ISL78227 Datasheet, PDF(41/43 Page) Intersil Corporation – 2-Phase Boost Controller with Integrated Drivers

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ISL78227 Datasheet, PDF (41/43 Pages) Intersil Corporation – 2-Phase Boost Controller with Integrated Drivers

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ISL78227

FIGURE 67. RECOMMENDED LAYOUT PATTERN FOR VIAS IN THE

IC BOTTOM PAD

7. Place the 10ÂµF decoupling ceramic capacitor at the PVCC pin

and as close as possible to the IC. Put multiple vias close to

the ground pad of this capacitor.

8. Place the 1ÂµF decoupling ceramic capacitor at the VCC pin

and as close as possible to the IC. Put multiple vias close to

the ground pad of this capacitor.

9. Keep the bootstrap capacitors as close as possible to the IC.

10. Keep the driver traces as short as possible and with relatively

large width (25mil to 40mil is recommended), and avoid

using via or minimal number of vias in the driver path to

achieve the lowest impedance.

11. Place the current sense setting resistors and the filter

capacitors (shown as RSETxB, RBIASxB and CISENx in Figure 60

on page 31) as close as possible to the IC. Keep each pair of

the traces close to each other to avoid undesired switching

noise injections.

12. The current-sensing traces must be laid out very carefully

since they carry tiny signals with only tens of mV.

For the current-sensing traces close to the power sense resistor

(RSENx), the layout pattern shown in Figure 68 is recommended.

Assuming the RSENx is placed in the top layer (red), route one

current sense connection from the middle of one RSENx pad in

the top layer under the resistor (red trace). For the other current-

sensing trace, from the middle of the other pad on RSENx in top

layer, after a short distance, via down to the second layer and

route this trace right under the top layer current sense trace.

13. Keep the current-sensing traces far from the noisy traces like

gate driving traces (LGx, UGx and PHx), phase nodes in power

stage, BOOTx signals, output switching pulse currents, driving

bias traces and input inductor ripple current signals, etc.

FIGURE 68. RECOMMENDED LAYOUT PATTERN FOR CURRENT

SENSE TRACES REGULATOR

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FN8808.2

February 24, 2016

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