LM2599SX-12/NOPB National Semiconductor, LM2599SX-12/NOPB Datasheet - Page 10

• Manufacturer Part Number: LM2599SX-12/NOPB
• Description: IC REG SW 12V 3A STP DN TO-263-7
• Manufacturer: National Semiconductor
• Series: SIMPLE SWITCHER®r
• Type: Step-Down (Buck)r

Specifications of LM2599SX-12/NOPB

• Internal Switch(s): Yes
• Synchronous Rectifier: No
• Number Of Outputs: 1
• Voltage - Output: 12V
• Current - Output: 3A
• Frequency - Switching: 150kHz
• Voltage - Input: 4.5 ~ 40 V
• Operating Temperature: -40°C ~ 125°C
• Mounting Type: Surface Mount
• Package / Case: D²Pak, TO-263 (7 leads + tab)
• For Use With: 551011367-021 - BOARD WEBENCH BUILD IT LM2599
• Lead Free Status / RoHS Status: Lead free / RoHS Compliant
• Power - Output: -
• Other names: *LM2599SX-12; *LM2599SX-12/NOPB; LM2599SX-12

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LM2599 Series Buck Regulator Design Procedure (Fixed Output)
Given:
V
V
I
1. Inductor Selection (L1)
A. Select the correct inductor value selection guide from
Figure 4 , Figure 5 , or 6. (Output voltages of 3.3V, 5V, or 12V
respectively.) For all other voltages, see the design proce-
dure for the adjustable version.
B. From the inductor value selection guide, identify the in-
ductance region intersected by the Maximum Input Voltage
line and the Maximum Load Current line. Each region is
identified by an inductance value and an inductor code
(LXX).
C. Select an appropriate inductor from the four manufactur-
er’s part numbers listed in Figure 8 .
2. Output Capacitor Selection (C
A. In the majority of applications, low ESR (Equivalent Series
Resistance) electrolytic capacitors between 82 µF and 820
µF and low ESR solid tantalum capacitors between 10 µF
and 470 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 820 µF.
For additional information, see section on output capaci-
tors in application information section.
B. To simplify the capacitor selection procedure, refer to the
quick design component selection table shown in Figure 2 .
This table contains different input voltages, output voltages,
and load currents, and lists various inductors and output
capacitors that will provide the best design solutions.
C. The capacitor voltage rating for electrolytic capacitors
should be at least 1.5 times greater than the output voltage,
and often much higher voltage ratings are needed to satisfy
the low ESR requirements for low output ripple voltage.
D. For computer aided design software, see Switchers
Made Simple (version 4.2.1 or later).
LOAD
OUT
IN
(max) = Maximum DC Input Voltage
(max) = Maximum Load Current
PROCEDURE (Fixed Output Voltage Version)
= Regulated Output Voltage (3.3V, 5V or 12V)
OUT
)
10
Given:
V
2. Output Capacitor Selection (C
V
I
1. Inductor Selection (L1)
A. Use the inductor selection guide for the 5V version shown
in Figure 5 .
B. From the inductor value selection guide shown in Figure 5 ,
the inductance region intersected by the 12V horizontal line
and the 3A vertical line is 33 µH, and the inductor code is
L40.
C. The inductance value required is 33 µH. From the table in
Figure 8 , go to the L40 line and choose an inductor part
number from any of the four manufacturers shown. (In most
instance, both through hole and surface mount inductors are
available.)
A. See section on output capacitors in application infor-
mation section.
B. From the quick design component selection table shown
in Figure 2 , locate the 5V output voltage section. In the load
current column, choose the load current line that is closest to
the current needed in your application, for this example, use
the 3A line. In the maximum input voltage column, select the
line that covers the input voltage needed in your application,
in this example, use the 15V line. Continuing on this line are
recommended inductors and capacitors that will provide the
best overall performance.
The capacitor list contains both through hole electrolytic and
surface mount tantalum capacitors from four different capaci-
tor manufacturers. It is recommended that both the manufac-
turers and the manufacturer’s series that are listed in the
table be used.
In this example aluminum electrolytic capacitors from several
different manufacturers are available with the range of ESR
numbers needed.
C. For a 5V output, a capacitor voltage rating at least 7.5V or
more is needed. But even a low ESR, switching grade, 220
µF 10V aluminum electrolytic capacitor would exhibit ap-
proximately 225 m
the ESR vs voltage rating). This amount of ESR would result
in relatively high output ripple voltage. To reduce the ripple to
1% of the output voltage, or less, a capacitor with a higher
value or with a higher voltage rating (lower ESR) should be
selected. A 16V or 25V capacitor will reduce the ripple volt-
age by approximately half.
LOAD
OUT
IN
(max) = 12V
330 µF 35V Panasonic HFQ Series
330 µF 35V Nichicon PL Series
(max) = 3A
= 5V
EXAMPLE (Fixed Output Voltage Version)
of ESR (see the curve in Figure 17 for
OUT
)