Current Output Control Stabilizing DCO Jitter
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Solution Overview
Problem
Digital PLLs with digitally controlled oscillators face issues with jitter characteristics due to glitches during input code switching, leading to unstable oscillation frequencies and increased power consumption in intermittent operation scenarios.
Innovation Solution
A current output control device with a current cell array section and a code conversion section that adjusts the number of current cell circuits based on input codes, ensuring a monotonically increasing or decreasing control current to stabilize oscillation frequency switching.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If digital code switching is performed to change oscillation frequency in a DCO, then frequency switching capability is improved, but jitter characteristics deteriorate due to glitches from clock frequency fluctuations
Solution Approach 1:
The patent applies preliminary action by pre-charging capacitive elements before switching the digital code to change oscillation frequency. This pre-charging action prepares the circuit state in advance, ensuring that when the code switching occurs, the capacitive nodes are already at the appropriate voltage levels, thereby preventing glitches and maintaining stable jitter characteristics during frequency transitions
2Measurement precision
If transistor switching is used to change output current value in IDAC, then current control precision is improved, but abnormal current output occurs due to mismatched switch timing
Solution Approach 1:
The patent applies preliminary action by pre-charging capacitive elements connected to the transistor switches before the switching operation. This ensures that when transistors are switched to change the output current value, the capacitive nodes are already prepared, preventing abnormal current outputs caused by timing mismatches and ensuring stable current control precision
Solution Approach 2:
The patent applies beforehand cushioning by introducing capacitive elements that absorb transient current fluctuations during transistor switching. These capacitors act as cushions that smooth out the current transitions, preventing abnormal current outputs and ensuring reliable current control while maintaining precision
3Ease of operation
If charge amplifier is used in analogue PLL, then phase control capability is improved, but power consumption increases during intermittent operation due to repeated charging from zero
Solution Approach 1:
The patent applies preliminary action by maintaining the charge amplifier's capacitive elements in a pre-charged state even when the PLL is in standby or intermittent operation mode. This allows the phase control capability to be quickly restored without discharging and recharging from zero, significantly reducing power consumption during intermittent operation while preserving full phase control capability when needed
Data Source
AI summary
A current output control device is provided that includes: a current cell array section including plural current cell circuits that are each connected in parallel between a first terminal (power source) and a second terminal (ground) that connect between the first terminal and the second terminal in by operation ON so as to increase control current flowing between the first terminal and the second terminal; and a code conversion section (decoder) that generates signals (row codes, column codes) to ON/OFF control current cells so as to change the number of current cells that connect the first terminal and the second terminal according to change in an externally input code and that inputs the generated signals to the current cell array section.