NCP706B, NCP706AB
www.onsemi.com
8
APPLICATIONS INFORMATION
Input Decoupling (Cin)
A 2.2 mF capacitor either ceramic or tantalum is
recommended and should be connected as close as possible
to the pins of NCP706B device. Higher values and lower
ESR will improve the overall line transient response.
Output Decoupling (Cout)
The minimum decoupling value for
NCP706BMX300TAG and NCP706ABMX300TAG
devices is 2.2 mF. The regulator accepts ceramic chip
capacitors MLCC. If a tantalum capacitor is used, and its
ESR is large, the loop oscillation may result. Larger values
improve noise rejection and PSRR.
Enable Operation
The enable pin EN will turn on or off the regulator. These
limits of threshold are covered in the electrical specification
section of this data sheet. If the enable is not used then the
pin should be connected to V
IN
.
Hints
Please be sure the V
in
and GND lines are sufficiently wide.
If their impedance is high, noise pickup or unstable
operation may result.
Set external components, especially the output capacitor,
as close as possible to the circuit.
The sense pin SNS trace is recommended to be kept as far
from noisy power traces as possible and as close to load as
possible.
Thermal
As power across the NCP706B/AB 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 also the
ambient temperature affect the rate of temperature rise for
the part. This is stating that when the NCP706B/AB has
good thermal conductivity through the PCB, the junction
temperature will be relatively low with high power
dissipation.
The power dissipation across the device can be roughly
represented by the equation:
P
D
+
ǒ
V
IN
* V
OUT
Ǔ
*I
OUT
[W]
(eq. 1)
The maximum power dissipation depends on the thermal
resistance of the case and circuit board, the temperature
differential between the junction and ambient, PCB
orientation and the rate of air flow.
The maximum allowable power dissipation can be
calculated using the following equation:
P
MAX
+
ǒ
T
J
* T
A
Ǔ
ńq
JA
[W]
(eq. 2)
Where (T
J
− T
A
) is the temperature differential between
the junction and the surrounding environment and q
JA
is the
thermal resistance from the junction to the ambient.
Connecting the exposed pad and non connected pin 3 to
a large ground pad or plane helps to conduct away heat and
improves thermal relief.
Overcurrent Latch Operation
The NCP706B/AB is equipped with latched overcurrent
protection feature which will automatically disable the LDO
in case of permanent output short circuit.
Initally during the OCP condition the current flowing
from the input to the output of the LDO is typically 1.65 A.
This current cause the die to heat−up and eventually when
the temperature rises up to the thermal shutdown threshold
the LDO becomes disabled. To resume the operation of the
device it is necessary to toggle the EN to ‘OFF’ state and
than back to ‘ON’ state again.
Figure 18. Overcurrent Latch Operation
Output Voltage
Enable Voltage
1.2 V
3.0 V
600 mA
1.65 A
Output Current
1.65 A
0 mA
0 mA
600 mA
3.0 V
0 V0 V
0 V 0 V
0 V
t<t
blank
t>tblank
t
1.2 V
