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부품번호 | NCP1547 기능 |
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기능 | Buck Regulator | ||
제조업체 | ON Semiconductor | ||
로고 | |||
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NCP1547
1.5 A, 340 kHz, Buck
Regulator with
Synchronization Capability
The NCP1547 is a 1.5 A buck regulator IC operating at a
fixed−frequency of 340 kHz. The device uses the V2t control
architecture to provide unmatched transient response, the best overall
regulation and the simplest loop compensation for today’s high−speed
logic. The NCP1547 accommodates input voltages from 4.5 V to 40 V
and contains synchronization circuitry.
The on−chip NPN transistor is capable of providing a minimum of
1.5 A of output current, and is biased by an external “boost” capacitor
to ensure saturation, thus minimizing on−chip power dissipation.
Protection circuitry includes thermal shutdown, cycle−by−cycle
current limiting and frequency foldback.
Features
• V2 Architecture Provides Ultra−Fast Transient Response, Improved
Regulation and Simplified Design
• 2.0% Error Amp Reference Voltage Tolerance
• Switch Frequency Decrease of 4:1 in Short Circuit Conditions
Reduces Short Circuit Power Dissipation
• BOOST Lead Allows “Bootstrapped” Operation to Maximize
Efficiency
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• Sync Function for Parallel Supply Operation or Noise Minimization
• Shutdown Lead Provides Power−Down Option
• 1.0 mA Quiescent Current During Power−Down
• Thermal Shutdown
• Soft−Start
• This is a Pb−Free Device
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MARKING
DIAGRAM
1 18
18
1
18−LEAD DFN
MN SUFFIX
CASE 505
NCP1547
AWLYYWW G
G
A = Assembly Location
WL = Wafer Lot
YY = Year
WW = Work Week
E = Automotive Grade
G = Pb−Free Package
(Note: Microdot may be in either location)
ORDERING INFORMATION
See detailed ordering and shipping information in the package
dimensions section on page 12 of this data sheet.
© Semiconductor Components Industries, LLC, 2007
March, 2007 − Rev. 0
1
Publication Order Number:
NCP1547/D
NCP1547
ELECTRICAL CHARACTERISTICS (0°C < TJ < 70°C, 4.5 V< VIN < 40 V; unless otherwise specified.)
Characteristic
Test Conditions
Min
Oscillator
Operating Frequency
− 306
Frequency Line Regulation
−−
Maximum Duty Cycle
− 85
VFB Frequency Foldback Threshold
PWM Comparator
− 0.29
Slope Compensation Voltage
Minimum Output Pulse Width
Power Switch
Fix VFB, DVC/DTON
VFB to VSW
5.0
−
Current Limit
Foldback Current
Saturation Voltage
Current Limit Delay
VFB > 0.36 V
VFB < 0.29 V
IOUT = 1.5 A, VBOOST = VIN + 2.5 V
(Note 3)
1.6
0.9
0.4
−
Error Amplifier
Internal Reference Voltage
− 1.244
Reference PSRR
(Note 3)
−
FB Input Bias Current
−−
Output Source Current
Output Sink Current
Output High Voltage
Output Low Voltage
Unity Gain Bandwidth
VC = 1.270 V, VFB = 1.0 V
VC = 1.270 V, VFB = 2.0 V
VFB = 1.0 V
VFB = 2.0 V
(Note 3)
15
15
1.39
5.0
−
Open Loop Amplifier Gain
(Note 3)
−
Amplifier Transconductance
(Note 3)
−
Sync
Sync Frequency Range
− 377
Sync Pin Bias Current
Sync Threshold Voltage
VSYNC = 5.0 V
−
−
0.9
Shutdown
Shutdown Threshold Voltage
− 1.0
Shutdown Pin Bias Current
Thermal Shutdown
VSHDNB = 0 V
0.14
Overtemperature Trip Point
(Note 3)
175
Thermal Shutdown Hysteresis
(Note 3)
−
3. Guaranteed by design, not 100% tested in production.
Typ
340
0.05
90
0.32
9.0
100
2.3
1.5
0.7
120
1.270
40
0.02
25
25
1.46
20
500
70
6.4
−
360
1.5
1.3
5.00
185
42
Max
374
0.15
95
0.36
17
200
3.0
2.1
1.0
160
1.296
−
0.1
35
35
1.53
60
−
−
−
710
485
1.9
1.6
35
195
−
Unit
kHz
%/V
%
V
mV/ms
ns
A
A
V
ns
V
dB
mA
mA
mA
V
mV
kHz
dB
mA/V
kHz
mA
V
V
mA
°C
°C
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4
4페이지 NCP1547
duty cycle of the sync pulses can vary from 10% to 90%. The
frequency foldback feature is disabled during the sync
mode.
Figure 4. A NCP1547 Buck Regulator is
Synchronized to an External 443 kHz Pulse Signal
Power Switch and Current Limit
The collector of the built−in NPN power switch is
connected to the VIN pin, and the emitter to the VSW pin.
When the switch turns on, the VSW voltage is equal to the
VIN minus switch Saturation Voltage. In the buck regulator,
the VSW voltage swings to one diode drop below ground
when the power switch turns off, and the inductor current is
commutated to the catch diode. Due to the presence of high
pulsed current, the traces connecting the VSW pin, inductor
and diode should be kept as short as possible to minimize the
noise and radiation. For the same reason, the input capacitor
should be placed close to the VIN pin and the anode of the
diode.
The saturation voltage of the power switch is dependent
on the switching current, as shown in Figure 5.
0.7
0.6
0.5
0.4
0.3
0.2
0.1
0
0 0.5 1.0 1.5
SWITCHING CURRENT (A)
Figure 5. The Saturation Voltage of the Power Switch
Increases with the Conducting Current
The NCP1547 contains pulse−by−pulse current limiting
to protect the power switch and external components. When
the peak of the switching current reaches the Current Limit,
the power switch turns off after the Current Limit Delay. The
switch will not turn on until the next switching cycle. The
current limit threshold is independent of switching duty
cycle. The maximum load current, given by the following
formula under continuous conduction mode, is less than the
Current Limit due to the ripple current.
IO(MAX)
+
ILIM
*
VO(VIN * VO)
2(L)(VIN)(fs)
where:
fS = switching frequency,
ILIM = current limit threshold,
VO = output voltage,
VIN = input voltage,
L = inductor value.
When the regulator runs under current limit, the
subharmonic oscillation may cause low frequency
oscillation, as shown in Figure 6. Similar to current mode
control, this oscillation occurs at the duty cycle greater than
50% and can be alleviated by using a larger inductor value.
The current limit threshold is reduced to Foldback Current
when the FB pin falls below Foldback Threshold. This
feature protects the IC and external components under the
power up or over−load conditions.
Figure 6. The Regulator in Current Limit
BOOST Pin
The BOOST pin provides base driving current for the
power switch. A voltage higher than VIN provides required
headroom to turn on the power switch. This in turn reduces
IC power dissipation and improves overall system
efficiency. The BOOST pin can be connected to an external
boost−strapping circuit which typically uses a 0.1 mF capacitor
and a 1N914 or 1N4148 diode, as shown in Figure 1.
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DataSheet.kr | 2020 | 연락처 | 링크모음 | 검색 | 사이트맵 |