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FEATURES RS-232 and RS-422 on One Chip Single +5 V Supply 0.1 F Capacitors Short Circuit Protection Excellent Noise Immunity Low Power BiCMOS Technology High Speed, Low Skew RS-422 Operation -40 C to +85 C Operations APPLICATIONS DTE-DCE Interface Packet Switching Local Area Networks Data Concentration Data Multiplexers Integrated Services Digital Network (ISDN) GENERAL DESCRIPTION
+5 V Powered RS-232/RS-422 Transceiver AD7306
FUNCTIONAL BLOCK DIAGRAM
V+ C1+ C1- R2 IN T1OUT T2OUT VCC R1 IN (B) R1 IN /R1 IN (A) T3OUT (B) T3OUT (A) NC 1 2 3 4 5 6 7 8 9 10 11 12 NC = NO CONNECT 24 23 22 21 20 V- C2- C2+ R2 OUT T1IN T2IN GND R1 OUT T3IN 232/422 SEL GND NC
AD7306 SOIC
TOP VIEW (Not to Scale)
19 18 17 16 15 14 13
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 F capacitors. This gives a considerable saving in printed circuit board space over conventional products which can use up to 10 F capacitors. The charge pump output voltages may also be used to power external circuitry which requires dual supplies.
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 (V T
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 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 POWER SUPPLY CURRENT ICC CHARGE PUMP VOLTAGE GENERATOR V+ Output Voltage V- Output Voltage Generator Rise Time
Specifications subject to change without notice.
CC
MAX
= +5 V 5%, C1 = C2 = C3 = C4 = 0.1 F. All specifications TMIN to unless otherwise noted.)
Typ Max 0.8 Units V V A V V mA V/s V/s V V V V k V V V V A V V V V mA V V mV k V V V V A mA V V s Test Conditions/Comments
Min
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
10
30
VIN = 0 V to VCC RL = 3 k RL = 3 k VOUT = 0 V, TA = 0C to +70C CL = 50 pF, RL = 3 k CL = 2500 pF, RL = 3 k VCC = 0 V, VOUT = 3 V
+15 1.3 1.7 0.4 5 0.2 4.8 2.4 1.0 7 0.4
IOUT = +4 mA IOUT = -4 mA
0.8 2.0 0.1 2 3 0.2 150 7 +0.2 70 5 0.2 4.8 7 0.4 10 5.0
VIN = 0 V to VCC VCC = 5 V, RL Diff = ; Figure 3 RL Diff = 100 ; Figure 3 RL Diff = 100 0 V VCMR +7 V Typical RS-422 Input Voltage <5 V VCM = 0 V IOUT = +4.0 mA IOUT = -4.0 mA
35
-0.2 3 3.5
0.8 2.0 0.1 10 9 -9 200 10 15
VIN = 0 V to VCC Outputs Unloaded RS-232 Output Unloaded; See Typical Performance Curves RS-232 Outputs Unloaded; See Typical Performance Curves
-2-
REV. B
AD7306 TIMING SPECIFICATIONS
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)
(VCC = +5 V 5%, C1 = C2 = C3 = C4 = 0.1 F. All specifications TMIN to TMAX unless otherwise noted.)
Typ 35 2 15 70 70 70 5 1000 100 20 Max 100 10 40 200 200 200 Units ns ns ns ns ns ns MHz ns kHz kHz Test Conditions/Comments RL Diff = 100 . CL1 = CL2 = 100 pF, Figures 2 & 4 RL Diff = 100 . CL1 = CL2 = 100 pF, Figures 2 & 4 RL Diff = 100 . CL1 = CL2 = 100 pF, Figures 2 & 4 CL = 15 pF. Figure 5 Figure 6 Figure 6
CL = 50 pF CL = 2.5 nF
ABSOLUTE MAXIMUM RATINGS*
(TA = +25C 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)
Short Circuit Duration TOUT . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Continuous Power Dissipation Small Outline . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 650 mW DIP . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 650 mW Operating Temperature Range Commercial (J Version) . . . . . . . . . . . . . . . . . 0C to +70C Industrial (A Version) . . . . . . . . . . . . . . . . -40C to +85C Storage Temperature Range . . . . . . . . . . . . -65C to +150C Lead Temperature (Soldering, 10 secs) . . . . . . . . . . . +300C
*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!
ESD SENSITIVE DEVICE
ORDERING GUIDE
Model AD7306JR AD7306JN AD7306AR AD7306AN
Temperature Range Package Description 0C to +70C 0C to +70C -40C to +85C -40C to +85C 24-Lead SOIC 24-Pin DIP 24-Lead SOIC 24-Pin DIP
Package Option R-24 N-24 R-24 N-24
REV. B
-3-
AD7306
PIN FUNCTION DESCRIPTION
SOIC Pin 1 2, 3 4 5 6 7 8 9 10 11 12, 13 14, 18 15 16 17 19 20 21 22, 23 24
DIP Pin 19 20, 22 23 24 1 2 3 4 5 6 16, 21 7, 11 8 9 10 12 13 14 15, 17 18
Mnemonic V+ C1+, C1- R2IN T1OUT T2OUT VCC R1IN (B) R1IN/R1IN (A) T3OUT (B) T3OUT (A) NC GND 232/422 SEL T3IN R1OUT T2IN T1IN R2OUT C2+, C2- V-
Function Internally Generated Positive Supply (+9 V nominal). A 0.1 F capacitor must be connected between this pin and GND. External Capacitor 1 Terminals. A 0.1 F 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 F capacitor must be connected between these pins. Internally Generated Negative Supply (-9 V nominal). A 0.1 F capacitor must be connected between this pin and GND.
PIN CONFIGURATIONS SOIC DIP
V+ C1+ C1- R2 IN T1OUT T2OUT VCC R1 IN (B) R1 IN /R1 IN (A) T3OUT (B) T3OUT (A) NC
1 2 3 4 5 6 7 8 9 10 11 12 NC = NO CONNECT
24 23 22 21 20
V- C2- C2+ R2 OUT T1IN T2IN GND R1 OUT T3IN 232/422 SEL GND NC
T2OUT VCC R1 IN (B) R1 IN /R1 IN (A) T3OUT (B) T3OUT (A) GND 232/422 SEL T3IN R1 OUT GND T2 IN
1 2 3 4 5 6 7 8 9 10 11 12 NC = NO CONNECT
24
T1OUT
23 R2 IN 22 C1-
21 NC 20 C1+ V+ V- C2- NC C2+ R2 OUT T1 IN
AD7306 SOIC
TOP VIEW (Not to Scale)
19 18 17 16 15 14 13
AD7306 DIP
TOP VIEW (Not to Scale)
19 18 17 16 15 14 13
-4-
REV. B
AD7306
+5V INPUT 0.1F
7 2
3V 1.5V 0V
1
1.5V
V CC C1+ 0.1F
T3 OUT (A) 1/2 VO
t PLH
VO T3 OUT (B)
t PHL
0.1F
0.1F
V+ 10V C1- POWER 22 24 SUPPLY C2+ V- GENERATOR 23 C2-
3 20 5
0.1F
t SKEW
T1 OUT
VO
t SKEW
90% POINT
T1 IN TTL/CMOS INPUTS
19
T1
6 10 16
T2 IN T3 IN
T2
T2 OUT
RS-232 OUTPUTS RS-422 OUTPUT
90% POINT
0V -VO
10% POINT 10% POINT
T3
11
T3 OUT (B) T3 OUT (A)
tR
tF
AD7306
21 4
R2 OUT TTL/CMOS OUTPUTS R1 OUT
17
R2 R1
R2 IN
9
RS-232 INPUT
Figure 4. RS-422 Driver. Propagation Delay Rise/Fall Timing
2.5V 0V -2.5V 0V
RS-232/ R1IN /R1 IN (A) RS-422 INPUT R1 IN (B) RS-422 INPUT
8
DIFFERENTIAL INPUT R1 IN (B) - R1 IN (A)
232/422 SEL
15
t PHL
18 14
t PLH
VOH
R1 OUT
Figure 1. AD7306 Application Circuit
T3 OUT (B) C L1 = 100pF T3 IN T3 RL DIFF = 100 C L2 = 100pF T3 OUT (A)
VOL
Figure 5. RS-422 Receiver Timing
232/422 SEL
1.5V
1.5V
t EN1
t EN2
VOH VOH VOL RS-422 RS-232
Figure 2. RS-422 Driver. Propagation Delay Test Circuit
T3 OUT (B)
R1 OUT VOL RS-232
VOD
T3 IN
T3
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. 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 F capacitors.
V+ +5V INPUT SUPPLY VCC 10V POWER SUPPLY GENERATOR V- C1+ C1- C2+ C2- C4 0.1F C3 0.1F +10V OUTPUT
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/s 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. The powered-down output impedance is typically 10 M. This is considerably larger than the 300 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.
RS-232 Receivers
-10V OUTPUT
C1 0.1F
C2 0.1F
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. 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. The generator rise time after power up is 200 s 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.
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 k 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 s in duration.
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.
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 k typical. With the receiver inputs unconnected (floating), internal biasing ensures that the receiver output is a Logic "1." Excellent noise immunity and high transmission speed is achieved using the differential configuration.
-6-
REV. B
Typical Performance Characteristics-AD7306
10 V+ 8 VOLTAGE OUTPUT - V VRS-232 TRANSMITTER OUTPUT VOLTAGE - V
10 +VE CURRENT 8
6
6
-VE CURRENT
4
VCC = 5V T + 25C
4
2
2
0 0 5 10 15 20 25 30 OUTPUT CURRENT - mA
0 0 2 4 6 8 RS-232 TRANSMITTER OUTPUT CURRENT - mA 10
Figure 8. V+ and V- Voltage vs. Current
25
Figure 11. RS-232 Driver Output Voltage vs. Current
6 VCC = 5.25V
20 -VE
SLEW RATE -V/s
DIFFERENTIAL O/P VOLTAGE - V
+VE
5
4 VCC = 5.0V 3 VCC = 4.75V
15
10
2
5
1
0 0
0 500 1000 1500 2000 2500 0 10 20 30 40 50 60 LOAD CAPACITANCE - pF DIFFERENTIAL O/P CURRENT - mA
Figure 9. RS-232 Driver Slew Rate vs. Load Capacitance
Figure 12. RS-422 Driver Output Current vs. Output Voltage
A4 -0 370 V
100 90 100 90
A3
2 4V
10 0%
10 0%
5V
5V
1s
1V
1V
5
10ns
Figure 10. RS-232 Driver; RL = 5 k, CL = 50 pF
Figure 13. RS-422 Driver; RLDIFF = 100 , CL1 = CL2 = 100 pF
REV. B
-7-
AD7306
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.
DATA IN TX RS-232 CHANNEL RX DATA OUT
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 TX RS-422 CHANNEL RX DATA OUT
Figure 14. Single-Ended RS-232 Interface
Figure 15. Differential RS-422 Interface
Table I. Comparison of RS-232 and RS-422 Interface Standards
Specification 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
EIA-232E Single-Ended 20 kB/s Load Dependent 5 V 30 V/s max 3 k to 7 k 3 V 15 V 1 1
OUTLINE DIMENSIONS
Dimensions shown in inches and (mm).
RS-422 Differential 10 MB/s 4000 ft. 1.5 V 4 k min 200 mV 7 V 1 10
24-Lead SOIC (R-24)
0.6141 (15.60) 0.5985 (15.20)
24 13
24-Lead Pin Plastic DIP (N-24)
0.260 0.001 (6.61 0.03)
0.4193 (10.65) 0.3937 (10.00)
0.2992 (7.60) 0.2914 (7.40)
1.228 (31.19) 1.226 (31.14) 0.130 (3.30) 0.128 (3.25) SEATING PLANE
0.32 (8.128) 0.30 (7.62)
1
12
PIN 1
0.1043 (2.65) 0.0926 (2.35)
0.0291 (0.74) x 45 0.0098 (0.25)
0.011 (0.28) 0.009 (0.23)
0.0118 (0.30) 0.0040 (0.10)
0.0500 (1.27) BSC
8 0.0192 (0.49) 0 SEATING 0.0125 (0.32) 0.0138 (0.35) PLANE 0.0091 (0.23)
0.0500 (1.27) 0.0157 (0.40)
0.02 (0.5) 0.016 (0.41)
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.
C1624a-2-8/94

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