L6714 datasheet(66/70 Pages) STMICROELECTRONICS

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Embedding L6714 - Based VR

L6714

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Embedding L6714 - Based VR

When embedding the VRD into the application, additional care must be taken since the

whole VRD is a switching DC/DC regulator and the most common system in which it has to

work is a digital system such as MB or similar. In fact, latest MB has become faster and

powerful: high speed data bus are more and more common and switching-induced noise

produced by the VRD can affect data integrity if not following additional layout guidelines.

Few easy points must be considered mainly when routing traces in which high switching

currents flow (high switching currents cause voltage spikes across the stray inductance of

the trace causing noise that can affect the near traces):

Keep safe guarding distance between high current switching VRD traces and data buses,

especially if high-speed data bus to minimize noise coupling.

Keep safe guard distance or filter properly when routing bias traces for I/O sub-systems that

must walk near the VRD.

Possible causes of noise can be located in the PHASE connections, MOSFET gate drive

and Input voltage path (from input bulk capacitors and HS drain). Also PGND connections

must be considered if not insisting on a power ground plane. These connections must be

carefully kept far away from noise-sensitive data bus.

Since the generated noise is mainly due to the switching activity of the VRM, noise

emissions depend on how fast the current switches. To reduce noise emission levels, it is

also possible, in addition to the previous guidelines, to reduce the current slope by properly

tuning the HS gate resistor and the PHASE snuber network.

L6714 Datasheet(PDF) 66 Page - STMicroelectronics