7306 features proprietary ESD protection circuitry, permanent damage may occur on devices subjected to high energy electrostatic discharges. Therefore, proper ESD precautions are recommended to avoid performance degradation or loss of functionality. WARNING! ORDERING GUIDE REV. B Model Temperature Range Package Description Package Option AD7306JR AD7306JN AD7306AR AD7306AN 0°C to +70°C 0°C to +70°C –40°C to +85°C –40°C to +85°C R-24 N-24 R-24 N-24 24-Lead SOIC 24-Pin DIP 24-Lead SOIC 24-Pin DIP –3– ESD SENSITIVE DEVICE AD7306 PIN FUNCTION DESCRIPTION SOIC Pin DIP Pin Mnemonic Function 1 19 V+ 2, 3 4 5 6 7 8 9 20, 22 23 24 1 2 3 4 C1+, C1– R2IN T1OUT T2OUT VCC R1IN (B) R1IN/R1IN (A) 10 11 12, 13 14, 18 15 5 6 16, 21 7, 11 8 T3OUT (B) T3OUT (A) NC GND 232/422 SEL 16 17 19 20 21 22, 23 24 9 10 12 13 14 15, 17 18 T3IN R1OUT T2IN T1IN R2OUT C2+, C2– V– Internally Generated Positive Supply (+9 V nominal). A 0.1 µF capacitor must be connected between this pin and GND. External Capacitor 1 Terminals. A 0.1 µF capacitor must be connected between these pins. RS-232 Receiver R2 Input. This input accepts RS-232 input voltages. RS-232 Transmitter (Driver) T1 Output (Typically ± 7.5 V). RS-232 Transmitter (Driver) T2 Output (Typically ± 7.5 V). Power Supply Input (5 V ± 5%). RS-422 Receiver R1, Differential Input B. Receiver R1 Input. May be configured to accept either single ended RS-232 levels or differential RS-422 levels. It is configured using the 232/422 SEL pin. RS-422 Transmitter (Driver) T3, Differential Output B. RS-232 Transmitter (Driver) T3, Differential Output A. No Connect Pins. Ground Pin. Must be connected to 0 V. Select Input. This input configures Receiver R1 to accept either RS-232 or RS-422 signal levels. A Logic 1 on this input selects 232 operation while a Logic 0 selects 422 operation. TTL/CMOS Input to the RS-422 Transmitter T3. TTL/CMOS Output from Receiver R1. TTL/CMOS Input to RS-232 Transmitter T2. TTL/CMOS Input to RS-232 Transmitter T1. TTL/CMOS Output from Receiver R2. External Capacitor 2 Terminals. A 0.1 µF capacitor must be connected between these pins. Internally Generated Negative Supply (–9 V nominal). A 0.1 µF capacitor must be connected between this pin and GND. PIN CONFIGURATIONS SOIC DIP V+ 1 24 V– T2OUT 1 C1+ 2 23 C2– VCC 2 23 R2 IN C1– 3 22 C2+ R1 IN (B) 3 22 R2 IN 4 21 R2 OUT R1 IN /R1 IN (A) 4 21 NC T1OUT 5 20 T1IN T3OUT (B) 5 20 C1+ T2OUT 6 19 T2IN T3OUT (A) 6 19 V+ VCC 7 18 GND GND 7 18 V– R1 IN (B) 8 17 R1 OUT 232/422 SEL 8 17 C2– R1 IN /R1 IN (A) 9 16 T3IN T3IN 9 16 NC T3OUT (B) 10 15 232/422 SEL R1 OUT 10 15 C2+ T3OUT (A) 11 14 GND GND 11 14 R2 OUT NC 12 13 NC T2 IN 12 13 T1 IN AD7306 SOIC TOP VIEW (Not to Scale) NC = NO CONNECT 24 AD7306 DIP TOP VIEW (Not to Scale) T1OUT C1– NC = NO CONNECT –4– REV. B AD7306 3V +5V INPUT 0.1µF 1.5V 7 V CC 2 1 C1+ V+ ±10V C1– POWER 22 24 SUPPLY C2+ V– GENERATOR 23 C2– 0.1µF 20 T1 1/2 VO VO 0.1µF T3 OUT (B) t SKEW T1 OUT 19 TTL/CMOS INPUTS T3 OUT (A) 5 T1 IN 6 T2 T2 IN VO RS-232 OUTPUTS T2 OUT 10 16 T3 IN T3 11 t PHL t PLH 0.1µF 3 0.1µF 1.5V 0V 90% POINT 0V –VO RS-422 OUTPUT T3 OUT (B) t SKEW 90% POINT 10% POINT 10% POINT tR tF T3 OUT (A) Figure 4. RS-422 Driver. Propagation Delay Rise/Fall Timing AD7306 21 4 R2 R2 OUT TTL/CMOS OUTPUTS R2 IN R1 17 9 R1 OUT RS-232 INPUT RS-232/ R1IN /R1 IN (A) RS-422 INPUT 8 232/422 SEL R1 IN (B) 15 2.5V DIFFERENTIAL INPUT R1 IN (B) - R1 IN (A) RS-422 INPUT 0V 0V –2.5V t PHL 18 t PLH 14 VOH R1 OUT VOL Figure 1. AD7306 Application Circuit T3 OUT (B) Figure 5. RS-422 Receiver Timing C L1 = 100pF T3 IN RL DIFF = 100Ω T3 C L2 = 100pF 232/422 SEL 1.5V 1.5V T3 OUT (A) t EN1 Figure 2. RS-422 Driver. Propagation Delay Test Circuit RS-232 VOD T3 VOH VOH VOL VOL R1 OUT T3 OUT (B) T3 IN t EN2 RS-422 RS-232 RL DIFF Figure 6. RS-232/RS-422 Receiver Enable Timing T3 OUT (A) Figure 3. RS-422 Driver. Voltage Measurement Test Circuit REV. B –5– AD7306 GENERAL DESCRIPTION RS-232 Drivers The AD7306 drivers/receivers provide an interface which is compatible with RS-232/RS-422 standard interfaces. As both standards are widely accepted it is often necessary to provide an interface which is compatible with both. The AD7306 is ideally suited to this type of application as both standards may be met using a single package. This part contains two RS-232 drivers, one RS-422 driver, one RS-232 receiver, and one receiver path which can be configured as either RS-232 or RS-422. This receiver is configured using the 232/422 SEL pin. The RS-232 drivers in the AD7306 meet the EIA RS-232 specifications. The drivers are inverting level shifters which convert TTL/CMOS levels into RS-232 output levels. The input switching threshold is typically 1.3 V. With a typical RS-232 load, the output levels are ± 7.5 V. Under worst case load conditions, the drivers are guaranteed to provide ± 5 V which meets the minimum RS-232 requirement. The output slew rate is internally limited to <30 V/µs without the need for an external slew limiting capacitor. Short circuit protection is also provided which prevents damage in the event of output fault conditions. Active current limiting is used which limits the output short circuit current to less than 12 mA in the event of an output fault. This type of current limiting does not degrade the output voltage swing under normal loading conditions as would be the case with conventional passive limiting. This part also contains an internal charge pump voltage converter which facilitates operation using a single +5 V power supply. Charge Pump DC-DC Voltage Generator The charge pump voltage generator uses a switched capacitor technique to develop ± 10 V levels from an input +5 V supply. A highly efficient charge pump design coupled with a high frequency internal oscillator permit operation using four 0.1 µF capacitors. V+ +5V INPUT SUPPLY ±10V POWER SUPPLY GENERATOR VCC C3 0.1µF V– C1+ C1– C1 0.1µF C2+ C2– C4 0.1µF The powered-down output impedance is typically 10 MΩ. This is considerably larger than the 300 Ω minimum value required by the RS-232 specification. It provides additional protection under fault conditions where another powered-up transmitter output is inadvertently shorted to the powered-down device. +10V OUTPUT RS-232 Receivers The receivers are inverting level shifters which accept RS-232 input levels (± 3 V to ± 15 V) and translates them into 5 V TTL/CMOS levels. The input switching thresholds are 0.8 V minimum and 2.4 V maximum which are well within the RS-232 requirement of ± 3 V. Internal 5 kΩ pull-down resistors to GND are provided on the receiver inputs. This ensures that an unconnected input will be interpreted as a low level giving a Logic “1” on the TTL/CMOS output. Excellent noise immunity is achieved by the use of hysteresis and internal filtering circuitry. The filter rejects noise glitches of up to 0.5 µs in duration. –10V OUTPUT C2 0.1µF Figure 7. Charge Pump Voltage Generator Capacitors C1 and C2 act as charge storage capacitors while C3 and C4 provide output smoothing. For correct operation all four capacitors must be included. Either polarized or nonpolarized capacitors may be used for C1–C4. If a polarized type is used, then the correct polarity should be observed. This may be ignored with nonpolarized type capacitors. RS-422 Driver The RS-422 driver on the AD7306 accepts a TTL/CMOS input and translates it into a differential RS-422 level signal. The input switching threshold is typically 1.3 V. The unloaded output differential voltage is typically ± 5 V (see Typical Performance Characteristics). Short circuit protection is provided on the output which limits the current to less than 150 mA. The charge pump output voltages, V+ and V–, are used internally to power the RS-232 transmitters. This permits RS-232 output levels to be developed on the RS-232 transmitter outputs. The charge pump output voltages may also be used to power external circuitry if the current requirements are small. Please refer to the Typical Performance Characteristics. RS-422 Receiver The RS-422 receiver on the AD7306 accepts a differential input signal and translates it into a TTL/CMOS output level. The input resistance on both differential inputs is 5 kΩ typical. With the receiver inputs unconnected (floating), internal biasing ensures that the receiver output is a Logic “1.” The generator rise time after power up is 200 µs typical. This time is necessary to completely charge the storage capacitors in the charge pump. Therefore, RS-232 data transmission should not be initiated until this time has elapsed after switch on. This will ensure that valid data is always transmitted. Excellent noise immunity and high transmission speed is achieved using the differential configuration. –6– REV. B Typical Performance Characteristics–AD7306 10 RS-232 TRANSMITTER OUTPUT VOLTAGE – ±V 10 V+ VOLTAGE OUTPUT ± – V 8 V- 6 VCC = 5V T + 25 °C 4 2 0 +VE CURRENT 8 –VE CURRENT 6 4 2 0 5 0 10 15 20 25 30 0 2 4 6 8 RS-232 TRANSMITTER OUTPUT CURRENT – mA OUTPUT CURRENT ± – mA Figure 11. RS-232 Driver Output Voltage vs. Current Figure 8. V+ and V– Voltage vs. Current 6 25 DIFFERENTIAL O/P VOLTAGE – V +VE 20 SLEW RATE –V/µs –VE 15 10 5 VCC = 5.25V 5 4 VCC = 5.0V 3 VCC = 4.75V 2 1 0 0 500 0 1000 1500 2000 0 2500 10 A4 -0 370 V 100 100 90 90 10 10 0% 0% 5V 30 40 50 60 Figure 12. RS-422 Driver Output Current vs. Output Voltage Figure 9. RS-232 Driver Slew Rate vs. Load Capacitance 5V 20 DIFFERENTIAL O/P CURRENT – mA LOAD CAPACITANCE – pF 1µs A3 2 4V 1V 1V 5 10ns Figure 13. RS-422 Driver; RLDIFF = 100 Ω, CL1 = CL2 = 100 pF Figure 10. RS-232 Driver; RL = 5 kΩ, CL = 50 pF REV. B 10 –7– Single-Ended Data Transmission Differential Data Transmission Single-ended interfaces are used for low speed, short distance communications such as from a computer terminal to a printer. A single line is used to carry the signal. Various standards have been developed to standardize the communication link, the most popular of these being the RS-232. The RS-232 standard was introduced in 1962 by the EIA and has been widely used throughout the industry. The standard has been revised several times, and the current revision is known as EIA-232E. The RS-232 standard is suitable for single-ended data transmission at relatively slow data rates over short distances. A typical RS-232 interface is shown in Figure 14. When transmitting at high data rates, over long distances and through noisy environments, single-ended data transmission is often inadequate. In this type of application, differential data transmission offers superior performance. Differential transmission uses two signal lines to transmit data. It rejects ground shifts and is insensitive to noise signals which appear as common mode voltages on the transmission lines. To accommodate faster data communication, the differential RS-422 standard was developed. Therefore, it can be used to reliably transmit data at higher speeds and over longer distances than single-ended transmission. A typical RS-422 interface is shown in Figure 15. DATA IN DATA IN DATA OUT RX TX RS-422 CHANNEL TX C1624a–2–8/94 AD7306 DATA OUT RX RS-232 CHANNEL Figure 15. Differential RS-422 Interface Figure 14. Single-Ended RS-232 Interface Table I. Comparison of RS-232 and RS-422 Interface Standards Specification EIA-232E RS-422 Transmission Type Maximum Data Rate Maximum Cable Length Minimum Driver Output Voltage Slew Rate Receiver Input Resistance Receiver Input Sensitivity Receiver Input Voltage Range No. of Drivers per Line No. of Receivers per Line Single-Ended 20 kB/s Load Dependent ±5 V 30 V/µs max 3 kΩ to 7 kΩ ±3 V ± 15 V 1 1 Differential 10 MB/s 4000 ft. ± 1.5 V 4 kΩ min ± 200 mV ±7 V 1 10 OUTLINE DIMENSIONS Dimensions shown in inches and (mm). 24-Lead Pin Plastic DIP (N-24) 24-Lead SOIC (R-24) 0.6141 (15.60) 0.5985 (15.20) 0.260 ± 0.001 (6.61 ± 0.03) 12 PIN 1 0.0118 (0.30) 0.0040 (0.10) 0.1043 (2.65) 0.0926 (2.35) 0.0500 (1.27) BSC 0.32 (8.128) 0.30 (7.62) 1.228 (31.19) 1.226 (31.14) 0.130 (3.30) 0.128 (3.25) SEATING PLANE 0.0291 (0.74) x 45° 0.0098 (0.25) 8° 0.0192 (0.49) 0° SEATING 0.0125 (0.32) 0.0138 (0.35) PLANE 0.0091 (0.23) 0.011 (0.28) 0.009 (0.23) 0.02 (0.5) 0.016 (0.41) 0.0500 (1.27) 0.0157 (0.40) 0.11 (2.79) 0.09 (2.28) 0.07(1.78) 0.05 (1.27) 0° - 15° NOTES 1. LEAD NO. 1 IDENTIFIED BY DOT OR NOTCH. 2. PLASTIC LEADS WILL BE EITHER SOLDER DIPPED OR TIN LEAD PLATED IN ACCORDANCE WITH MIL-M-385 10 REQUIREMENTS. –8– REV. B PRINTED IN U.S.A. 1 0.4193 (10.65) 0.3937 (10.00) 13 0.2992 (7.60) 0.2914 (7.40) 24