LTC1265I Ver la hoja de datos (PDF) - Linear Technology

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Fabricante

LTC1265I

1.2A, High Efficiency Step-Down DC/DC Converter

Linear Technology 

LTC1265/LTC1265-3.3/LTC1265-5

APPLICATIONS INFORMATION

Board Layout Checklist

When laying out the printed circuit board, the following

checklist should be used to ensure proper operation of the

LTC1265. These items are also illustrated graphically in

the layout diagram of Figure 5. Check the following in your

layout:

1. Are the signal and power grounds segregated? The

LTC1265 signal ground (Pin 11) must return to the (–)

plate of COUT. The power ground (Pin 12) returns to the

anode of the Schottky diode, and the (–) plate of CIN,

whose leads should be as short as possible.

2. Does the (+) plate of the CIN connect to the power VIN

(Pins 1,13) as close as possible? This capacitor pro-

vides the AC current to the internal P-channel MOSFET

and its driver.

3. Is the input decoupling capacitor (0.1µF) connected

closely between power VIN (Pins 1,13) and power

ground (Pin 12)? This capacitor carries the high fre-

quency peak currents.

4. Is the Schottky diode closely connected between the

power ground (Pin 12) and switch (Pin 14)?

5. Does the LTC1265 SENSE– (Pin 7) connect to a point

close to RSENSE and the (+) plate of COUT? In adjustable

applications, the resistive divider, R1 and R2, must be

connected between the (+) plate of COUT and signal

ground.

6. Are the SENSE– and SENSE+ leads routed together with

minimum PC trace spacing? The 1000pF capacitor

between Pins 7 and 8 should be as close as possible to

the LTC1265.

7. Is SHDN (Pin 10) actively pulled to ground during

normal operation? The SHDN pin is high impedance

and must not be allowed to float.

10

1k

3900pF

1 PWR VIN

VIN

2

VIN

14

SW

D1

PWR VIN 13

LTC1265

3

LBOUT

12

PGND

+

CIN

0.1µF

L

1000pF

4

LBIN

11

SGND

5

10

CT

SHDN

SHDN

R1

6

ITH

7 SENSE–

9

N/C (VFB)

SENSE+ 8

COUT

RSENSE

R2

VOUT

1000pF

OUTPUT DIVIDER REQUIRED

WITH ADJUSTABLE VERSION ONLY

BOLD LINES INDICATE

LTC1265 F05 HIGH PATH CURRENTS

Figure 5. LTC1265 Layout Diagram (See Board Layout Checklist)

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