Question 1

What is AEC-Q200? What is IATF 16949?

Accepted Answer

A.

AEC-Q200 was created by the Automotive Electronics Council (AEC), an organization that was founded in the 1990s by three of the United States’ major automobile manufactures – Chrysler, Ford, and General Motors. Its purpose was to establish global common part-qualification and quality-system standards for automotive electronic components. They are the standardization body responsible for establishing reliability and certification benchmarks for electronic components. Components that meet the specifications and standards set by the committee are suitable for use in the harsh automotive environment without additional component-level qualification testing.
The standard’s core requirements, include:

Stress Testing: Components are subjected to various stress tests such as temperature cycling, humidity, vibration, mechanical shock, and more.
Electrical Performance: Testing for electrical parameters like capacitance, resistance, inductance, and insulation resistance.
Mechanical Performance: Ensuring mechanical robustness and integrity.
Environmental Testing: Exposure to environmental factors like salt spray, thermal shock, and moisture resistance.

Components must pass a series of tests specified in AEC-Q200 to be qualified. The testing process ensures that components meet the necessary reliability and durability standards for automotive use.

IATF 16949 was developed by the International Automotive Task Force (IATF) and is aligned with ISO 9001, incorporating additional requirements specific to the automotive industry. This international standard for quality management systems (QMS) is specifically designed for the automotive sector. It focuses on continuous improvement, defect prevention, and reduction of variation and waste in the supply chain from design to delivery.
The standard’s core requirements, include:

Quality Management System (QMS): Establishing a structured QMS that meets customer and regulatory requirements
Leadership and Commitment: Involvement of top management in the QMS
Planning: Risk management, setting quality objectives and planning changes
Support: Resource management, including human resources, infrastructure and environment
Operation: Product lifecycle processes, from design to delivery
Performance Evaluation: Monitoring, measurement, analysis, and evaluation of QMS performance
Improvement: Continuous improvement and corrective actions

Question 2

What is a quartz crystal oscillator?

Accepted Answer

A.

The main function is to convert mechanical energy and electrical energy into a basic signal source through the piezoelectric effect, providing a fixed clock signal for frequency control and timing. Any device that requires a frequency signal can utilize the oscillation of quartz crystal through its piezoelectric effect. It is an essential component for most electronic products.

It is an electronic component that uses the piezoelectric effect of quartz crystal (also known as crystal) to generate a highly precise oscillating frequency.

A quartz crystal (referred to as "crystal" or "Xtal") is a quartz blank packaged with electrodes and an outer casing. It is also called a quartz resonator. This is a passive component and does not contain active elements, meaning it requires an external circuit to generate oscillations. Quartz crystals are typically two-pin electronic components.
A quartz crystal oscillator (abbreviated as OSC or XO) is a module containing both the quartz crystal and the oscillation circuit, which requires a power supply and can directly output an oscillating signal. Since it contains active electronic components, the entire module is classified as an active component. Quartz oscillators are usually four-pin electronic components, with two pins for power supply, one pin for oscillation signal output, and the remaining pin either unused or for control purposes.

Question 3

What is PPM/PPB? How to determine PPM/PPB?

Accepted Answer

A.

"ppm" stands for parts per million, and "ppb" stands for parts per billion. In frequency components, ppm/ppb represents the ratio of frequency deviation to the nominal frequency. These units are commonly used in the frequency control product (FCP) industry to describe the frequency variation range of crystal oscillators.
Example:

Nominal frequency (N.F.) = 25.000000 MHz

Actual frequency (A.F.) = 24.999950 MHz
⇒ (A.F. - N.F.) / N.F. = (24.999950 - 25.000000) / 25.000000
= -0.000002
= -2 × 10⁻⁶ (parts per million)
= -2 ppm

Nominal frequency (N.F.) = 40.000000000 MHz

Actual frequency (A.F.) = 40.000000040 MHzz
⇒ (A.F. - N.F.) / N.F. = (40.000000040 - 40.000000000) / 40.000000000
= +0.000000001
= +1 × 10⁻⁹ (parts per billion)
= +1 ppb

Question 4

How to calculate CL and external capacitance?

Accepted Answer

A.

The calculation formula is as follows:
CL=(CL1XCL2)/ (CL1+CL2)+Cs

Where:
CL1and CL2are the external capacitors in the oscillator circuit.
Csis the stray capacitance in the circuit, generally about 2-5 pF.

Stray capacitance refers to the capacitance that includes:
The capacitance within the IC itself.
The capacitance between the layout traces.
The capacitance between different layers of the PCB, and so on.

Question 5

Why is there no signal output from the crystal?

Accepted Answer

A.

If there is no signal output across the crystal terminals using an oscilloscope or spectrum analyzer, please follow these troubleshooting steps:

Check Voltage at Input and Output: Ensure that there is voltage output at the input terminal (Xin) and output terminal (Xout) of the crystal, and that it meets the specifications required by the IC.
Remove the Crystal and Test: Remove the crystal and use a professional testing instrument to check whether its parameters meet the specifications. You can also send it to your supplier for testing.
Verify Crystal Quality: If the crystal is confirmed to be functional but still does not oscillate, the issue may be due to insufficient negative resistance in the oscillation loop. Generally, negative resistance should be greater than five times of ESR for optimal performance.

∣−R∣=Re+VR, Negative resistance margin is defined as: Gain Margin=∣−R∣/ESRmax ≥ 5

Check Drive Level: If the drive level is too high, it can cause unstable frequency, amplitude, and higher resistance, or if the drive level is too low, it may also stop oscillation.
Adjust External Components: If the problem still cannot be solved after adjusting parameters through external components, please contact the field application engineer of the crystal or IC manufacturer for further assistance.

FAQ