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PDF LTC1334ISW Data sheet ( Hoja de datos )
| Número de pieza | LTC1334ISW | |
| Descripción | Single 5V RS232/RS485 Multiprotocol Transceiver | |
| Fabricantes | Linear Technology | |
| Logotipo |  |
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FEATURES
s Four RS232 Transceivers or Two RS485
Transceivers on One Chip
s Operates from a Single 5V Supply
s Withstands Repeated ±10kV ESD Pulses
s Uses Small Charge Pump Capacitors: 0.1µF
s Low Supply Current: 8mA Typical
s 10µA Supply Current in Shutdown
s Self-Testing Capability in Loopback Mode
s Power-Up/Down Glitch-Free Outputs
s Driver Maintains High Impedance in Three-State,
Shutdown or with Power Off
s Thermal Shutdown Protection
s Receiver Inputs Can Withstand ±25V
U
APPLICATIO S
s Low Power RS485/RS422/RS232/EIA562 Interface
s Software-Selectable Multiprotocol Interface Port
s Cable Repeaters
s Level Translators
LTC1334
Single 5V RS232/RS485
Multiprotocol Transceiver
DESCRIPTIO
The LTC®1334 is a low power CMOS bidirectional trans-
ceiver featuring two reconfigurable interface ports. It can
be configured as two RS485 differential ports, as two dual
RS232 single-ended ports or as one RS485 differential
port and one dual RS232 single-ended port. An onboard
charge pump requires four 0.1µF capacitors to generate
boosted positive and negative supplies, allowing the RS232
drivers to meet the RS232 ±5V output swing requirement
with only a single 5V supply. A shutdown mode reduces
the ICC supply current to 10µA.
The RS232 transceivers are in full compliance with RS232
specifications. The RS485 transceivers are in full compli-
ance with RS485 and RS422 specifications. All interface
drivers feature short-circuit and thermal shutdown pro-
tection. An enable pin allows RS485 driver outputs to be
forced into high impedance, which is maintained even
when the outputs are forced beyond supply rails or power
is off. Both driver outputs and receiver inputs feature
±10kV ESD protection. A loopback mode allows the driver
outputs to be connected back to the receiver inputs for
diagnostic self-test.
, LTC and LT are registered trademarks of Linear Technology Corporation.
TYPICAL APPLICATIO
VCC1
5V
2
3
RX OUT
DR ENABLE
DR IN
5V
5V
DR IN
DR IN
RX OUT
RX OUT
26
24
23
22
21
20
19
18
17
16
15
1 28
LTC1334
27 27
4
5
6
7
8 5V
9 0V
11
10
13
12
14
120Ω
RS485 INTERFACE
120Ω
4000-FT 24-GAUGE TWISTED PAIR
RS232 INTERFACE
13
12
11
10
9
5V
0V 8
4
5
6
7
14
ALL CAPACITORS: 0.1µF MONOLITHIC CERAMIC TYPE
28 1
LTC1334
2
3
26
17
RX OUT
18
DR ENABLE
19 DR IN
21 5V
20 5V
24 RX OUT
25
RX OUT
22
DR IN
23
DR IN
15
VCC2
5V
LTC1334 • TA01
1
1 page  
TYPICAL PERFORMANCE CHARACTERISTICS
Receiver Output Current
vs Output High Voltage
20
18
TA = 25°C
VCC = 5V
16
14
12
10
8
6
4
2
0
2.0 2.5 3.0 3.5 4.0 4.5 5.0
OUTPUT VOLTAGE (V)
LTC1334 • TPC04
Charge Pump Output Voltage
vs Temperature
10
8
6 VDD (–10mA LOAD)
VDD (NO LOAD)
4
2
0 VCC = 5V
–2
–4
–6 VEE (10mA LOAD)
–8
–10
–50 –25
VEE (NO LOAD)
0 25 50 75 100 125
TEMPERATURE (°C)
LTC1334 • TPC07
RS485 Driver Differential Output
Voltage vs Temperature
2.6
2.5 RL = 54Ω
VCC = 5V
2.4
2.3
2.2
2.1
2.0
1.9
1.8
1.7
1.6
–50 –25
0 25 50 75 100 125
TEMPERATURE (°C)
LTC1334 • TPC10
Receiver Output Current
vs Output Low Voltage
40
TA = 25°C
35 VCC = 5V
30
25
20
15
10
5
0
0 0.5 1.0 1.5 2.0 2.5 3.0
OUTPUT VOLTAGE (V)
LTC1334 • TPC05
Supply Current
vs Temperature (RS485)
25
VCC = 5V
NO LOAD
20 SEL 1 = SEL 2 = HIGH
15
10
5
0
–50 –25
0 25 50 75 100 125
TEMPERATURE (°C)
LTC1334 • TPC08
RS485 Driver Differential Output
Current vs Output Voltage
70
TA = 25°C
60 VCC = 5V
50
40
30
20
10
0
01 2 345
DIFFERENTIAL OUTPUT VOLTAGE (V)
LTC1334 • TPC11
LTC1334
RS232 Receiver Input Threshold
Voltage vs Temperature
2.0
VCC = 5V
1.8
INPUT HIGH
1.6
1.4
1.2
INPUT LOW
1.0
0.8
–50 –25
0 25 50 75 100 125
TEMPERATURE (°C)
LTC1334 • TPC06
Supply Current
vs Temperature (RS232)
10
9 VCC = 5V
NO LOAD
8 SEL 1 = SEL 2 = HIGH
7
6
5
4
3
2
1
0
–50 –25
0 25 50 75 100 125
TEMPERATURE (°C)
LTC1334 • TPC09
RS485 Driver Skew
vs Temperature
15
VCC = 5V
12
9
6
3
0
–50 –25
0 25 50 75 100 125
TEMPERATURE (°C)
LTC1334 • TPC12
5
5 Page 
LTC1334
APPLICATI S I FOR ATIO
Basic Theory of Operation
The LTC1334 has two interface ports. Each port may be
configured as a pair of single-ended RS232 transceivers
or as a differential RS485 transceiver by forcing the
port’s selection input to a low or high, respectively. The
LTC1334 provides two RS232 drivers and two RS232
receivers or one RS485 driver and one RS485 receiver
per port. All the interface drivers feature three-state
outputs. Interface outputs are forced into high imped-
ance when the driver is disabled, in the shutdown mode
or with the power off.
All the interface driver outputs are fault-protected by a
current limiting and thermal shutdown circuit. The ther-
mal shutdown circuit disables both the RS232 and RS485
driver outputs when the die temperature reaches 150°C.
The thermal shutdown circuit reenables the drivers when
the die temperature cools to 130°C.
In RS485 mode, shutdown mode or with the power off, the
input resistance of the receiver is 24k. The input resistance
drops to 5k in RS232 mode.
A logic low at the ON/OFF pin shuts down the device and
forces all the outputs into a high impedance state. A logic
high enables the device. An internal 4µA current source to
VCC pulls the ON/OFF pin high if it is left open.
In RS485 mode, an internal 4µA current source pulls the
driver enable pin high if left open. The RS485 receiver has
a 4µA current source at the noninverting input. If both the
RS485 receiver inputs are open, the output goes to a high
state. Both the current sources are disabled in the RS232
mode. The receiver output B is inactive in RS485 mode
and has a 50k pull-up resistor to provide a known output
state in this mode.
A loopback mode enables internal connections from driver
outputs to receiver inputs for self-test when the LB pin has
a low logic state. The driver outputs are not isolated from
the external loads. This allows transmitter verification
under the loaded condition. An internal 4µA current source
pulls the LB pin high if left open and disables the loopback
configuration.
RS232/RS485 Applications
The LTC1334 can support both RS232 and RS485 levels
with a single 5V supply as shown in Figure 11.
Multiprotocol Applications
The LTC1334 is well-suited for software controlled inter-
face mode selection. Each port has a selection pin as
shown in Figure 12. The single-ended transceivers sup-
port both RS232 and EIA562 levels. The differential trans-
ceivers support both RS485 and RS422.
C1
VDD
0.1µF
RS485 I/O 120Ω
1
0.1µF 2
3
4
5
6
7
5V 8
9
≥ ±5V INTO
3kΩ LOAD
RS232 DR OUT
RS232 DR OUT
RS232 RX IN
RS232 RX IN
11
10
13
12
14
LTC1334
28
27 0.1µF
C2
26
24
RX OUT
23
DR ENABLE
VCC
5V
0.1µF
22
DR IN
21
5V
20 5V
19 DR IN
18
DR IN
17 RX OUT
16 RX OUT
15 VEE
0.1µF
LTC1334 • F11
Figure 11. RS232/RS485 Interfaces
11
11 Page | ||
| Páginas | Total 16 Páginas | |
| PDF Descargar | [ Datasheet LTC1334ISW.PDF ] | |
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