AM79C02 Datasheet PDF

Power-On Reset and Power Sequencing for the Am79C02/03/031 DSLAC™ Devices Application Note The purpose of this application note is to consider the behavior of the Dual Subscriber Line AudioProcessing Circuit (DSLAC™) device on a linecard during power-up. It is necessary to understand the behavior of the DSLAC device during power-up to ensure a successful linecard design. This application note discusses the following topics: s Power-on reset circuit operation s Warm start s Sequence for the application of signals and power rails The DSLAC Power-On Reset Circuit All DSLAC devices have an internal circuit for generating a power-on reset when power is first applied to the VCC rail. Power-On Reset Circuit Operation A simplified circuit diagram for the power-on reset of the DSLAC devices is shown in Figure 1. VCC T3 VCC VCC T2 C1 Figure 1. Simplified Power-On Reset Circuit The reset signal is designed to be Low at initial powerup and become High shortly after VCC reaches its normal operating voltage.