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參數(shù)資料
| 型號： | NCP9001 |
| 廠商： | ON SEMICONDUCTOR |
| 英文描述： | 1.5 MHz, 600 mA, High−Efficiency, Low Quiescent Current, Adjustable Output Voltage Step−Down Converter |
| 文件頁數(shù)： | 9/12頁 |
| 文件大?。?/td> | 192K |
| 代理商： | NCP9001 |
NCP9001
http://onsemi.com
9
Cycle
by
Cycle Current Limitation
From the block diagram (Figure 3), an I
LIM
comparator
is used to realize cycle
by
cycle current limit protection.
The comparator compares the LX pin voltage with the
reference voltage, which is biased by a constant current. If
the inductor current reaches the limit, the I
LIM
comparator
detects the LX voltage falling below the reference voltage
and releases the signal to turn off the switch Q1. The
cycle
by
cycle current limit is set at 1200 mA (nom).
Short Circuit Protection
When the output is shorted to ground, the device limits
the inductor current. The duty
cycle is minimum and the
consumption on the input line is 300 mA (Typ). When the
short circuit condition is removed, the device returns to the
normal mode of operation.
Soft
Start
The NCP9001 uses soft
start (300 s Typ) to limit the
inrush current when the device is initially enabled.
Soft
start is implemented by gradually increasing the
reference voltage until it reaches the full reference voltage.
During startup, a pulsed current source charges the internal
soft
start capacitor to provide gradually increasing
reference voltage. When the voltage across the capacitor
ramps up to the nominal reference voltage, the pulsed
current source will be switched off and the reference
voltage will switch to the regular reference voltage.
Shutdown Mode
When the EN pin has a voltage applied of less than 0.4 V,
the NCP9001 will be disabled. In shutdown mode, the
internal reference, oscillator and most of the control
circuitries are turned off. Therefore, the typical current
consumption will be 0.3 A (typical value). Applying a
voltage above 1.2 V to EN pin will enable the device for
normal operation. The typical threshold is around 0.7 V.
The device will go through soft
start to normal operation,
however, the EN pin should be tied low while the input
voltage on V
IN
pin is rising up.
Thermal Shutdown
Internal Thermal Shutdown circuitry is provided to
protect the integrated circuit in the event that the maximum
junction temperature is exceeded. If the junction
temperature exceeds 160 C, the device shuts down. In this
mode switch Q1 and Q2 and the control circuits are all
turned off. The device restarts in soft
start after the
temperature drops below 135 C. This feature is provided
to prevent catastrophic failures from accidental device
overheating, and it is not intended as a substitute for proper
heatsinking.
Low Dropout Operation
The NCP9001 offers a low input to output voltage
difference. The NCP9001 can operate at 100% duty cycle.
In this mode the PMOS (Q1) switches completely on.
The minimum input voltage to maintain regulation can
be calculated as:
VIN(min)
VOUT(max)
(IOUT
(RDS(on)
(eq. 1)
RINDUCTOR))
V
OUT
: Output Voltage (Volts)
I
OUT
: Max Output Current
R
DS(on)
: P
Channel Switch R
DS(on)
R
INDUCTOR
: Inductor Resistance (DCR)
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|---|---|
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| NCP9003 | 制造商:ONSEMI 制造商全稱:ON Semiconductor 功能描述:Compact Backlight LED Boost Driver |
| NCP9003SNT1G | 功能描述:LED照明驅(qū)動器 SBN_BE LED DRIEVR RoHS:否 制造商:STMicroelectronics 輸入電壓:11.5 V to 23 V 工作頻率: 最大電源電流:1.7 mA 輸出電流: 最大工作溫度: 安裝風(fēng)格:SMD/SMT 封裝 / 箱體:SO-16N |
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