FD5T Series Programmable

CMOS Clock Oscillator

November 2008

www.pletronics.com

425-776-1880

2

Description:

The FD5T series Programmable CMOS Clock Oscillator is a modular PLL-based low cost, high-

performance oscillator. The frequency range is from 12KHz to 230MHZ.

The FD5T base frequency, as noted in the device part number, is established during manufacture and is

permanently fixed. For convenience, the divider for output OUT characteristics may be pre-programmed

at the factory, or field programmed.

The FD5T has a separate output supply pin, V

device supply, V

The deep M/N PLL divider ratio allows the generation of zero-ppm clocks for applications such as WLAN,

BlueTooth, Ethernet, USB, IEEE1394, etc. from the base frequency.

The PLL supports Spread Spectrum Clocking (SSC). SSC may be programmed to be either center-

spread or down-spread. This is an important technique to reduce electro-magnetic interference (EMI).

The device supports non-volatile eePROM programming for easy customization of the device. As

shipped, the device is pre-programmed. Standard combinations are denoted by three characters in the

device part number. However, the FD5T may be reprogrammed to a different configuration.

Reprogramming may be either prior to assembly, or in-circuit via a 2-wire SDA/SCL I

programming is not allowed if the VCXO function is needed.

Two programmable control inputs, S1 and S2, may be used to control various aspects of FD55T operation

including selection of alternative frequency set(s), selection of SSC functionality, output tri-state and

power-down.

Reference Oscillator

The Reference Oscillator is an AT cut quartz crystal based oscillator. This oscillator is very similar to the

Pletronics SM77xxH product oscillator. This signal is the lowest jitter and can be an output or can be

divided down by the Divider #1. The user may specify any frequency between 12MHz and 32MHz for

this reference. All output frequencies are derived from (referenced to) this Reference Oscillator.

The VCXO input has a limited voltage range, the VCXO is associated with the internal 1.8V core. A

resistor in series with the Vcontrol input will permit interfacing to 3.3V analog circuits, the voltage range

that changes the frequency will still be limited but the larger voltages swings will not cause problems.

The VCXO function is only enabled (internally connected) if the part number indicates a VCXO

specification. When the VCXO function is enabled the I

PLL Multipliers

The PLL Multiplier can multiply the Reference Oscillator frequency from 1 (bypass mode) to any value

that is <=230MHz (the lowest frequency is the Reference Oscillator frequency).

The PLL Multipliers can have two setup options, 0 or 1, depending on which option is chosen and set by

the Sx control signals and the user’s definitions are stored in eePROM.

Spread Spectrum