NCP4681(2011) 데이터 시트보기 (PDF) - ON Semiconductor
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NCP4681 Datasheet PDF : 18 Pages
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NCP4681, NCP4684
TYPICAL CHARACTERISTICS
6
4
2
Chip Enable
0
4.0
3.0
2.0
IOUT = 1 mA
IOUT = 30 mA
1.0
0
−1.0
0
IOUT = 150 mA
10 20 30 40 50 60 70 80 90 100
t (ms)
Figure 40. Shutdown, 3.3 V Version NCP4681D,
VIN = 4.3 V
APPLICATION INFORMATION
A typical application circuits for NCP4681 and NCP4684
series are shown in Figure 41.
output and ground pins. Larger capacitor values and lower
ESR improves dynamic parameters.
VIN
C1
100n
NCP4681x
VIN
VOUT
CE
GND
VOUT
C2
100n
Enable Operation (NCP4681 Only)
The enable pin CE may be used for turning the regulator
on and off. The IC is switched on when a high level voltage
is applied to the CE pin. The enable pin has an internal pull
down current source. If the enable function is not needed
connect CE pin to VIN.
VIN
C1
100n
NCP4684
VIN
VOUT
GND
VOUT
C2
100n
Figure 41. Typical Application Schematics
Input Decoupling Capacitor (C1)
A 0.1 mF ceramic input decoupling capacitor should be
connected as close as possible to the input and ground pin of
the NCP4681/4. Higher values and lower ESR improves line
transient response.
Output Decoupling Capacitor (C2)
A 0.1 mF ceramic output decoupling capacitor is enough
to achieve stable operation of the IC. If a tantalum capacitor
is used, and its ESR is high, loop oscillation may result. The
capacitors should be connected as close as possible to the
Constant Slope Circuit
The constant slope circuit is used as a soft start circuit that
allows the output voltage to start up slowly with a defined
slope. This circuit minimizes inrush current at start up and
also prevents against overshoot of the output voltage. The
Constant slope circuit is fully built in and no external
components are needed. Start up time and the output voltage
slope is defined internally and there is no way for the user to
change it. Start up into bigger output capacitor doesn’t make
any problem due to cooperation of constant slope circuit and
current limit circuit.
Current Limit
This regulator includes a fold−back current limiting
circuit. This type of protection doesn’t limit output current
up to specified current capability in normal operation, but
when an over current situation occurs, the output voltage and
current decrease until the over current condition ends.
Typical characteristics of this protection scheme are shown
in the Output voltage versus Output current graphs in the
characterization section of this datasheet.
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