參數(shù)資料
型號(hào)： LM2595SX-12
元件分類： 基準(zhǔn)電壓源/電流源
英文描述： Voltage-Mode SMPS Controller
中文描述： 電壓模式開關(guān)電源控制器
文件頁(yè)數(shù)： 12/28頁(yè)
文件大?。?/td> 739K
代理商： LM2595SX-12
LM2594/LM2594HV Series Buck Regulator Design Procedure (Adjustable
Output)
(Continued)
PROCEDURE (Adjustable Output Voltage Version)
EXAMPLE (Adjustable Output Voltage Version)
1. Programming Output Voltage
(Selecting R
1
and R
2
, as
shown in Figure 1
Use the following formula to select the appropriate resistor
values.
Select a value for R
between 240
and 1.5 k
. The lower
resistor values minimize noise pickup in the sensitive feed-
back pin. (For the lowest temperature coefficient and the best
stability with time, use 1% metal film resistors.)
1. Programming Output Voltage
(Selecting R
1
and R
2
, as
shown in Figure 1 )
Select R
1
to be 1 k
, 1%. Solve for R
2
.
R
2
= 1k (16.26 1) = 15.26k, closest 1% value is 15.4 k
.
R
2
= 15.4 k
.
2. Inductor Selection (L1)
A.
Calculate
E
T (V
μs) , from the following formula:
the
inductor
Volt
microsecond
constant
where V
SAT
= internal switch saturation voltage = 0.9V
and V
D
= diode forward voltage drop = 0.5V
B.
Use the E
T value from the previous formula and match
it with the E
T number on the vertical axis of the Inductor
Value Selection Guide shown in Figure 7
C.
on the horizontal axis, select the maximum load current.
D.
Identify the inductance region intersected by the E
T
value and the Maximum Load Current value. Each region is
identified by an inductance value and an inductor code
(LXX).
E.
Select an appropriate inductor from the four manufactur-
er’s part numbers listed in Figure 8
2. Inductor Selection (L1)
A.
Calculate the inductor Volt
microsecond constant (E
T)
,
B.
E
T = 35.2 (V
μs)
C.
I
LOAD
(max) = 0.5A
D.
From the inductor value selection guide shown in Figure 7
the inductance region intersected by the 35 (V
μs) horizon-
tal line and the 0.5A vertical line is 150 μH, and the inductor
code is L19.
E.
From the table in Figure 8 locate line L19, and select an
inductor part number from the list of manufacturers part num-
bers.
3. Output Capacitor Selection (C
OUT)
A.
In the majority of applications, low ESR electrolytic or solid
tantalum capacitors between 82 μF and 220 μF provide the
best results. This capacitor should be located close to the IC
using short capacitor leads and short copper traces. Do not
use capacitors larger than 220 μF.
For additional informa-
tion, see section on output capacitors in application in-
formation section.
B.
To simplify the capacitor selection procedure, refer to the
quick design table shown in Figure 3 This table contains dif-
ferent output voltages, and lists various output capacitors
that will provide the best design solutions.
C.
The capacitor voltage rating should be at least 1.5 times
greater than the output voltage, and often much higher volt-
age ratings are needed to satisfy the low ESR requirements
needed for low output ripple voltage.
3. Output Capacitor SeIection (C
OUT
)
A.
See section on C
OUT
in Application Information section.
B.
From the quick design table shown in Figure 3 locate the
output voltage column. From that column, locate the output
voltage closest to the output voltage in your application. In
this example, select the 24V line. Under the output capacitor
section, select a capacitor from the list of through hole elec-
trolytic or surface mount tantalum types from four different
capacitor manufacturers. It is recommended that both the
manufacturers and the manufacturers series that are listed in
the table be used.
In this example, through hole aluminum electrolytic capaci-
tors from several different manufacturers are available.
82 μF
50V
Panasonic HFQ Series
120 μF
50V
Nichicon PL Series
C.
For a 20V output, a capacitor rating of at least 30V or
more is needed. In this example, either a 35V or 50V capaci-
tor would work. A 50V rating was chosen because it has a
lower ESR which provides a lower output ripple voltage.
Other manufacturers or other types of capacitors may also
be used, provided the capacitor specifications (especially the
100 kHz ESR) closely match the types listed in the table. Re-
fer to the capacitor manufacturers data sheet for this informa-
tion.
L
www.national.com
12
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相關(guān)代理商/技術(shù)參數(shù)
參數(shù)描述
LM2595SX-12/NOPB 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
LM2595SX-3.3 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
LM2595SX-3.3/NOPB 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
LM2595SX-5.0 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
LM2595SX-5.0/E7001023 制造商:Texas Instruments 功能描述:
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