LM3671MF-1.25 National Semiconductor, LM3671MF-1.25 Datasheet - Page 17

• Manufacturer Part Number: LM3671MF-1.25
• Description: DC/DC CONVERTER, 1.25V, SMD, 3671
• Manufacturer: National Semiconductor

Specifications of LM3671MF-1.25

• Primary Input Voltage: 2.25V
• No. Of Outputs: 1
• Output Voltage: 1.25V
• Output Current: 600mA
• Voltage Regulator Case Style: SOT-23
• No. Of Pins: 5
• Operating Temperature Range: -25°C To +85°C
• Svhc: No
• Lead Free Status / RoHS Status: Lead free / RoHS Compliant

4.7 µF for C
10 µF for C
Application Information
OUTPUT CAPACITOR SELECTION
A ceramic output capacitor of 10 µF, 6.3V is sufficient for
most applications. Use X7R or X5R types; do not use Y5V.
DC bias characteristics of ceramic capacitors must be con-
sidered when selecting case sizes like 0805 and 0603. DC
bias characteristics vary from manufacturer to manufacturer
and dc bias curves should be requested from them as part of
the capacitor selection process.
The minimum output capacitance to guarantee good
performance is 5.75µF at 1.8V dc bias including toler-
ances and over ambient temperature range. The output
filter capacitor smoothes out current flow from the inductor to
the load, helps maintain a steady output voltage during
transient load changes and reduces output voltage ripple.
These capacitors must be selected with sufficient capaci-
tance and sufficiently low ESR to perform these functions.
The output voltage ripple is caused by the charging and
discharging of the output capacitor and by the R
be calculated as:
Voltage peak-to-peak ripple due to capacitance can be ex-
pressed as follow:
Voltage peak-to-peak ripple due to ESR can be expressed
as follow:
V
Micro SMD PACKAGE ASSEMBLY AND USE
Use of the Micro SMD package requires specialized board
layout, precision mounting and careful re-flow techniques, as
detailed in National Semiconductor Application Note 1112.
Refer to the section "Surface Mount Technology (SMD) As-
sembly Considerations". For best results in assembly, align-
ment ordinals on the PC board should be used to facilitate
placement of the device. The pad style used with Micro SMD
PP-ESR
GRM21BR60J475K
GRM21BR60J106K
C2012X5R0J475K
C1608X5R0J475K
C2012X5R0J106K
C1608X5R0J106K
JMK212BJ475K
JMK212BJ106K
LPO3310-222MX
CDRH2D14-2R2
DO3314-222MX
ELL5GM2R2N
= (2 * I
Model
OUT
IN
Model
RIPPLE
) * R
ESR
Ceramic, X5R
Ceramic, X5R
Ceramic, X5R
Ceramic, X5R
Ceramic, X5R
Ceramic, X5R
Ceramic, X5R
Ceramic, X5R
TABLE 2. Suggested Capacitors and Their Suppliers
TABLE 1. Suggested Inductors and Their Suppliers
Type
Panasonic
Coilcraft
Coilcraft
Vendor
Sumida
(Continued)
ESR
and can
Taiyo-Yuden
Taiyo-Yuden
Vendor
Murata
Murata
TDK
TDK
TDK
TDK
17
Dimensions LxWxH(mm)
Because these two components are out of phase the rms
(root mean squared) value can be used to get an approxi-
mate value of peak-to-peak ripple.
The peak-to-peak ripple voltage, rms value can be ex-
pressed as follow:
Note that the output voltage ripple is dependent on the
inductor current ripple and the equivalent series resistance
of the output capacitor (R
The R
dependent); make sure the value used for calculations is at
the switching frequency of the part.
package must be the NSMD (non-solder mask defined) type.
This means that the solder-mask opening is larger than the
pad size. This prevents a lip that otherwise forms if the
solder-mask and pad overlap, from holding the device off the
surface of the board and interfering with mounting. See
Application Note 1112 for specific instructions how to do this.
The 5-Bump package used for LM3671 has 300 micron
solder balls and requires 10.82 mils pads for mounting on
3.2 x 3.2 x 1.55
3.3 x 3.3 x 1.4
3.3 x 3.3 x 1.0
5.2 x 5.2 x 1.5
ESR
is frequency dependent (as well as temperature
Voltage Rating
6.3V
6.3V
6.3V
6.3V
6.3V
6.3V
6.3V
6.3V
ESR
).
D.C.R (max)
0805 (2012)
0805 (2012)
0805 (2012)
0603 (1608)
0805 (2012)
0805 (2012)
0805 (2012)
0603 (1608)
Inch (mm)
Case Size
200 mΩ
150 mΩ
53 mΩ
94 mΩ
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