This application note discusses the use of clock distribution circuits in smart phone system design. As smart phones become more popular in the market, additional features such as A-GPS, Bluetooth, WLAN, and DVB-H are now included in cell phone designs. In all of these application modules, a master clock is needed, which is typically an external crystal oscillator. The master clock modulates the transmitted or received data to the proper frequency. This application note compares conventional clock trees that use discrete crystals for different modules or discrete buffer solutions to the clock solution using the integrated STCD1020/1030/1040 series circuits from STMicroelectronics (referred to as STCD10x0 throughout this application note, please refer to the STCD1020, STCD1030, STCD1040 datasheet). The benefits of using STCD10x0 are illustrated, and technical hints are given to help cell phone system designers use the STCD10x0 clock distribution solution.
This document discusses the design of clock distribution circuits for smart phones incorporating features like A-GPS, Bluetooth, WLAN, and DVB-H. It compares three approaches: using dedicated crystals for each module, using discrete buffer solutions, and using the integrated STCD10x0 series circuits from STMicroelectronics. The note illustrates the benefits of the STCD10x0 solution, such as reduced PCB area and lower quiescent current, compared to conventional methods.
| Quiescent current (4-channel, 10 pF load) | 2.8 mA |
|---|---|
| Output voltage versions | 1.8 V and 2.8 V |
| Capacitive load per output | 10 pF |
The STCD10x0 offers up to 60% less PCB area and at least 30% less quiescent current compared to discrete buffer solutions.
Yes, each output channel can be enabled or disabled individually to save current when the module is not in use.