LTC1482 Linear Technology, LTC1482 Datasheet

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LTC1482

Manufacturer Part Number
LTC1482
Description
Low Power RS485 Transceiver with Carrier Detect and Receiver Fail-Safe
Manufacturer
Linear Technology
Datasheet

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FEATURES
APPLICATIO S
TYPICAL APPLICATIO
, LTC and LT are registered trademarks of Linear Technology Corporation.
No Damage or Latchup to 15kV (Human Body
Model), IEC1000-4-2 Level 4 ( 8kV) Contact and
Level 3 ( 8kV) Air Discharge
Active Low Carrier Detect Output
Guaranteed High Receiver Output State for
Floating, Shorted or Terminated Inputs with
No Signal Present
Drives Low Cost Residential Telephone Wires
Low Power: I
I
20 A Max Quiescent Current in Shutdown Mode
Single 5V Supply
– 7V to 12V Common Mode Range Permits 7V
Ground Difference Between Devices on the Data Line
Maximum Data Rate of 4Mbps
Power Up/Down Glitch-Free Driver Outputs
Up to 32 Transceivers on the Bus
Available in 8-Lead MSOP, PDIP and SO Packages
Battery-Powered RS485/RS422 Applications
Low Power RS485/RS422 Transceiver
Level Translator
CC
DI1/SHDN1
= 900 A Max in Driver Mode Without Load
RO1
CD1
DE1
CC
LTC1482
= 700 A Max with Driver Disabled
D
U
R
B1
A1
RS485 Interface
V
GND1
CC1
120
U
GND2
V
120
CC2
B2
A2
LTC1482
R
D
1482 TA01
RO2
CD2
DE2
DI2/SHDN2
DESCRIPTIO
The LTC
ceiver that offers an active low carrier detect output. The
open-drain carrier detect pin allows several transceivers
to share the same carrier detect line and can be used to
detect the insertion or removal of a driven RS485/RS422
cable.
Enhanced ESD protection allows the LTC1482 to with-
stand 15kV (human body model), IEC-1000-4-2 level 4
( 8kV) contact and level 3 ( 8kV) air discharge ESD
without latchup or damage.
The LTC1482 receiver stays alive at all times except in
shutdown. The supply current is a maximum of 700 A
and 900 A when the driver is disabled and enabled
respectively. In shutdown, the quiescent current of the
LTC1482 drops to a maximum of 20 A.
When the driver is disabled or the LTC1482 is in shut-
down, the driver outputs are three-stated and remain in
a high impedance state over the RS485 common mode
range.
Excessive power dissipation caused by bus contention or
faults is prevented by a thermal shutdown circuit, which
forces the driver outputs into a high impedance state.
The LTC1482 is fully specified over the commercial and
industrial temperature ranges and is available in 8-lead
MSOP, PDIP and SO packages.
Low Power RS485 Transceiver
®
1482 is a low power RS485 compatible trans-
with Carrier Detect and
Carrier Detect Output (2000 Foot STP Cable)
CD2
DE1
A2
B2
DE1
DE2 = 0
1k PULL-UP AT CD
U
Receiver Fail-Safe
Dl1 = V
Dl2 = V
CC
CC
LTC1482
1482 TA01a
1

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LTC1482 Summary of contents

Page 1

... A when the driver is disabled and enabled respectively. In shutdown, the quiescent current of the LTC1482 drops to a maximum When the driver is disabled or the LTC1482 is in shut- down, the driver outputs are three-stated and remain in a high impedance state over the RS485 common mode range ...

Page 2

... Input Current (A, B) with Driver Disabled IN2 V Differential Input Threshold Voltage for Receiver THRO 2 U RATINGS Junction Temperature .......................................... 125 C + 0.3V) Operating Temperature Range CC LTC1482C ........................................ 0.3V) LTC1482I ...................................... – Storage Temperature Range .................. – 150 C Lead Temperature (Soldering, 10 sec)................... 300 C + 0.3V ORDER PART NUMBER RO 1 LTC1482CMS8 CD ...

Page 3

... L1 L2 (Figures 100pF, DIFF L1 L2 (Figures 100pF, DIFF L1 L2 (Figures 4, 10) DI/SHDN = 100pF, DIFF L1 L2 (Figures 4, 10) DI/SHDN = V LTC1482 MIN TYP MAX – 0.20 0.20 30 3.4 3.5 0 580 900 CC 430 700 250 35 250 7 85 ...

Page 4

... LTC1482 U SWITCHING CHARACTERISTICS temperature range, otherwise specifications are at T SYMBOL PARAMETER t Receiver Input to CD Output High at Shutdown CDH(SHDN) t Receiver Input to CD Output Low from Shutdown CDL(SHDN) t Receiver Enable from Shutdown to Output High ZH(SHDN) t Receiver Enable from Shutdown to Output Low ZL(SHDN) t Receiver Disable from High on Shutdown ...

Page 5

... Voltage vs Output Current 5 4.75V CC 4 4.0 3.5 3.0 2.5 2.0 1.5 1.0 0.5 0 –35 –30 –25 –20 –15 –10 –5 0 OUTPUT CURRENT ( A) 1482 G11 LTC1482 Receiver Input Threshold Voltage vs Supply Voltage –0.02 –0.04 –0.06 V THRO(HIGH) –0.08 –0.10 V –0.12 THRO(LOW) –0.14 –0.16 –0.18 –0.20 4.5 4.75 5 5.25 5.5 SUPPLY VOLTAGE (V) 1482 G06 ...

Page 6

... LTC1482 W U TYPICAL PERFOR A CE CHARACTERISTICS Receiver Output High Voltage vs Temperature 4 4.75V CC 4 8mA 4.4 4.2 4.0 3.8 3.6 3.4 3.2 3.0 –55 –35 – 105 125 TEMPERATURE ( C) 1482 G13 Receiver Propagation Delay vs Temperature 200 180 160 t PLH 140 120 t PHL 100 –55 –35 –15 ...

Page 7

... 12V 4. OD3 1.0 DI/SD HIGH SEE FIGURE 2 0.5 V FOR V = 4.5V TO 5.25V OD3 CC 0 –0.5 –55 –35 – 105 125 TEMPERATURE ( C) 1482 G29 LTC1482 Driver Differential Output Voltage vs Temperature 3 100 L 3.0 2 5.25V 2 4.75V 4.5V CC 1.5 1.0 0 4.5V TO 5.25V OD ...

Page 8

... A weak internal pull-up removes the need for an external pull-up resistor if fast rise times and low if are not important. Several LTC1482s can share the same THRO(MAX) CD line forces RO to the high fail-safe state. In shutdown three-stated. This pin can be pulled above V but should not be taken above 8V to avoid damage ...

Page 9

... TO 12V 375 1482 F02 B Figure 2. Driver DC Test Load # UNDER TEST 15pF 1482 F04 LTC1482 < 5.25V – (Note (Internal Pull-Up) V < (A – B) < THCD(MIN) THCD(MAX) A and B are Open 1 A and B are Shorted ...

Page 10

... LTC1482 U W SWITCHI WAVEFOR S 3V DI/SHDN 1. PLH t DSKEW V O 90% 10% 50% – 1/2 V SKEW O NOTE 1. 2. 2.3V 0V NOTE FOR t ZL(SHDN) V OD2 A – – V OD2 NOTE – ...

Page 11

... A – – V OD2 NOTE: 1k PULL- 1. OD2 A – B – V OD2 NOTE: 1k PULL- INPUT t CDL 1.5V Figure 10. Carrier Detect Timing 1.5V t CDH(SHDN) 1.5V THREE-STATE Figure 11. Shutdown Carrier Detect Timing LTC1482 t CDH 1.5V 1482 F10 t CDL(SHDN) 1.5V 1482 F11 11 ...

Page 12

... I Shutdown Mode CC The supply current of the LTC1482 is reduced max by taking both the DE and DI/SHDN pins low. In shutdown, all internal circuits are powered down and the driver and receiver outputs are three-stated. The CD output is taken high by the weak internal pull-up ...

Page 13

... LTC1482. ESD Protection The ESD performance of the LTC1482 A and B pins is characterized to meet 15kV using the Human Body Model (100pF, 1.5k ), IEC-1000-4-2 Level 4 ( 8kV) contact mode and IEC-1000-4-2 Level 3 ( 8kV) air dis- charge mode ...

Page 14

... LTC1482 PACKAGE DESCRIPTION 0.007 0 – 6 TYP (0.18) 0.021 0.006 (0.53 0.015) * DIMENSION DOES NOT INCLUDE MOLD FLASH, PROTRUSIONS OR GATE BURRS. MOLD FLASH, PROTRUSIONS OR GATE BURRS SHALL NOT EXCEED 0.006" (0.152mm) PER SIDE ** DIMENSION DOES NOT INCLUDE INTERLEAD FLASH OR PROTRUSIONS. INTERLEAD FLASH OR PROTRUSIONS SHALL NOT EXCEED 0.006" (0.152mm) PER SIDE 0.300 – ...

Page 15

... TYP 0.014 – 0.019 (0.355 – 0.483) TYP LTC1482 0.150 – 0.157** (3.810 – 3.988 0.004 – 0.010 (0.101 – 0.254) 0.050 (1 ...

Page 16

... Differential Driver and Receiver Pair with Fail-Safe Receiver Output LT1785 60V Fault Protected RS485 Transceiver Linear Technology Corporation 16 1630 McCarthy Blvd., Milpitas, CA 95035-7417 (408) 432-1900 FAX: (408) 434-0507 www.linear-tech.com Fail-Safe “0” Application (Idle State = Logic “0”) 5V LTC1482 ...

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