LTC1487
Ultra-Low Power RS485
with Low EMI, Shutdown
and High Input Impedance
DESCRIPTIO
EA U
F T RES
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High Input Impedance: Up to 256 Transceivers The LTC 1487 is an ultra-low power differential line trans-
on the Bus ceiver designed with high impedance inputs allowing up to
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Low Power: I = 120m A Max with Driver Disabled 256 transceivers to share a single bus. It meets the
CC
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I = 200m A Max with Driver Enabled, No Load requirements of RS485 and RS422. The LTC1487 features
CC
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1m A Quiescent Current in Shutdown Mode output drivers with controlled slew rate, decreasing the
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Controlled Slew Rate Driver for Reduced EMI EMI radiated from the RS485 lines, and improving signal
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Single 5V Supply fidelity with misterminated lines. The CMOS design offers
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ESD Protection to 10kV On Receiver Inputs and significant power savings without sacrificing ruggedness
Driver outputs against overload or ESD damage. Typical quiescent cur-
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7V to 12V Common-Mode Range Permits 7V rent is only 80m A while operating and 1m A in shutdown.
Ground Difference Between Devices on the Data Line
The driver and receiver feature three-state outputs, with
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Thermal Shutdown Protection
the driver outputs maintaining high impedance over the
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Power Up/Down Glitch-Free Driver Outputs Permit
entire common-mode range. Excessive power dissipation
Live Insertion or Removal of Transceiver
caused by bus contention or faults is prevented by a
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Driver Maintains High Impedance in Three-State
thermal shutdown circuit which forces the driver outputs
or with the Power Off
into a high impedance state. The receiver has a fail-safe
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Pin Compatible with the LTC485
feature which guarantees a high output state when the
inputs are left open. I/O pins are protected against multiple
ESD strikes of over 10kV using the Human Body Model.
APPLICATI S
The LTC1487 is fully specified over the commercial tem-
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Battery-Powered RS485/RS422 Applications
perature range and is available in 8-pin DIP and SO
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Low Power RS485/RS422 Transceiver
packages.
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Level Translator
, LTC and LT are registered trademarks of Linear Technology Corporation.
TYPICAL APPLICATI
LTC1487 LTC1487
1 1
RO R R RO
2000 FEET OF TWISTED-PAIR WIRE
2 2 DI
RE RE
3 3
7 7
DE DE
4 4
DI D 120W 120W D DI
A
6 6
B
330W
4.7nF
RO
EQUIVALENT LOAD OF 256
LTC1487 TA01
LTC1487 TRANSCEIVERS
LTC1487 TA02
sn1487 1487fs
1
RECEIVER INPUT
UO
UO
ULTC1487
ABSOLUTEXAI U RATI GS
PACKAGE/ORDER I FOR ATIO
(Note 1)
Supply Voltage (V ) .............................................. 12V
ORDER PART
CC
TOP VIEW
NUMBER
Control Input Voltage..................... 0.5V to V + 0.5V
CC
RO 1 V
8
Driver Input Voltage....................... 0.5V to V + 0.5V CC
CC
R
LTC1487CN8
RE 2 7 B
Driver Output Voltage ........................................... 14V
LTC1487CS8
DE 3 6 A
Receiver Input Voltage.......................................... 14V
D
DI 4 5 GND
Receiver Output Voltage ................ 0.5V to V + 0.5V
CC
Operating Temperature Range ............. 0 C T 70 C S8 PART MARKING
N8 PACKAGE S8 PACKAGE
A
8-LEAD PDIP 8-LEAD PLASTIC SO
Storage Temperature Range ................ 65 C to 150 C
1487
Lead Temperature (Soldering, 10 sec)................. 300 C T = 125 C, q = 130 C/ W (N8)
JMAX JA
T = 125 C, q = 150 C/ W (S8)
JMAX JA
Consult factory for Industrial and Military grade parts.
0 C T 70 C, V = 5V (Notes 2, 3) unless otherwise noted.
ELECTRICAL CHARACTERISTICS
A CC
SYMBOL PARAMETER CONDITIONS MIN TYP MAX UNITS
V Differential Driver Output Voltage (Unloaded) I = 0 l 5V
OD1 O
V Differential Driver Output Voltage (with Load) R = 50W (RS422) l 2.0 V
OD2
R = 27W (RS485), Figure 1 l 1.5 5 V
D V Change in Magnitude of Driver Differential Output R = 27W or R = 50W , Figure 1 l 0.2 V
OD
Voltage for Complementary Output States
V Driver Common-Mode Output Voltage R = 27W or R = 50W , Figure 1 l 3V
OC
D V Change in Magnitude of Driver Common-Mode R = 27W or R = 50W , Figure 1 l 0.2 V
OC
Output Voltage for Complementary Output States
V Input High Voltage DE, DI, RE l2V
IH
V Input Low Voltage DE, DI, RE l 0.8 V
IL
I Input Current DE, DI, RE l 2 m A
IN1
I Input Current (A, B) DE = 0, V = 0V or 5.25V, V = 12V l 0.30 mA
IN2 CC IN
DE = 0, V = 0V or 5.25V, V = 7V l 0.15 mA
CC IN
V Differential Input Threshold Voltage for Receiver 7V V 12V l 0.2 0.2 V
TH CM
D V Receiver Input Hysteresis V = 0V l 45 mV
TH CM
V Receiver Output High Voltage I = 4mA, V = 200mV l 3.5 V
OH O ID
V Receiver Output Low Voltage I = 4mA, V = 200mV l 0.4 V
OL O ID
I Three-State (High Impedance) Output V = Max, 0.4V V 2.4V l 1 m A
OZR CC O
Current at Receiver
R Receiver Input Resistance 7V V 12V l 70 96 kW
IN CM
I Supply Current No Load, Output Enabled l 120 200 m A
CC
No Load, Output Disabled l 80 120 m A
I Supply Current in Shutdown Mode DE = 0V, RE = V 110 m A
SHDN CC
I Driver Short-Circuit Current, V = HIGH 7V V 12V l 35 250 mA
OSD1 OUT O
I Driver Short-Circuit Current, V = LOW 7V V 12V l 35 250 mA
OSD2 OUT O
I Receiver Short-Circuit Current 0V V V l785mA
OSR O CC
sn1487 1487fs
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