EMI Suppression Filters (EMC and Noise Suppression)Noise Suppression for MIPI D-PHY

1What is MIPI D-PHY?

MIPI D-PHY is an interface standard used in the exchange of signals for displays and cameras within a mobile device.
In version 2 of D-PHY, communication speeds of up to 4.5 Gbps per lane are possible. This technology supports the greater volumes of video data that are occurring due to the higher resolutions in smartphones and other mobile devices.

A C-PHY standard is also available, and it enables communication speeds of up to 6 Gbps per lane.

  • Usage Applications(LCD-CPU, Camera-CPU)

2Noise Suppression for MIPI D-PHY

Noise is emitted from the FPC cable by digital signals that pass through MIPI D-PHY lines between the main board and module, and this noise can enter the antenna in the wireless circuit, which can result in reduced reception sensitivity of the antenna. For this reason, noise passing through MIPI D-PHY lines must be removed.

3Measures for suppressing noise for MIPI D-PHY

A noise filter is inserted into the interface section of the main board for reducing the outflow of noise to the FPC cable.

4Notes on Noise Suppression for MIPI D-PHY

Example of noise suppression in conventional interface

Conventional interfaces were either differential transmission systems or single-ended systems.

Differential transmission line → Common mode choke coil

Single-ended transmission line → LC filter, etc.

No issues arose when usage was divided as shown above.

However, in MIPI, differential signals and single-ended signals are mixed.

→ This requires a noise suppression method that does not affect the waveforms of both high-speed differential and single-ended signals.

5Noise filters for noise suppression for MIPI D-PHY

The following common mode choke coils and noise filters are recommended for MIPI D-PHY version 2.0. These minimize the effect on both differential and single-ended signals for reducing common mode noise.

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Part Number Search
inventory
Size
[mm]
Effective frequency band
700M-900MHz
LTE/GSM
1.5GHz-2.6GHz
LTE/GSM
2.4GHz
Wifi/BT
3.5GHz
LTE
DLM0QSN500HY2 0605
DLM0NSN500HY2 0806
DLP11SA900HL2 1210
DLP11TB800UL2

6Example of noise suppression effect

The DLM0QSN500HY2 was used to successfully reduce noise entering the antenna in the LTE low-band/high-band and Wifi 2.4 GHz wide-area band.

7Example of effect on differential signal waveform
(Use of DLM0QSN500HY2)

Inserting a filter has no negative effect on the signal waveform.

8Conclusion

In mobile devices, noise emitted from the MIPI D-PHY interface used in connections between displays and cameras can enter the antenna of the device and reduce the antenna sensitivity. One effective measure for preventing this noise is to use a common mode choke coil and noise filter at the interface outlet.

Because the MIPI D-PHY uses both differential signals and single-ended signals, care must be taken to select a component that does not distort the signal waveforms.
Use of the common mode choke coils and noise filters described below is recommended.

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Filters recommended for noise suppression for MIPI D-PHY
Part Number Search
inventory
Size
[mm]
Effective frequency band
700M-900MHz
LTE/GSM
1.5GHz-2.6GHz
LTE/GSM
2.4GHz
Wifi/BT
3.5GHz
LTE
DLM0QSN500HY2 0605
DLM0NSN500HY2 0806
DLP11SA900HL2 1210
DLP11TB800UL2

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