Murata Examples of Actions Taken to Comply With CISPR25

Measures to Suppress Noise Signal Lines (SL)

        •  Details of measures taken under the CISPR25 Class 5 standard in the USB 2.0 mode (see SL SECTION FOR USB 2.0)
        •  Details of measures taken under the CISPR25 Class 5 standard in the USB 3.0 mode (see SL SECTION FOR USB 3.0)
        •  Summary of measures taken for CISPR25 Class 5 standard signal lines (SL) (see SL SUMMARIES)

SL Section for USB 2.0

Signal Line Details of Noise Suppression Measures Taken in USB 2.0 Mode
When interfaces compliant with the USB 3.0 standard are to be operated as an equivalent to the USB 2.0 standard, signal lines used for USB 2.0 are used. As USB 2.0 signal lines have both transmission (TX) and reception (RX) functions, common mode choke coils are inserted into these lines.

Noise measurement results to suppress noise in USB 2.0 SL using DLM11SN900HZ2

By adding a common mode choke coil (DLM11SN900HZ2), the noise was successfully reduced (maximum reduction of approximately 37dB at a vertically polarized wave frequency of 240MHz).

Noise measurement results to suppress noise in USB 2.0 SL using DLW21SZ900HQ2

By adding a common mode choke coil (DLW21SZ900HQ2), the noise was successfully reduced (maximum reduction of approximately 37dB at a vertically polarized wave frequency of 240MHz).

SL Section for USB 3.0

Signal Line Details of Noise Suppression Measures Taken in USB 3.0 Mode
In the USB 3.0 SuperSpeed mode, separate signal lines are used for TX and RX, unlike in the 2.0 mode. Murata inserted a common mode choke coil into the TX signal line.

Noise measurement results to suppress noise in USB 3.0 SL using DLM11SN900HZ2

By adding a common mode choke coil (DLM11SN900HZ2), the noise was successfully reduced.

Noise measurement results to suppress noise in USB 3.0 SL using DLW21SZ900HQ2

By adding a common mode choke coil (DLW21SZ900HQ2), the noise was successfully reduced.

SL Summaries

Summary of Signal Line Noise Suppression Measures
Communication in the USB 2.0 and USB 3.0 modes was initiated between a PC and hard drive and, in an environment compliant with the CISPR25 standard, the noise radiated from the USB cables was evaluated. Murata discovered that without filters, noise radiated from the USB cables during both USB 2.0 and USB 3.0 communication. A high level of harmonic noise, approximately 57dB (µV/m), was found at a vertically polarized wave frequency of 240MHz during USB 2.0 communication.

As a measure taken to suppress the noise, these components were added to the signal lines:
        •  DLM11SN900HZ2L
        •  DLW21SZ900HQ2L

Murata then confirmed the noise in both the USB 2.0 and USB 3.0 modes was successfully reduced. In the USB 2.0 mode, the noise was successfully reduced by a maximum of approximately 37dB (at a vertically polarized wave frequency of 240MHz).

Measures to Suppress Noise Power Lines (PL)

        •  Details of measures taken under the CISPR25 Class 5 standard in the USB 2.0 mode (see PL SECTION FOR USB 2.0 & 3.0)
        •  Details of measures taken under the CISPR25 Class 5 standard in the USB 3.0 mode (see PL SECTION FOR USB 2.0 & 3.0)
        •  Summary of measures taken for CISPR25 Class 5 standard power lines (see PL SUMMARIES)

PL Section for USB 2.0 & 3.0

Power Line Details of Noise Suppression Measures Taken in USB 2.0 and 3.0 Modes
The same power lines are used in both operation modes, equivalent to USB 2.0 and the SuperSpeed operation mode that is the USB 3.0 full standard. This means components supporting the 900mA current in compliance with the USB 3.0 standard are required.

Noise measurement results to suppress noise in USB 2.0 power lines using BLM31PG601SH1

By adding chip ferrite beads (BLM31PG601SH1), the noise was successfully reduced (approximately 14dB reduction at a horizontally polarized wave frequency of 76MHz and approximately 13dB reduction at a vertically polarized wave frequency of 227MHz).

Noise measurement results to suppress noise in USB 3.0 power lines using BLM31PG601SH1

By adding chip ferrite beads (BLM31PG601SH1), the noise was successfully reduced (approximately 9dB reduction at a vertically polarized wave frequency of 111MHz).

PL Summaries

Summary of Power Line Noise Suppression Measures
Communication in the USB 2.0 and USB 3.0 modes was initiated between a PC and hard drive and, in an environment complying with the CISPR25 standard, the noise radiated from the USB cables was evaluated. As a result, the following was verified when the BLM31PG601SH1 was inserted into the power line:

The noise during USB 2.0 communication was reduced by:
Approximately 14dB (at a horizontally polarized wave frequency of 76MHz)
Approximately 13dB (at a vertically polarized wave frequency of 227MHz)

The noise during USB 3.0 communication was reduced by approximately 9dB (at a vertically polarized wave frequency of 111MHz).

Community Forum

Murata Community Forum provides searchable content with various discussion topics, popular blogs, and articles. The Murata broad market support team holds regular reviews to discuss open issues, allowing inquiries to be answered in a timely manner. The forum content is freely accessible to the public. However, users must log in to post questions or answers. Registration is free of charge.