LTM4607 datasheet(16/26 Pages) LINER

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LTM8055

8055fb

For more information www.linear.com/LTM8055

2. Place the CIN capacitor as close as possible to the VIN

and GND connection of the LTM8055.

3. Place the COUT capacitor as close as possible to the

VOUT and GND connection of the LTM8055.

4. Minimize the trace resistance between the optional

outputcurrentsenseresistor,ROUT,andVOUT.Minimize

the loop area of the IOUT trace and the trace from VOUT

to ROUT.

5. Minimizethetraceresistancebetweentheoptionalinput

current sense resistor, RIN and VIN. Minimize the loop

area of the IIN trace and the trace from VIN to RIN.

6. Place the CIN and COUT capacitors such that their

ground current flow directly adjacent or underneath

the LTM8055.

7. Connect all of the GND connections to as large a copper

pour or plane area as possible on the top layer. Avoid

breaking the ground connection between the external

components and the LTM8055.

8. Use vias to connect the GND copper area to the board’s

internal ground planes. Liberally distribute these GND

vias to provide both a good ground connection and

thermal path to the internal planes of the printed circuit

board. Pay attention to the location and density of the

thermal vias in Figure 6. The LTM8055 can benefit from

the heat sinking afforded by vias that connect to internal

GND planes at these locations, due to their proximity

to internal power handling components. The optimum

number of thermal vias depends upon the printed

circuit board design. For example, a board might use

very small via holes. It should employ more thermal

vias than a board that uses larger holes.

Hot-Plugging Safely

The small size, robustness and low impedance of ceramic

capacitors make them an attractive option for the input

bypass capacitor of LTM8055. However, these capacitors

can cause problems if the LTM8055 is plugged into a live

supply (see Linear Technology Application Note 88 for a

complete discussion). The low loss ceramic capacitor

combined with stray inductance in series with the power

source forms an underdamped tank circuit, and the volt-

age at the VIN pin of the LTM8055 can ring to more than

twice the nominal input voltage, possibly exceeding the

LTM8055’sratinganddamagingthepart.Iftheinputsupply

is poorly controlled or the LTM8055 is hot-plugged into an

energized supply, the input network should be designed

APPLICATIONS INFORMATION

Figure 6. Layout Showing Suggested External Components,

GND Plane and Thermal Vias

ROUT

OUTPUT

SENSE

VOUT SIGNAL VIA

GND

GND/THERMAL VIAS

GND

INPUT

RIN

INPUT

SENSE

8055 F06

COUT

VOUT

IOUT

VIN

CIN

SVIN

MODE SYNC

RUN

IIN

IOUT

VOUT SIGNAL VIA

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