NCP500, NCV500
www.onsemi.com
12
DEFINITIONS
Load Regulation
The change in output voltage for a change in output load
current at a constant temperature.
Dropout Voltage
The input/output differential at which the regulator output
no longer maintains regulation against further reductions in
input voltage. Measured when the output drops 2% below its
nominal. The junction temperature, load current, and
minimum input supply requirements affect the dropout level.
Output Noise Voltage
This is the integrated value of the output noise over a
specified frequency range. Input voltage and output load
current are kept constant during the measurement. Results
are expressed in
mVRMS
or nV Hz
Ǹ
.
Quiescent Current
The current which flows through the ground pin when the
regulator operates without a load on its output: internal IC
operation, bias, etc. When the LDO becomes loaded, this
term is called the Ground current. It is actually the difference
between the input current (measured through the LDO input
pin) and the output current.
Line Regulation
The change in output voltage for a change in input voltage.
The measurement is made under conditions of low
dissipation or by using pulse technique such that the average
chip temperature is not significantly affected.
Line Transient Response
Typical over and undershoot response when input voltage
is excited with a given slope.
Thermal Protection
Internal thermal shutdown circuitry is provided to protect
the integrated circuit in the event that the maximum junction
temperature is exceeded. When activated at typically 160°C,
the regulator turns off. This feature is provided to prevent
failures from accidental overheating.
Maximum Package Power Dissipation
The power dissipation level at which the junction
temperature reaches its maximum operating value, i.e.
125°C.
APPLICATIONS INFORMATION
The NCP500 series regulators are protected with internal
thermal shutdown and internal current limit. A typical
application circuit is shown in Figure 27.
Input Decoupling (C1)
A 1.0 mF capacitor either ceramic or tantalum is
recommended and should be connected close to the NCP500
package. Higher values and lower ESR will improve the
overall line transient response.
Output Decoupling (C2)
The NCP500 is a stable component and does not require
a minimum Equivalent Series Resistance (ESR) or a
minimum output current. The minimum decoupling value is
1.0 mF and can be augmented to fulfill stringent load
transient requirements. The regulator accepts ceramic chip
capacitors as well as tantalum devices. Larger values
improve noise rejection and load regulation transient
response. Figure 29 shows the stability region for a range of
operating conditions and ESR values.
Noise Decoupling
The NCP500 is a low noise regulator without the need of
an external bypass capacitor. It typically reaches a noise level
of 50 mVRMS overall noise between 10 Hz and 100 kHz. The
classical bypass capacitor impacts the start up phase of
standard LDOs. However, thanks to its low noise
architecture, the NCP500 operates without a bypass element
and thus offers a typical 20 ms start up phase.
Enable Operation
The enable pin will turn on or off the regulator. These
limits of threshold are covered in the electrical specification
section of 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 is not to be used then the pin should be connected
to V
in
.
Thermal
As power across the NCP500 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
effect the rate of junction temperature rise for the part. This
is stating that when the NCP500 has good thermal
conductivity through the PCB, the junction temperature will
be relatively low with high power dissipation applications.
