LT1932 查看數據表（PDF） - Linear Technology

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LT1932

Constant-Current DC/DC LED Driver in ThinSOT

Linear Technology 

APPLICATIO S I FOR ATIO

IIN

VIN

L1

6.8µH

D1

C1

4.7µF

6

1

VIN

SW

LT1932

5

SHDN

3

LED

RSET

GND

4

2

RSET

1.50k

Q1

2N3904

VOUT

C3

0.047µF

C2

1µF

R1

1.5k

SOFT-START

CIRCUIT

1932 F07

Figure 7. Soft-Start Circuit for the LT1932

LT1932

VOUT

5V/DIV

VOUT

5V/DIV

IIN

200mA/DIV

100µs/DIV

1932 F08

Figure 8. Input Current at Start-Up Without Soft-Start

Board Layout Considerations

As with all switching regulators, careful attention must be

paid to the PCB board layout and component placement.

To maximize efficiency, switch rise and fall times are made

as short as possible. To prevent radiation and high fre-

quency resonance problems, proper layout of the high

frequency switching path is essential. Minimize the length

and area of all traces connected to the SW pin and always

use a ground plane under the switching regulator to

minimize interplane coupling. The signal path including

the switch, output diode D1 and output capacitor C2,

contains nanosecond rise and fall times and should be

kept as short as possible. In addition, the ground connec-

tion for the RSET resistor should be tied directly to the GND

pin and not be shared with any other component, ensuring

a clean, noise-free connection. Recommended compo-

nent placement is shown in Figure 10.

IIN

200mA/DIV

100µs/DIV

1932 F09

Figure 9. Input Current at Start-Up with Soft-Start

L1

C1

D1

C2

1

6

2

5

3

4

GND

VIN

SHDN

RSET

1932 F10

DIMMING

CONTROL

Figure 10. Recommended Component Placement

1932f

9

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