PEB2085 SIEMENS [Siemens Semiconductor Group], PEB2085 Datasheet - Page 86

• Manufacturer Part Number: PEB2085
• Description: ISDN SubscribernAccess Controller
• Manufacturer: SIEMENS [Siemens Semiconductor Group]

Protection Circuit for Transmitter
Figure 47
External Circuitry for Transmitters
Figure 47 illustrates the secondary protection circuit recommended for the transmitter. An
ideal protection circuit should limit the voltage at the SX pins from – 0.4 V to V
Via the two resistors (typ. 33 ) the transmitted pulse amplitude is adjusted to comply with the
requirements. Two mutually reversed diode paths protect the device against positive or
negative overvoltages on both lines.
In figure 47 the pin voltage range is increased from – 1.4 V to V
forward voltage of 2.5 V will prevent the protection circuit to become active if the 96 kHz test
signal is applied while no supply voltage is present. Alternatively to the 1.8 V Zener diode in
the V
Semiconductor Group
DD
path two to three standard diodes connected in series achieve the same effect.
SX2
SX1
GND
20-40
20-40
86
1.8 V
V
DD
Functional Description
DD
ITS05641
S0 Bus
+ 2.5 V. The resulting
DD
+ 0.4 V.