lt3693 Linear Technology Corporation, lt3693 Datasheet - Page 18

• Manufacturer Part Number: lt3693
• Description: 36v, 3.5a, 2.4mhz Step-down Switching Regulator
• Manufacturer: Linear Technology Corporation

APPLICATIONS INFORMATION
LT3693
TYPICAL APPLICATIONS
High Temperature Considerations
The PCB must provide heat sinking to keep the LT3693
cool. The Exposed Pad on the bottom of the package must
be soldered to a ground plane. This ground should be tied
to large copper layers below with thermal vias; these lay-
ers will spread the heat dissipated by the LT3693. Place
additional vias can reduce thermal resistance further. With
these steps, the thermal resistance from die (or junction)
to ambient can be reduced to
100 LFPM airfl ow, this resistance can fall by another 25%.
Further increases in airfl ow will lead to lower thermal re-
sistance. Because of the large output current capability of
the LT3693, it is possible to dissipate enough heat to raise
the junction temperature beyond the absolute maximum of
125°C. When operating at high ambient temperatures, the
maximum load current should be derated as the ambient
temperature approaches 125°C.
18
6.5V TO 36V
10 F
V
IN
JA
= 35°C/W or less. With
D: ON SEMI MBRA340
L: NEC MPLC0730L4R7
680pF
15k
63.4k
ON OFF
5V Step-Down Converter
f = 600kHz
RUN/SS
V
RT
PG
SYNC
C
V
IN
LT3693
GND
Power dissipation within the LT3693 can be estimated by
calculating the total power loss from an effi ciency measure-
ment and subtracting the catch diode loss and inductor
loss. The die temperature is calculated by multiplying the
LT3693 power dissipation by the thermal resistance from
junction to ambient.
Other Linear Technology Publications
Application Notes 19, 35 and 44 contain more detailed
descriptions and design information for buck regulators
and other switching regulators. The LT1376 data sheet
has a more extensive discussion of output ripple, loop
compensation and stability testing. Design Note 100
shows how to generate a bipolar output supply using a
buck regulator.
BD
BOOST
SW
FB
100k
0.47 F
D
536k
4.7 H
L
3693 TA02
47 F
V
5V
3.5A
OUT
3693f