Current steering DAC
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Solution Overview
Problem
Conventional multi-channel current steering DACs experience variations in full-scale current when one channel is powered down due to voltage drops caused by wiring resistance, leading to inconsistent analog output.
Innovation Solution
A multi-channel current steering DAC design where a reference current source is provided in each current source matrix, allowing for the selection and use of an active reference current source to maintain a constant full-scale current across channels, even when one channel is powered down, by switching between multiple reference current sources based on control signals.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Area of stationary object
If a shared bias circuit is used to reduce area, then area is reduced, but full-scale current varies when channels are powered down
Solution Approach 1:
The patent divides the shared bias circuit into separate bias circuits for each channel. Each channel has its own bias circuit that generates bias current independently, ensuring that powering down one channel does not affect the bias current or full-scale current of other channels. This segmentation resolves the contradiction by maintaining full-scale current consistency while accepting increased area.
2Use of energy by moving object
If channels are individually powered down to reduce power consumption, then power consumption is reduced, but voltage drop varies causing full-scale current to vary
Solution Approach 1:
The patent segments the power supply system so that each channel has independent power control through its own bias circuit. When a channel is powered down, only its specific bias circuit is disabled, while other channels continue to receive stable bias current. This allows individual channel power-down without affecting other channels' full-scale current, resolving the contradiction between power reduction and current consistency.
Solution Approach 2:
The patent applies local quality by providing each channel with its own dedicated bias circuit that maintains stable bias current locally. This ensures that the power-down state of one channel does not create voltage drops affecting other channels, allowing power consumption to be reduced selectively while maintaining full-scale current consistency in active channels.
3Reliability
If reference current source is provided in each current source matrix, then full-scale current consistency is maintained, but device complexity increases
Solution Approach 1:
The patent segments the reference current source functionality into separate bias circuits for each channel. Each bias circuit contains its own reference current source that generates bias current independently. This segmentation ensures that the reference current in one channel is not affected by the power-down state of other channels, maintaining full-scale current consistency while organizing the complexity into manageable modular units.
Data Source
AI summary
In a multi-channel current steering DA converter, e.g., a two-channel current steering DA converter, reference current sources Irefa and Irefb that can serve as current mirror sources for current sources Ia and Ib are provided in current source matrices 2a and 2b of the channels, respectively. During an operation, the reference current source Irefa or Irefb that is provided in the current source matrix of a channel that is not powered down is selected and used in accordance with control signals 6a and 6b. Therefore, even when one channel is powered down, the full-scale current of the other channel can be maintained at a constant value, i.e., unchanged.