Datasheet

LT3487

3487f

APPLICATIO S I FOR ATIO

WUU

and the inductors directly from the battery for higher ef-

ﬁ ciency. When the part goes into shutdown, the output

load is isolated from the 12V source as soon as the CAP

node falls to below V

BAT

plus 1.2V (13.2V in this case).

The V

BAT

pin is also useful in a system using a 2V supply

(such as a 2-cell alkaline battery), below the operating

range of the LT3487. A boost converter designed for low

voltage operation can provide 3.3V for the LT3487 V

pin,

while the inductors and V

BAT

can still be powered from the

2V supply. In shutdown, the 3.3V supply will turn off, but

the output disconnect will still decouple the output load

as soon as CAP falls below 3.2V .

Figure 6. Recommended Component Placement

Board Layout Consideration

As with all switching regulators, careful attention must be

paid to the PCB board layout and component placement.

To maximize efﬁ ciency, switch rise and fall times are made

as short as possible. To prevent electromagnetic interfer-

ence (EMI) problems, proper layout of the high frequency

switching path is essential. The voltage signals of the

SWP and SWN pins have rise and fall times of a few ns.

Minimize the length and area of all traces connected to

the SWP and SWN pins and always use a ground plane

under the switching regulator to minimize interplane

coupling. Recommended component placement is shown

in Figure 6.

NEG

BAT

POS

RUN

3487 F06

FBP

CAP

L1 L1

C2 C1