Epson OG7050CAN oven-controlled crystal oscillator (OCXO)

As communication data traffic continues to grow, power consumption at base stations and data centres is expected to sharply increase, driving demand for low-power oven-controlled crystal oscillator (OCXOs) used as reference signal sources. To meet this demand, Epson drew on its crystal device, semiconductor and mounting technologies to develop the OG7050CAN — an OCXO that consumes 56% less power (0.2 W at 25°C) than its earlier products and is 85% smaller, measuring just 7 x 5 mm with a height of 3.3 mm (typ). This improvement was enabled in large part by the miniaturisation of the oven and the stress compensated (SC) cut crystal unit.

Unlike AT-cut crystal units used in ordinary crystal oscillators, SC-cut crystal units are highly stable and resistant to thermal shock and vibration. Earlier products employed a circular SC-cut crystal unit with a diameter of 6 mm, requiring a large oven and a large amount of power to maintain a constant temperature. To solve this problem, Epson redesigned the crystal unit, using a rectangular structure instead of a circular one. Not only did the company significantly reduce the size of the SC-cut crystal unit, it also improved performance and reduced power consumption. The redesign also reduced the cubic volume of the oven.

Another challenge the developers faced was to achieve a low-power oven structure. Epson developed and optimised its own oscillator IC and heater IC to hold the SC-cut crystal unit in the oven at a constant temperature while minimising power consumption. The oven is bonded inside the OCXO package with an adhesive that has low thermal conductivity to improve internal insulation, which limits the loss of heat from the heater IC and keeps power consumption low. By using a digital means of controlling the temperature of the SC-cut crystal unit instead of the conventional analog method, the developers were able to keep the crystal unit’s temperature stable even when the ambient temperature fluctuates.