LM2672M-ADJ/NOPB National Semiconductor, LM2672M-ADJ/NOPB Datasheet - Page 19

• Manufacturer Part Number: LM2672M-ADJ/NOPB
• Description: IC REG SIMPLE SWITCHER 8-SOIC
• Manufacturer: National Semiconductor
• Series: SIMPLE SWITCHER®r
• Type: Step-Down (Buck)r

Specifications of LM2672M-ADJ/NOPB

• Internal Switch(s): Yes
• Synchronous Rectifier: No
• Number Of Outputs: 1
• Voltage - Output: 1.21 ~ 37 V
• Current - Output: 1A
• Frequency - Switching: 260kHz
• Voltage - Input: 6.5 ~ 40 V
• Operating Temperature: -40°C ~ 125°C
• Mounting Type: Surface Mount
• Package / Case: 8-SOIC (3.9mm Width)
• Primary Input Voltage: 40V
• No. Of Outputs: 1
• Output Voltage: 37V
• Output Current: 1.55A
• No. Of Pins: 8
• Operating Temperature Range: -40°C To +125°C
• Msl: MSL 1 - Unlimited
• Filter Terminals: SMD
• Rohs Compliant: Yes
• Lead Free Status / RoHS Status: Lead free / RoHS Compliant
• Power - Output: -
• Other names: *LM2672M-ADJ; *LM2672M-ADJ/NOPB; LM2672M-ADJ

5. Input Capacitor (C
A low ESR aluminum or tantalum bypass capacitor is needed
between the input pin and ground to prevent large voltage
transients from appearing at the input. This capacitor should be
located close to the IC using short leads. In addition, the RMS
current rating of the input capacitor should be selected to be at least
½ the DC load current. The capacitor manufacturer data sheet must
be checked to assure that this current rating is not exceeded. The
curves shown in Figure 14 show typical RMS current ratings for
several different aluminum electrolytic capacitor values. A parallel
connection of two or more capacitors may be required to increase
the total minimum RMS current rating to suit the application
requirements.
For an aluminum electrolytic capacitor, the voltage rating should be
at least 1.25 times the maximum input voltage. Caution must be
exercised if solid tantalum capacitors are used. The tantalum
capacitor voltage rating should be twice the maximum input
voltage. The tables in Figure 15 show the recommended
application voltage for AVX TPS and Sprague 594D tantalum
capacitors. It is also recommended that they be surge current
tested by the manufacturer. The TPS series available from AVX,
and the 593D and 594D series from Sprague are all surge current
tested. Another approach to minimize the surge current stresses
on the input capacitor is to add a small inductor in series with the
input supply line.
Use caution when using ceramic capacitors for input bypassing,
because it may cause severe ringing at the V
6. Boost Capacitor (C
This capacitor develops the necessary voltage to turn the switch
gate on fully. All applications should use a 0.01 μF, 50V ceramic
capacitor.
If the soft-start and frequency synchronization features are desired,
look at steps 6 and 7 in the fixed output design procedure.
Note 7: SM - Surface Mount, TH - Through Hole
Style (Note 7)
SM and TH
SM and TH
SM and TH
SM and TH
SM and TH
SM and TH
SM and TH
SM and TH
SM and TH
SM and TH
PROCEDURE (Adjustable Output Voltage Version)
Case
TH
IN
B
)
)
Voltage (V)
1.21–2.50
2.50–3.75
10.0–12.5
12.5–15.0
15.0–20.0
20.0–30.0
30.0–37.0
3.75–5.0
5.0–6.25
6.25–7.5
7.5–10.0
Output
FIGURE 16. Capacitor Code Selection Guide
C14
C15
C18
C21
C23
C8
C9
22
IN
—
—
—
—
pin.
C10
C11
C16
C19
C22
C24
C4
C4
33
—
—
—
19
5. Input Capacitor (C
The important parameters for the input capacitor are the input
voltage rating and the RMS current rating. With a maximum input
voltage of 28V, an aluminum electrolytic capacitor with a voltage
rating of at least 35V (1.25 × V
The RMS current rating requirement for the input capacitor in a
buck regulator is approximately ½ the DC load current. In this
example, with a 1A load, a capacitor with a RMS current rating of
at least 500 mA is needed. The curves shown in Figure 14 can be
used to select an appropriate input capacitor. From the curves,
locate the 35V line and note which capacitor values have RMS
current ratings greater than 500 mA.
For a through hole design, a 330 μF/35V electrolytic capacitor
(Panasonic HFQ series, Nichicon PL, Sanyo MV-GX series or
equivalent) would be adequate. Other types or other
manufacturers' capacitors can be used provided the RMS ripple
current ratings are adequate. Additionally, for a complete surface
mount design, electrolytic capacitors such as the Sanyo CV-C or
CV-BS and the Nichicon WF or UR and the NIC Components NACZ
series could be considered.
For surface mount designs, solid tantalum capacitors can be used,
but caution must be exercised with regard to the capacitor surge
current rating and voltage rating. In this example, checking Figure
15, and the Sprague 594D series datasheet, a Sprague 594D 15
μF, 50V capacitor is adequate.
6. Boost Capacitor (C
For this application, and all applications, use a 0.01 μF, 50V
ceramic capacitor.
C11
C12
C17
C20
C22
C24
C4
C7
C7
47
—
—
EXAMPLE (Adjustable Output Voltage Version)
Inductance (μH)
C12
C12
C17
C20
C22
C25
C1
C5
C6
C6
68
—
IN
B
)
)
C13
C13
C17
C20
C22
C25
100
C1
C2
C6
C6
C6
IN
) would be needed.
C13
C13
C17
C20
C22
C25
150
C2
C3
C6
C6
C6
www.national.com
C13
C13
C17
C20
C22
C25
220
C3
C3
C6
C6
C6