LTC3261

9

3261f

APPLICATIONS INFORMATION

should be consulted to ensure the desired capacitance at

all temperatures and voltages. Table 1 is a list of ceramic

capacitor manufacturers and their websites.

Table 1

AVX

www.avxcorp.com

Kemet

www.kemet.com

Murata

www.murata.com

Taiyo Yuden

www.t-yuden.com

Vishay

www.vishay.com

TDK

www.component.tdk.com

Layout Considerations

Due to high switching frequency and high transient currents

produced by LTC3261, careful board layout is necessary

for optimum performance. A true ground plane and short

connections to all the external capacitors will improve

performance and ensure proper regulation under all condi-

tions. Figure 3 shows an example layout for the LTC3261.

at a high frequency. These nodes should not be routed

close to sensitive pins such as the RT pin .

Thermal Management

At high input voltages and maximum output current, there

can be substantial power dissipation in the LTC3261. If

the junction temperature increases above approximately

175°C, the thermal shutdown circuitry will automatically

deactivate the output. To reduce the maximum junction

temperature, a good thermal connection to the PC board

groundplaneisrecommended.Connectingtheexposedpad

of the package to a ground plane under the device on two

layers of the PC board can reduce the thermal resistance

of the package and PC board considerably.

Derating Power at High Temperatures

To prevent an overtemperature condition in high power

applications, Figure 4 should be used to determine the

maximum combination of ambient temperature and power

dissipation.

The power dissipated in the LTC3261 should always fall

under the line shown for a given ambient temperature.

The power dissipated in the LTC3261 is:

The derating curve in Figure 4 assumes a maximum thermal

achieved from a printed circuit board layout with a solid

ground plane and a good connection to the exposed pad

of the LTC3261 package.

It is recommended that the LTC3261 be operated in the

tion as shown in Figure 4. Short-term operation may be

in this region should be avoided as it may reduce the life of

the part will be in thermal shutdown.

Figure 3. Recommended Layout

Figure 4. Maximum Power Dissipation vs Ambient Temperature

AMBIENT TEMPERATURE (°C)

–50

0

6

4

5

2

3

1

75

50

25

0

125

100

–25

175

150

3261 F04

THERMAL

SHUTDOWN

RECOMMENDED

OPERATION

GND

GND

3261 F03

EN

MODE