NCP629
http://onsemi.com
10
Noise Decoupling
The NCP629 is a low noise regulator and needs no
external noise reduction capacitor. Unlike other low noise
regulators which require an external capacitor and have slow
startup times, the NCP629 operates without a noise
reduction capacitor, has a typical 15 ms startup delay and
achieves a 50 mV
rms
overall noise level between 10 Hz and
100 kHz.
Enable Operation
The enable pin will turn the regulator on or off. The
threshold limits are covered in the electrical characteristics
table in this data sheet. The turn-on/turn-off transient
voltage being supplied to the enable pin should exceed a
slew rate of 10 mV/ms to ensure correct operation. If the
enable function is not to be used then the pin should be
connected to V
in
.
Thermal
As power in the NCP629 increases, it might 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 NCP629 has good thermal conductivity through the
PCB, the junction temperature will be relatively low with
high power applications. The maximum dissipation the
NCP629 can handle is given by:
P
D(MAX)
+
T
J(MAX)
* T
A
R
qJA
(eq. 1)
Since T
J
is not recommended to exceed 125_C, then the
NCP629 soldered on 645 mm2, 1 oz copper area, FR4 can
dissipate up to 360 mW when the ambient temperature (T
A
)
is 25_C. See Figure 26 for R
thJA
versus PCB area.
The power dissipated by the NCP629 can be calculated
from the following equations:
(eq. 2)
P
D
[ V
in
ǒ
I
GND
@I
out
Ǔ
) I
out
ǒ
V
in
* V
out
Ǔ
or
V
in(MAX)
[
P
D(MAX)
) (V
out
I
out
)
I
out
) I
GND
(eq. 3)
200
220
240
260
280
300
320
340
0 100 200 300 400 500 600 700
Figure 26. R
thJA
vs. PCB Copper Area
PCB COPPER AREA (mm
2
)
R
thJA
, THERMAL RESISTANCE JUNCTION-TO-AMBIENT (°C/W)
(1 oz)
(2 oz)
Hints
V
in
and GND printed circuit board traces should be as
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 NCP629, and
make traces as short as possible.
DEVICE ORDERING INFORMATION
Device Version Marking Code Package Shipping
†
NCP629FC15T2G 1.5 V AAA
5 Pin Flip-Chip 3000/Tape & Reel
NCP629FC18T2G 1.8 V AAC
NCP629FC28T2G 2.8 V AAD
NCP629FC30T2G 3.0 V AAE
NCP629FC33T2G 3.3 V AAF
NCP629FC35T2G 3.5 V AAG
NCP629FC50T2G 5.0 V AAH
†For information on tape and reel specifications, including part orientation and tape sizes, please refer to our Tape and Reel Packaging
Specifications Brochure, BRD8011/D.
