IL3585 Datasheet, PDF (6/8 Pages) List of Unclassifed Manufacturers – PROFIBUS Compatible Isolated RS485 Interface

IL3585
Power Consumption
Isoloop devices achieve their low power consumption by detecting
the edge transitions of the input logic signal and converting these to
narrow current pulses. This technique creates a supply current
which is proportional to data rate, which has obvious advantages
over optocouplers whose power consumption is dependent on
mark:space ratio.
Table 2. Typical Dynamic Supply Currents.
Data Rate (Mbps)
1
10
20
40
I_DD1
300 µA
3 mA
6 mA
12 mA
I_DD2
300 µA
3 mA
6 mA
12 mA
Power Supplies
It is required that low ESR capacitors such as ceramic are used to
decouple the supplies. Both V_DD1 and V_DD2 must be bypassed with
47 nF capacitors. These should be placed as close as possible to
V_DD pins for proper operation. In addition, V _DD2 should have a
10 µF tantalum capacitor connected in parallel with the 47 nF
capacitor.
DC Correctness
The IL3585 incorporates a patented refresh circuit which
effectively maintains the correct output state with respect to data
input. At power up, the bus outputs will follow the Function Table
shown on Page 1. It is recommended that the DE input is always
held low during power up to eliminate false drive data pulses from
the bus. The use of an external power supply monitor to minimize
glitches caused by slow power-up and power-down transients is not
required.
Application Information_______________________
Receiver Features
The IL3585 receiver includes a “fail-safe if open” function that
guarantees a high level receiver output if the receiver inputs are
unconnected (floating). IL3585 receiver outputs have tri-state
capability via the active low RE input.
Driver Features
The RS-485 driver is a differential output device that delivers at
least 1.5 V across a 54 Ω load. The drivers feature low propagation
delay skew to maximize bit width and to minimize EMI. The
IL3585 drivers have tri-state capability via the active high DE
input.
Receiver Data Rate, Cables and Terminations
This device is intended for network lengths up to 4000', but the
maximum system data rate decreases as the transmission line length
increases. Twisted pair cable should be used in all networks since
they tend to pick up noise and other electromagnetically induced
voltages as common mode signals, which are effectively rejected
by the differential receivers in these ICs.
6
NVE Corporation 11409 Valley View Road Eden Prairie, MN 55344-3617 USA Telephone: [phone] Fax [phone] Internet: www.isoloop.com