MSK5900RH MSK, MSK5900RH Datasheet - Page 4

• Manufacturer Part Number: MSK5900RH
• Description: RAD TOLERANT ULTRA LOW DROPOUT ADJUSTABLE POSITIVE LINEAR REGULATOR
• Manufacturer: MSK

HEAT SINK SELECTION
ing formula for convective heat flow may be used.
Governing Equation:
Where
perature. The absolute maximum allowable junction tem-
perature is 150°C. The equation may now be rearranged
to solve for the required heat sink to ambient thermal
resistance (R
Example:
V
ambient temperature is +25°C. The maximum desired
junction temperature is +125°C.
R
greases
Solve for R
of no more than 51°C/W must be used to maintain a
junction temperature of no more than 125°C.
THERMAL LIMITING
down temperature of approximately 150°C. This ther-
mal shutdown can be used as a protection feature, but
for continuous operation, the junction temperature of the
pass transistor must be maintained below 150°C. Proper
heat sink selection is essential to maintain these condi-
tions. Exceeding the thermal limit activates the latch fea-
ture of the MSK 5900RH. See LATCH pin description for
instructions to reset the latch or disable the latch fea-
ture.
OUT
To select a heat sink for the MSK 5900RH, the follow-
The MSK 5900RH control circuitry has a thermal shut-
JC
In this example, a heat sink with a thermal resistance
APPLICATION NOTES CONT.
Next, the user must select a maximum junction tem-
An MSK 5900RH is connected for V
T
P
R
R
R
T
=7.5°C/W and R
=+3.3V. I
R
J
D
A
JC
CS
SA
SA
T
= 51.2°C/W
Power Dissipation=(5V-3.3V) x (1A)
=
Power Dissipation=(V
J
= Junction Temperature
= Total Power Dissipation
= Junction to Case Thermal Resistance
= Case to Heat Sink Thermal Resistance
= Heat Sink to Ambient Thermal Resistance
= Ambient Temperature
SA:
=
125°C - 25°C
SA
P
).
D
OUT
X (R
1.7W
is a continuous 1A DC level. The
CS
JC
=0.15°C/W for most thermal
+ R
=1.7Watts
-7.5°C/W - 0.15°C/W
CS
IN
+ R
-V
OUT
SA
) x I
) + T
IN
OUT
=+5V and
A
4
TYPICAL APPLICATIONS CIRCUIT
OUTPUT VOLTAGE SELECTION
the formula for output voltage selection is
A good starting point for this output voltage selection is
to set R2=1K. By rearranging the formula it is simple to
calculate the final R1 value.
Table 1 below lists some of the most probable resistor
combinations based on industry standard usage.
As noted in the above typical applications circuit,
VOLTAGE
OUTPUT
1.5
1.8
2.0
2.5
2.8
3.3
4.0
5.0
(V)
V
V
OUT
R1=R2
OUT
=1.265
=1.265(1+R1/R2)
TABLE 1
( )
R2
1K
1K
1K
1K
1K
1K
1K
1K
1.265
V
1+
OUT
R1
R2
-1
R1 (nearest 1%)
1.21K
1.62K
2.15K
2.94K
187
422
576
976
Rev. H 11/06
( )