TCXO Selection Guide: Specs, Packages & Top Picks for Precision Timing

Why a 50-Cent Crystal Isn't Enough

A plain AT-cut crystal gives you ±20ppm over -20°C to +70°C. That's fine for UART clocks and basic MCU timing. But when you're running a GPS receiver that needs ±0.5ppm to maintain lock, or an LTE modem where frequency error above ±0.1ppm causes dropped packets, you need a TCXO.

In 2026, GNSS modules in everything from asset trackers to autonomous drones have pushed TCXOs into high demand. The good news: supply has stabilized for standard grades. The bad news: high-stability (±0.1ppm) and small-package (2.0×1.6mm) parts from NDK and TXC still command premium pricing. We've seen those prices — budget for them.

TCXO Stability Grades: What the Numbers Mean

TCXO stability is specified as frequency deviation over the operating temperature range, in ppm (parts per million). Here's what each grade actually buys you:

A ±2.5ppm TCXO is fine for Wi-Fi. Your router's reference clock can be off by 2.5ppm and 802.11 still works. But GPS is unforgiving — a 1ppm frequency error translates to roughly 1.5km of position drift in cold start. That's why GNSS modules spec ±0.5ppm max. We start there when ordering for a receiver board.

Frequency vs. temperature slope (Δf/ΔT): Most datasheets give you stability over the full range, but the rate of change matters too. A TCXO that drifts rapidly between -10°C and 0°C will cause more acquisition problems than one with linear, slow drift across the whole range. Look for the frequency-temperature curve, not just the max deviation number.

Output Type: Clipped Sine vs. CMOS vs. LVDS

• Clipped sine wave: The standard for GNSS TCXOs. 0.8Vp-p into 10kΩ || 10pF load. Low EMI, simple termination. You'll see this on 90% of GPS TCXOs.
• CMOS: Square wave, rail-to-rail. Used for clocking MCUs, FPGAs, and Ethernet PHYs. Drives higher capacitive loads but radiates more EMI.
• LVDS / LVPECL: Differential outputs for high-speed clocks (>100MHz). Lower jitter, better noise immunity. Overkill for a TCXO application — if you need this, you're probably looking at an OCXO or high-end XO instead.

Supply voltage: The industry has largely converged on 3.3V and 1.8V. A 1.8V TCXO is increasingly common for low-power GNSS modules like the u-blox M10 series. Check your receiver's reference input spec — feeding 3.3V into a 1.8V clock input destroys the receiver. We usually go with 3.3V unless the module forces 1.8V.

Phase Noise and Why It Matters for Wireless

TCXOs aren't immune to phase noise. Close-in phase noise (10Hz to 1kHz offset) affects PLL lock time and reciprocal mixing in receivers. A TCXO with -85dBc/Hz at 10Hz offset will give you noticeably better GPS TTFF (time to first fix) than one with -75dBc/Hz. This isn't on the summary datasheet — you need to pull the phase noise plot. It's usually why spec-identical parts behave differently in the field.

Popular TCXOs Engineers Stock

The NDK NT2016SA in the 2.0×1.6mm package is ubiquitous in cellular IoT modules. Small, reliable, and available in volume — that's the part we reach for first. The Abracon ASTX-H11 series is a solid alternative when NDK lead times stretch, just mind the 2016 vs 3225 package.

TCXO Supply Considerations

Standard 26MHz TCXOs (the mobile/GPS sweet spot) are commodity parts with 4-8 week lead times. But specialty frequencies (19.2MHz for certain cellular chipsets, 38.4MHz for some timing applications) can be 12+ weeks. Search TCXOs on PartsCube Global before you design in a non-standard frequency — if nobody stocks it, the schedule slips.

Need a TCXO you can actually get in production quantities? Check inventory at partscubeglobal.com.

References

• IPC Standards Library
• IEEE Xplore Digital Library