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19-0367; Rev 0; 2/95
20A, 18-Unit-Load, Slew-Rate-Limited RS-485 Transceivers
_______________General Description
The MAX1482 and MAX1483 are low-power transceivers for RS-485 and RS-422 communication. Both feature slew-rate-limited drivers that minimize EMI and reduce reflections caused by improperly terminated cables. Data rates are guaranteed up to 250kbps. The MAX1482/MAX1483 draw only 20A of supply current. Additionally, they have a low-current shutdown mode that consumes only 0.1A. Both parts operate from a single +5V supply. Drivers are short-circuit current limited and are protected against excessive power dissipation by thermal shutdown circuitry that places the driver outputs into a high-impedance state. The receiver input has a fail-safe feature that guarantees a logic-high output if the input is open circuit. The MAX1482 is full duplex and the MAX1483 is half duplex. Both parts have a 18-unit-load input impedance that guarantees up to 256 transceivers on the bus.
____________________________Features
o Low 20A Operating Current o Slew-Rate Limited for Reduced EMI and Reduced Reflections o 0.1A Low-Current Shutdown Mode o Designed for RS-485 and RS-422 Applications o Operate from a Single +5V Supply o -7V to +12V Common-Mode Input Voltage Range o Allows up to 256 Transceivers on the Bus-- Guaranteed (18-unit load) o Current Limiting and Thermal Shutdown for Driver Overload Protection
MAX1482/MAX1483
______________Ordering Information
PART MAX1482CPD MAX1482CSD MAX1482EPD MAX1482ESD MAX1483CPA MAX1483CSA MAX1483CUA MAX1483EPA MAX1483ESA TEMP. RANGE 0C to +70C 0C to +70C -40C to +85C -40C to +85C 0C to +70C 0C to +70C 0C to +70C -40C to +85C -40C to +85C PIN-PACKAGE 14 Plastic DIP 14 SO 14 Plastic DIP 14 SO 8 Plastic DIP 8 SO 8 MAX 8 Plastic DIP 8 SO
________________________Applications
Low-Power RS-485/RS-422 Networks Transceivers for EMI-Sensitive Applications Industrial-Control Local Area Networks Large 256-Node LANs
_________Typical Operating Circuits
_________________Pin Configurations
TOP VIEW
RO 1 R 8 7 6 D 5 VCC B A GND
+5V
DE
MAX1483
RO 1 R RE 2 DE 3 DI 4 D 8 7B Rt 6 A 5 GND A R RE VCC B Rt D
RE 2
DI
DE 3 DI 4
RO
DIP/SO
B VCC 1 2 3 8 A GND DI DE
MAX1483
7 6 5
NOTE: PIN LABELS Y AND Z ON TIMING, TEST, AND WAVEFORM DIAGRAMS REFER TO PINS A AND B WHEN DE IS HIGH. TYPICAL OPERATING CIRCUIT SHOWN WITH DIP/SO PACKAGE.
RO
RE 4
MAX
MAX1482 appears at end of data sheet.
MAX1482 appears at end of data sheet.
1
________________________________________________________________ Maxim Integrated Products
Call toll free 1-800-998-8800 for free samples or literature.
20A, 18-Unit-Load, Slew-Rate-Limited RS-485 Transceivers MAX1482/MAX1483
ABSOLUTE MAXIMUM RATINGS
Supply Voltage (VCC) ...............................................................7V Control Input Voltages (RE, DE) .................-0.5V to (VCC + 0.5V) Driver Input Voltage (DI).............................-0.5V to (VCC + 0.5V) Driver Output Voltages ..........................................-7.5V to 12.5V Receiver Input Voltages (A, B) ..............................-7.5V to 12.5V Receiver Output Voltage (RO)....................-0.5V to (VCC + 0.5V) Continuous Power Dissipation (TA = +70C) 8-Pin Plastic DIP (derate 9.09mW/C above +70C) .....727mW 14-Pin Plastic DIP (derate 10.00mW/C above +70C) .800mW 8-Pin SO (derate 5.88mW/C above +70C)..................471mW 14-Pin SO (derate 8.33mW/C above +70C)................667mW 8-Pin MAX (derate 4.10mW/C above +70C) .............330mW Operating Temperature Ranges MAX148_C_ _ .......................................................0C to +70C MAX148_E_ _.....................................................-40C to +85C Storage Temperature Range .............................-65C to +160C Lead Temperature (soldering, 10sec) .............................+300C
Stresses beyond those listed under "Absolute Maximum Ratings" may cause permanent damage to the device. These are stress ratings only, and functional operation of the device at these or any other conditions beyond those indicated in the operational sections of the specifications is not implied. Exposure to absolute maximum rating conditions for extended periods may affect device reliability.
DC ELECTRICAL CHARACTERISTICS
(VCC = 5V 5%, TA = TMIN to TMAX, unless otherwise noted. Typical values are at TA = +25C.) (Note 1) PARAMETER Differential Driver Output (no load) Differential Driver Output (with load) Change in Magnitude of Driver Differential Output Voltage for Complementary Output States Driver Common-Mode Output Voltage Change in Magnitude of Driver Common-Mode Output Voltage for Complementary Output States Three-State (high impedance) Output Current at Driver Logic Input High Voltage Logic Input Low Voltage Logic Input Current Input Current (A, B) Receiver Differential Threshold Voltage Receiver Input Hysteresis Receiver Output High Voltage Receiver Output Low Voltage Three-State (high impedance) Output Current at Receiver Receiver Input Resistance SYMBOL VOD1 VOD2 VOD VOC VOD R = 50 (RS-422), Figure 1 R = 27 (RS-485), Figure 1 R = 27 or 50, Figure 1 R = 27 or 50, Figure 1 R = 27 or 50, Figure 1 MAX1482 only, -7V < VY and VZ < 12V -- -- DE, DI, RE -- -- DE, DI, RE -- -- DE, DI, RE MAX1482, DE = 0V, VCC = 0V or 5.25V MAX1483, DE = 0V, VCC = 0V or 5.25V -7V VCM 12V VCM = 0V IO = -4mA, VID = 200mV IO = 4mA, VID = -200mV 0.4V VO 2.4V -7V VCM 12V 96 3.5 0.4 1 VIN = 12V VIN = -7V VIN = 12V VIN = -7V -0.2 75 2 1.5 CONDITIONS MIN TYP MAX 5 5 5 0.2 3 0.2 UNITS V V
V V V
IOZD VIH VIL IIN1
50 2.0 0.8 2 150 -100 200 -150 0.2
A V V A
IIN2
A
VTH VTH VOH VOL IOZR RIN
V mV V V A k
Note 1: All currents into device pins are positive; all currents out of device pins are negative. All voltages are referenced to device ground unless otherwise specified.
2
_______________________________________________________________________________________
20A, 18-Unit-Load, Slew-Rate-Limited RS-485 Transceivers
DC ELECTRICAL CHARACTERISTICS (continued)
(VCC = 5V 5%, TA = TMIN to TMAX, unless otherwise noted. Typical values are at TA = +25C.) (Note 1) PARAMETER SYMBOL MAX1482, RE = 0V or VCC MAX1483, RE = 0V or VCC DE = 0V, RE = VCC DI = high or low, -7V VO 12V (Note 2) 0V VO VCC 35 7 CONDITIONS DE = VCC DE = 0V DE = VCC DE = 0V MIN TYP 25 20 55 20 0.1 MAX 45 35 85 35 10 250 95 A mA mA A UNITS
MAX1482/MAX1483
No-Load Supply Current
ICC
Supply Current in Shutdown Driver Short-Circuit Current Receiver Short-Circuit Current
ISHDN IOSD IOSR
SWITCHING CHARACTERISTICS
(VCC = 5V 5%, TA = TMIN to TMAX, unless otherwise noted. Typical values are at TA = +25C.) (Note 1) PARAMETER Driver Input to Output Driver Output Skew to Output Driver Rise or Fall Time Driver Enable to Output High Driver Enable to Output Low Driver Disable Time from Low Driver Disable Time from High Receiver Input to Output SYMBOL tPLH tPHL tSKEW tR, tF tZH tZL tLZ tHZ tPLH, tPHL tSKD tZL tZH tLZ tHZ fMAX tSHDN CONDITIONS Figures 3 and 5, RDIFF = 54, CL1 = CL2 = 100pF Figures 3 and 5, RDIFF = 54, CL1 = CL2 = 100pF Figures 3 and 5, RDIFF = 54, CL1 = CL2 = 100pF Figures 4 and 6, CL = 100pF, S2 closed Figures 4 and 6, CL = 100pF, S1 closed Figures 4 and 6, CL = 15pF, S1 closed Figures 4 and 6, CL = 15pF, S2 closed Figures 3 and 7, RDIFF = 54, CL1 = CL2 = 100pF Figures 3 and 7, RDIFF = 54, CL1 = CL2 = 100pF Figures 2 and 8, CRL = 15pF, S1 closed Figures 2 and 8, CRL = 15pF, S2 closed Figures 2 and 8, CRL = 15pF, S1 closed Figures 2 and 8, CRL = 15pF, S2 closed (Note 3) 250 50 200 0.25 0.2 0.1 0.3 0.3 0.25 160 90 90 90 90 600 2 2 3 3 MIN TYP MAX 2 2 800 2 2 2 3.0 3.0 2.25 UNITS s ns s s s s s s ns ns ns ns ns kbps ns s s s s
| tPLH - tPHL | Differential
Receiver Skew Receiver Enable to Output Low Receiver Enable to Output High Receiver Disable Time from Low Receiver Disable Time from High Maximum Data Rate Time to Shutdown
Driver Enable from Shutdown to tZH(SHDN) Figures 4 and 6, CL = 100pF, S2 closed Output High Driver Enable from Shutdown to tZL(SHDN) Output Low Figures 4 and 6, CL = 100pF, S1 closed
Receiver Enable from Shutdown Figures 2 and 8, CL = 15pF, S2 closed, tZH(SHDN) to Output High A - B = 2V Receiver Enable from Shutdown tZL(SHDN) to Output Low Figures 2 and 8, CL = 15pF, S1 closed, B - A = 2V
Note 2: Applies to peak current. See Typical Operating Characteristics. -- -- Note 3: The MAX1482/MAX1483 are put into shutdown by bringing RE high and DE low. If the inputs are in this state for less than 50ns, the parts are guaranteed not to enter shutdown. If the inputs are in this state for at least 600ns, the parts are guaranteed to have entered shutdown. See Low-Power Shutdown Mode section.
_______________________________________________________________________________________
3
20A, 18-Unit-Load, Slew-Rate-Limited RS-485 Transceivers MAX1482/MAX1483
__________________________________________Typical Operating Characteristics
(TA = +25C, unless otherwise noted.)
RECEIVER PROPAGATION DELAY vs. TEMPERATURE
MAX1482-01
DRIVER PROPAGATION DELAY vs. TEMPERATURE
MAX1482-02
DRIVER OUTPUT CURRENT vs. DIFFERENTIAL OUTPUT VOLTAGE
80 OUTPUT CURRENT (mA) 70 60 50 40 30 20 10 0
MAX1482-03
1400 RECEIVER PROPAGATION DELAY (ns) 1300 1200 1100 1000 900 800 -40 -20 0 20 40 60 80
1200 DRIVER PROPAGATION DELAY (ns) 1100 1000 900 800 700 600 500 400 -40 -20 0 20 40 60 80
90
100
100
0.5 1.0 1.5 2.0 2.5 3.0 3.5 4.0 4.5 5.0 OUTPUT VOLTAGE (V)
TEMPERATURE (C)
TEMPERATURE (C)
DRIVER DIFFERENTIAL OUTPUT VOLTAGE vs. TEMPERATURE
DIFFERENTIAL OUTPUT VOLTAGE (V) R = 54 3.0
MAX1482-04
OUTPUT CURRENT vs. DRIVER OUTPUT LOW VOLTAGE
MAX1482-05
OUTPUT CURRENT vs. DRIVER OUTPUT HIGH VOLTAGE
MAX1482-06
3.5
140 120 OUTPUT CURRENT (mA) 100 80 60 40 20
120 100 OUTPUT CURRENT (mA) 80 60 40 20 0
2.5
2.0
1.5 -40 -20 0 20 40 60 80 100 TEMPERATURE (C)
0 0 2 4 6 8 10 12 OUTPUT LOW VOLTAGE (V)
-7 -6 -5 -4 -3 -2 -1 0
12
34
5
OUTPUT LOW VOLTAGE (V)
MAX1482 SUPPLY CURRENT vs. TEMPERATURE
MAX1482-07
MAX1483 SUPPLY CURRENT vs. TEMPERATURE
70 SUPPLY CURRENT (A) 60 50 40 30 20 10 0 DE = GND DE = VCC
MAX1482-08
80 70 SUPPLY CURRENT (A) 60 50 40 30 20 10 0 -40 -20 0 20 40 60 80 DE = VCC DE = 0V
80
100
-40
-20
0
20
40
60
80
100
TEMPERATURE (C)
TEMPERATURE (C)
4
_______________________________________________________________________________________
20A, 18-Unit-Load, Slew-Rate-Limited RS-485 Transceivers
______________________________________________________________Pin Description
PIN MAX1482 DIP/SO 2 MAX1483 DIP/SO MAX 1 3 NAME FUNCTION Receiver Output. With the receiver output enabled (RE low), RO is high if A > B by 200mV or when A and B are not connected, and RO is low if A < B by 200mV. Receiver Output Enable. When RE is low, RO is enabled. When RE is high, RO is high impedance. If RE is high and DE is low, the MAX1482/MAX1483 enter a low-power (0.1A) shutdown state. Driver Output Enable. The driver outputs, A and B, (Y and Z for the MAX1482) are enabled by bringing DE high. When DE is low, the driver outputs are high impedance, and the devices can function as line receivers if RE is low. If RE is high and DE is low, the parts will enter a low-power (0.1A) shutdown state. If the driver outputs are enabled, the devices function as line drivers. Driver Input. With DE high, a low on DI forces output Y low and output Z high, and a high on DI forces output Y high and output Z low. Ground Noninverting Driver Output Inverting Driver Output Noninverting Receiver Input and Noninverting Driver Output Noninverting Receiver Input Inverting Receiver Input and Inverting Driver Output Inverting Receiver Input Positive Supply: 4.75V to 5.25V No Connect--not internally connected
MAX1482/MAX1483
RO
3
2
4
RE
4
3
5
DE
5 6, 7 9 10 -- 12 -- 11 14 1, 8, 13
4 5 -- -- 6 -- 7 -- 8 --
6 7 -- -- 8 -- 1 -- 2 --
DI GND Y Z A A B B VCC N.C.
_______________________________________________________________________________________
5
20A, 18-Unit-Load, Slew-Rate-Limited RS-485 Transceivers MAX1482/MAX1483
_________________________________________________________________Test Circuits
Y R VOD R Z VOC S2 TEST POINT RECEIVER OUTPUT CRL 15pF 1k VCC S1 1k
Figure 1. Driver DC Test Load
Figure 2. Receiver Timing Test Load
3V DE DI Y VID Z
CL1 RDIFF
A RO B RE 500 OUTPUT UNDER TEST CL S2 S1
VCC
CL2
Figure 3. Driver/Receiver Timing Test Circuit
Figure 4. Driver Timing Test Load
6
_______________________________________________________________________________________
20A, 18-Unit-Load, Slew-Rate-Limited RS-485 Transceivers
_______________________________________________________Switching Waveforms
MAX1482/MAX1483
3V DI 0V 1.5V tPLH tPHL 1.5V 1/2 VO
3V DE 0V tZL(SHDN), tZL tLZ VOL + 0.5V 1.5V 1.5V
Z VO Y 1/2 VO VO VDIFF 0V -VO 10% tR tSKEW = | tPLH - tPHL | VDIFF = V (Y) - V (Z) 90% 90% tF 10%
Y, Z VOL Y, Z 2.3V 0V tZH(SHDN), tZH tHZ 2.3V OUTPUT NORMALLY LOW OUTPUT NORMALLY HIGH VOH - 0.5V
Figure 5. Driver Propagation Delays
Figure 6. Driver Enable and Disable Times
3V RE 0V RO VOH VOL VID -VID 0V 1.5V tPHL INPUT OUTPUT tPLH 0V OUTPUT NORMALLY HIGH RO 0V tZH(SHDN), tZH tHZ 1.5V VOH - 0.5V 1.5V tZL(SHDN), tZL VCC RO tLZ VOL + 0.5V 1.5V 1.5V
1.5V OUTPUT NORMALLY LOW
A-B
Figure 7. Receiver Propagation Delays
Figure 8. Receiver Enable and Disable Times
_______________________________________________________________________________________
7
20A, 18-Unit-Load, Slew-Rate-Limited RS-485 Transceivers MAX1482/MAX1483
100pF Z TTL IN tR, tF < 6ns D Y 10dB/div 100pF R = 54 A B R RECEIVER OUT
0Hz
500kHz/div
5MHz
Figure 9. Driver Output Waveform and FFT, Transmitting 250kbps (125kHz) Signal
Figure 10. Receiver Propagation-Delay Test Circuit
Table 1. Transmitting
INPUTS RE X X X DE 1 1 0 DI 1 0 X Z 0 1 High-Z OUTPUTS Y 1 0 High-Z
Table 2. Receiving
INPUTS RE 0 0 0 1 DE* 0 0 0 0 A-B > +0.2V < -0.2V Inputs open X OUTPUT RO 1 0 1 High-Z
X = Don't Care High-Z = High Impedance
X = Don't Care High-Z = High Impedance * DE = 0 for MAX1483 and is a Don't Care for MAX1482.
__________Applications Information
The MAX1482/MAX1483 are low-power transceivers for RS-485 and RS-422 communications. The MAX1482 and MAX1483 are specified for data rates of at least 250kbps. The MAX1482 is a full-duplex transceiver while the MAX1483 is half duplex. When disabled, the driver and receiver outputs are high impedance. The 96k, 1/8-unit-load receiver input impedance of the MAX1482/MAX1483 allows up to 256 transceivers on a bus, compared to the 1-unit load (12k input impedance) of standard RS-485 drivers (32 transceivers maximum). Any combination of MAX1482/MAX1483 and other RS-485 transceivers with a total of 32 unit loads or less can be put on the bus.
Reduced EMI and Reflections
The MAX1482/MAX1483 are slew-rate limited, minimizing EMI and reducing reflections caused by improperly terminated cables. Figure 9 shows both the driver output waveform of a MAX1482/MAX1483 transmitting a 125kHz signal and the Fourier analysis of that signal. High-frequency harmonics have much lower amplitudes, and the potential for EMI is significantly reduced.
8
_______________________________________________________________________________________
20A, 18-Unit-Load, Slew-Rate-Limited RS-485 Transceivers MAX1482/MAX1483
A
B
500mV/div
500mV/div
B RO 5V/div
A 5V/div RO
500ns/div
500ns/div
Figure 11. Receiver tPHL
Figure 12. Receiver tPLH
Low-Power Shutdown Mode
A low-power shutdown mode is initiated by bringing RE high and DE low. The devices will not shut down unless both the driver and receiver are disabled. In shutdown, the devices typically draw only 0.1A of supply current. RE and DE may be driven simultaneously; the parts are guaranteed not to enter shutdown if RE is high and DE is low for less than 50ns. If the inputs are in this state for at least 600ns, the parts are guaranteed to enter shutdown. For the receiver, the tZH and tZL enable times assume the part was not in the low-power shutdown state. The t ZH(SHDN) and t ZL(SHDN) enable times assume the parts were shut down (see Electrical Characteristics). It takes the receivers longer to become enabled from the low-power shutdown state (tZH(SHDN), tZL(SHDN)) than from the operating mode (tZH, tZL). (The parts are in operating mode if the RE , DE inputs equal a logical 0,1 or 1,1 or 0,0.)
Driver Output Protection
Excessive output current and power dissipation caused by faults or by bus contention are prevented by two mechanisms. A foldback current limit on the output stage provides immediate protection against short circuits over the whole common-mode voltage range (see Typical Operating Characteristics). In addition, a thermal shutdown circuit forces the driver outputs into a high-impedance state if the die temperature rises excessively.
Propagation Delay
Digital encoding schemes depend on the driver and receiver skew. Skew is defined as the difference between the rising and falling propagation delay times. Typical propagation delays are shown in Figures 11 and 12 using Figure 10's test circuit. The difference in receiver delay times, | tPLH - tPHL |, is typically under 160ns. The driver skew times are typically 160ns (800ns max).
_______________________________________________________________________________________
9
20A, 18-Unit-Load, Slew-Rate-Limited RS-485 Transceivers MAX1482/MAX1483
Line Length vs. Data Rate
5 DI 0
1 RECEIVER INPUT VY-VZ 0
The RS-485/RS-422 standard covers line lengths up to 4000 feet. For line lengths greater than 4000 feet, see Figure 16. Figure 13 shows the system differential voltage for the parts driving 4000 feet of 26AWG twisted-pair wire at 110kHz into 120 loads. Even after 4000 feet of cable, the MAX1482/MAX1483 output shows virtually no distortion.
Typical Applications
-1
5 RO 0
2s/div
Figure 13. System Differential Voltage at 250kbps (125kHz) Driving 4000 Feet of Cable
The MAX1482/MAX1483 transceivers are designed for bidirectional data communications on multipoint bus transmission lines. Figures 14 and 15 show typical network applications circuits. These parts can also be used as line repeaters, with cable lengths longer than 4000 feet, as shown in Figure 16. To minimize reflections, the line should be terminated at both ends in its characteristic impedance, and stub lengths off the main line should be kept as short as possible (although the slew-rate-limited MAX1482 and MAX1483 are more tolerant of imperfect termination than standard RS-485 ICs).
Isolated RS-485
For isolated RS-485 applications, see the MAX253 and MAX1480 data sheets.
120 DI B
120 B DE
D
DE RO RE A B A B A A
D
DI
R R D D R
R
RO RE
MAX1483
DI DE RO RE DI DE RO RE
Figure 14. MAX1483 Typical Half-Duplex RS-485 Network
10
______________________________________________________________________________________
20A, 18-Unit-Load, Slew-Rate-Limited RS-485 Transceivers MAX1482/MAX1483
A RO RE DE Z DI
Y 120 120 Z DE B 120 120 Y Z B A Y Z B A A RE RO
R
B
D
DI
D
Y
R
R D D
R
MAX1482
DI
DE RE RO
DI
DE RE RO
NOTE: RE AND DE ON.
Figure 15. MAX1482 Full-Duplex RS-485 Network
Typical Operating Circuits ________________________(continued)
DE 4 VCC 14 VCC RE
MAX1482
A RO RE DE Z DI 120 Y
RO 2
MAX1482
120
9 Y Rt 10 Z 12 A
R
B
DATA IN
DI
5
D
R
RO
R
Rt 11 B
D
DI
D
DATA OUT
N.C. 1, 8, 13
3 6, 7 RE GND
GND
DE
NOTE: RE AND DE ON.
Figure 16. Line Repeater for MAX1482
______________________________________________________________________________________
11
20A, 18-Unit-Load, Slew-Rate-Limited RS-485 Transceivers MAX1482/MAX1483
____Pin Configurations (continued)
TOP VIEW
__________________Chip Information
TRANSISTOR COUNT: 294
MAX1482
N.C. RO RE DE DI 1 2 3 4 5 D R 14 VCC 13 N.C. 12 A 11 B 10 Z 9Y 8 N.C.
GND 6 GND 7
DIP/SO
________________________________________________________Package Information
DIM
C A 0.101mm 0.004 in B A1 L
e
A A1 B C D E e H L
INCHES MAX MIN 0.044 0.036 0.008 0.004 0.014 0.010 0.007 0.005 0.120 0.116 0.120 0.116 0.0256 0.198 0.188 0.026 0.016 6 0
MILLIMETERS MIN MAX 0.91 1.11 0.10 0.20 0.25 0.36 0.13 0.18 2.95 3.05 2.95 3.05 0.65 4.78 5.03 0.41 0.66 0 6
E
H
8-PIN MAX MICROMAX SMALL OUTLINE PACKAGE
D
Maxim cannot assume responsibility for use of any circuitry other than circuitry entirely embodied in a Maxim product. No circuit patent licenses are implied. Maxim reserves the right to change the circuitry and specifications without notice at any time.
12 __________________Maxim Integrated Products, 120 San Gabriel Drive, Sunnyvale, CA 94086 (408) 737-7600 (c) 1995 Maxim Integrated Products Printed USA is a registered trademark of Maxim Integrated Products.

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