NCP690 ONSEMI [ON Semiconductor], NCP690 Datasheet - Page 12

• Manufacturer Part Number: NCP690
• Description: 1 A, Low IGND, Very Low Dropout Regulator (VLDO) with/without Enable
• Manufacturer: ONSEMI [ON Semiconductor]

divider network as shown on Figure 4. The output voltage
and resistors should be chosen using Equations 1 and 2.
Choose R
current and to minimize noise contribution to the output
voltage. Use Equation 2 to find the required value for R
Thermal Characteristics
become necessary to provide some thermal relief. The
maximum power dissipation supported by the device is
dependent upon board design and layout. Mounting pad
configuration on the PCB, the board material, and the
ambient temperature affect the rate of junction temperature
rise for the part. When the NCP690 has good thermal
conductivity through the PCB, the junction temperature will
be relatively low with high power applications. The
maximum dissipation the NCP690 can handle is given by:
then the NCP690 can dissipate up to 1 W when the ambient
temperature (T
Input bias current I
As power dissipated in the NCP690 increases, it might
Since T
V
R
OUT
2
J
1
^ R
is not recommended to exceed 125°C (T
arbitrarily to minimize errors due to the bias
+ 1.250 1 )
A
1
) is 25°C.
P
V
1.25
D(MAX)
OUT
1
* 1
ADJ
+
is typically less than 210 nA.
[T
R
R
1
2
J(MAX)
) (I
R
qJA
* T
ADJ
A
@ R
]
1
)
J(MAX)
(eq. 1)
(eq. 2)
(eq. 3)
http://onsemi.com
2
.
),
12
from the following equations:
or
Hints
wide as possible. When the impedance of these traces is
high, there is a chance to pick up noise or cause the regulator
to malfunction. Place external components, especially the
output capacitor, as close as possible to the NCP690, and
make traces as short as possible.
The power dissipated by the NCP690 can be calculated
V
250
200
150
100
50
Figure 32. Thermal Resistance vs. Copper Area
IN
0
P
0
and GND printed circuit board traces should be as
D
[ V
V
IN(MAX)
IN
FR4 − 1.0 oz
FR4 − 2.0 oz
(I
GND
200
COPPER AREA (mm
[
@I
P
OUT
D(MAX)
) ) I
I
OUT
) (V
400
OUT
) I
OUT
(V
GND
2
IN
)
* V
I
OUT
600
OUT
)
)
(eq. 4)
(eq. 5)
800