FD5T

The FD5T is derived from the PLE FD51T series Programmable CMOS Clock Oscillator which is a modular PLL-based low cost, high-performance oscillator. The frequency output is set to 32.768KHz. The FD51xxT-32.768K base frequency is a 24.576MHz AT cut fundamental mode crystal.

The FD5T has a separate output supply pin, V_DDOUT, for either 1.8, 2.5 or 3.3V output logic levels. The device supply, V_DD which provides power to all the internal circuits, is nominally 1.8V.

The PLL FD5T is only utilized to support Spread Spectrum Clocking (SSC), in all other cases the PLL is disabled to reduce power. 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 FD5T supports non-volatile eePROM programming for easy customization of the device. As shipped, the device is pre-programmed. However, the FD51xxT-32.768K may be reprogrammed to a different configuration. Reprogramming may be either prior to assembly, or in-circuit via a 2-wire SDA/SCL I²C bus. In-circuit 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 FD5T operation including selection of alternative frequency set(s), selection of SSC functionality, output tri-state and power-down.