描述The CDCE949 is amodular PLL-based low-cost high-performance programmable clock synthesizer, multiplier, and divider. It generates up to 9 output clocks from a single input frequency. Each output can be programmed in-system for any clock frequency up to 230 MHz, using up to four independent configurable PLLs. The CDCE949 has separate output supply pins, VDDOUT, of 2.5 V to 3.3 V.The input accepts an external crystal or LVCMOS clock signal. If an external crystal is used, an on-chip load capacitor is adequate for most applications. The value of the load capacitor is programmable from 0 to 20 pF. Additionally, an on-chip VCXO is selectable, allowing synchronization of the output frequency to an external control signal, that is, a PWM signal. The deep M/N divider ratio allows the generation of zero-ppm audio/video, networking (WLAN, BlueTooth™, Ethernet, GPS) or Interface (USB, IEEE1394, Memory Stick) clocks from a reference input frequency, such as 27 MHz. All PLLs support SSC (Spread-Spectrum Clocking). SSC can be Center-Spread or Down-Spread clocking. This is a common technique to reduce electro-magnetic interference (EMI). Based on the PLL frequency and the divider settings, the internal loop-filter components are automatically adjusted to achieve high stability, and to optimize the jitter-transfer characteristics of each PLL. The device supports non-volatile EEPROM programming for easy customization of the device to the application. It is preset to a factory-default configuration (see the Default device Configuration section). It can be reprogrammed to a different application configuration before PCB assembly, or reprogrammed by in-system programming. All device settings are programmable through the SDA/SCL bus, a 2-wire serial interface. Three programmable control inputs, S0, S1 and S2, can be used to control various aspects of operation including frequency selection, changing the SSC parameters to lower EMI, PLL bypass, power down, and choosing between low level or 3-state for the output-disable function. The CDCE949 operates in a 1.8 V environment. It operates within a temprateure range of –40°C to 125°C.特性 Qualified for Automotive Applications Member of Programmable Clock Generator Family CDCE913/CDCEL913: 1 PLLs, 3 Outputs CDCE925/CDCEL925: 2 PLLs, 5 Outputs CDCE937/CDCEL937: 3 PLLs, 7 Outputs CDCE949: 4 PLLs, 9 Outputs In-System Programmability and EEPROM Serial Programmable Volatile RegisterNon-Volatile EEPROM to Store Customer Settings Highly Flexible Clock Driver Three User-Definable Control Inputs [S0/S1/S2]; e.g,. SSC-Selection, Frequency Switching, Output Enable or Power Down Generates Highly-Accurate Clocks for Video, Audio, USB, IEEE1394, RFID, Generates Common Clock Frequencies Used with TI DaVinci™, OMAP™, DSPs BlueTooth™, WLAN, Ethernet and GPS Programmable SSC Modulation Enables 0-PPM Clock GenerationSelectable Output Frequency up to 230 MHz Flexible Input Clocking Concept External Crystal: 8 to 32 MHz On-Chip VCXO: Pull-Range ±150 ppm Single-Ended LVCMOS up to 160 MHz Low-Noise PLL Core Integrated PLL Loop Filter ComponentsVery Low Period Jitter (typ 60 ps) Separate Output Supply Pins 3.3 V and 2.5 V 1.8 V Device Power Supply Latch-Up Performace Meets 100 mAPer JESD 78, Class I Wide Temperature Range –40°C to 125°C Packaged in TSSOPDevelopment and Programming Kit for Ease PLL Design and Programming (TI-Pro Clock) APPLICATIONS D-TV, HD-TV, STB, IP-STB, DVD-Player, DVD-Recorder, Printer General Purpose Frequency Synthesizing