Crystal Loop Analysis

The majority of oscillating components on the market are made of piezoelectric materials. Among all materials, oscillators made by quartz are the most stable. It can provide a stable and accurate frequency to the IC/ MCU once the oscillation circuit is optimized. Therefore, when using a quartz resonator or crystal, it is very important to pursue the optimization of the oscillation circuit,  and the purpose of oscillation circuit evaluation is to optimize the configuration.

Standard oscillation circuit and measuring criterion

In a standard oscillator circuit, the accuracy of the frequency comes from the adjustment of the combination of two capacitors to ground (CG/CD); the purpose of the current-limiting resistor (RD) is to reduce the current flowing through the quartz resonator or crystal to reduce the risk of accelerated aging; Furthermore, the oscillation circuit needs to be evaluated whether it is healthy enough in order to perform oscillation.

Therefore, there are three important test criteria in the oscillation circuit evaluation:


1. Frequency accuracymeasure whether the frequency is accurate
(Criteriawithin +/-10ppm)

2. Current consumptionmeasure the current flowing through the quartz resonator or crystal and calculate the consumption.(Criteria:within the definition of the item specification)

3. Negative resistance:Measure the health of the oscillation circuit to avoid the risk of no/ or unstable oscillation.(Criteria:five times of equivalent series resistance defined in the specification)

Why perform oscillation circuit evaluation?


Don't Do

Able avoid poor oscillation problem

Unable avoid poor oscillation problem

Save time to adjust capacitors for engineers 

Spend time to adjust capacitors for engineers

Reduce developing time for projects

Unable Reduce developing time for projects


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