LM3671MF-1.6 National Semiconductor, LM3671MF-1.6 Datasheet - Page 19

• Manufacturer Part Number: LM3671MF-1.6
• Description: IC CONV DC/DC STEP-DOWN SOT23-5
• Manufacturer: National Semiconductor
• Series: PowerWise®r
• Type: Step-Down (Buck)r

Specifications of LM3671MF-1.6

• Internal Switch(s): Yes
• Synchronous Rectifier: Yes
• Number Of Outputs: 1
• Voltage - Output: 1.6V
• Current - Output: 600mA
• Frequency - Switching: 2MHz
• Voltage - Input: 2.7 ~ 5.5 V
• Operating Temperature: -30°C ~ 85°C
• Mounting Type: Surface Mount
• Package / Case: SOT-23-5, SC-74A, SOT-25
• Power - Output: 770mW
• Lead Free Status / RoHS Status: Lead free / RoHS Compliant
• Other names: LM3671MF-1.6; LM3671MF-1.6TR

4.7 µF for C
10 µF for C
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 considered
when selecting case sizes like 0805 and 0603. DC bias char-
acteristics vary from manufacturer to manufacturer and dc
bias curves should be requested from them as part of the ca-
pacitor selection process.
The minimum output capacitance to guarantee good per-
formance is 5.75µF at 1.8V dc bias including tolerances
and over ambient temperature range. The output filter ca-
pacitor 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 ca-
pacitors must be selected with sufficient capacitance and
sufficiently low ESR to perform these functions.
The output voltage ripple is caused by the charging and dis-
charging of the output capacitor and by the R
calculated as:
Voltage peak-to-peak ripple due to capacitance can be ex-
pressed as follow:
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
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
GRM21BR60J475K
GRM21BR60J106K
C2012X5R0J475K
C1608X5R0J475K
C2012X5R0J106K
C1608X5R0J106K
JMK212BJ475K
JMK212BJ106K
CDRH2D14NP-2R2NC
Model
LPO3310-222MX
OUT
DO3314-222MX
IN
ELL5GM2R2N
Model
Ceramic, X5R
Ceramic, X5R
Ceramic, X5R
Ceramic, X5R
Ceramic, X5R
Ceramic, X5R
Ceramic, X5R
Ceramic, X5R
TABLE 2. Suggested Capacitors and Their Suppliers
Type
TABLE 1. Suggested Inductors and Their Suppliers
Panasonic
Coilcraft
Coilcraft
ESR
Vendor
Sumida
and can be
Taiyo-Yuden
Taiyo-Yuden
Vendor
Murata
Murata
TDK
TDK
TDK
TDK
19
Voltage peak-to-peak ripple due to ESR can be expressed as
follow:
V
Because these two components are out of phase the rms (root
mean squared) value can be used to get an approximate val-
ue of peak-to-peak ripple.
The peak-to-peak ripple voltage, rms value can be expressed
as follow:
Note that the output voltage ripple is dependent on the induc-
tor 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.
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 the circuit board.
The trace to each pad should enter the pad with a 90° entry
angle to prevent debris from being caught in deep corners.
Initially, the trace to each pad should be 7 mil wide, for a sec-
tion approximately 7 mil long or longer, as a thermal relief.
Then each trace should neck up or down to its optimal width.
The important criteria is symmetry. This ensures the solder
bumps on the LM3671 re-flow evenly and that the device sol-
ders level to the board. In particular, special attention must be
paid to the pads for bumps A1 and A3, because V
PP-ESR
Dimensions LxWxH(mm)
ESR
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
= (2 * I
is frequency dependent (as well as temperature
Voltage Rating
RIPPLE
ESR
6.3V
6.3V
6.3V
6.3V
6.3V
6.3V
6.3V
6.3V
) * R
).
ESR
0805 (2012)
0805 (2012)
0805 (2012)
0603 (1608)
0805 (2012)
0805 (2012)
0805 (2012)
0603 (1608)
Inch (mm)
Case Size
D.C.R (max)
200 mΩ
150 mΩ
53 mΩ
94 mΩ
www.national.com
IN
and GND