DS481 Datasheet, PDF (7/10 Pages) National Semiconductor (TI) – Low Power RS-485/RS-422 Multipoint Transceiver with Sleep Mode

Unit Load (Continued)
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 compo-
nents like resistors.
DS012919-16
FIGURE 15. Input Current vs Input Voltage
Operating Range
Applications Information (Continued)
Sleep Mode
The DS481 features an automatic sleep mode that allows
the device to save power when not transmitting data. Since
the sleep mode is automatic, no external components are re-
quired. It may be used as little or as much as the application
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 de-
vice will enter sleep mode after 50 ns. The DS481 is guaran-
teed 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. Re-
fer 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.
Multipoint RS-485 Application
DS012919-17
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