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參數(shù)資料
| 型號： | NCV2574 |
| 廠商： | ON SEMICONDUCTOR |
| 英文描述： | 0.5 A, Adjustable Output Voltage, Step-Down Switching Regulator(0.5A,可調(diào)輸出電壓,降壓型開關(guān)穩(wěn)壓器) |
| 中文描述： | 0.5甲，可調(diào)輸出電壓，降壓型開關(guān)穩(wěn)壓器（0.5A的，可調(diào)輸出電壓，降壓型開關(guān)穩(wěn)壓器） |
| 文件頁數(shù)： | 9/26頁 |
| 文件大小： | 295K |
| 代理商： | NCV2574 |
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LM2574, NCV2574
http://onsemi.com
9
PIN FUNCTION DESCRIPTION
Pin
Symbol
Description (Refer to Figure 1)
SO16W
PDIP8
12
5
V
in
This pin is the positive input supply for the LM2574 stepdown switching regulator. In order to
minimize voltage transients and to supply the switching currents needed by the regulator, a
suitable input bypass capacitor must be present (C
in
in
Figure 1).
14
7
Output
This is the emitter of the internal switch. The saturation voltage V
sat
of this output switch is
typically 1.0 V. It should be kept in mind that the PCB area connected to this pin should be kept
to a minimum in order to minimize coupling to sensitive circuitry.
4
2
Sig Gnd
Circuit signal ground pin. See the information about the printed circuit board layout.
6
4
Pwr Gnd
Circuit power ground pin. See the information about the printed circuit board layout.
3
1
Feedback
This pin senses regulated output voltage to complete the feedback loop. The signal is divided by
the internal resistor divider network R2, R1 and applied to the noninverting input of the internal
error amplifier. In the Adjustable version of the LM2574 switching regulator, this pin is the direct
input of the error amplifier and the resistor network R2, R1 is connected externally to allow
programming of the output voltage.
5
3
ON/OFF
It allows the switching regulator circuit to be shut down using logic level signals, thus dropping the
total input supply current to approximately 80 A. The input threshold voltage is typically 1.5 V.
Applying a voltage above this value (up to +V
in
) shuts the regulator off. If the voltage applied to this
pin is lower than 1.5 V or if this pin is left open, the regulator will be in the “on” condition.
DESIGN PROCEDURE
Buck Converter Basics
The LM2574 is a “Buck” or StepDown Converter which
is the most elementary forwardmode converter. Its basic
schematic can be seen in
Figure 17.
The operation of this regulator topology has two distinct
time periods. The first one occurs when the series switch is
on, the input voltage is connected to the input of the inductor.
The output of the inductor is the output voltage, and the
rectifier (or catch diode) is reverse biased. During this
period, since there is a constant voltage source connected
across the inductor, the inductor current begins to linearly
ramp upwards, as described by the following equation:
IL(on)
Vin– Voutton
L
During this “on” period, energy is stored within the core
material in the form of magnetic flux. If the inductor is
properly designed, there is sufficient energy stored to carry
the requirements of the load during the “off” period.
Figure 17. Basic Buck Converter
D
V
in
R
Load
L
C
out
Power
Switch
The next period is the “off” period of the power switch.
When the power switch turns off, the voltage across the
inductor reverses its polarity and is clamped at one diode
voltage drop below ground by the catch diode. Current now
flows through the catch diode thus maintaining the load
current loop. This removes the stored energy from the
inductor. The inductor current during this time is:
IL(off)
Vout– VDtoff
L
This period ends when the power switch is once again
turned on. Regulation of the converter is accomplished by
varying the duty cycle of the power switch. It is possible to
describe the duty cycle as follows:
ton
T, where T is the period of switching.
For the buck converter with ideal components, the duty
cycle can also be described as:
Vout
d
d
Vin
Figure 18 shows the buck converter idealized waveforms
of the catch diode voltage and the inductor current.
Figure 18. Buck Converter Idealized Waveforms
Power
Switch
Power
Switch
Off
V
D
(FWD)
Power
Switch
Off
Power
Switch
On
Power
Switch
On
V
on(SW)
Time
Time
I
Load
(AV)
I
min
Diode
I
pk
Diode
Power
Switch
D
I
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相關(guān)代理商/技術(shù)參數(shù) |
參數(shù)描述 |
|---|---|
| NCV2574DW-ADJR2 | 功能描述:直流/直流開關(guān)調(diào)節(jié)器 ASECLSW REG RoHS:否 制造商:International Rectifier 最大輸入電壓:21 V 開關(guān)頻率:1.5 MHz 輸出電壓:0.5 V to 0.86 V 輸出電流:4 A 輸出端數(shù)量: 最大工作溫度: 安裝風(fēng)格:SMD/SMT 封裝 / 箱體:PQFN 4 x 5 |
| NCV2574DW-ADJR2G | 功能描述:直流/直流開關(guān)調(diào)節(jié)器 ASECLSW REG RoHS:否 制造商:International Rectifier 最大輸入電壓:21 V 開關(guān)頻率:1.5 MHz 輸出電壓:0.5 V to 0.86 V 輸出電流:4 A 輸出端數(shù)量: 最大工作溫度: 安裝風(fēng)格:SMD/SMT 封裝 / 箱體:PQFN 4 x 5 |
| NCV2574DW-ADJR2G | 制造商:ON Semiconductor 功能描述:Switching Regulator |
| NCV2575 | 制造商:ONSEMI 制造商全稱:ON Semiconductor 功能描述:1.0 A, Adjustable Output Voltage, Step-Down Switching Regulator |
| NCV2575D2T-12G | 功能描述:直流/直流開關(guān)調(diào)節(jié)器 ANA 12V 1A PW SW REG RoHS:否 制造商:International Rectifier 最大輸入電壓:21 V 開關(guān)頻率:1.5 MHz 輸出電壓:0.5 V to 0.86 V 輸出電流:4 A 輸出端數(shù)量: 最大工作溫度: 安裝風(fēng)格:SMD/SMT 封裝 / 箱體:PQFN 4 x 5 |
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