LTC3586 datasheet(33/36 Pages) LINER

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LTC3586/LTC3586-1

3586fb

applicaTions inForMaTion

emissions will occur. There should be a group of vias

under the grounded backside of the package leading

directly down to an internal ground plane. To minimize

parasitic inductance, the ground plane should be on the

second layer of the PC board.

The GATE pin for the external ideal diode controller has

extremely limited drive current. Care must be taken to

minimize leakage to adjacent PC board traces. 100nA of

leakage from this pin will introduce an offset to the 15mV

ideal diode of approximately 10mV. To minimize leakage,

the trace can be guarded on the PC board by surrounding

it with VOUT connected metal, which should generally be

less that one volt higher than GATE.

Furthermore,duetoitshighfrequencyswitchingcircuitry,

it is imperative that the input capacitors, inductors and

output capacitors be as close to the LTC3586/LTC3586-1

as possible and that there be an unbroken ground plane

under the LTC3586/LTC3586-1 and all of its external high

frequencycomponents.Highfrequencycurrents,suchas

the VBUS, VIN1, VIN2, VIN3, VOUT3, and VOUT4 currents on

the LTC3586/LTC3586-1, tend to ﬁnd their way along the

ground plane in a myriad of paths ranging from directly

back to a mirror path beneath the incident path on the

top of the board. If there are slits or cuts in the ground

plane due to other traces on that layer, the current will be

forced to go around the slits. If high frequency currents

are not allowed to flow back through their natural least-

area path, excessive voltage will build up and radiated

3586 F11

Figure 11. Higher Frequency Ground Currents Follow Their

Incident Path. Slices in the Ground Plane Cause High Voltage

and Increased Emmisions

LTC3586 Datasheet(PDF) 33 Page - Linear Technology