參數(shù)資料
型號(hào)： LM2577S-12X
廠商： NATIONAL SEMICONDUCTOR CORP
元件分類： 穩(wěn)壓器
英文描述： 6 A SWITCHING REGULATOR, 62 kHz SWITCHING FREQ-MAX, PSSO5
封裝： PLASTIC, TO-263, SMT-5
文件頁(yè)數(shù)： 7/31頁(yè)
文件大?。?/td> 1406K
代理商： LM2577S-12X
Application Hints (Continued)
STEP-UP (BOOST) REGULATOR
Figure 4 shows the LM1577-ADJ/LM2577-ADJ used as a
Step-Up Regulator. This is a switching regulator used for
producing an output voltage greater than the input supply
voltage.
The
LM1577-12/LM2577-12
and
LM1577-15/
LM2577-15 can also be used for step-up regulators with 12V
or 15V outputs (respectively), by tying the feedback pin
directly to the regulator output.
A basic explanation of how it works is as follows. The
LM1577/LM2577 turns its output switch on and off at a
frequency of 52 kHz, and this creates energy in the inductor
(L). When the NPN switch turns on, the inductor current
charges up at a rate of V
IN/L, storing current in the inductor.
When the switch turns off, the lower end of the inductor flies
above V
IN, discharging its current through diode (D) into the
output capacitor (C
OUT) at a rate of (VOUT VIN)/L. Thus,
energy stored in the inductor during the switch on time is
transferred to the output during the switch off time. The
output voltage is controlled by the amount of energy trans-
ferred which, in turn, is controlled by modulating the peak
inductor current. This is done by feeding back a portion of
the output voltage to the error amp, which amplifies the
difference between the feedback voltage and a 1.230V ref-
erence. The error amp output voltage is compared to a
voltage proportional to the switch current (i.e., inductor cur-
rent during the switch on time).
The comparator terminates the switch on time when the two
voltages are equal, thereby controlling the peak switch cur-
rent to maintain a constant output voltage.
Voltage and current waveforms for this circuit are shown in
Figure 5, and formulas for calculating them are given in
STEP-UP REGULATOR DESIGN PROCEDURE
The following design procedure can be used to select the
appropriate external components for the circuit in Figure 4,
based on these system requirements.
Given:
V
IN (min) = Minimum input supply voltage
V
OUT = Regulated output voltage
I
LOAD(max) = Maximum output load current
Before proceeding any further, determine if the LM1577/
LM2577 can provide these values of V
OUT and ILOAD(max)
when operating with the minimum value of V
IN. The upper
limits for V
OUT and ILOAD(max) are given by the following
equations.
V
OUT
≤ 60V
and
V
OUT
≤ 10xV
IN(min)
These limits must be greater than or equal to the values
specified in this application.
1. Inductor Selection (L)
A. Voltage Options:
1. For 12V or 15V output
From Figure 7 (for 12V output) or Figure 8 (for 15V
output), identify inductor code for region indicated by
V
IN (min)
and I
LOAD (max). The shaded region indicates con-
01146811
FIGURE 5. Step-Up Regulator Waveforms
Duty Cycle
D
Average
Inductor
Current
I
IND(AVE)
Inductor
Current Ripple
I
IND
Peak Inductor
Current
I
IND(PK)
Peak Switch
Current
I
SW(PK)
Switch
Voltage When
Off
V
SW(OFF)
V
OUT +VF
Diode
Reverse
Voltage
V
R
V
OUT VSAT
Average
Diode Current
I
D(AVE)
I
LOAD
Peak Diode
Current
I
D(PK)
Power
Dissipation of
LM1577/2577
P
D
VF = Forward Biased Diode Voltage
ILOAD = Output Load Current
FIGURE 6. Step-Up Regulator Formulas
LM1577/LM2577
www.national.com
15
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相關(guān)代理商/技術(shù)參數(shù)
參數(shù)描述
LM2577S-15 制造商:NSC 制造商全稱:National Semiconductor 功能描述:SIMPLE SWITCHER-R Step-Up Voltage Regulator
LM2577S-15/NOPB 功能描述:IC REG MULTI CONFIG 15V TO263-5 RoHS:是 類別:集成電路 (IC) >> PMIC - 穩(wěn)壓器 - DC DC 開關(guān)穩(wěn)壓器 系列:SIMPLE SWITCHER® 產(chǎn)品培訓(xùn)模塊:Lead (SnPb) Finish for COTS Obsolescence Mitigation Program 標(biāo)準(zhǔn)包裝:1 系列:- 類型:降壓（降壓） 輸出類型:固定 輸出數(shù):1 輸出電壓:3.3V 輸入電壓:4.5 V ~ 24 V PWM 型:- 頻率 - 開關(guān):- 電流 - 輸出:125mA 同步整流器:無 工作溫度:-40°C ~ 85°C 安裝類型:表面貼裝 封裝/外殼:SOT-23-6 包裝:Digi-Reel® 供應(yīng)商設(shè)備封裝:SOT-6 其它名稱:MAX1836EUT33#TG16DKR
LM2577S-15/NOPB 制造商:Texas Instruments 功能描述:DC/DC Converter IC
LM2577S-ADJ 功能描述:直流/直流開關(guān)轉(zhuǎn)換器 RoHS:否 制造商:STMicroelectronics 最大輸入電壓:4.5 V 開關(guān)頻率:1.5 MHz 輸出電壓:4.6 V 輸出電流:250 mA 輸出端數(shù)量:2 最大工作溫度:+ 85 C 安裝風(fēng)格:SMD/SMT
LM2577S-ADJ/NOPB 功能描述:直流/直流開關(guān)轉(zhuǎn)換器 STEP-UP VLTG REG RoHS:否 制造商:STMicroelectronics 最大輸入電壓:4.5 V 開關(guān)頻率:1.5 MHz 輸出電壓:4.6 V 輸出電流:250 mA 輸出端數(shù)量:2 最大工作溫度:+ 85 C 安裝風(fēng)格:SMD/SMT
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