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NCP629 Datasheet PDF : 11 Pages
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NCP629
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.
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 techniques such that the
average junction temperature is not significantly affected.
Line Transient Response
Typical output voltage overshoot and undershoot
response when the input voltage is excited with a given
slope.
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.
Disable and Ground Current
Ground Current (IGND) is the current that flows through
the ground pin when the regulator operates with a load on its
output. This consists of internal IC operation, bias, etc. It is
actually the difference between the input current (measured
through the LDO input pin) and the output load current. If
the regulator has an input pin that reduces its internal bias
and shuts off the output (enable/disable function), this term
is called the disable current (IDIS.)
Load Transient Response
Typical output voltage overshoot and undershoot
response when the output current is excited with a given
slope between low-load and high-load conditions.
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 175°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.
APPLICATIONS INFORMATION
The NCP629 series regulator is self-protected with
internal thermal shutdown and internal current limit. Typical
application circuit is shown in Figure 1.
Input Decoupling (Cin)
A ceramic or tantalum 1.0 mF capacitor is recommended
and should be connected close to the NCP629 package.
Higher capacitance and lower ESR will improve the overall
line transient response.
Output Decoupling (Cout)
The NCP629 is a stable component and does not require
a minimum Equivalent Series Resistance (ESR) for the
output capacitor. The minimum output decoupling value is
1.0 mF and can be augmented to fulfill stringent load
transient requirements. The regulator works with ceramic
chip capacitors as well as tantalum devices. Typical
characteristics were measured with Murata ceramic
capacitors GRM31MR71E105KA01 (1.0 mF, 25 V X7R,
1206). Larger values improve noise rejection and load
regulation transient response. Figure 23 shows the stability
region for a range of operating conditions and ESR values.
No-Load Regulation Considerations
The NCP629 contains an overshoot clamp circuit to
improve transient response during a load current step
release. When output voltage exceeds the nominal by
approximately 20 mV, this circuit becomes active and
clamps the output from further voltage increase. Tying the
ENABLE pin to Vin will ensure that the part is active
whenever the supply voltage is present, thus guaranteeing
that the clamp circuit is active whenever leakage current is
present.
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