DS481_00 Datasheet, PDF (7/8 Pages) National Semiconductor (TI) – Low Power RS-485/RS-422 Multipoint Transceiver with Sleep Mode

Unit Load (Continued)
The advantage of the ¹â„2 UL device is the increased number
of nodes on one bus. In a single master multi-slave type of
application where the number of slaves exceeds 32, the
DS481 may save in the cost of extra devices like repeaters,
extra media like cable, and/or extra components like resis-
tors.
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FIGURE 15. Input Current vs Input Voltage
Operating Range
the sleep mode is automatic, no external components are
required. It may be used as little or as much as the applica-
tion requires. The more the feature is utilized, the more
power it saves.
The sleep mode is automatically entered when both the
driver and receiver are disabled. This occurs when both the
DE pin is asserted to a logic low and the RE (Note 1) pin is
asserted to a logic high. Once both pins are asserted the
device will enter sleep mode after 50 ns. The DS481 is
guaranteed to go into sleep mode within 600 ns after both
pins are asserted. The device wakes up (comes out of sleep
mode) when either the DE pin is asserted to a logic high
and/or the RE (Note 1) pin is asserted to a logic low. After the
device enters sleep mode it will take longer for the device to
wake up than it does for the device to enable from TRI-
STATE. Refer to datasheet specifications t_PSL and t_PSH and
compare with t_PZL and t _PZH for timing differences.
The benefit of the DS481 is definitely its power savings.
When active the device has a maximum I_CC of 500 µA.
When in sleep mode the device has a maximum I_CC of only
10 µA, which is 50 times less power than when active. The
I_CC when the device is active is already very low but when in
sleep mode the I_CCis ultra low.
Applications Information
Sleep Mode
The DS481 features an automatic sleep mode that allows
the device to save power when not transmitting data. Since
Multipoint RS-485 Application
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