DS2480B Maxim Integrated Products, DS2480B Datasheet - Page 26

• Manufacturer Part Number: DS2480B
• Description: IC LINE DRVR W/SENSOR 1-W 8-SOIC
• Manufacturer: Maxim Integrated Products
• Type: Line Driver, Transmitterr

Specifications of DS2480B

• Number Of Drivers/receivers: 1/0
• Protocol: RS232
• Voltage - Supply: 4.5 V ~ 5.5 V
• Mounting Type: Surface Mount
• Package / Case: 8-SOIC (3.9mm Width)
• Lead Free Status / RoHS Status: Contains lead / RoHS non-compliant

Figure 11c. ±12V RS232
In the interface to a true RS232C system (±12V, Figure 11c) the power for the DS2480B is stolen from
DTR and RTS. The software must make sure that at least one of these signals constantly provides the 12V
operating voltage. The 6.8kW resistor and the 4.7V Zener diode in the TXD line limit the positive voltage
at the TXD pin of the DS2480B. The Schottky diode limits the negative voltage to 0.3V maximum. The
Schottky diode in series with capacitor forms a parasitic supply to generate the negative bias for the
host’s receive channel. The positive signal is switched in through the P-channel MOSFET that connects
to the RXD output of the DS2480B. In this circuit diagram the MOSFET switches the RXD line to +5V,
which normally is sufficient for RS232C systems.
Switching to 12V is also possible, but requires a P-channel transistor with a different threshold voltage.
The signal inversion caused by the transistor is compensated through the DS2480B by using a value code
of 100, 101, 110, or 111 for the RS232 baud rate setting.
or µC
UART
Start
L
SIN
(RXD)
RTS
DTR
SOUT
(TXD)
1 µf
1
0
Power Stealing
M
Stop
2.7K
* only one DS950x ESD protection device with 5V
Regulator
BSS110
5V
6.8K
26 of 31
4.7V
S
D
See Text
VDD
RXD
TXD
DS2480
GND
VPP
POL
1-W
+12VDC Programming
Return
1-Wire Bus
DS9503
DS9503
*