Datasheet

DS2480B
Maxim Integrated ........................................................................................................................................................................................... 25
Figure 11a. UART DIRECT
SIN (RXD)
SOUT (TXD)
UART
or µC
Start
Stop
1
0
L
M
1-Wire Bus
Return
12 V
GND
1-W
POL
VDD
VPP
RXD
TXD
DS2480B
5V
Regulator
5 V
* only one DS950x ESD protection device with 5V
With EPROM Programming
5V Operation Only
GND
1-W
POL
VDD
VPP
RXD
TXD
DS2480B
*
470 pF
62 Ohms
Optional filter
DS9503
DS9503
DS9503
Figure 11b. ±5V RS232
SIN (RXD)
SOUT (TXD)
UART
or µC
Start
Stop
1
0
L
M
1-Wire Bus
Return
DTR
Power Stealing
GND
1-W
POL
VPP
VDD
RXD
TXD
DS2480B
62 Ohms
Optional filter
RTS
See Text
22 µF
0.1 µF
DS9503
470 pF
The signals DTR and RTS provide the power to operate the DS2480B. The resistor in the TXD line and
the Schottky diode limit the negative voltage at the TXD pin of the DS2480B to 0.3V maximum. The
resistor is typically 4.7kΩ. If the inverting driver is current-limited to 1mA the resistor is not required.
From the DS2480B’s perspective, this circuit will work with inverted signals of ±5V as well as 0 to 5V.
Depending on the voltage levels the host expects, it may be necessary to generate a negative voltage on
the RXD line. Figure 11c shows how this can be accomplished for a true RS232C system.