Data Sheet
THEORY OF OPERATION
DIFFERENTIAL DATA TRANSMISSION
Differential data transmission is used to reliably transmit data at high rates over long distances and through noisy environments. Differential transmission nullifies the effects of ground shifts and noise signals that appear as common-mode voltages on the line. The two main standards approved by the EIA specify the electrical characteristics of transceivers used in differential data transmission: ?
RS-422 standard specifies data rates up to 10 MBaud andline lengths up to 4000 ft. A single driver can drive atransmission line with up to 10 receivers.
RS-485 standard was defined to cater to true multipointcommunications. This standard meets or exceeds all therequirements of RS-422, but also allows multiple driversand receivers to be connected to a single bus. An extendedcommon-mode range of ?7 V to +12 V is defined.
ADM3491-1
As with any transmission line, it is important that reflections be minimized. This can be achieved by terminating the extreme ends of the line using resistors equal to the characteristic impedance of the line. Stub lengths of the main line should also be kept as short as possible. A properly terminated transmission line appears purely resistive to the driver.
RECEIVER OPEN-CIRCUIT FAIL-SAFE FEATURE
The receiver input includes a fail-safe feature that guarantees a logic high on the receiver when the inputs are open circuit or floating.
3.3V0.1μF3.3V0.1μF?
REROVCCARBYZVCCDEDIDThe most significant differentiator of the RS-485 standard is that the drivers can be disabled, thereby allowing more than one to be connected to a single line. Only one driver should be enabled at a time, but the RS-485 standard contains additional specifications to guarantee device safety in the event of line contention.
Table 6. Comparison of RS-422 and RS-485 Interface Standards
Specification
Transmission Type
Maximum Cable Length
Minimum Driver Output Voltage Driver Load Impedance Receiver Input Resistance Receiver Input Sensitivity Receiver Input Voltage Range
RS-422 Differential 4000 ft. ±2 V 100 Ω 4 kΩ min ±200 mV ?7 V to +7 V
RS-485 Differential 4000 ft. ±1.5 V 54 Ω
12 kΩ min ±200 mV ?7 V to +12 V
ADM3491-1ZDIDYRS-485/RS-422 LINKBAADM3491-1RORREDEGNDGNDFigure 26. ADM3491-1 Full-Duplex Data Link
Table 7. Transmitting Truth Table REXX0 1InputsDE110 0DI10X XZOutputsY0110Hi-Z Hi-Z Hi-Z Hi-ZCABLE AND DATA RATE
The transmission line of choice for RS-485 communications is a
twisted pair. Twisted pair cable tends to cancel common-mode noise and also causes cancellation of the magnetic fields gener-ated by the current flowing through each wire, thereby reducing the effective inductance of the pair.
The ADM3491-1 is designed for bidirectional data communica-tions on multipoint transmission lines. A typical application showing a multipoint transmission network is illustrated in Figure 26. Only one driver can transmit at a particular time, but multiple receivers can be enabled simultaneously.
Table 8. Receiving Truth Table InputsRE000 1DEXXX XA–BOutputsRO≥ +0.2 V 0≤ ?0.2 V 0Inputs O/C 1 XHi-ZRev. C | Page 11 of 16
05234-026ADM3491-1 OUTLINE DIMENSIONS
0.775 (19.69)0.750 (19.05)0.735 (18.67)1418Data Sheet
70.280 (7.11)0.250 (6.35)0.240 (6.10)0.325 (8.26)0.310 (7.87)0.300 (7.62)0.060 (1.52)MAX0.015(0.38)MIN0.195 (4.95)0.130 (3.30)0.115 (2.92)PIN 10.100 (2.54)BSC0.210(5.33)MAX0.150 (3.81)0.130 (3.30)0.110 (2.79)0.022 (0.56)0.018 (0.46)0.014 (0.36)0.015 (0.38)GAUGEPLANESEATINGPLANE0.430 (10.92)MAX0.005 (0.13)MIN0.070 (1.78)0.050 (1.27)0.045 (1.14)0.014 (0.36)0.010 (0.25)0.008 (0.20)COMPLIANT TO JEDEC STANDARDS MS-001-AACONTROLLING DIMENSIONS ARE IN INCHES; MILLIMETER DIMENSIONS(IN PARENTHESES) ARE ROUNDED-OFF INCH EQUIVALENTS FORREFERENCE ONLY AND ARE NOT APPROPRIATE FOR USE IN DESIGN.CORNER LEADS MAY BE CONFIGURED AS WHOLE OR HALF LEADS.Figure 27. 14-Lead Plastic Dual In-Line Package [PDIP]
Narrow Body (N-14)
Dimensions shown in inches and (millimeters)
8.75 (0.3445)8.55 (0.3366)4.00 (0.1575)3.80 (0.1496)141876.20 (0.2441)5.80 (0.2283)0.25 (0.0098)0.10 (0.0039)COPLANARITY0.101.27 (0.0500)BSC1.75 (0.0689)1.35 (0.0531)0.50 (0.0197)? 45°0.25 (0.0098)0.51 (0.0201)0.31 (0.0122)SEATINGPLANE8°0.25 (0.0098)0°1.27 (0.0500)0.40 (0.0157)0.17 (0.0067)COMPLIANT TO JEDEC STANDARDS MS-012-ABCONTROLLING DIMENSIONS ARE IN MILLIMETERS; INCH DIMENSIONS(IN PARENTHESES) ARE ROUNDED-OFF MILLIMETER EQUIVALENTS FORREFERENCE ONLY AND ARE NOT APPROPRIATE FOR USE IN DESIGN.Figure 28. 14-Lead Standard Small Outline Package [SOIC_N]
Narrow Body (R-14)
Dimensions shown in millimeters and (inches)
5.105.004.901694.504.404.30186.40BSCPIN 10.150.050.65BSC0.300.19COPLANARITY0.101.20MAX0.200.09SEATINGPLANE8°0°0.750.600.45COMPLIANT TO JEDEC STANDARDS MO-153-ABFigure 29. 16-Lead Thin Shrink Small Outline Package [TSSOP]
(RU-16)
Dimensions shown in millimeters
Rev. C | Page 12 of 16
ADM3491-1
PIN CONFIGURATIONS AND FUNCTION DESCRIPTIONS
VCC1NC23456781615Data Sheet
NCABNCZYNC05234-003NC1RO2RE3DE4DI5GND6GND71413VCCVCCABZY05234-002ROREDEDINCGNDADM3491-1TOP VIEW(Not to Scale)14131211109ADM3491-1TOP VIEW(Not to Scale)12111098NCNCNC = NO CONNECTNC = NO CONNECTFigure 2. 14-Lead PDIP and 14-Lead SOIC Pin Configuration
Figure 3. 16-Lead TSSOP Pin Configuration
Table 5. Pin Function Descriptions Pin Number Mnemonic PDIP/SOIC TSSOP 1, 8 2, 7, 9, 10, 13, 16 NC 2 3 4 5 6, 7 9 10 11 12 13, 14 3 4 5 6 8 11 12 14 15 1 RO RE DE DI GND Y Z B A VCC Description No Connect. Receiver Output. High when A > B by 200 mV; low when A < B by 200 mV. Receiver Output Enable. When RE is low, the receiver output RO is enabled. When RE is high, the output is high impedance. If RE is high and DE is low, the ADM3491-1 enters a shutdown state. Driver Output Enable. A high level enables the driver differential outputs, Y and Z. A low level places the part in a high impedance state. Driver Input. When the driver is enabled, a logic low on DI forces Y low and Z high; a logic high on DI forces Y high and Z low. Ground Connection, 0 V. Noninverting Driver Output Y. Inverting Driver Output Z. Inverting Receiver Input B. Noninverting Receiver Input A. Power Supply, 3.3 V ± 0.3 V. Rev. C | Page 6 of 16
Data Sheet
TYPICAL PERFORMANCE CHARACTERISTICS
14121412ADM3491-1
OUTPUT CURRENT (mA)OUTPUT CURRENT (mA)1086420108642005234-01600.511.522.533.500.511.522.533.54OUTPUT VOLTAGE (V)OUTPUT HIGH VOLTAGE (V)Figure 4. Output Current vs. Receiver Output Low Voltage
0.80.70.60.50.40.30.2IRO = 2.5mAFigure 7. Output Current vs. Receiver Output High Voltage
3.33.25OUTPUT VOLTAGE (V)OUTPUT VOLTAGE (V)3.2IRO = –1.5mA3.153.13.0505234-01705234-0200.10–40–200204060801003–40–20020406080100TEMPERATURE (°C)TEMPERATURE (°C)Figure 5. Receiver Output Low Voltage vs. Temperature
120Figure 8. Receiver Output High Voltage vs. Temperature
2.62.51002.4OUTPUT CURRENT (mA)OUTPUT VOLTAGE (V)802.32.22.12.01.91.8604005234-0181.71.6–40–20020406080000.511.52DIFFERENTIAL O/P VOLTAGE (V)2.53100TEMPERATURE (°C)Figure 6. Output Current vs. Driver Differential Output Voltage
Figure 9. Driver Differential Output Voltage vs. Temperature
Rev. C | Page 7 of 16
05234-0212005234-019Data Sheet
ORDERING GUIDE
Model1
ADM3491ANZ-1 ADM3491AR-1 ADM3491ARZ-1 ADM3491ARZ-1REEL ADM3491ARZ-1REEL7 ADM3491ARU-1 ADM3491ARU-1REEL ADM3491ARUZ-1 ADM3491ARUZ-1REEL ADM3491ARUZ-1REEL7
1
ADM3491-1
Package
Option Ordering Quantity N-14 R-14 R-14 R-14 2,500 R-14 1,000 RU-16 RU-16 2,500 RU-16 RU-16 2,500 RU-16 1,000
Temperature Range Package Description
?40°C to +85°C 14-Lead Plastic DIP ?40°C to +85°C 14-Lead Narrow Body Small Outline [SOIC]?40°C to +85°C 14-Lead Narrow Body Small Outline [SOIC]?40°C to +85°C 14-Lead Narrow Body Small Outline [SOIC]?40°C to +85°C 14-Lead Narrow Body Small Outline [SOIC]?40°C to +85°C 16-Lead Thin Shrink Small Outline [TSSOP] ?40°C to +85°C 16-Lead Thin Shrink Small Outline [TSSOP] ?40°C to +85°C 16-Lead Thin Shrink Small Outline [TSSOP] ?40°C to +85°C 16-Lead Thin Shrink Small Outline [TSSOP] ?40°C to +85°C 16-Lead Thin Shrink Small Outline [TSSOP]
Z = RoHS Compliant Part.
Rev. C | Page 13 of 16
MEMORY存储芯片ADM3485ARZ-REEL7中文规格书 - 图文
