FEATURE WEARABLES AND IOT
Variable supply voltage oscillators for battery powered applications
Both, battery power and high data volume, require an adjustable circuit to ensure accurate functionality and longevity. Susanna Engel
M.Sc., business development manager at IQD Frequency Products explores a suitable clock source to ensure this
a warm environment. Both the influence of time and temperature are shown in Figure 1. The drop in voltage is particularly clear at -20°C, shown in black. All these influences mean that a battery cannot provide a fixed supply voltage on a permanent basis. A perfect solution for this problem is
Figure 1: T
he development of portable electronic devices has been rapid.
From tools to measuring instruments, to computers and game consoles, from large devices and sensors to watches and socks with built-in electronics, you can find everything. While still offline and equipped with electronics that merely controlled their function, these devices are now increasingly online, can be networked and form part of the growing world of smart electronics. This development, however, brings
two hurdles with it: on the one hand, an electronic circuit must be adapted to the characteristics of a battery, and on the other hand, the ever-increasing amounts of data processed and sent by these devices require a reliable and accurate clock. This is the only way to ensure that the devices work effectively Crystals or oscillators have always
been used for the clock of any electronic circuit. Although other alternatives are increasingly available, such as the improving integrated clocks in microcontrollers or Micro-Electro- Mechanical-Systems (MEMS), the classic crystal-based clock is still the
36 FEBRUARY 2021 | ELECTRONICS
most common. While a crystal requires the design of the oscillator circuit itself, an oscillator has the simplicity of a ready-to-use integrated crystal circuit. Only a supply voltage needs to be applied to generate a clock frequency. For an oscillator to oscillate according
to its specification, it needs a minimum supply voltage. Traditionally, this is a fixed supply voltage to which the oscillator is calibrated and even small fluctuations of 5 - 10 % can lead to deviations in the accuracy of an oscillator and thus the clock. This in turn can lead to problems or even failure of the device. Unfortunately, it is (still) in the nature of the battery that it cannot provide a constant voltage over its discharge cycle. The battery charge and therefore the
energy it can deliver depends on several factors: The most important factor is time. Over the course of its service life, the battery gives off power and thus gradually loses charge. Another major factor is the load on the battery - the more a device is used, the faster it discharges. The third major factor is the temperature - a battery discharges much faster in cold temperatures than in
Discharge of battery Lithium-Ion over time at different temperatures
an oscillator that can accept a variable input voltage. This ensures that the clock frequency is kept within the required specification regardless of temperature, charge status and battery load, thus providing the required accuracy. Changes of the supply voltage will have no influence on the frequency accuracy. Furthermore, this type of oscillator offers overall lower power consumption due to the adjustability of the supply voltage - this further protects the battery and increases its lifetime. In addition to the undeniable technical
advantage, oscillators with variable input voltage also offer great potential for logistic and economic cost savings in the long term. A wide voltage range allows several oscillators with fixed supply voltage to be replaced by one variable input voltage oscillator. By reducing the number of
components within a company, it is possible to save costs in many ways. By combining quantities, a price reduction can often be achieved. By reducing the number of single reels, freight costs as well as costs for storage, retrieval and warehousing can be saved. Furthermore, additional time and thus costs for pick and place can be reduced and less variation in components generally results in less administrative work. In conclusion, a variable supply voltage
Susanna Engel –
M.Sc., business development manager at IQD Frequency Products
oscillator is an ideal solution for both fluctuating battery performance and the need for an accurate clock. In addition to the technical advantages, there are also economic benefits.
IQD Frequency Products,
www.iqdfrequencyproducts.com
/ ELECTRONICS
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