July 2009

Contents

Using Low-Cost Crystals with MachXO PLDs

In many applications, such as industrial process control and sensors, system designers need to provide a clock source to the PLD. Typically, the clock source is generated by a stand-alone integrated oscillator which increases the total board cost. A less-expensive option is to generate the clock signal by using a discrete crystal connected directly to the PLD. As illustrated in the table below, the primary advantage of using a discrete crystal as a clock source is lower board cost.

Discrete Crystal Using Pierce Circuit vs. Integrated Oscillator
	Crystal	Oscillator
Approximate cost	$0.30 to $0.80	$1.80 to $3.00
Design effort	Pierce circuit must be designed	Minimal / none
Available frequency	30KHz to 50MHz	1MHz to 250MHz

The MachXO PLD family is an ideal fit for industrial applications. It can be connected directly to a discrete crystal circuit resulting in significantly lower board cost. The popular MachXO Mini Development Kit demonstrates this technique.

Combining an optimized look-up table (LUT) architecture with low-cost embedded Flash process technology, the instant-on, easy-to-use MachXO devices are the most versatile, non-volatile PLDs for low-density applications.

MachXO Mini Evaluation Board

To Learn More

For further information on how to use a discrete crystal as a PLD clock source, refer to application note AN8080, Using a Discrete Crystal as a PLD Clock Source. For more information about the MachXO PLD family and MachXO Mini Development Kit, visit the Lattice website or contact your local Lattice sales representative.