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

3 Description

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

The CDCEx949 has separate output supply pins (VDDOUT): 1.8V for the CDCEL949 and 2.5V to 3.3V for the 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 0pF to 20pF. 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 0ppm audio or video, networking (WLAN, BlueTooth™, Ethernet, GPS) or Interface (USB, IEEE1394, Memory Stick) clocks from a reference input frequency, such as 27MHz.

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.

Package Information
PART NUMBERPACKAGE(1)PACKAGE SIZE(2)
CDCE949
CDCEL949		PW (TSSOP, 24)7.8mm × 6.4mm
(1) For all available packages, see Section 12.
(2) The package size (length × width) is a nominal value and includes pins, where applicable.

The device supports non-volatile EEPROM programming for easy customization of the device to the application. The CDCEx949 is preset to a factory-default configuration. The device 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 1.8V environment within a temperature range of –40°C to 85°C.

GUID-D373EB43-AD70-4443-9304-971649795AF4-low.gifTypical Application Schematic