Transmitter De-emphasis Circuit for High-Speed Image Sensor Signal Integrity
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
High-speed image data transmission in image sensors is limited by channel loss, leading to inter-symbol interference and noisy signals, which degrade the quality of the data received by the processor, especially at high data rates like 4.5 Gbps as specified in the MIPI DPHY 2.0 standard.
Innovation Solution
The implementation of transfer-side de-emphasis in the transmitter circuitry, which reduces the signal swing for subsequent bits after a data transition and includes an additional replica bias loop to integrate de-emphasis functionality within the transmitter circuitry, reducing processing steps and chip space, while maintaining driver output impedance.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Speed
If high-speed data transmission is implemented in image sensors, then data transfer rate is improved, but channel loss increases causing inter-symbol interference and noisy signals
Solution Approach 1:
The transmitter circuitry applies de-emphasis to preemptively counteract the effects of channel loss and inter-symbol interference before the signal is transmitted through the channel. By reducing signal swing for subsequent bits after a data transition, the circuit anticipates and prevents signal degradation that would otherwise occur during high-speed transmission.
Solution Approach 2:
The de-emphasis circuit dynamically changes the signal swing parameter based on the data pattern being transmitted. When a data transition is detected, the circuit reduces the voltage swing for subsequent bits, adapting the transmission parameters to compensate for channel loss and maintain signal integrity at high data rates.
2Reliability
If de-emphasis circuitry is added to the transmitter, then inter-symbol interference is reduced, but device complexity increases
Solution Approach 1:
The de-emphasis functionality is merged with the existing driver circuitry in the transmitter. The de-emphasis circuit shares the same output node and integrates with the differential driver structure, eliminating the need for completely separate de-emphasis circuitry and reducing overall device complexity.
Solution Approach 2:
The driver circuitry is designed to perform multiple functions: it drives the differential output signal and simultaneously implements de-emphasis through shared circuit elements. The same transistors and output structure serve both as the driver and as part of the de-emphasis mechanism, making the circuit multi-functional and reducing total component count.
3Reliability
If traditional de-emphasis implementation is used, then signal quality is improved, but chip space and power pads are consumed
Solution Approach 1:
The de-emphasis circuit is merged with the driver output stage, sharing the same output node and physical location on the chip. This integration eliminates the need for separate de-emphasis circuitry and its associated power pads, conserving valuable chip real estate while maintaining signal quality.
Solution Approach 2:
The driver circuitry serves itself by incorporating de-emphasis functionality within its own structure. The driver transistors and output circuitry perform both driving and de-emphasis functions, eliminating the need for external components and dedicated power pads that would otherwise be required.
Data Source
AI summary
A transmitter circuit coupled to output image data from an image sensor includes a plurality of transmitters. The transmitters may include a plurality of drivers coupled to receive a data signal, and output a differential signal in response to receiving the data signal. A de-emphasis circuit is coupled between a first output of a first driver in the plurality of drivers, and a second output of a second driver in the plurality of drivers. The de-emphasis circuit is coupled to receive a de-emphasis control signal, and in response to receiving the de-emphasis control signal, the de-emphasis circuit reduces a magnitude of the differential signal.