High-precision MEMS oscillators aim to transforms telecom, networking timing markets

 

For the telecom and networking-timing markets, a new
group of MEMS-based temperature-controlled oscillators (TCXOs) and differential
oscillators were engineered to solve telecommunications/networking equipment problems
that are coming to the fore today. As SiTime CEO Rajesh Vashist
explains, “Network
densification is driving rapid deployment of equipment in uncontrolled
environments such as basements, curbsides, rooftops, and on poles.” As a
result, oscillators must now operate in the presence of high temperature,
thermal shock, vibration, and unpredictable airflow—conditions that are
extremely challenging to quartz-based-oscillator performance.

 

rurc_sitime_oct2016_lres

To
overcome these environmental challenges, the devices in the group, which is referred to as the Elite Platform,
are based on a dual-MEMS architecture that uses extremely rapid compensation
algorithms. The architecture has three key elements. The first is robust,
reliable, and proven MEMS technology, TempFlat, that eliminates activity dips
and enables 30 times better vibration immunity than quartz. The second is use
of two separate MEMS devices, one of which is dedicated to temperature sensing,
thereby enabling 40 times faster temperature. The third is highly integrated
mixed-signal circuits with on-chip regulators, a temperature to digital
converter, and a low-noise phase-locked loop; the circuitry delivers five times
better immunity to power-supply noise than other devices, 30 µK resolution (10
times better than quartz), and support for any frequency between 1 and 700 MHz.
Because of this architecture, all Elite
Platforms solutions offer 0.1
ppb/g vibration immunity and do not
have activity dips or micro-jumps. (See video below.)

Elite-video-image

Click for video

As to the individual devices, the high-end device is a
Stratum-3-compliant,
precision Super-TCXOs for core and edge networks. Over a 1 to 200-MHz range, it
offers ±100 ppb
frequency stability over −40°C to 105°C, the widest operating temperature available
with any TCXO, and a 1 to 5 ppb/°C frequency slope (ΔF/ΔT) at an extremely fast
temperature ramp rate of 10°C/minute,
a performance level that is unique among timing devices It also provides a 3e-11
Allan deviation (ADEV) at 10 second averaging time, 10 times better than
typical quartz TCXOs, and 0.2 ps/mV power supply noise rejection (PSNR), which eliminates
the need for a low-dropout (LDO) regulator to clean up power. Using built-in I2C/SPI
frequency tuning eliminates the need for an external DAC. The second device — the
Super-TCXO — is intended for GNSS, industrial, and automotive applications, with
similar performance to the precision Super-TCXO but with slightly lower
frequency stability, ±0.5 ppm, over the same wide −40°C to 105°C range.

The
high-temp, high-rel, differential VCXO operates to 105°C
in the 1 to 700 MHz range, with a wide pull range of ±25 to ±3,600 ppm, and 0.1% frequency-tuning
linearity under all conditions, 50 times better than quartz. The
ultra-low jitter differential oscillator (XO), which operates over a 1 to 700
MHz range, has just 0.23 ps of integrated rms phase jitter from 12 kHz to 20
MHz, and 0.1 ps integrated rms phase jitter under Ethernet mask for
10G/40G/100G. Frequency stability over the specified −40°C to 95°

Engineering
samples of the latter two oscillators are available now to qualified customers,
with the prices from $5.5 ea. in 1k quantities. Samples of and pricing for the Super-TCXOs
are expected in the first half of 2017.