Datasheet

LTM8021
12
8021fc
APPLICATIONS INFORMATION
High Temperature Considerations
The die temperature of the LTM8021 must be lower than
the maximum rating of 125°C, so care should be taken
in the layout of the circuit to ensure good heat sinking of
the LTM8021. To estimate the junction temperature, ap-
proximate the power dissipation within the LTM8021 by
applying the typical effi ciency stated in this data sheet to
the desired output power, or, if one has an actual module,
by taking a power measurement. Then, calculate the tem-
perature rise of the LTM8021 junction above the surface
of the printed circuit board by multiplying the module’s
power dissipation by the thermal resistance. The actual
thermal resistance of the LTM8021 to the printed circuit
board depends on the layout of the circuit board, but the
thermal resistance given in the Pin Confi guration, which
is based upon a 40.3cm
2
4-layer FR4 PC board, can be
used a guide.
Finally, be aware that at high ambient temperatures the
internal Schottky diode will have signifi cant leakage current
(see the Typical Performance Characteristics) increasing
the quiescent current of the LTM8021.
+
LTM8021
4.7μF
V
IN
CLOSING SWITCH
SIMULATES HOT PLUG
I
IN
(5a)
(5b)
LOW
IMPEDANCE
ENERGIZED
24V SUPPLY
STRAY
INDUCTANCE
DUE TO 6 FEET
(2 METERS) OF
TWISTED PAIR
+
LTM8021
4.7μF0.1μF
0.7Ω
(5c)
+
LTM8021
4.7μF
22μF
AI.EI.
+
V
IN
20V/DIV
I
IN
10A/DIV
20μs/DIV
DANGER
RINGING V
IN
MAY EXCEED
ABSOLUTE MAXIMUM RATING
V
IN
20V/DIV
I
IN
10A/DIV
20μs/DIV
8021 F05
V
IN
20V/DIV
I
IN
10A/DIV
20μs/DIV
Figure 5. Ensures Reliable Operation When the LTM8021 is Connected to a Live Supply