Tech News: Power Consumption

  • July 31, 2020

Design engineers often need to consider the power consumption of electronic devices, especially for battery operated equipment, whereby the total power consumption has to be minimized, so the battery used has sufficient life to make it practical for its intended application. 

In order to show what is considered as low current-limit values, manufacturers often publish specifications where current limits are specified under 'no-load' test conditions. The "low-power" figures may be misleading, as the oscillator in a practical situation will be connected to another device and is expected to drive that circuit accordingly. Hence, the device then draws extra current beyond the stated specification, which may affect the design calculations for battery life. This type of specification anomaly also makes it hard for engineers to draw a true comparison when comparing the electrical specifications of similar manufacturers' parts. 

Dynamic Engineers oscillator specifications are mostly quoted 'with-load' to provide more realistic values when determining design suitability. Moreover, the current consumption values stated on our specifications are generally maximum values. Kindly be noted for various reasons such as developed frequency breaks, the current draw will be quoted for a given range of frequencies. Higher frequencies can draw more current, therefore the lower frequencies within that range may have notably less current draw than the maximum value on the specification.

The issue of low power can also cause confusion when considering devices with Tri-state Enable/Disable or Standby function. These three terms used are really two possible functions; Tri-State and Enable/Disable can often be classed as the same functionality whereby the output buffer of the oscillator can be switched on and off and the output goes to a high impedance state while leaving the internal oscillator circuitry still operating. The supply current may be reduced slightly but as the internal oscillator circuit is still functioning, the current draw may still be near normal levels. The Standby function is conversely slightly different where the internal oscillator is powered-down and the supply current drops to very low levels, often in the µA range.

Indeed, the output start-up time for both methods will be different with Tri-State or Enable/Disable generally in the nanosecond range whereas the Standby function may be in milliseconds. This function can be used to reduce the overall power consumption if the application circuit allows the oscillator to be powered down some of the time. In most instances, the need for low current at standby is due to battery powered applications and therefore portable devices. With older technology and before these power constraints, the start-up time was considered more important. For this reason, smaller devices are usually quoted with a power down function while larger and older style packages are often specified with the output disable function.

Another issue regarding overall power usage is the output waveform. A HCMOS output oscillator will generally draw more current than a device with a clipped sine output. A typical HCMOS output TCXO device may be in the range of 5 to 10mA whereas a clipped sine TCXO may be sub 2mA. Of course, the clip-sine device has a much lower output level waveform and thus may need additional circuitry if the oscillator needs to drive other devices which can increase the power required in other areas.

Dynamic Engineers has a huge range of devices with different supply voltages, current consumption levels, and output types. Please feel free to contact Dynamic Engineers to discuss your specific requirements to ensure you specify the right frequency product solution.

For additional information regarding Power Consumption or other RF / microwave topics, please contact your local Dynamic Engineers sales representative or Inquiry@DynamicEngineers.com