Using clock distribution circuits in smart phone system design



Category: Telephone, cellular phone and intercom
Manufacture: ST Microelectronics, Inc.
Datasheet: Download this application note


Description:
AN2760 Application note
Using clock distribution circuits in smart phone system design
As smart phones become more and more popular in the market, additional features such as A-GPS, Bluetooth, WLAN and DVB-H are now included in the cell phone design. In all of these application modules, there is a common need for a master clock which is typically an external crystal oscillator. With the master clock the data transmitted or received is modulated to the proper frequency. In this application note, conventional clock trees which use discrete crystals for different modules or discrete buffer solutions are compared to the clock solution using the integrated STCD1020/1030/1040 series circuits from STMicroelectronics (referenced 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.
1 Conventional cell phone clock solutions compared to the STCD10x0 integrated solution . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4
1.1 1.2 1.3 1.4 1.5 Conventional clock solution - dedicated crystals for dedicated modules . . 4 Conventional clock solution - discrete buffer solution . . . . . . . . . . . . . . . . . 4 Integrated clock solution - STCD10x0 . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5 Integrated STCD10x0 clock solution in MID application . . . . . . . . . . . . . . 7 Integrated STCD10x0 clock solution in multimode RF front-end . . . . . . . . 7
Cell phone system design with STCD10x0 clock solution . . . . . . . . . . 8
2.1 Preparation to use STCD10x0 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 8
2.1.1 2.1.2 Setting a common clock frequency for each application . . . . . . . . . . . . . 8 Choosing the right clock source . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 9
Power supply VCC of STCD10x0 and decoupling . . . . . . . . . . . . . . . . . . . 9 Connection of the MCLK pin to external clock source . . . . . . . . . . . . . . . . 9 Connecting STCD10x0 outputs to application modules . . . . . . . . . . . . . . 10 Power-down sequence . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 10
Conclusion . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 12 Revision history . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 13

 
0-C     D-L     M-R     S-Z