SCAS844G August   2007  – January 2024 CDCE949 , CDCEL949

PRODUCTION DATA  

  1.   1
  2. 1 Features
  3. 2 Applications
  4. 3 Description
  5. 4 Pin Configuration and Functions
  6. 5 Specifications
    1. 5.1 Absolute Maximum Ratings
    2. 5.2 ESD Ratings
    3. 5.3 Recommended Operating Conditions
    4. 5.4 Thermal Information
    5. 5.5 Electrical Characteristics
    6. 5.6 EEPROM Specification
    7. 5.7 Timing Requirements: CLK_IN
    8. 5.8 Timing Requirements: SDA/SCL
    9. 5.9 Typical Characteristics
  7. 6 Parameter Measurement Information
  8. 7 Detailed Description
    1. 7.1 Overview
    2. 7.2 Functional Block Diagram
    3. 7.3 Feature Description
      1. 7.3.1 Control Terminal Setting
      2. 7.3.2 Default Device Setting
      3. 7.3.3 SDA/SCL Serial Interface
      4. 7.3.4 Data Protocol
    4. 7.4 Device Functional Modes
      1. 7.4.1 SDA/SCL Hardware Interface
    5. 7.5 Programming
  9. 8 Application and Implementation
    1. 8.1 Application Information
    2. 8.2 Typical Application
      1. 8.2.1 Design Requirements
      2. 8.2.2 Detailed Design Procedure
        1. 8.2.2.1 Spread Spectrum Clock (SSC)
        2. 8.2.2.2 PLL Frequency Planning
        3. 8.2.2.3 Crystal Oscillator Start-Up
        4. 8.2.2.4 Frequency Adjustment With Crystal Oscillator Pulling
        5. 8.2.2.5 Unused Inputs and Outputs
        6. 8.2.2.6 Switching Between XO and VCXO Mode
      3. 8.2.3 Application Curves
    3. 8.3 Power Supply Recommendations
    4. 8.4 Layout
      1. 8.4.1 Layout Guidelines
      2. 8.4.2 Layout Example
  10. 9 Register Maps
    1. 9.1 SDA/SCL Configuration Registers
  11. 10Device and Documentation Support
    1. 10.1 Device Support
      1. 10.1.1 Development Support
    2. 10.2 Related Documentation
    3. 10.3 Related Links
    4. 10.4 Receiving Notification of Documentation Updates
    5. 10.5 Support Resources
    6. 10.6 Trademarks
    7. 10.7 Electrostatic Discharge Caution
    8. 10.8 Glossary
  12. 11Revision History
  13. 12Mechanical, Packaging, and Orderable Information

Package Options

Mechanical Data (Package|Pins)
Thermal pad, mechanical data (Package|Pins)
Orderable Information

7.1 Overview

The CDCE949 and CDCEL949 devices are modular PLL-based, low-cost, high-performance, programmable clock synthesizers, multipliers, and dividers. They generate up to nine output clocks from a single input frequency. Each output can be programmed in-system for any clock frequency up to 230 MHz, using one of the four integrated configurable PLLs.

The CDCEx949 has separate output supply pins, VDDOUT, which is 1.8 V for CDCEL949 and 2.5 V to 3.3 V for CDCE949.

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, a selectable on-chip VCXO allows synchronization of the output frequency to an external control signal, that is, the PWM signal.

The deep M/N divider ratio allows the generation of 0-ppm audio and 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 spread-spectrum clocking (SSC). 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. The internal EEPROM of the CDCEx949 is preset to a factory-default configuration (see Default Device Setting). The EEPROM 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 and 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 CDCEx949 operates in a 1.8-V environment within a temperature range of –40°C to 85°C.