參數(shù)資料
型號(hào)： LM2574-5
廠商： Motorola, Inc.
英文描述： EASY SWITCHERE⑩ 0.5 A STEP-DOWN VOLTAGE REGULATOR
中文描述： 易SWITCHERE⑩0.5降壓穩(wěn)壓器
文件頁(yè)數(shù)： 11/24頁(yè)
文件大?。?/td> 397K
代理商： LM2574-5
LM2574
11
MOTOROLA ANALOG IC DEVICE DATA
Procedure (Fixed Output Voltage Version) (continued)
In order to simplify the switching regulator design, a step–by–step
design procedure and example is provided.
Procedure
Example
5. Output Capacitor Selection (Cout)
A.
Since the LM2574 is a forward–mode switching regulator
with voltage mode control, its open loop 2–pole–1–zero
frequency characteristic has the dominant pole–pair
determined by the output capacitor and inductor values. For
stable operation and an acceptable ripple voltage,
(approximately 1% of the output voltage) a value between
100
μ
F and 470
μ
F is recommended.
B.
Due to the fact that the higher voltage electrolytic capacitors
generally have lower ESR (Equivalent Series Resistance)
numbers, the output capacitor’s voltage rating should be at
least 1.5 times greater than the output voltage. For a 5.0 V
regulator, a rating at least 8.0 V is appropriate, and a 10 V
or 16 V rating is recommended.
5. Output Capacitor Selection (Cout)
A.
Cout = 100
μ
F to 470
μ
F standard aluminium electrolytic.
B.
Capacitor voltage rating = 20 V.
Procedure (Adjustable Output Version: LM2574–ADJ)
Procedure
Example
Given Parameters:
Vout = Regulated Output Voltage
Vin(max) = Maximum DC Input Voltage
ILoad(max) = Maximum Load Current
Given Parameters:
Vout = 24 V
Vin(max) = 40 V
ILoad(max) = 0.4 A
1. Programming Output Voltage
To select the right programming resistor R1 and R2 value (see
Figure 2) use the following formula:
where Vref = 1.23 V
Resistor R1 can be between 1.0 k
and 5.0 k
. (For best
temperature coefficient and stability with time, use 1% metal
film resistors).
Vout
Vref
Vout
Vref1.0
R2
R1
R2
R1
1.0
1. Programming Output Voltage (selecting R1 and R2)
Select R1 and R2 :
Vout = 1.23
Select R1 = 1.0 k
R2 = 18.51 k
, choose a 18.7 k
metal film resistor.
1.0
R2
R1
R2
R1
Vout
Vref
1.0
1.0 k
10 V
1.23 V
1.0
2. Input Capacitor Selection (Cin)
To prevent large voltage transients from appearing at the input
and for stable operation of the converter, an aluminium or
tantalum electrolytic bypass capacitor is needed between the
input pin +Vin and ground pin Gnd. This capacitor should be
located close to the IC using short leads. This capacitor should
have a low ESR (Equivalent Series Resistance) value.
For additional information see input capacitor section in the
“EXTERNAL COMPONENTS” section of this data sheet.
2. Input Capacitor Selection (Cin)
A 22
μ
F aluminium electrolytic capacitor located near the input
and ground pin provides sufficient bypassing.
3. Catch Diode Selection (D1)
A.
Since the diode maximum peak current exceeds the
regulator maximum load current the catch diode current
rating must be at least 1.2 times greater than the maximum
load current. For a robust design, the diode should have a
current rating equal to the maximum current limit of the
LM2574 to be able to withstand a continuous output short.
B.
The reverse voltage rating of the diode should be at least
1.25 times the maximum input voltage.
3. Catch Diode Selection (D1)
A.
For this example, a 1.0 A current rating is adequate.
B.
Use a 50 V MBR150 Schottky diode or any suggested fast
recovery diodes in Table 1.
相關(guān)PDF資料
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相關(guān)代理商/技術(shù)參數(shù)
參數(shù)描述
LM2574-5.0 WAF 制造商:Texas Instruments 功能描述:
LM2574-5.0BN 功能描述:IC REG BUCK 5V 0.5A 8DIP RoHS:否 類別:集成電路 (IC) >> PMIC - 穩(wěn)壓器 - DC DC 開(kāi)關(guān)穩(wěn)壓器 系列:- 標(biāo)準(zhǔn)包裝:20 系列:SIMPLE SWITCHER® 類型:降壓（降壓） 輸出類型:固定 輸出數(shù):1 輸出電壓:12V 輸入電壓:4 V ~ 60 V PWM 型:電壓模式 頻率 - 開(kāi)關(guān):52kHz 電流 - 輸出:1A 同步整流器:無(wú) 工作溫度:-40°C ~ 125°C 安裝類型:通孔 封裝/外殼:16-DIP（0.300"，7.62mm） 包裝:管件 供應(yīng)商設(shè)備封裝:16-DIP 其它名稱:*LM2575HVN-12LM2575HVN-12
LM2574-5.0BWM 制造商:Rochester Electronics LLC 功能描述:- Bulk
LM2574-5.0YN 功能描述:直流/直流開(kāi)關(guān)調(diào)節(jié)器 0.5A Step-Down SMPS Regulator (Lead Free) RoHS:否 制造商:International Rectifier 最大輸入電壓:21 V 開(kāi)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
LM2574-ADJ 制造商:MOTOROLA 制造商全稱:Motorola, Inc 功能描述:EASY SWITCHERE⑩ 0.5 A STEP-DOWN VOLTAGE REGULATOR
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