NCP51460 Просмотр технического описания (PDF) - ON Semiconductor
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NCP51460 Datasheet PDF : 12 Pages
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NCP51460
A 0.1 mF or larger input capacitor will help to decrease the
dv/dt of the input voltage and improve stability during large
load current changes.
During the Turn−On for certain conditions the output
voltage can exhibit an overshoot. The amount of the
overshoot strongly depends on application conditions i.e.
input voltage level, slew rate, input and output capacitors,
and output current. The maximum value of the overshoot
isn’t guaranteed for this device.
The figure below shows an example of the Turn−On
overshoot.
6
4
2
0
3
2
VIN = 0 V to 6 V,
1
COUT = 0 mF,
IOUT = 1 mA, TA = 25°C,
0
trise = 30 ms
TIME (10 ms/DIV)
Figure 29.
Turn−Off Response
The Turn−Off response time is directly proportional to the
output capacitor value and inversely proportional to the load
value.
The NCP51460 device does not have any dedicated
internal circuitry to discharge the output capacitor when the
input voltage is turned−off or disconnected. This is why
when large output capacitors are used and very small output
current is drawn, it can take a considerable amount of time
to discharge the capacitor. If short turn−off times are
required, the output capacitor value should be minimized i.e.
with no output capacitor a 20 ms turn−off time can be
achieved.
Protection Features
The NCP51460 device is equipped with reverse input
voltage protection which will help to protect the device
when Input voltage polarity is reversed. In this circumstance
the Input current will be minimized to typically less than
0.1 mA.
The short circuit protection will protect the device under
the condition that the VOUT is suddenly shorted to ground.
The short circuit protection will work properly up to an Input
Voltage of 27 V at TA = 25°C. Depending on the PCB trace
width and thickness, air flow and process spread this value
can be slightly different and should be confirmed in the end
application.
No external voltage source should be connected directly
to the VOUT pin of NCP51460 regulator. If the external
source forces the output voltage to be greater than the
nominal output voltage level, the current will start to flow
from the Voltage Source to the VOUT pin. This current will
increase with the Output Voltage applied and can cause
damage to the device if VOUT > 10 V Typ. at 25°C
(Figure 30).
24
20
COUT = 0 mF,
TA = 25°C
16
12
8
4
0
3
4
5
6
7
8
9
10
VOUT, OUTPUT VOLTAGE (V)
Figure 30.
Output Noise
The NCP51460 Output Voltage Noise strongly depends
on the output capacitor value and load value. This is caused
by the fact that the bandwidth of the Reference is inversely
proportional to the capacitor value and directly proportional
to the output current. The Reference bandwidth directly
determines the point where the output voltage noise starts to
fall. This can be observed at the Figure 31 below.
2.2
2.0
VIN = 5.8 V
1.8
IOUT = 0 mA,
COUT = 0 − 10 mF MLCC,
1.6
TA = 25°C
1.4
COUT = 1.0 mF
1.2
COUT = 0.1 mF
1.0
0.8
COUT = 10 mF
0.6
0.4
COUT = 0 mF
0.2
0.0
10
100
1000
10k
100k
1M
f, FREQUENCY (Hz)
Figure 31.
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