psb21391 Infineon Technologies Corporation, psb21391 Datasheet - Page 95

• Manufacturer Part Number: psb21391
• Description: Siemens Codec With Upn Transceiver
• Manufacturer: Infineon Technologies Corporation

2.3.11
Using a 3.3V power supply a 1:1 transformer has to be connected to the 2 wire U
interface.
Using a 5V power supply a 2:1 transformer has to be used. Therefore the TRS bit in the
TR_CONF2 register has to be set to ’1’.
The connection of the line transformer is shown in figure 49. External to the line interface
pins Lla and Llb a transformer and external resistors are connected as shown. Note that
the internal resistors of the transformer are calculated as zero. The actual values of the
external resistors must take into account the real resistor of the chosen transformer.
Figure 49
Connection of the Line Transformers and Power Supply to the SCOUT-P(X)
Data Sheet
U
PN
SCOUT-P(X)
SCOUT-P(X)
Interface Circuitry
LIa
LIb
LIa
LIb
Transformer Ratio 2:1
Transformer Ratio 1:1
3.3V Supply Voltage
5V Supply Voltage
100nF
10
10
160
160
100nF
50
50
40
40
85
2:1
1:1
UPNTRAN.DRW
330nF
330nF
U
U
PSB 21391
PSB 21393
PN
PN
Interfaces
2001-03-07
PN