LTM8049 datasheet(26/32 Pages) LINER

26 / 32 page

LTM4653

Rev 0

For more information www.analog.com

Figure 26. 24V to 15VOUT Derating

Curve, with BGA Heat Sink

Figure 27. 48V to 15VOUT Derating

Curve, with BGA Heat Sink

Figure 28. 48V to 24VOUT Derating

Curve, with BGA Heat Sink

APPLICATIONS INFORMATION—DERATING CURVES

APPLICATIONS INFORMATION

Safety Considerations

The LTM4653 does not provide galvanic isolation from VIN

to VOUT. There is no internal fuse. If required, a slow blow

fuse with a rating twice the maximum input current needs

to be provided to protect the unit from catastrophic failure.

The fuse or circuit breaker, if used, should be selected to

limit the current to the regulator in case of a MT MOSFET

fault. If MT fails, the system’s input supply will source

very large currents to VOUT through MT. This can cause

excessive heat and board damage depending on how

much power the input voltage can deliver to this system.

A fuse or circuit breaker can be used as a secondary fault

protector in this situation. The LTM4653 does feature

overcurrent and overtemperature protection.

Layout Checklist/Example

The high integration of LTM4653 makes the PCB board

layout straightforward. However, to optimize its electrical

and thermal performance, some layout considerations

are still necessary.

• Use large PCB copper areas for high current paths,

including VIN, PGND and VOUT. Doing so helps to

minimize the PCB conduction loss and thermal stress.

• Place high frequency ceramic input and output ca-

pacitors next to the VIN, VD, PGND and VOUT pins to

minimize high frequency noise.

• Place a dedicated power ground layer underneath the

LTM4653.

• To minimize the via conduction loss and reduce module

thermal stress, use multiple vias for interconnection

between top layer and other power layers.

• Do not put vias directly on pads, unless they are capped

or plated over.

• Use a separate SGND copper plane for components

connected to signal pins. Connect SGND to PGND

directly under the module.

• For parallel module applications, connect the VOUT,

VOSNS, RUN, ISETa, COMPa and PGOOD pins together

as shown in Figure 32.

• Bring out test points on the signal pins for monitoring.

Figure 29 gives a good example of the recommended

LTM4653 layout.

100

120

AMBIENT TEMPERATURE (°C)

4653 F26

0.0

0.5

1.0

1.5

2.0

2.5

3.0

3.5

4.0

400LFM

200LFM

OLFM

100

120

AMBIENT TEMPERATURE (°C)

4653 F27

0.0

0.5

1.0

1.5

2.0

2.5

3.0

3.5

4.0

400LFM

200LFM

OLFM

100

120

AMBIENT TEMPERATURE (°C)

4653 F28

0.0

0.5

1.0

1.5

2.0

2.5

3.0

3.5

4.0

400LFM

200LFM

OLFM

See Table 1 for fSW and REXTVCC.

LTM8049 Datasheet(PDF) 26 Page - Linear Technology

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