參數(shù)資料
型號: LM2596S-ADJ
廠商: NATIONAL SEMICONDUCTOR CORP
元件分類: 穩(wěn)壓器
英文描述: SIMPLE SWITCHER Power Converter 150 kHz 3A Step-Down Voltage Regulator
中文描述: 7.5 A SWITCHING REGULATOR, 173 kHz SWITCHING FREQ-MAX, PSSO5
封裝: TO-263, SMT-5
文件頁數(shù): 13/31頁
文件大小: 736K
代理商: LM2596S-ADJ
LM2596 Series Buck Regulator Design Procedure (Adjustable Output)
PROCEDURE (Adjustable Output Voltage Version)
EXAMPLE (Adjustable Output Voltage Version)
Given:
V
OUT
= Regulated Output Voltage
V
IN
(max) = Maximum Input Voltage
I
LOAD
(max) = Maximum Load Current
F = Switching Frequency (Fixed at a nominal 150 kHz).
Given:
V
OUT
= 20V
V
IN
(max) = 28V
I
LOAD
(max) = 3A
F = Switching Frequency (Fixed at a nominal 150 kHz).
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
1
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 the inductor Volt
microsecond constant E
T (V
μs), from the following formula:
where V
SAT
= internal switch saturation voltage = 1.16V
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 identi-
fied by an inductance value and an inductor code (LXX).
E.
Select an appropriate inductor from the four manufacturer’s
part numbers listed in Figure 8
2. Inductor Selection (L1)
A.
Calculate the inductor Volt
microsecond constant
(E
T),
B.
E
T = 34.2 (V
μs)
C.
I
LOAD
(max) = 3A
D.
From the inductor value selection guide shown in Figure 7
the inductance region intersected by the 34 (V
μs) horizontal
line and the 3A vertical line is 47 μH, and the inductor code is
L39.
E.
From the table in Figure 8 locate line L39, and select an
inductor part number from the list of manufacturers part num-
bers.
L
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