SCAS891A February   2010  – May 2025 CDCE949-Q1

PRODUCTION DATA  

  1.   1
  2. 1 Features
  3. 2 Applications
  4. 3 Description
  5. 4 Pin Functions
  6. 5 Specifications
    1. 5.1  Absolute Maximum Ratings
    2. 5.2  ESD Ratings
    3. 5.3  Thermal Resistance Characteristics
    4. 5.4  Recommended Operating Conditions
    5. 5.5  Recommended Crystal/VCXO Specifications
    6. 5.6  EEPROM Specification
    7. 5.7  Electrical Characteristics
    8. 5.8  Timing Requirements
      1. 5.8.1 CLK_IN Timing Requirements
      2. 5.8.2 SDA/SCL Timing Requirements
    9. 5.9  Timing Diagrams
      1. 5.9.1 Timing Diagram for the SDA/SCL Serial Control Interface
    10. 5.10 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 Configuration
      2. 7.3.2 Default Device Setting
      3. 7.3.3 SDA/SCL Serial Interface
      4. 7.3.4 Data Protocol
      5. 7.3.5 PLL Multiplier/Divider Definition
    4. 7.4 Device Functional Modes
      1. 7.4.1 SDA/SCL Hardware Interface
    5. 7.5 Programming
      1. 7.5.1 Generic Programming Sequence
      2. 7.5.2 Byte Write Programming Sequence
      3. 7.5.3 Byte Read Programming Sequence
      4. 7.5.4 Block Write Programming Sequence
      5. 7.5.5 Block Read Programming Sequence
  9. 8 Register Maps
    1. 8.1 SDA and SCL Registers
    2. 8.2 Configuration Registers
      1. 8.2.1 Generic Configuration Register
      2. 8.2.2 PLL1 Configuration Register
      3. 8.2.3 PLL2 Configuration Register
      4. 8.2.4 PLL3 Configuration Register
      5. 8.2.5 PLL4 Configuration Register
  10. 9 Application and Implementation
    1. 9.1 Application Information
    2. 9.2 Typical Application
      1. 9.2.1 Design Requirements
      2. 9.2.2 Detailed Design Procedure
        1. 9.2.2.1 Spread Spectrum Clock (SSC)
        2. 9.2.2.2 PLL Frequency Planning
        3. 9.2.2.3 Crystal Oscillator Start-Up
        4. 9.2.2.4 Frequency Adjustment With Crystal Oscillator Pulling
        5. 9.2.2.5 Unused Inputs and Outputs
        6. 9.2.2.6 Switching Between XO and VCXO Mode
      3. 9.2.3 Application Performance Plots
    3. 9.3 Power Supply Recommendations
    4. 9.4 Layout
      1. 9.4.1 Layout Guidelines
      2. 9.4.2 Layout Example
  11. 10Device and Documentation Support
    1. 10.1 Documentation Support
      1. 10.1.1 Related Documentation
    2. 10.2 Receiving Notification of Documentation Updates
    3. 10.3 Support Resources
    4. 10.4 Trademarks
    5. 10.5 Electrostatic Discharge Caution
    6. 10.6 Glossary
  12. 11Revision History
  13. 12Mechanical, Packaging, and Orderable Information

3 Description

The CDCE949-Q1 is a modular PLL-based low-cost high-performance programmable clock synthesizer, multiplier, and divider. The device generates up to 9 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 CDCE949-Q1 has separate output supply pins, VDDOUT, of 2.5V to 3.3V.

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 zero-ppm audio/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 technique is common for reducing 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 to the application. The CDCE949-Q1 is preset to a factory-default configuration (see the Default Device Configuration section). 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/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-Q1 operates in a 1.8V environment. The device operates within a temperature range of –40°C to 125°C.

Table 3-1 Package Information
DEVICE PACKAGE(1) PACKAGE SIZE(2)
CDCE949-Q1 PW (TSSOP, 24) 7.8mm × 6.4mm
(1) For more information, see Section 12.
(2) The package size (length × width) is a nominal value and includes pins, where applicable.
CDCE949-Q1