US3018CW Просмотр технического описания (PDF) - Unisem

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US3018CW

5 BIT PROGRAMMABLE SYNCHRONOUS BUCK PLUS LDO CONTROLLER AND 200mA LDO ON BOARD

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8) Place the 2.5V output capacitor, C18 close to the

pin13 of the IC and the 1.5V output capacitor, C17 close

to the Q2 MOSFET. Note: It is better to place the

1.5V linear regulator components close to the 3018 and

then run a trace from the output of the regulator to the

load. However, if this is not possible then the trace from

the linear drive output pin, pin 16 must be run away

from any high frequency data signals.

It is critical, to place high frequency ceramic ca-

pacitors close to the clock chip and termination

resistors to provide local bypassing.

9) Place R12 and C10 close to pin 20.

10) Place C9 close to pin 9.

Component connections:

Note : It is extremely important that no data bus

should be passing through the switching regulator

section specifically close to the fast transition nodes

such as PWM drives or the inductor voltage.

Using the 4 layer board, dedicate on layer to GND, an-

other layer as the power layer for the 5V, 3.3V, Vcore,

1.5V and if it is possible for the 2.5V.

Connect all grounds to the ground plane using di-

rect vias to the ground plane.

Use large low inductance/low impedance plane to con-

nect the following connections either using component

side or the solder side.

a) C14 to Q3 Drain

b) Q3 Source to Q4 Drain

c) Q4 drain to L3

d) L3 to the output capacitors, C16

e) C16 to the load, slot 1

f) Input filter L1 to the C16 and C3

g) C1 to Q2 drain

h) C17 to the Q2 source

I) A minimum of 0.2 inch width trace from the C18 ca-

pacitor to pin 13

Connect the rest of the components using the shortest

connection possible

US3018

Rev. 1.4

12/8/00

4-15

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