NCV5500 ON Semiconductor, NCV5500 Datasheet - Page 6

• Manufacturer Part Number: NCV5500
• Description: 500 mA Linear Regulator
• Manufacturer: ON Semiconductor

DEFINITION OF TERMS
Dropout Voltage: The input−to−output voltage differential
at which the circuit ceases to regulate against further
reduction input voltage. Measured when the output voltage
has dropped 2% relative to the value measured at 6.0 V
input, dropout voltage is dependent upon load current and
junction temperature.
Input Voltage: The DC voltage applied to the input
terminals with respect to ground.
Line Regulation: The change in output voltage for a change
in the input voltage. The measurement is made under
conditions of low dissipation or by using pulse techniques
such that the average chip temperature is not significantly
affected.
Load Regulation: The change in output voltage for a change
in load current at constant chip temperature. Pulse loading
techniques are employed such that the average chip
temperature is not significantly affected.
Quiescent Current: The part of the positive input current
that does not contribute to the positive load current. The
regulator ground pin current with no load.
Ripple Rejection: The ratio of the peak−to−peak input ripple
voltage to the peak−to−peak output ripple voltage.
Current Limit: Peak current that can be delivered to the
output.
Calculating Power Dissipation
regulator (Figure 3) is:
Where
V
V
I
I
P
OUT(max)
GND
IN(max)
OUT(min)
The maximum power dissipation for a single output
D(max)
is the ground current at I
+ V
is the maximum input voltage,
is the maximum output current for the application,
is the minimum output voltage,
IN(max)
* V
OUT(min)
OUT(max)
I
OUT(max)
) V
.
IN(max)
I
q
http://onsemi.com
(eq. 1)
6
Once the value of P
permissible value of R
package section of the data sheet. Those packages with R
less than the calculated value in Equation 2 will keep the die
temperature below 150°C.
dissipate the heat generated by the IC, and an external heat
sink will be required.
Heat sinks
package to improve the flow of heat away from the IC and
into the surrounding air.
outside environment will have a thermal resistance. Like
series electrical resistances, these resistances are summed to
determine the value of R
where
R
R
R
R
functions of the package type, heat sink and the interface
between them. These values appear in data sheets of heat
sink manufacturers.
further discussed in ON Semiconductor Application Note
AN1040/D.
R
R
qJC
qCS
qSA
qJA
The value of R
In some cases, none of the packages will be sufficient to
A heat sink effectively increases the surface area of the
Each material in the heat flow path between the IC and the
R
Thermal, mounting, and heat sink considerations are
qJA
qJA
qJC
, it too is a function of package type. R
is the junction−to−case thermal resistance,
is the case−to−heatsink thermal resistance,
is the heatsink−to−ambient thermal resistance.
+
+ R
appears in the package section of the data sheet. Like
150 C * T
qJC
°
) R
P
D
qJA
qCS
can then be compared with those in the
A
) R
qJA
D(max)
qJA
can be calculated:
qSA
:
is known, the maximum
qCS
and R
qSA
(eq. 2)
(eq. 3)
qJA
are