- 您現(xiàn)在的位置：買賣IC網 > PDF目錄44548 > LM2578MWC (NATIONAL SEMICONDUCTOR CORP) 0.75 A SWITCHING REGULATOR, 100 kHz SWITCHING FREQ-MAX, UUC PDF資料下載
參數(shù)資料
| 型號： | LM2578MWC |
| 廠商： | NATIONAL SEMICONDUCTOR CORP |
| 元件分類： | 穩(wěn)壓器 |
| 英文描述： | 0.75 A SWITCHING REGULATOR, 100 kHz SWITCHING FREQ-MAX, UUC |
| 封裝： | WAFER |
| 文件頁數(shù)： | 2/24頁 |
| 文件大?。?/td> | 1127K |
| 代理商： | LM2578MWC |
Typical Applications (Continued)
Figure 15 is a 15V to 5V buck regulator with an output cur-
rent, I
o, of 350 mA. The circuit becomes discontinuous at
20% of I
o(max), has 10 mV of output voltage ripple, an effi-
ciency of 75%, a load regulation of 30 mV (70 mA to 350 mA)
and a line regulation of 10 mV (12
≤ V
in ≤ 18V).
Component values are selected as follows:
R1 = (V
o 1) x R2 where R2 = 10 k
R3 = V/I
sw(max)
R3 = 0.15
where:
V is the current limit sense voltage, 0.11V
I
sw(max) is the maximum allowable current thru the output
transistor.
L1 is the inductor and may be found from the inductance cal-
culation chart (
Figure 16) as follows:
Given
V
in = 15V
V
o = 5V
I
o(max) = 350 mA
f
OSC = 50 kHz
Discontinuous at 20% of I
o(max).
Note that since the circuit will become discontinuous at 20%
of I
o(max), the load current must not be allowed to fall below
70 mA.
Step 1: Calculate the maximum DC current through the in-
ductor, I
L(max). The necessary equations are indicated at the
top of the chart and show that I
L(max) = Io(max) for the buck
configuration. Thus, I
L(max) = 350 mA.
Step 2: Calculate the inductor Volts-sec product, E-T
op, ac-
cording to the equations given from the chart. For the Buck:
E-T
op = (Vin Vo)(Vo/Vin) (1000/fosc)
=(15 5) (5/15) (1000/50)
= 66V-s.
with the oscillator frequency, f
osc, expressed in kHz.
Step 3: Using the graph with axis labeled “Discontinuous At
% I
OUT” and “IL(max, DC)” find the point where the desired
maximum inductor current, I
L(max, DC) intercepts the desired
discontinuity percentage.
In this example, the point of interest is where the 0.35A line
intersects with the 20% line. This is nearly the midpoint of the
horizontal axis.
Step 4: This last step is merely the translation of the point
found in Step 3 to the graph directly below it. This is accom-
plished by moving straight down the page to the point which
intercepts the desired E-T
op. For this example, E-Top is
66V-s and the desired inductor value is 470 H. Since this
example was for 20% discontinuity, the bottom chart could
have been used directly, as noted in step 3 of the chart
instructions.
DS008711-5
FIGURE 14. Basic Buck Regulator
DS008711-6
Vin = 15V
R3 = 0.15
Vo = 5V
C1 = 1820 pF
Vripple = 10 mV
C2 = 220 F
Io = 350 mA
C3 = 20 pF
fosc = 50 kHz
L1 = 470 H
R1 = 40 k
D1 = 1N5818
R2 = 10 k
FIGURE 15. Buck or Step-Down Regulator
www.national.com
10
相關PDF資料 |
PDF描述 |
|---|---|
| LM2586-5.0MDC | 7 A SWITCHING REGULATOR, 200 kHz SWITCHING FREQ-MAX, UUC |
| LM2586-5.0MWC | 7 A SWITCHING REGULATOR, 200 kHz SWITCHING FREQ-MAX, UUC |
| LM2586-ADJMDC | 7 A SWITCHING REGULATOR, 200 kHz SWITCHING FREQ-MAX, UUC |
| LM2586SX-12/NOPB | 3 A SWITCHING REGULATOR, 200 kHz SWITCHING FREQ-MAX, PSSO7 |
| LM2587SX-3.3/NOPB | 5 A SWITCHING REGULATOR, 100 kHz SWITCHING FREQ-MAX, PSSO5 |
相關代理商/技術參數(shù) |
參數(shù)描述 |
|---|---|
| LM2581 | 制造商:NEC 功能描述:258 NEC'90 SMT TUBES N9F8A |
| LM258-1 | 制造商:NEC 功能描述:258 NEC'90 SMT TUBES N9F8A |
| LM2585S-12 | 功能描述:直流/直流開關轉換器 RoHS:否 制造商:STMicroelectronics 最大輸入電壓:4.5 V 開關頻率: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 安裝風格:SMD/SMT |
| LM2585S-12/NOPB | 功能描述:直流/直流開關轉換器 RoHS:否 制造商:STMicroelectronics 最大輸入電壓:4.5 V 開關頻率: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 安裝風格:SMD/SMT |
| LM2585S-3.3 | 功能描述:直流/直流開關轉換器 RoHS:否 制造商:STMicroelectronics 最大輸入電壓:4.5 V 開關頻率: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 安裝風格:SMD/SMT |
發(fā)布緊急采購，3分鐘左右您將得到回復。