Datasheet

DS36C279
www.ti.com SNLS098B –JULY 2000–REVISED APRIL 2013
The advantage of the ½ UL and ¼ UL devices 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 DS36C278/279/280 may save in the
cost of extra devices like repeaters, extra media like cable, and/or extra components like resistors.
Figure 20. Input Current vs Input Voltage Operating Range
The DS36C279 and DS36C280 have an additional feature which offers more advantages. The DS36C279 has
an automatic sleep mode function for power conscious applications. The DS36C280 has a slew rate control for
EMI conscious applications. Refer to the sleep mode and slew rate control portion of the application information
section in the corresponding datasheet for more information on these features.
SLEEP MODE
The DS36C279 features an automatic shutdown mode that allows the device to save power when not
transmitting data. Since the shutdown mode is automatic, no external components are required. 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* pin is asserted to a logic high. Once both pins are asserted the
device will enter sleep mode typically in 50 ns. The DS36C279 is ensured 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* 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 data specifications t
PSL
and t
PSH
and compare with t
PZL
and t
PZH
for timing differences.
The benefit of the DS36C279 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
CC
is ultra low.
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