Datasheet

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LTC488/LTC489

4889fb

TYPICAL APPLICATION

DESCRIPTION

Quad RS485 Line Receiver

The LTC

488 and LTC489 are low power differential bus/

line receivers designed for multipoint data transmission

standard RS485 applications with extended common

mode range (12V to –7V). They also meet the require-

ments of RS422.

The CMOS design offers signiﬁ cant power savings over

its bipolar counterpart without sacriﬁ cing ruggedness

against overload or ESD damage.

The receiver features three-state outputs, with the receiver

output maintaining high impedance over the entire com-

mon mode range.

The receiver has a fail-safe feature which guarantees a

high output state when the inputs are left open.

Both AC and DC speciﬁ cations are guaranteed 4.75V to

5.25V supply voltage range.

L, LT, LTC and LTM are registered trademarks of Linear Technology Corporation. All other

trademarks are the property of their respective owners.

FEATURES

APPLICATIONS

Low Power: I

= 7mA Typ

Designed for RS485 or RS422 Applications

Single 5V Supply

–7V to 12V Bus Common Mode Range Permits ±7V

Ground Difference Between Devices on the Bus

60mV Typical Input Hysteresis

Receiver Maintains High Impedance in Three-State or

with the Power Off

28ns Typical Receiver Propagation Delay

Pin Compatible with the SN75173 (LTC488)

Pin Compatible with the SN75175 (LTC489)

Low Power RS485/RS422 Receivers

Level Translator

120Ω

4000 FT 24 GAUGE TWISTED PAIR

RECEIVER

1/4 LTC488

120Ω

DRIVER

1/4 LTC486

120Ω

4000 FT 24 GAUGE TWISTED PAIR

RECEIVER

1/4 LTC489

120Ω

DRIVER

1/4 LTC487

EN12

4889 TA01

Summary of content (12 pages)

PAGE 1
LTC488/LTC489 Quad RS485 Line Receiver FEATURES DESCRIPTION n The LTC®488 and LTC489 are low power differential bus/ line receivers designed for multipoint data transmission standard RS485 applications with extended common mode range (12V to –7V). They also meet the requirements of RS422.
PAGE 2
LTC488/LTC489 ABSOLUTE MAXIMUM RATINGS (Note 1) Supply Voltage (VCC) ................................................12V Control Input Currents .......................... –25mA to 25mA Control Input Voltages ..................–0.5V to (VCC + 0.5V) Receiver Input Voltages ..........................................±14V Receiver Output Voltages ..............–0.5V to (VCC + 0.5V) Operating Temperature Range LTC488C/LTC489C ................................... 0°C to 70°C LTC488I/LTC489I.......................
PAGE 3
LTC488/LTC489 ORDER INFORMATION LEAD FREE FINISH TAPE AND REEL PART MARKING PACKAGE DESCRIPTION TEMPERATURE RANGE LTC488CN#PBF LTC488CN#TRPBF LTC488CN 16-Lead Plastic DIP 0°C to 70°C LTC488CSW#PBF LTC488CSW#TRPBF LTC488CSW 16-Lead Plastic SO 0°C to 70°C LTC488IN#PBF LTC488IN#TRPBF LTC488IN 16-Lead Plastic DIP –40°C to 85°C LTC488ISW#PBF LTC488ISW#TRPBF LTC488ISW 16-Lead Plastic SO –40°C to 85°C LTC489CN#PBF LTC489CN#TRPBF LTC489CN 16-Lead Plastic DIP 0°C to 70°C LTC489CSW#PBF
PAGE 4
LTC488/LTC489 TYPICAL PERFORMANCE CHARACTERISTICS Receiver Output Low Voltage vs Temperature at I = 8mA Receiver Output High Voltage vs Temperature at I = 8mA –18 0.8 4.6 –16 0.7 4.4 –14 0.6 0.5 0.4 0.3 4.2 4.0 3.8 3.6 0.2 3.4 0.1 3.2 0 –50 –25 0 75 25 50 TEMPERATURE (°C) 100 125 OUTPUT CURRENT (mA) 4.8 OUTPUT VOLTAGE (V) OUTPUT VOLTAGE (V) 0.9 Receiver Output High Voltage vs Output Current at TA = 25°C –12 –10 –8 –6 –4 –2 3.
PAGE 5
LTC488/LTC489 PIN FUNCTIONS B 1 (Pin 1): Receiver 1 Input. GND (Pin 8): Ground Connection. A1 (Pin 2): Receiver 1 Input. B3 (Pin 9): Receiver 3 Input. RO1 (Pin 3): Receiver 1 Output. If the receiver output is enabled, then if A > B by 200mV, RO1 will be high. If A < B by 200mV, then RO1 will be low. A3 (Pin 10): Receiver 3 Input. EN (Pin 4) LTC488: Receiver Output Enabled. See Function Table for details. EN12 (Pin 4) LTC489: Receiver 1, Receiver 2 Output Enabled. See Function Table for details.
PAGE 6
LTC488/LTC489 TEST CIRCUITS 100pF A D DRIVER RO RECEIVER 54Ω CL B 100pF 4889 F01 Figure 1. Receiver Timing Test Circuit Note: The input pulse is supplied by a generator having the following characteristics: f = 1MHz, Duty Cycle = 50%, tr < 10ns, tf ≤ 10ns, ZOUT = 50Ω S1 RECEIVER OUTPUT 1k VCC CL 1k S2 4889 F02 Figure 2. Receiver Enable and Disable Timing Test Circuit SWITCHING TIME WAVEFORMS INPUT VOD2 INPUT A, B f = 1MHz; tr ≤ 10ns; tf ≤ 10ns 0V 0V –VOD2 tPHL tPLH VOH RO 1.5V 1.
PAGE 7
LTC488/LTC489 APPLICATIONS INFORMATION Typical Application Cables and Data Rate A typical connection of the LTC488/LTC489 is shown in Figure 5. Two twisted-pair wires connect up to 32 driver/ receiver pairs for half-duplex data transmission. There are no restrictions on where the chips are connected to the wires, and it isn’t necessary to have the chips connected at the ends. However, the wires must be terminated only at the ends with a resistor equal to their characteristic impedance, typically 120Ω.
PAGE 8
LTC488/LTC489 APPLICATIONS INFORMATION data rate. With lower quality PVC cables, the dielectric loss factor can be 1000 times worse. PVC twisted-pairs have terrible losses at high data rates (> 100kbps), and greatly reduce the maximum cable length. At low data rates however, they are acceptable and much more economical. Cable Termination The proper termination of the cable is very important. If the cable is not terminated with its characteristic impedance, distorted waveforms will result.
PAGE 9
LTC488/LTC489 APPLICATIONS INFORMATION Receiver Open-Circuit Fail-Safe Some data encoding schemes require that the output of the receiver maintains a known state (usually a logic 1) when the data is ﬁnished transmitting and all drivers on the line are forced in three-state. The receiver of the LTC488/LTC489 has a fail-safe feature which guarantees the output to be in a logic 1 state when the receiver inputs are left ﬂoating (open-circuit).
PAGE 10
LTC488/LTC489 PACKAGE DESCRIPTION N Package 16-Lead PDIP (Narrow .300 Inch) (Reference LTC DWG # 05-08-1510) .770* (19.558) MAX 16 15 14 13 12 11 10 9 1 2 3 4 5 6 7 8 .255 ± .015* (6.477 ± 0.381) .130 ± .005 (3.302 ± 0.127) .300 – .325 (7.620 – 8.255) .008 – .015 (0.203 – 0.381) ( +.035 .325 –.015 +0.889 8.255 –0.381 NOTE: 1. DIMENSIONS ARE ) .045 – .065 (1.143 – 1.651) .020 (0.508) MIN .065 (1.651) TYP .120 (3.048) MIN .100 (2.
PAGE 11
LTC488/LTC489 PACKAGE DESCRIPTION SW Package 16-Lead Plastic Small Outline (Wide .300 Inch) (Reference LTC DWG # 05-08-1620) .050 BSC .045 ±.005 .030 ±.005 TYP .398 – .413 (10.109 – 10.490) NOTE 4 16 N 15 14 13 12 11 10 9 N .325 ±.005 .420 MIN .394 – .419 (10.007 – 10.643) NOTE 3 1 2 3 N/2 N/2 RECOMMENDED SOLDER PAD LAYOUT 1 .005 (0.127) RAD MIN .009 – .013 (0.229 – 0.330) .291 – .299 (7.391 – 7.595) NOTE 4 .010 – .029 × 45° (0.254 – 0.737) 3 4 5 6 7 .093 – .104 (2.362 – 2.
PAGE 12
LTC488/LTC489 TYPICAL APPLICATION RS232 Receiver RS232 IN 5.