Negative Charge Pump Switching to Prevent RF Supply Slump
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Solution Overview
Problem
Voltage slumps in power supplies, particularly in RF circuits, cause undesired performance degradation due to slow switching times in power switches, especially when internal negative power supplies are used and load capacitors are small, leading to insufficient charge delivery during transitions.
Innovation Solution
An integrated circuit with an internal negative power supply and a detector and control circuit that dynamically switches between using an external and internal power supply based on availability, allowing for larger load capacitors to be used externally without occupying die space, ensuring consistent negative bias voltage delivery.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Area of stationary object
If an internal negative power supply with a small load capacitor is used, then the die space is saved, but voltage slumps occur during switching transitions causing slow settling times
Solution Approach 1:
The patent applies preliminary action by pre-charging the load capacitor to a voltage higher than the target negative voltage before the switching transition occurs. The detector circuit monitors the switching signal and activates the charge pump early to charge the capacitor to a predetermined voltage level (e.g., -5V or -6V) before the actual switching event. This pre-charging action ensures that when the switch transitions from ON to OFF state, the capacitor can rapidly discharge through the switch to achieve the target negative voltage (e.g., -3.5V) without causing voltage slumps, thereby maintaining voltage stability during switching while keeping the capacitor size small.
2Reliability
If a larger load capacitor is used to prevent voltage slumps, then voltage stability during switching is improved, but the die space occupation increases
Solution Approach 1:
The patent applies parameter changes by dynamically changing the voltage parameter of the load capacitor rather than changing its physical size. Instead of using a large capacitor to store more charge, the system changes the voltage level to which the capacitor is charged. The detector circuit monitors the switching signal and controls the charge pump to charge the capacitor to a predetermined voltage level higher than the target negative voltage. This voltage parameter change allows the same small capacitor to deliver the required charge during switching transitions, achieving voltage stability without increasing die space occupation.
3Reliability
If the charge pump continuously charges the load capacitor, then adequate charge is always available, but power consumption increases
Solution Approach 1:
The patent applies periodic action by activating the charge pump only periodically when needed, rather than continuously. The detector circuit monitors the switching signal and activates the charge pump in response to detected switching events. The charge pump operates in periodic pulses, charging the load capacitor to the predetermined voltage level only when a switching transition is anticipated or detected. Between switching events, the charge pump remains inactive, allowing the load capacitor to maintain its charge and supply power to the circuit. This periodic activation ensures adequate charge availability during switching transitions while minimizing power consumption during idle periods.
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 solution maintains fast switching times and reduces voltage slumps by ensuring adequate charge delivery, enhancing circuit performance and flexibility in power supply availability scenarios.
Implementation Method 1
negative power supply (130) further includes a negative charge pump (131)
Implementation Method 2
load capacitor (CL) coupled to terminal (N2)
Data Source
AI summary
Methods and devices to reduce or remove slumps in power supplies are disclosed. The disclosed teachings can serve various applications, such as applications implementing RF switches. Using such teachings, an integrated method can benefit from two different modes of operation where either an external or an internal charge pump can be used to provide a desired negative voltage to various components within the integrated circuit. This can be done by disposing a larger load capacitor outside the integrated circuit and without compromising any die space requirement.