SLIC电源设计-SLIC Power-Supply Des

Abstract: Integrated communicaTIon systems incorporate voice service with data service. Such systems use subscriber-line interface card (SLIC) funcTIons to maintain compaTIbility with legacy equipment. The voltages required in these systems vary from country to country and depends on the parTIcular application. This article discusses how to derive various voltages required in such systems using the MAX668 boost controller. Split feedback to improve cross-regulation is presented. An example of an isolated power supply is also presented.

Subscriber-line interface cards (SLICs) provide the interface between the telephone-service provider and the telephone handset in your home. They operate in two main modes: On-hook refers to when the handset is idle and waiting for a signal indicating that someone wants to make a connection, and off-hook refers to when the handset is active and the user is trying to complete a connection. Telephone-system voltages are traditionally negative to prevent electromigration from eroding the installed copper wiring.

Telephone systems require certain special voltages that vary from application to application and country to country. This article presents circuits for deriving these voltages from commonly available supply voltages. Table 1 summarizes the input and output characteristics of the circuits.

Table 1. Inputs and Outputs
Circuit Input Output 1 Output 2 Output 3 Figure 1