ClockMaster
8/8/2002
4
www.spincore.com
2. System Architecture
Block diagram
Figure 1 presents the general architecture of the ClockMaster
.
Fig. 1. ClockMaster
system architecture.
ClockMaster™, Fig. 1, contains a high performance Direct Digital Synthesis
(DDS) system equipped with additional circuitry for frequency control and
output interface. At the core of the ClockMaster™ board is a numerically
controlled oscillator (NCU) with an internal sine lookup table. Digital
output values of the DDS core are converted to sinusoidal waveforms via the
Digital-to-Analog (DAC) converter. The DAC’s output is then filtered,
amplified, and routed to the SMA output connector.
For the purpose of generating low-jitter digital output signals, the
ClockMaster™ is also equipped with a fast Schmidt trigger that extracts the
sign bit information of the generated analog waveforms. The sign bit is the
digital output signal of the system. By generating analog waveforms, low-
pass filtering them, and then extracting the sign bit, the resulting digital
output signals are of improved quality and reduced jitter, compared to the
standard approach where only the Most Significant Bit (MSB) of the DDS’s sine
lookup table is used.
The on-board Schmidt trigger is supplied off of a 2.5 V power supply line
and generates a maximum of 2.5 V voltage swing at the output pin.