NCP4682, NCP4685
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APPLICATION INFORMATION
A typical application circuits for NCP4682 and NCP4685
series is shown in Figure 58.
VIN VOUT
CE
GND
C1
C2
100n
100n
VIN VOUT
NCP4682x
VIN VOUT
GND
C1 C2
100n 100n
VIN VOUT
NCP4685x
Figure 58. Typical Application Schematic
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 NCP4682/5. 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
output and ground pins. Larger values and lower ESR
improves dynamic parameters.
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.
Enable Operation (NCP4682 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.
Output Discharger (NCP4682 Only)
The NCP4682D version includes a transistor between
VOUT and GND that is used for faster discharging of the
output capacitor. This function is activated when the IC goes
into disable mode.
Thermals
As a power across the IC increase, 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 increase for the
part. When the device has good thermal conductivity
through the PCB the junction temperature will be relatively
low in high power dissipation applications.
PCB layout
Make the VIN and GND line as large as practical. If their
impedance is high, noise pickup or unstable operation may
result. Connect capacitors C1 and C2 as close as possible to
the IC, and make wiring as short as possible.
