psb2120 Infineon Technologies Corporation, psb2120 Datasheet - Page 9

• Manufacturer Part Number: psb2120
• Description: Isdn Remote Power Controller
• Manufacturer: Infineon Technologies Corporation

PSB 2120
PSB 2120 Applications in ISDN-Environments
Figure 3 shows an example out of the wide application field of the PSB 2120. In the network
termination one PSB 2120 supplies the internal IC’s directly from the U–interface. A second IRPC,
also powered from the U-line, supplies the S–interface if the main supply of the NT is out of order.
A third IRPC is used in the main supply to regulate the S-line feeding voltage.
In the subscriber terminal the PSB 2120 is used for feeding the internal circuits.
The PSB 2120 accommodates both galvanically isolated and non-isolated configuration.
Considering the diversity of DC/DC-converter applications, this part of the specification only shows
how to use the special ISDN-features of the PSB 2120.
The switching frequency of the SMPS is programmable by two external components.
R
C
Figure 4 shows the switching frequency as a function of
and
.
T
T
The minimum configuration so as to be able to use the PSB 2120 in ISDN-applications is by using
a flyback converter (figure 5).
C
The time constant of the soft start circuit is programmed by a capacitor at Pin
.
SS
C
Figure 6 shows the primary start-up current limitation by connecting Pin
. To reduce chip-power-
IN
dissipation, an auxiliary winding of the transformer is used to switch off the internal linear CMOS-
V
supply (pin
). Polarity reversal is detected by pin POL.
EXT
Figure 7 shows the realization of a microprocessor-reset-signal with the universal usable
comparator of the IRPC.
Figure 8 shows the PSB 2120 in flyback configuration with transformer isolation.
Figure 9 shows the PSB 2120 in flyback configuration with opto isolation, which is useful for a high
reliability galvanically isolated application.
Semiconductor Group
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