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PDF HWD491 Data sheet ( Hoja de datos )
| Número de pieza | HWD491 | |
| Descripción | (HWD481 - HWDxxx) Slew-Rate-Limited RS-485/RS-422 Transceivers | |
| Fabricantes | ETC | |
| Logotipo |  |
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Low-Power, Slew-Rate-Limited
RS-485/RS-422 Transceivers
General Description
The HWD481, HWD483, HWD485, HWD487–HWD491, and
HWD1487 are low-power transceivers for RS-485 and RS-
422 communication. Each part contains one driver and one
receiver. The HWD483, HWD487, HWD488, and HWD489
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 HWD481, HWD485, HWD490,
HWD491, and HWD1487 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 HWD481, HWD483, and HWD487
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 HWD487 and HWD1487 feature quarter-unit-load
receiver input impedance, allowing up to 128 HWD487/
HWD1487 transceivers on the bus. Full-duplex communi-
cations are obtained using the HWD488–HWD491, while
the HWD481, HWD483, HWD485, HWD487, and HWD1487
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
♦ For Fault-Tolerant Applications
HWD3430: ±80V Fault-Protected, Fail-Safe, 1/4
Unit Load, +3.3V, RS-485 Transceiver
HWD3440E–HWD3444E: ±15kV ESD-Protected,
±60V Fault-Protected, 10Mbps, Fail-Safe,
RS-485/J1708 Transceivers
♦ For Space-Constrained Applications
HWD3460–HWD3464: +5V, Fail-Safe, 20Mbps,
Profibus RS-485/RS-422 Transceivers
HWD3362: +3.3V, High-Speed, RS-485/RS-422
Transceiver in a SOT23 Package
HWD3280E–HWD3284E: ±15kV ESD-Protected,
52Mbps, +3V to +5.5V, SOT23, RS-485/RS-422,
True Fail-Safe Receivers
HWD3293/HWD3294/HWD3295: 20Mbps, +3.3V,
SOT23, RS-855/RS-422 Transmitters
♦ For Multiple Transceiver Applications
HWD3030E–HWD3033E: ±15kV ESD-Protected,
+3.3V, Quad RS-422 Transmitters
♦ For Fail-Safe Applications
HWD3080–HWD3089: Fail-Safe, High-Speed
(10Mbps), Slew-Rate-Limited RS-485/RS-422
Transceivers
♦ For Low-Voltage Applications
HWD3483E/HWD3485E/HWD3486E/HWD3488E/
HWD3490E/HWD3491E: +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 DATA RATE SLEW-RATE LOW-POWER
NUMBER DUPLEX
(Mbps)
LIMITED SHUTDOWN
HWD481
Half
2.5
No Yes
HWD483
Half
0.25
Yes
Yes
HWD485
Half
2.5
No
No
HWD487
Half
0.25
Yes
Yes
HWD488
Full
0.25
Yes
No
HWD489
Full
0.25
Yes
No
HWD490
Full
2.5
No
No
HWD491
Full
2.5
No
No
HWD1487
Half
2.5
No
No
RECEIVER/
DRIVER
ENABLE
Yes
Yes
Yes
Yes
No
Yes
No
Yes
Yes
QUIESCENT
CURRENT
(µA)
300
120
300
120
120
120
300
300
230
NUMBER OF
TRANSMITTERS
ON BUS
32
32
32
128
32
32
32
32
128
PIN
COUNT
8
8
8
8
8
14
8
14
8
1
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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 HWD481/HWD483/HWD487 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.
__________________________________________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)
5
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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 HWD481/
HWD485/HWD490/HWD491/HWD1487 Transmitting a 150kHz
Signal
0Hz 5MHz
500kHz/div
Figure 13. Driver Output Waveform and FFT Plot of HWD483/
HWD487–HWD489 Transmitting a 150kHz Signal
Low-Power Shutdown Mode
(HWD481/HWD483/HWD487)
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 HWD481, HWD483, and HWD487, the tZH and
tZL enable times assume the part was not in the low-
power shutdown state (the HWD485/HWD488–HWD491
and HWD1487 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.)
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 HWD481, HWD485,
HWD490, HWD491, and HWD1487 and is typically less
than 100ns for the HWD483 and HWD487–HWD489.
The driver skew times are typically 5ns (10ns max) for
the HWD481, HWD485, HWD490, HWD491, and
HWD1487, and are typically 100ns (800ns max) for the
HWD483 and HWD487–HWD489.
11
11 Page | ||
| Páginas | Total 20 Páginas | |
| PDF Descargar | [ Datasheet HWD491.PDF ] | |
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