DS276
two similar devices over short distances, and into larger loads than the 3 kΩ=RS-232 standard (Figure 2).
If Vdrv+ is increased to 5V, and Vdrv- decreased (to less than -2V) communication with standard RS-232
devices is possible, although of course the output voltage swing of the DS276 remains below the RS-232
specification. The Vdrv- supply can be derived using the “stealing” technique shown in Figure 4.
5V OPERATION
The use of a single 5V supply for VCC and Vdrv+, and Vdrv- derived using the circuit in Figure 4 can
produce reliable communication with standard RS-232 devices, although the DS276 output voltage
swings are below the RS-232 minimum (Figure 3).
Increasing the magnitude of the voltage to Vdrv+ to 10 volts or more will result in “true” RS-232 output
voltage levels.
SINGLE 3V OPERATION Figure 2
(See Note 3)
SINGLE 5V OPERATION Figure 3
(not true RS-232)
(See Note 1 and 3)
"STEALING" NEGATIVE SUPPLY Figure 4
(See Note 2)
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DALLAS [ DALLAS SEMICONDUCTOR ]
