DS36C279TM datasheet(8/10 Pages) NSC

8 / 10 page

Unit Load (Continued)

allow signals to be transferred to and from each individual

seat to 1 main station. Usually there is one or two less seats

in the last row of the aircraft near the restrooms and food

storage area. This frees the node for the main station.

The DS36C278, the DS36C279, and the DS36C280 all have

⁄2 unit load and 1⁄4 unit load (UL) options available. These

devices will allow up to 64 nodes or 128 nodes guaranteed

over temperature depending upon which option is selected.

The 1⁄2 UL option is available in industrial temperature and

the 1⁄4 UL is available in commercial temperature.

First, for a 1⁄2 UL device the top and bottom borders shown in

Figure 19 are scaled. Both 0 mA reference points at +5V and

−3V stay the same. The other reference points are +12V at

+0.5 mA for the top border and −7V at −0.4 mA for the bot-

tom border (see

Figure 19). Second, for a 1⁄4 UL device the

top and bottom borders shown in

Figure 19 are scaled also.

Again, both 0 mA reference points at +5V and −3V stay the

same. The other reference points are +12V at +0.25 mA for

the top border and −7V at −0.2 mA for the bottom border

(see

Figure 19).

The advantage of the 1⁄2 UL and 1⁄4 UL devices is the in-

creased 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.

The DS36C279 and DS36C280 have an additional feature

which offers more advantages. The DS36C279 has an auto-

matic 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 corre-

sponding 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 compo-

nents 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 guar-

anteed 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. Re-

fer to datasheet specifications t

PSL and tPSH and compare

with t

PZL and tPZH 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

CC when the device is active is already very low but when in

sleep mode the I

CC is ultra low.

DS012053-20

FIGURE 19. Input Current vs Input Voltage

Operating Range

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