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.
The CDCEx949 has separate output supply pins, VDDOUT, 1.8 V for
the 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, 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 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 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. 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 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. It operates within a temperature range of
–40°C to 85°C.
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