LTC1685
52Mbps, Precision Delay,
RS485 Fail-Safe Transceiver
DESCRIPTIO
FEATURES
n
Precision Propagation Delay Over Temperature: The LTC 1685 is a high speed, precision delay RS485
Receiver/Driver: 18.5ns 3.5ns transceiver that can operate at data rates as high as 52Mbps.
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High Data Rate: 52Mbps
The device also meets the requirements of RS422.
n
Low t /t Skew:
PLH PHL
A unique architecture provides very stable propagation
Receiver/Driver: 500ps Typ
delays and low skew over a wide common mode and
n
7V to 12V RS485 Input Common Mode Range
ambient temperature range.
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Guaranteed Fail-Safe Receiver Operation Over the
The driver and receiver feature three-state outputs, with
Entire Common Mode Range
n disabled driver outputs maintaining high impedance over
High Receiver Input Resistance: 22k, Even When
the entire common mode range. A short circuit feature
Unpowered
n detects shorted outputs and substantially reduces driver
Short-Circuit Protected
n output current. A similar feature also protects the receiver
Thermal Shutdown Protected
n output from short circuits. Thermal shutdown circuitry
Driver Maintains High Impedance in Three-State or
protects from excessive power dissipation.
with Power Off
n
Single 5V Supply
The receiver has a fail-safe feature that guarantees a high
n
Pin Compatible with LTC485
output state when the inputs are shorted or are left floating.
n
45dB CMRR at 26MHz
The LTC1685 RS485 transceiver guarantees receiver fail-
U
safe operation over the entire common mode range (7V
APPLICATIO S
to 12V). Input resistance will remain 22k when the device
is unpowered or disabled.
n
High Speed RS485/RS422 Transceivers
n
Level Translator
The LTC1685 operates from a single 5V supply and draws
n
Backplane Transceiver
only 7mA of supply current.
n
STS-1/OC-1 Data Transceiver
, LTC and LT are registered trademarks of Linear Technology Corporation.
n
Fast-20, Fast-40 SCSI Transceivers
TYPICAL APPLICATION
10Mbps Data Pulse
400ft Category 5 UTP
RO1
V
CC1
R
RE1
DRIVER INPUT
2V/DIV
Rt
CABLE DELAY
DE1
D
DI1
GND1
RECEIVER
1V/DIV
INPUT
Rt
RO2
V
CC2
R
RE2
RECEIVER
5V/DIV
OUTPUT
DE2
DI2 D
GND2
100ns/DIV
1685 TA01
1685 TA02
1
U
ULTC1685
O
ABS LUTEXAI U RATI GS PACKAGE/ORDER I FOR ATIO
(Note 1)
Supply Voltage (V ) .............................................. 10V
DD
TOP VIEW ORDER PART
Control Input Currents .................... 100mA to 100mA
NUMBER
RO 1 8 V
Control Input Voltages .................. 0.5V to V + 0.5V DD
DD
R
RE 2 B
7
Driver Input Voltages .................... 0.5V to V + 0.5V
LTC1685CS8
DD
DE 3 6 A
Driver Output Voltages .................................. +12V/7V
LTC1685IS8
DI D GND
4 5
Receiver Input Voltages ................................. +12V/7V
S8 PART MARKING
Receiver Output Voltages ............. 0.5V to V + 0.5V
DD
S8 PACKAGE
8-LEAD PLASTIC SO
Receiver Input Differential ...................................... 10V
1685
T = 125 C, q = 150 C/ W
Short-Circuit Duration (Driver V : 7V to 10V,
JMAX JA
OUT
1685I
Receiver V : 0V to V ) ............................... Indefinite
OUT DD
Consult factory for Military grade parts.
Operating Temperature Range
LTC1685C ............................................... 0 C to 70 C
LTC1685I............................................. 40 C to 85 C
Storage Temperature Range ................ 65 C to 150 C
Lead Temperature (Soldering, 10 sec)................. 300 C
DC ELECTRICAL CHARACTERISTICS
The l denotes the specifications which apply over the full operating
temperature range, otherwise specifications are at T = 25 C. V = 5V 5%, unless otherwise noted. (Notes 2, 3)
A DD
SYMBOL PARAMETER CONDITIONS MIN TYP MAX UNITS
V Differential Driver Output (Unloaded) I = 0 l V V
OD1 OUT DD
V Differential Driver Output (With Load) R = 50W (RS422) 2 V
OD2
R = 27W (RS485), Figure 1 l 1.5 V V
DD
D V Change in Magnitude of Driver Differential R = 27W or 50W , Figure 1 l 0.2 V
OD
Output Voltage for Complementary
Output States
V Driver Common Mode Output Voltage R = 27W or 50W , V = 5V, Figure 1 l 23 V
OC DD
V Change in Magnitude of Driver Common R = 27W or 50W , Figure 1 l 0.2 V
OC
Mode 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 1 1 m A
IN1
I Input Current (A, B) V , V = 12V, DE = 0, V = 0V or 5.25V l 500 m A
IN2 A B DD
V , V = 7V, DE = 0, V = 0V or 5.25V l 500 m A
A B DD
V Differential Input Threshold Voltage 7V V 12V l 0.3 0.3 V
TH CM
for Receiver
D V Receiver Input Hysteresis V = 0V 25 mV
TH CM
V Receiver Output High Voltage I = 4mA, V = 300mV l 3.5 4.8 V
OH OUT ID
V Receiver Output Low Voltage I = 4mA, V = 300mV l 0.4 V
OL OUT ID
I Three-State (High Impedance) Output 0.4V V 2.4V l 1 1 m A
OZR OUT
Current at Receiver
I Supply Current No Load, Pins 2, 3, 4 = 0V or V l 712 mA
DD DD
I Driver Short-Circuit Current, V = HIGH V = 7V or 10V (Note 5) l 20 mA
OSD1 OUT OUT
2
D
U WU U W W W