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PDF MAX491 Data sheet ( Hoja de datos )
| Número de pieza | MAX491 | |
| Descripción | Slew-Rate-Limited RS-485/RS-422 Transceivers | |
| Fabricantes | Maxim Integrated | |
| Logotipo |  |
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Hay una vista previa y un enlace de descarga de MAX491 (archivo pdf) en la parte inferior de esta página. Total 17 Páginas | ||
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MAX481/MAX483/MAX485/
MAX487–MAX491/MAX1487
Low-Power, Slew-Rate-Limited
RS-485/RS-422 Transceivers
General Description
The MAX481, MAX483, MAX485, MAX487–MAX491, and
MAX1487 are low-power transceivers for RS-485 and RS-
422 communication. Each part contains one driver and one
receiver. The MAX483, MAX487, MAX488, and MAX489
feature reduced slew-rate drivers that minimize EMI and
reduce reflections caused by improperly terminated cables,
thus allowing error-free data transmission up to 250kbps.
The driver slew rates of the MAX481, MAX485, MAX490,
MAX491, and MAX1487 are not limited, allowing them to
transmit up to 2.5Mbps.
These transceivers draw between 120µA and 500µA of
supply current when unloaded or fully loaded with disabled
drivers. Additionally, the MAX481, MAX483, and MAX487
have a low-current shutdown mode in which they consume
only 0.1µA. All 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-imped-
ance state. The receiver input has a fail-safe feature that
guarantees a logic-high output if the input is open circuit.
The MAX487 and MAX1487 feature quarter-unit-load
receiver input impedance, allowing up to 128 MAX487/
MAX1487 transceivers on the bus. Full-duplex communi-
cations are obtained using the MAX488–MAX491, while
the MAX481, MAX483, MAX485, MAX487, and MAX1487
are designed for half-duplex applications.
________________________Applications
Low-Power RS-485 Transceivers
Low-Power RS-422 Transceivers
Level Translators
Transceivers for EMI-Sensitive Applications
Industrial-Control Local Area Networks
__Next Generation Device Features
o For Fault-Tolerant Applications
MAX3430: ±80V Fault-Protected, Fail-Safe, 1/4
Unit Load, +3.3V, RS-485 Transceiver
MAX3440E–MAX3444E: ±15kV ESD-Protected,
±60V Fault-Protected, 10Mbps, Fail-Safe,
RS-485/J1708 Transceivers
o For Space-Constrained Applications
MAX3460–MAX3464: +5V, Fail-Safe, 20Mbps,
Profibus RS-485/RS-422 Transceivers
MAX3362: +3.3V, High-Speed, RS-485/RS-422
Transceiver in a SOT23 Package
MAX3280E–MAX3284E: ±15kV ESD-Protected,
52Mbps, +3V to +5.5V, SOT23, RS-485/RS-422,
True Fail-Safe Receivers
MAX3293/MAX3294/MAX3295: 20Mbps, +3.3V,
SOT23, RS-485/RS-422 Transmitters
o For Multiple Transceiver Applications
MAX3030E–MAX3033E: ±15kV ESD-Protected,
+3.3V, Quad RS-422 Transmitters
o For Fail-Safe Applications
MAX3080–MAX3089: Fail-Safe, High-Speed
(10Mbps), Slew-Rate-Limited RS-485/RS-422
Transceivers
o For Low-Voltage Applications
MAX3483E/MAX3485E/MAX3486E/MAX3488E/
MAX3490E/MAX3491E: +3.3V Powered, ±15kV
ESD-Protected, 12Mbps, Slew-Rate-Limited,
True RS-485/RS-422 Transceivers
Ordering Information appears at end of data sheet.
______________________________________________________________Selection Table
PART HALF/FULL
NUMBER DUPLEX
MAX481
MAX483
MAX485
MAX487
MAX488
MAX489
MAX490
MAX491
MAX1487
Half
Half
Half
Half
Full
Full
Full
Full
Half
DATA
RATE
(Mbps)
2.5
0.25
2.5
0.25
0.25
0.25
2.5
2.5
2.5
SLEW-RATE
LIMITED
LOW-
POWER
SHUTDOWN
RECEIVER/
DRIVER
ENABLE
QUIESCENT
CURRENT
(μA)
NUMBER OF
RECEIVERS ON
BUS
No Yes Yes 300
32
Yes Yes Yes 120
32
No No Yes 300
32
Yes Yes Yes 120
128
Yes No No 120
32
Yes No Yes 120
32
No No No 300
32
No No Yes 300
32
No No Yes 230
128
PIN
COUNT
8
8
8
8
8
14
8
14
8
For pricing, delivery, and ordering information, please contact Maxim Direct at
1-888-629-4642, or visit Maxim Integrated’s website at www.maximintegrated.com.
19-0122; Rev 10; 9/14
1 page  
MAX481/MAX483/MAX485/
MAX487–MAX491/MAX1487
Low-Power, Slew-Rate-Limited
RS-485/RS-422 Transceivers
NOTES FOR ELECTRICAL/SWITCHING CHARACTERISTICS
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.
Note 2: All typical specifications are given for VCC = 5V and TA = +25°C.
Note 3: Supply current specification is valid for loaded transmitters when DE = 0V.
Note 4: Applies to peak current. See Typical Operating Characteristics.
Note 5: The MAX481/MAX483/MAX487 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 (MAX481/MAX483/MAX487) section.
__________________________________________Typical Operating Characteristics
(VCC = 5V, TA = +25°C, unless otherwise noted.)
OUTPUT CURRENT vs.
RECEIVER OUTPUT LOW VOLTAGE
45
40
35
30
25
20
15
10
5
0
0 0.5 1.0 1.5 2.0 2.5
OUTPUT LOW VOLTAGE (V)
OUTPUT CURRENT vs.
RECEIVER OUTPUT HIGH VOLTAGE
-20
-18
-16
-14
-12
-10
-8
-6
-4
-2
0
1.5
2.0 2.5 3.0 3.5 4.0 4.5 5.0
OUTPUT HIGH VOLTAGE (V)
RECEIVER OUTPUT HIGH VOLTAGE vs.
TEMPERATURE
4.8
4.6 IRO = 8mA
4.4
4.2
4.0
3.8
3.6
3.4
3.2
3.0
-50 -25
0 25 50 75 100 125
TEMPERATURE (°C)
RECEIVER OUTPUT LOW VOLTAGE vs.
TEMPERATURE
0.9
0.8 IRO = 8mA
0.7
0.6
0.5
0.4
0.3
0.2
0.1
0
-50 -25
0 25 50 75 100 125
TEMPERATURE (°C)
DRIVER OUTPUT CURRENT vs.
DIFFERENTIAL OUTPUT VOLTAGE
90
80
70
60
50
40
30
20
10
0
0 0.5 1.0 1.5 2.0 2.5 3.0 3.5 4.0 4.5
DIFFERENTIAL OUTPUT VOLTAGE (V)
DRIVER DIFFERENTIAL OUTPUT VOLTAGE
vs. TEMPERATURE
2.4
2.3 R = 54Ω
2.2
2.1
2.0
1.9
1.8
1.7
1.6
1.5
-50 -25
0 25 50 75 100 125
TEMPERATURE (°C)
Maxim Integrated
5
5 Page 
MAX481/MAX483/MAX485/
MAX487–MAX491/MAX1487
Low-Power, Slew-Rate-Limited
RS-485/RS-422 Transceivers
10dB/div
10dB/div
0Hz 5MHz
500kHz/div
Figure 12. Driver Output Waveform and FFT Plot of MAX481/
MAX485/MAX490/MAX491/MAX1487 Transmitting a 150kHz
Signal
Low-Power Shutdown Mode
(MAX481/MAX483/MAX487)
A low-power shutdown mode is initiated by bringing
both 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 0.1µA 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 MAX481, MAX483, and MAX487, the tZH and
tZL enable times assume the part was not in the low-
power shutdown state (the MAX485/MAX488–MAX491
and MAX1487 can not be shut down). The tZH(SHDN)
and tZL(SHDN) enable times assume the parts were shut
down (see Electrical Characteristics).
It takes the drivers and receivers longer to become
enabled from the low-power shutdown state
(tZH(SHDN), tZL(SHDN)) than from the
(tZH, tZL). (The parts are in operating
ompoedreatiinf gthemoR–—dE–e,
DE inputs equal a logical 0,1 or 1,1 or 0, 0.)
0Hz 5MHz
500kHz/div
Figure 13. Driver Output Waveform and FFT Plot of MAX483/
MAX487–MAX489 Transmitting a 150kHz Signal
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 cir-
cuits over the whole common-mode voltage range (see
Typical Operating Characteristics). In addition, a ther-
mal shutdown circuit forces the driver outputs into a
high-impedance state if the die temperature rises
excessively.
Propagation Delay
Many digital encoding schemes depend on the differ-
ence between the driver and receiver propagation
delay times. Typical propagation delays are shown in
Figures 15–18 using Figure 14’s test circuit.
The difference in receiver delay times, | tPLH - tPHL |, is
typically under 13ns for the MAX481, MAX485,
MAX490, MAX491, and MAX1487 and is typically less
than 100ns for the MAX483 and MAX487–MAX489.
The driver skew times are typically 5ns (10ns max) for
the MAX481, MAX485, MAX490, MAX491, and
MAX1487, and are typically 100ns (800ns max) for the
MAX483 and MAX487–MAX489.
Maxim Integrated
11
11 Page | ||
| Páginas | Total 17 Páginas | |
| PDF Descargar | [ Datasheet MAX491.PDF ] | |
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