MIC2155 datasheet(32/33 Pages) MICREL

32 / 33 page

Micrel, Inc.

MIC2155/2156

May 2009

M9999-052709-A

(408) 944-0800

ground planes.

Ceramic

capacitors

are

recommended

for

most

decoupling and filtering applications because of their low

impedance

and

small

size.

Depending

the

application, most dielectrics (X5R, X7R, NPO) are

acceptable, however, Z5U type Ceramic capacitor

dielectrics are not recommended due to their large

change in capacitance over temperature and voltage.

Design and Layout Checklist

• Ceramic capacitor placed between the HS FET drain

and the LSFET source.

• MOSFET gate drive traces must be low inductance

and routed away from noise sensitive analog signals,

components and ground planes.

• The signal and power ground planes must be

separated to prevent high current and fast switching

signals from interfering with the low level, noise

sensitive analog signals. These planes should be

connected at only 1 point, next to the MIC2155/6

controller.

• The following signals and their components should be

decoupled or referenced to the power ground plane:

VIN1, VIN2, VDD, PGND1, PGND2

• These analog signals should be referenced or

decoupled to the analog ground plane:

AVDD, SYNC, EN, SS, PGOOD, COMP1, COMP2,

FB2, EA2, VOUT, FB1, AGND

• Place the current sharing RC components (that

connect across the inductor) and any related filtering

components close to the FB2, EA2+ and VOUT pins

(18, 17, 20). The traces connecting the inductors and

these components should be routed close together to

minimize pickup or EMI radiation.

• Place the overcurrent sense resistor close to the CS1

pin (pin 4). The trace coming from the switch node to

this resistor has high dv/dt and should be routed away

from other noise sensitive components and traces.

• The remote sense traces must be routed close

together or on adjacent layers to minimize noise

pickup. The traces should be routed away from the

switch node, inductors, MOSFETs and other high

dv/dt or di/dt sources.

MIC2155 Datasheet(PDF) 32 Page - Micrel Semiconductor

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