OCXO Frequently Asked Questions

Q1: What phase noise level do I actually need for my OCXO application?

For RF synthesis and high-resolution ADC/DAC, you need at least -150 dBc/Hz at 10 kHz offset. USB audio at 192 kHz doesn't require better than -140 dBc/Hz — the jitter contribution from OCXO is dwarfed by USB packet jitter. Choose based on your application, not the highest number.

Q2: How long does OCXO warm-up actually take?

Standard OCXOs take 2-5 minutes to reach thermal equilibrium. Traditional units can take 10+ minutes. For frequently power-cycled portable test gear, choose low-power OCXOs with 20-second warm-up to ±1 ppm. Always-on DAC or server hardware only warms up once, so standard warm-up is acceptable.

Q3: Can I use an OCXO in a battery-powered device?

Standard OCXOs draw 500mA-1A during warm-up and 100-200mA steady state, which is too much for battery operation. Modern ultra-low-power OCXOs reduce steady-state current to 23mA at 3.3V, making them viable for battery backup systems. Check the steady-state current, not just warm-up current.

Q4: How do I verify that an OCXO's claimed specs are real?

Request per-unit test reports showing drift under thermal cycling, not just typical values. Verify phase noise measurements at multiple offset frequencies (1Hz, 10Hz, 100Hz, 1kHz, 10kHz). Reputable suppliers provide ISO 9001 certification, RoHS declarations, and lot traceability with every shipment.

Q5: What is the typical batch-to-batch variation for OCXOs?

Budget OCXOs from unknown suppliers can have 10-20% variation between lots, especially on phase noise and temperature stability. Quality manufacturers control lot-to-lot variation to under 5% through 100% testing and crystal grading. Always request lot traceability documentation for production orders.

Q6: What MOQ should I expect when buying OCXOs for prototyping?

Most Chinese suppliers require MOQ of 500-3000 pieces, which is impractical for prototyping. Specialist suppliers offer samples from 1-5 pieces with volume pricing starting at 50 units. Expect to pay 2-3x the unit price for small sample orders compared to production quantities.

Q7: How long is the typical lead time for OCXO orders?

In-stock standard models ship in 5-15 business days. Custom or high-precision OCXOs take 4-6 weeks, with fully custom designs requiring 8-12 weeks. Emergency restocks risk mixed lots and missing documentation, so plan lead times in your project schedule.

Q8: Is it worth buying OCXOs from Chinese suppliers instead of established brands?

Chinese manufacturers have evolved from budget alternatives to serious competitors in precision timing. Modern Chinese OCXOs now match Western brands on core specs — phase noise, temperature stability, and ADEV — at 40-60% lower price points. For mission-critical aerospace and medical programs requiring decades of field-proven heritage and global supply chain redundancy, established Tier 1 brands remain the standard. For industrial, test & measurement, and commercial applications where you need guaranteed performance without the premium price tag, qualified Chinese manufacturers deliver identical specifications at a fraction of the total cost of ownership.

Q9: Which OCXO stability class do I need for my application?

5G small cells and IoT modules need ±0.5ppm stability. Test equipment and lab references require ±0.01ppm or better. Precision metrology and space applications demand sub-ppb performance. Always match the stability class to your application — over-specifying wastes 3-5x the cost.

Q10: Will OCXO heat generation affect nearby components on my PCB?

OCXOs run at 70-85°C internally, which can heat adjacent components. Keep OCXOs away from hot airflow sources and sensitive analog circuits. Add thermal guard zones in PCB layout and separate copper pour under the OCXO can. Low-power OCXOs generate significantly less heat than traditional units.

Q11: How much does an OCXO drift over one year of operation?

Premium OCXOs drift less than 0.1 Hz at 10 MHz per year (≈10ppb). Budget OCXOs can drift 1-5 Hz per year (100-500ppb). Aging rate depends on crystal quality and burn-in process. Well-aged crystals show logarithmic aging — most drift happens in the first year.

Q12: What is a typical MTBF for industrial OCXOs?

Quality OCXOs have MTBF exceeding 100,000 hours (over 11 years of continuous operation). The main failure point is the heater circuit, not the crystal itself. Confirm accelerated life test (ALT) data from suppliers, and check if they offer extended warranty options for critical applications.

Q13: Should I choose CMOS or sine wave output for my OCXO?

CMOS output is simpler for direct FPGA/MCU interfacing but has higher jitter. Sine wave output provides lower phase noise and better signal purity for RF and high-speed DAC applications. Most modern OCXOs offer both output options — choose based on your downstream circuit requirements.

Need help choosing the right OCXO for your application? Contact our engineering team for technical support and sample requests.