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CDCE937-Q1, CDCEL937-Q1

www.ti.com

SCAS892C – FEBRUARY 2010 – REVISED DECEMBER 2016

Product Folder Links: CDCE937-Q1 CDCEL937-Q1

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Copyright © 2010–2016, Texas Instruments Incorporated

10 Detailed Description

10.1 Overview

The

CDCE937-Q1

and

CDCEL937-Q1

devices

are

modular

PLL-based

low-cost

high-performance

programmable clock synthesizers, multipliers, and dividers. It generates up to seven 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

three independent configurable PLLs.

The CDCEx937-Q1 has separate output supply pins, VDDOUT, which is 1.8 V for CDCEL937-Q1 and from 2.5 V

to 3.3 V for CDCE937-Q1.

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 pF to 20 pF.

Additionally, an on-chip VCXO is selectable which allows synchronization of the output frequency to an external

control signal (that is, PWM signal).

The deep M/N divider ratio allows the generation of zero ppm audio or video, networking (WLAN, Bluetooth,

Ethernet, GPS) or Interface (USB, IEEE1394, Memory Stick) clocks from a reference input frequency such as

27 MHz.

All PLLs supports SSC (spread-spectrum clocking). SSC can be center-spread or down-spread clocking which 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 optimized jitter transfer characteristic of each PLL.

The device supports non-volatile EEPROM programming for ease-customized application. It is preset to a factory

default configuration (see Default Device Setting). It can be reprogrammed to a different application configuration

before PCB assembly, or reprogrammed by in-system programming. All device settings are programmable

through 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 output-disable function.

The CDCEx937-Q1 operates in 1.8-V environment. It is characterized for operation from –40°C to 125°C.