# ECE 697 SD - Midterm Organizer

###### tags: `ECE697SD` `Midterm`

## What's [MEMs Oscillators](https://www.mouser.com/applications/timer-mems-oscillators/)

An electrical oscillator produces an output with a precise frequency to generate timing pulses and synchronize events.

### Micro-Electro-Mechanical Systems (MEMs) technology

MEMs can provide a **accurate frequency** generation with **low-power**

> Why traditional solution being replaced?

### Traditional Oscillator Types
1. lowest-cost option is an RC oscillator
> uses a network of passive components and an amplifier to produce an oscillating signal using positive feedback
2. Integrated silicon oscillator uses similar circuitry
> but all of the components are on a single die, giving more precise operation and improved performance over temperature.
3. For more precision applications, a traditional way has been a circuit based on a vibrating quartz crystal.
> This integrated device is called a piezoelectric device. When the voltage is applied, the device can produce a precise frequency. Vibrating element can be changed into a ceramic material.
#### Check Table. 1 on the website
>Some types of traditional applications might sensitive to EMI(ElectroMagnetic Interface), a noise to oscillators.
##### This is probably the reason why traditional approaches cannot be applied on a embedded system.(? not sure)

## The advance of the semiconductor
A MEMs technology is based on semiconductor products, and it is designed to vibrate with a high frequency.

**The resonant frequency of a MEMs resonator is inversely proportional to its size** (What does it mean?)

1. Resonators in the kHz
Are optimized for low power consumption. They are typically used for time-keeping applications such as real-time clocks, or provide sleep and wake-up functions for power management systems.
2. Rsonators in the MHz
provide precise references for serial and parallel communication where data transfer speed is critical.

### Performance
current-generation devices can achieve stability as low as ±5ppm. For portable use, low-power devices can attain a frequency tolerance of ±20ppm and a stability of ±100ppm.

### Design awareness
e.g., In most applications, a single 0.1 μF capacitor between the power supply voltage and power return will shunt much of the power supply noise to ground. For greater noise reduction designers may implement RC or LC power supply filtering strategies.

##### Proper Design is important !

### Challenge: Reduce EMI
#### How EMI is produced?
A signal generated in one device can couple into other devices, causing errors or malfunctions. The oscillator is often the major source of EMI.

#### How to solve?
Filtering, shielding, and good layout practices can limit EMI, but add cost and consume board space. An alternate approach is to reduce clock-generated noise by modulating the clock frequency slowly over time.

## Related materials
1. [crystal](https://ieee-uffc.org/presentation/ieee-milestone-dedication-piezoelectric-quartz-oscillator-1921-1923-walter-guyton-cady)
2. [MEMs oscillator review for frequency and timing applications](https://iopscience.iop.org/article/10.1088/0960-1317/22/1/013001/meta?casa_token=6ZW02Z4Kv2gAAAAA:kySBXf3ogPQy74CUupGauXxLpjTDBLAOTzUIzzp8posyZHdXToYqGDFpXD7dwnTsS7tS9oxYHYQ)
3. [Recent progress on MEMs oscillator](https://www.ion.org/publications/abstract.cfm?articleID=10629)
4. [High performance crystal oscillator:theory and applications](https://ieeexplore.ieee.org/abstract/document/318?casa_token=AMCBkuek6QYAAAAA:rdhqJBcoRnX4hHXvR6eSt7BqHpYD55UobcuxZUB1fyOLDLjVe-ay4ZydKXlGfnEg97aducKAZfqN)
5. [A review of the recent development of MEMS and crystal oscillators](https://ieeexplore.ieee.org/abstract/document/4803352?casa_token=oim5Xk7xQMYAAAAA:pijvPW5-aSX2DGZJtTuUfGvMY46_teXTXIsVMEYja60YqtG99iiMsj1TINcQLpdHcfk5PGJNUtP3)