Watch Shuige's video for a reward | MIPI D-PHY transmitter physical layer consistency test

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MIPI D-PHY Basics

The DPHY bus includes the DSI and CSI buses for display and camera. D-PHY is different from many existing mobile interfaces. It can switch between differential mode (high speed) and single-ended mode (low power) in real time, depending on whether a large amount of data needs to be transmitted or power needs to be saved. The DPHY interface can operate in a simplex or duplex configuration, supports one data path or multiple data paths, and can flexibly provide the required link. D-PHY uses 1 pair of source synchronous differential clocks and 1 to 4 pairs of differential data lines for data transmission. Data transmission adopts DDR mode, that is, data transmission occurs on the upper and lower edges of the clock.

MIPI D-PHY Test Challenges

MIPI D-PHY bus works in two working states: LP and HS:
LP (Low Power) state: the working rate does not exceed 10Mbps, the signal swing is 1.2V, and the termination impedance is high impedance;
HS (High Speed) state: the working rate is from 80Mbps to 4.5Gbps, the signal swing is 200mV, and the termination impedance is 50 ohms.
Due to the difference in signal swing, the dynamic range required for D-PHY signal testing is higher, and its tolerance to noise is lower. In actual testing, the signal quality may not be ideal, as shown in the figure below.

Difficulties in MIPI signal testing

1. CTS has many measurement items: 64 for D-PHY, 41 for C-PHY
2. Signal integrity and corresponding timing in two completely different working modes, HS and LP
3. Measurement by soldering probes
4. Measurement accuracy: Use reliable algorithms to filter out specific waveforms and make accurate measurements
5. The measured waveform is sometimes very poor
6. Automatically detect transition edges and measurement items
7. Minimize the loading effect of the probe
8. The density of the board is getting higher and higher, and the test points are difficult to solder
9. Automatic test settings to adapt to HS and LP modes

Want to see the complete MIPI D-PHY transmitter physical layer conformance test? Go to Shuige's Secret Book 2 to view more test videos. I wish you a higher level and a higher chance of getting a JD card!

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The DPHY bus includes the DSI and CSI buses for display and camera. Unlike many existing mobile interfaces, D-PHY can switch between differential mode (high speed) and single-ended mode (low power) in real time.