LM5111-2M National Semiconductor, LM5111-2M Datasheet - Page 9

• Manufacturer Part Number: LM5111-2M
• Description: Dual 5A Compound Gate Driver
• Manufacturer: National Semiconductor

Thermal Performance
We know that the junction temperature is given by
Or the rise in temperature is given by
For SOIC-8 package θ
conditions of natural convection.
Therefore T
CONTINUOUS CURRENT RATING OF LM5111
The LM5111 can deliver pulsed source/sink currents of 3A
and 5A to capacitive loads. In applications requiring continu-
ous load current (resistive or inductive loads), package
power dissipation, limits the LM5111 current capability far
below the 5A sink/3A source capability. Rated continuous
current can be estimated both when sourcing current to or
sinking current from the load. For example when sinking, the
maximum sink current can be calculated as:
where R
output stage of LM5111.
Consider T
package under the condition of natural convection and no air
DS
(on) is the on resistance of lower MOSFET in the
J
RISE
(max) of 125˚C and θ
T
T
RISE
is equal to
RISE
T
= 0.236 x 170 = 40.1˚C
J
= T
= P
JA
J
is estimated as 170˚C/W for the
D
− T
x θ
A
JA
= P
JA
+ T
of 170˚C/W for an SO-8
D
A
x θ
(Continued)
JA
9
flow. If the ambient temperature (T
S
yields I
peak pulsed currents.
Similarly, the maximum continuous source current can be
calculated as
where V
which varies over temperature and can be assumed to be
about 1.1V at T
eters as above, this equation yields I
(on) of the LM5111 output at T
SINK
DIODE
(max) of 391mA which is much smaller than 5A
is the voltage drop across hybrid output stage
J
(max) of 125˚C. Assuming the same param-
J
(max) is 2.5Ω, this equation
A
SOURCE
) is 60˚C, and the R
(max) of 347mA.
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