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“TCXO” installed in products that require highly accurate “frequency-temperature characteristics”
A TCXO is also called a "temperature compensated oscillator" and is a type of oscillator with a built-in temperature compensation circuit to correct the temperature characteristics of the frequency.
It is used when requiring a clock to have excellent frequency-temperature characteristics* in the final product or mounting board developed by the customer.
*Frequency-temperature characteristics are a very important performance indicator for clocks that shows how much the frequency changes in response to surrounding temperature fluctuations.
Clock is now indispensable for electronic devices, but the clock frequency can shift when surrounding temperature changes occur.
In the worst case, it may cause problems such as the electronic device system not working.
TCXO has the ability to quickly correct the original frequencywhen a frequency shift (change) occurs due to temperature change.
It will be installed in the following applications that require such highly accurate frequency-temperature characteristics.
This is the oscillator you should choose when the frequency-temperature characteristics of SPXO (general-purpose packaged oscillator) are not satisfactory.
[Main applications in which TCXO is installed]
・Mobile phone (small TCXO/so-called mobile TCXO type)
・Wireless modules such as GPS, Wi-Fi, BLE (small TCXO)
·wireless
・Broadcast equipment
·Medical equipment
*Reference information: SiTime's high-precision TCXO lineup
Four points to consider when selecting a TCXO
If you want to suppress frequency deviations due to temperature changes as much as possible, what points should you keep in mind when selecting a TCXO?
Now, I will explain ``four points you should keep in mind''.
Point ① Frequency deviation
The frequency deviation value guaranteed on the data sheet indicates "how much the standard frequency deviates due to operating conditions, etc.", and in most cases, the unit is expressed in ppm (PPM). ppm is an abbreviation for parts per million, and represents"some parts per million."
Although it is also expressed as "frequency tolerance," it may also include room temperature deviation, so when making comparisons, it is important to carefully check each condition in the data sheet of each product before making a selection.
Point ② Frequency aging
Also expressed as “long-term frequency stability.” This shows "how much the frequency deviates in each period unit (1 day, 30 days, 1 year, etc.) at a defined temperature."
It is also necessary to check the conditions and definitions listed in each data sheet in advance and compare them.
Point ③ Frequency temperature characteristics
One of the characteristics of the TCXO is that it has "little deviation due to temperature changes," but its performance varies depending on the product. Therefore, it is necessary to consider and assess the actual usage environment of the final product (application).
Rather than making judgments based only on the temperature characteristics listed in the datasheet, it is also necessary to evaluate the temperature close to the actual ambient temperature.
SiTime's TCXO has the resonator and temperature sensor physically close to each other, so it can compensate for frequency changes very quickly in response to changes in the resonator's temperature. (temperature compensation)
On the other hand, crystal oscillators have a temperature compensation function in the oscillation circuit near the PCB, which heats up before the resonator.
Because it is physically separated from the resonator, its frequency-temperature characteristics performance is slightly inferior compared to MEMS oscillators.
Point ④ Phase noise
Low phase noise performance is required for use as a reference signal in a hardware system.
Another point to pay attention to is the performance of phase jitter, which expresses the "shift" and "fluctuation" of a clock signal.
This also requires the customer to prepare a measurement environment, but SiTime has a wide range of evaluation tools.
If you are having trouble, it is also effective to utilize the evaluation tools and evaluation kits (DKs) prepared by these manufacturers.
Click here to learn about SiTime's Phase Noise evaluation tool
SiTime's TCXO lineup
SiTime's TCXO lineup is as follows.
In addition, this video provides an easy-to-understand comparison of the characteristics of SiTime's MEMS oscillator TCXO and crystal oscillator TCXO.
(Youtube will open. Each test has been conducted, and you can see the temperature characteristics, vibration and shock resistance, power supply noise resistance, etc. of both products mounted on the same board.)
| type name | frequency | Frequency deviation (ppm) | Output format | package size |
| SiT5155 | Choose from 12 types |
±0.5 |
LVCMOS Clipped sinewave |
5.0x3.2 |
| SiT5156 | 1~60MHz |
±0.5 ±1 ±2.5 |
LVCMOS Clipped sinewave |
5.0x3.2 |
| SiT5157 |
1~220MHz |
±0.5 ±1 ±2.5 |
LVCMOS |
5.0x3.2 |
| SiT5356/SiT5357 |
SiT5356：1~60MHz SiT5357：60~220MHz |
±0.1 ±0.2 ±0.25 |
SiT5356： LVCMOS Clipped sinewave SiT5357： LVCMOS |
5.0x3.2 |
| SiT5358/SiT5359 |
SiT5358：1~60MHz SiT5359：60~220MHz |
±0.05 |
SiT5358： LVCMOS Clipped sinewave SiT5359： LVCMOS |
5.0x3.2 |
| SiT5376/SiT5377 |
SiT5376：1~60MHz SiT5377：60~220MHz |
±0.1 ±0.2 ±0.25 |
SiT5376： LVCMOS Clipped sinewave SiT5377： LVCMOS |
5.0x3.5 |
| SiT5501/SiT5503 |
60~220MHz |
SiT5501： ±0.01 (±10 ppb) ±0.02 (±20 ppb) SiT5503： ±0.005 (±5 ppb) |
LVCMOS Clipped sinewave |
7.0x5.0 |