ltm8021 Linear Technology Corporation, ltm8021 Datasheet - Page 12

• Manufacturer Part Number: ltm8021
• Description: 36vin, 500ma Step-down Dc/dc ?module
• Manufacturer: Linear Technology Corporation

APPLICATIONS INFORMATION
LTM8021
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 datasheet 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
12
IMPEDANCE
24V SUPPLY
ENERGIZED
Figure 5. Ensures Reliable Operation When the LTM8021 is Connected to a Live Supply
LOW
+
+
+
SIMULATES HOT PLUG
CLOSING SWITCH
STRAY
INDUCTANCE
DUE TO 6 FEET
(2 METERS) OF
TWISTED PAIR
+
0.7Ω
0.1μF
I
22μF
AI.EI.
IN
V
IN
4.7μF
4.7μF
4.7μF
LTM8021
LTM8021
LTM8021
(5a)
(5b)
(5c)
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 on page 2, which is based upon
a 40.3cm
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.
20V/DIV
10A/DIV
20V/DIV
10A/DIV
20V/DIV
10A/DIV
V
V
V
I
I
I
IN
IN
IN
IN
IN
IN
2
4-layer FR4 PC board, can be used a guide.
DANGER
RINGING V
ABSOLUTE MAXIMUM RATING
20μs/DIV
20μs/DIV
20μs/DIV
IN
MAY EXCEED
8021 F05
8021fa