353LB3I480T

Oscillators

Oscillators are circuits that generate consistent repetitive signals or waves. This signal can be a voltage waveform which then serve as an input for processing devices like radio transmitters and receivers, audio systems and so forth. Oscillators enabled such devices to effectively control the frequency, amplitude and other parameters of waveforms that they produce. The most common type of oscillator are electronic oscillators built from Integrated Circuits (ICs) However, manually tuned or digitally controlled RC network oscillators are still being used in some niche fields.

353LB3I480T application field and working principle

The 353LB3I480T is a type of digitally-controlled oscillator integrated circuit (DC Oscillator IC) manufactured by ASA Telecom. The 353LB3I480T is commonly utilized in base station transceivers due to its many features and programmable functions.

This DC Oscillator IC has a pull up range of –20 to +85°C and is mostly used for GSM or WCDMA application. It features a low frequency output ranging from 0.4MHz to 4MHz and controls 10 positive logic inputs and 4 negative logic inputs, allowing it to be used in IEEE-1394, XAUI, Infra-Red and other telecom applications.

The 353LB3I480T working principle is based around the phase-locked loop (PLL) oscillator principle utilizing a negative resistor working in tandem with a VCO.

Negative resistors are made up of small transistors which operate as an active circuit that exhibits negative resistance which in turn is used to generated a voltage through the circuit and working as part of a negative feedback loop with the VCO. The output voltage is then compared to a stable reference voltage and any difference between the two is the result of the negative resistor’s resistance. In this way the output voltage of the PLL oscillator is regulated since the PLL will always strive to keep the output and the reference voltage the same.

Additionally, digital temperature compensation (DTC) is used in the 353LB3I480T to adjust the oscillator’s output frequency with a parameter called “temperature factor” or ”t”, determined by an equalized comparison between the reference and output frequency, which results in a more precise phase-locked loop oscillator output.