Integrated Frequency-to-Current Converter With Low Ripple Output
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Conventional frequency-to-current converters are complex, consume large silicon area, and produce AC ripple output current, making them unsuitable for low-frequency applications and integrated CMOS mixed-signal applications like PLLs and ADCs.
Innovation Solution
A frequency-to-current converter design incorporating a digitally selectable capacitor, a sampling capacitor, and an integrator circuit with non-overlapping clock pulses, which operates as a transconductor to produce a current linearly proportional to the reference clock frequency, reducing complexity and AC ripple.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If conventional frequency-to-voltage and voltage-to-current converters are combined, then frequency-to-current conversion is achieved, but device complexity and silicon area increase significantly
Solution Approach 1:
The patent combines the frequency-to-voltage conversion and voltage-to-current conversion functions into a single integrated frequency-to-current converter circuit. The circuit uses a current source, switching network, and integrating amplifier configured to directly convert input frequency to output current without requiring separate F-V and V-I converter stages, thereby reducing overall device complexity while maintaining conversion capability.
2Reliability
If conventional frequency-to-voltage and voltage-to-current converters are combined, then frequency-to-current conversion is achieved, but silicon area consumption increases
Solution Approach 1:
The patent merges multiple conversion stages into a single compact circuit implementation that occupies minimal silicon area. By eliminating the need for separate F-V and V-I converter circuits and their associated components, the integrated design achieves frequency-to-current conversion in a space-efficient manner suitable for CMOS mixed-signal applications.
3Reliability
If conventional frequency-to-current converters are used, then frequency conversion is achieved, but AC ripple components appear in the output current
Solution Approach 1:
The patent introduces an integrating amplifier as an intermediary stage between the switching network and the output. This integrator acts as a low-pass filter that smooths the pulsed current from the switching network, eliminating AC ripple components and producing a clean DC output current proportional to the input frequency, thereby removing the harmful ripple effect.
4Reliability
If counting pulses over fixed period or low pass filtering is used, then frequency-to-current conversion is achieved, but response time increases and power consumption increases
Solution Approach 1:
The patent employs periodic switching action synchronized with the input frequency to directly generate the output current. The switching network switches at the input frequency, and the integrating amplifier processes these periodic pulses to produce a continuous DC current output. This direct periodic conversion method eliminates the time-consuming averaging process required by counting methods, achieving fast response time while maintaining accurate frequency-to-current conversion.
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
The solution achieves a fast start-up time, low AC ripple output current, and reduced silicon area requirements, enabling efficient integration in CMOS mixed-signal applications with improved accuracy and reduced power consumption.
Implementation Method 1
an integrator circuit operatively coupled via a second switch to the sampling capacitor. The integrator circuit is also operatively coupled to the gate of the transistor
Implementation Method 2
The integrator circuit is also operatively coupled to the gate of the transistor, used as one implementation of a transconductor
Data Source
AI summary
A frequency-to-current converter includes a digitally selectable capacitor, a sampling capacitor, an integrator circuit and an output transconductor. The sampling capacitor is operatively coupled via a first switch to the digitally selectable capacitor. The first switch is operated by a first clock pulse from a clock generator responsive to a reference clock. The integrator circuit has an output operatively coupled via a second switch to the sampling capacitor. The integrator circuit has an output operatively coupled to a control terminal of the transistor. The second switch is operated by a second, non-overlapping clock pulse from the clock generator. A current output by the frequency-to-current converter in response to the continuous question of first and second switches is linearly proportional to the frequency of the reference clock and the capacitance of the digitally selectable capacitor.