NCV8605, NCV8606
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moment when output voltage drops to 10% of its nominal
value at specific output current or resistive load.
Line Transient Response
Typical output voltage overshoot and undershoot response
when the input voltage is excited with a given slope.
Load Transient Response
Typical output voltage overshoot and undershoot
response when the output current is excited with a given
slope between no−load and full−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 175C,
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 NCV8605/NCV8606 regulator is self−protected with
internal thermal shutdown and internal current limit. Typical
application circuits are shown in Figures 1 to 4.
Input Decoupling (C
in
)
A ceramic or tantalum 1.0 mF capacitor is recommended
and should be connected close to the NCV8605/NCV8606
package. Higher capacitance and lower ESR will improve
the overall line transient response.
Output Decoupling (C
out
)
The NCV8605/NCV8606 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. Larger values
improve noise rejection and load regulation transient
response. Typical characteristics were measured with
Murata ceramic capacitors. GRM219R71E105K (1 mF,
25 V, X7R, 0805) and GRM21BR71A106K (10 mF, 10 V,
X7R, 0805).
No−Load Regulation Considerations
The NCV8605/NCV8606 adjustable regulator will
operate properly under conditions where the only load
current is through the resistor divider that sets the output
voltage. However, in the case where the
NCV8605/NCV8606 is configured to provide a 1.250 V
output, there is no resistor divider. If the part is enabled
under no−load conditions, leakage current through the pass
transistor at junction temperatures above 85C can approach
several microamps, especially as junction temperature
approaches 150C. If this leakage current is not directed into
a load, the output voltage will rise up to a level
approximately 20 mV above nominal.
The NCV8605/ NCV8606 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 V
in
(NCV8606 only) 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.
When the NCV8606 adjustable regulator is disabled, the
overshoot clamp circuit becomes inactive and the pass
transistor leakage will charge any capacitance on V
out
. If no
load is present, the output can charge up to within a few
millivolts of V
in
. In most applications, the load will present
some impedance to V
out
such that the output voltage will be
inherently clamped at a safe level. A minimum load of
10 mA is recommended.
Unlike LP8345, for NCV8605/606 fixed voltage versions
there is no limitation for minimum load current.
Noise Decoupling
The NCV8605/NCV8606 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 NCV8605/NCV8606 operates
without a noise reduction capacitor, has a typical 8 ms
turn−on time and achieves a 50 mV
rms
overall noise level
between 10 Hz and 100 kHz.
Enable Operation (NCV8606 Only)
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
.
Output Voltage Adjust
The output voltage can be adjusted from 1 times (Figure
4) to 4 times (Figure 3) the typical 1.250 V regulation
voltage via the use of resistors between the output and the
ADJ input. The output voltage and resistors are chosen using
Equation 1 and Equation 2.
V
out
+ 1.250
ǒ
1 )
R
1
R
2
Ǔ
)
ǒ
I
ADJ
R
1
Ǔ
(eq. 1)
(eq. 2)
R
2
^
R
1
V
out
1.25
* 1
