Negative Voltage Generator Poly-Phase Clocking Reduces Clock Feed-Through
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Solution Overview
Problem
Conventional methods for reducing clock feed-through in RF switches, such as using off-chip decoupling capacitors and large on-chip filtering networks, increase component count, cost, and complexity, and occupy valuable space, limiting the form factor of wireless devices while failing to adequately address spurious effects caused by switching between multiple frequency bands.
Innovation Solution
Implementing a poly-phase clocking scheme for the charge pump stages of a negative voltage generator, which provides control signals with non-zero phase differences to increase the frequency of electrical spurs beyond the natural frequency roll-off, reducing the amplitude of clock feed-through spurs through a combination of poly-phase clocking and low-pass filtering.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Object-generated harmful factors
If off-chip decoupling capacitors are used to reduce clock spurs, then the amplitude of clock feed-through spurs is reduced, but the component count, cost, and complexity increase
Solution Approach 1:
The harmful clock feed-through effect is extracted and targeted specifically at the charge pump circuitry. By identifying the clock signal as the source of spurs and applying针对性 filtering only where needed (at the charge pump outputs), the solution removes the harmful effect without requiring system-wide decoupling capacitors, thus reducing overall component count while effectively suppressing spurs
Solution Approach 2:
A low-pass filter is introduced as an intermediary element between the charge pump circuitry and the RF switch control inputs. This filter mediates the clock signal by allowing the necessary control signals to pass through while blocking the high-frequency clock feed-through spurs, thereby reducing harmful effects without requiring additional decoupling capacitors throughout the system
2Object-generated harmful factors
If large on-chip filtering networks are used to reduce spurs, then the amplitude of clock feed-through spurs is reduced, but valuable chip space is occupied and electrical noise and temperature increase
Solution Approach 1:
The filtering function is segmented and localized specifically to the charge pump output stages rather than implementing a large comprehensive filtering network across the entire chip. By placing small low-pass filters only where clock feed-through occurs (at the charge pump outputs), the solution reduces spurs effectively while minimizing the area occupied on the chip
Solution Approach 2:
Filtering is applied locally at the specific location where clock feed-through spurs are generated (the charge pump outputs) rather than using a large distributed filtering network. This localized approach uses small low-pass filters with minimal area footprint, reducing both chip space consumption and the thermal noise that would be generated by large filtering networks
3Adaptability or versatility
If conventional RF switch control is used to enable switching between multiple frequency bands, then frequency band switching capability is achieved, but undesirable spurious tones are produced in the output signal
Solution Approach 1:
The clock signal, which is the source of harmful spurious tones, is converted into a beneficial timing reference for the poly-phase clocking scheme. By using the clock signal to generate multiple phase-shifted control signals for the charge pumps, the system maintains frequency band switching capability while the poly-phase arrangement naturally cancels out the spurious tones that would otherwise be generated by single-phase switching
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
This approach effectively reduces clock feed-through spurs without the need for additional off-chip decoupling capacitors, minimizing electrical noise and temperature increases, while maintaining signal linearity and isolation between transmit and receive chains in wireless devices.
Implementation Method 1
charge pump circuitry coupled to the RF switch controller and configured to provide the control signals to the RF switch
Implementation Method 2
low-pass filtering to reduce the amplitude of the clock feed-through spurs
Implementation Method 3
provides control signals with non-zero phase differences to increase the frequency of electrical spurs beyond the natural frequency roll-off
Data Source
AI summary
Apparatus and methods for negative voltage generation with reduced clock feed-through are provided. In certain configurations, a method of negative voltage generation in a wireless device is provided. The method includes generating a regulated voltage from a battery voltage using a voltage regulator, powering a first charge pump and a second charge pump using the regulated voltage, generating a first negative voltage based on timing of a first clock phase using the first charge pump, generating a second negative voltage based on the first negative voltage and on timing of a second clock phase using the second charge pump, and generating the first clock phase and the second clock phase with different phases using a poly-phase oscillator such that the first charge pump and the second charge pump draw from the regulated voltage at different points in time.