Multi-Channel Current Steering DAC with Selectable Reference Bias
Find Innovative SolutionsGenerate Solutions
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 one or more reference current sources based on control signals to maintain a constant full-scale current across channels, even when one channel is powered down.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Area of stationary object
If a single shared bias circuit is used for multiple channels, then area is reduced, but full-scale current varies when channels are powered down
Solution Approach 1:
The patent divides the single shared bias circuit into multiple independent bias circuits, with each channel having its own dedicated bias circuit. This segmentation ensures that when one channel is powered down, the bias circuit for that channel is also powered down and does not affect the bias circuits of other channels, thereby maintaining stable full-scale current in active channels while accepting increased area consumption.
2Use of energy by moving object
If channels are individually powered down to reduce power consumption, then power 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 its own independent power control. When a channel is powered down, only its specific bias circuit and current sources are powered down, while other channels continue to operate with their dedicated bias circuits unaffected. This isolation prevents voltage drop variations from propagating between channels, maintaining full-scale current stability despite power consumption reduction.
3Device complexity
If reference current source is shared across channels, then device complexity is reduced, but analog output varies when channels are powered down
Solution Approach 1:
The patent assigns a dedicated reference current source to each channel instead of sharing a single reference current source across all channels. This segmentation ensures that the reference current for each channel is independent and not affected by the power state of other channels, thereby maintaining consistent analog output even when channels are selectively powered down, at the cost of increased device complexity.
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.