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DESCRIPTION

DEVICE INFORMATION

CDCE949

CDCEL949

SCAS844 – JUNE 2007

These devices have limited built-in ESD protection. The leads should be shorted together or the device placed in conductive foam

during storage or handling to prevent electrostatic damage to the MOS gates.

The CDCE949 and CDCEL949 are modular PLL-based low cost, high-performance, programmable clock

synthesizers, multipliers and dividers. They generate 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.

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, an on-chip VCXO is selectable, allowing synchronization of the output frequency to an external

control signal, i.e. 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 CDCx949 operates in a 1.8-V environment. It is characterized for operation from –40

°C to 85°C.

TERMINAL FUNCTIONS

TERMINAL

I/O

NAME

NO. (TSSOP24)

21, 19, 18, 7, 8,

Y1, Y2, ...Y9

O

LVCMOS outputs

16, 15, 11, 12

Xin/CLK

1

I

Crystal oscillator input or LVCMOS clock input (selectable via SDA/SCL bus)

Xout

24

O

Crystal oscillator output (leave open or pull up when not used)

4

I

VCXO control voltage (leave open or pull up when not used)

3, 13

Power

1.8V power supply for the device

CDCEL949: 1.8 V supply for all outputs

6, 10, 17

Power

CDCE949: 3.3 V or 2.5 V supply for all outputs

GND

5, 9, 14, 20

Ground

Ground

S0

2

I

User-programmable control input S0; LVCMOS inputs; internal pull-up 500 k

Ω

SDA: Bi-directional serial data input/output (default configuration), LVCMOS; internal

SDA / S1

23

I/O / I

pull-up 500 k

Ω; or

S1: User-programmable control input; LVCMOS inputs; internal pull-up 500 k

Ω

SCL: Serial clock input (default configuration), LVCMOS; internal pull-up 500 k

Ω; or

SCL / S2

22

I

S2: User-programmable control input; LVCMOS inputs; internal pull-up 500 k

Ω

2

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