PSB2120 データシートの表示（PDF） - Siemens AG

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PSB2120

ISDN Remote Power Controller (IRPC)

Siemens AG 

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.

Figure 4 shows the switching frequency as a function of RT and CT.

The minimum configuration so as to be able to use the PSB 2120 in ISDN-applications is by using

a flyback converter (figure 5).

The time constant of the soft start circuit is programmed by a capacitor at Pin CSS.

Figure 6 shows the primary start-up current limitation by connecting Pin CIN. To reduce chip-power-

dissipation, an auxiliary winding of the transformer is used to switch off the internal linear CMOS-

supply (pin VEXT). Polarity reversal is detected by pin POL.

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

9

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