Texas Instruments LM3242 6MHz, 750mA Miniature, Adjustable, Step-Down DC-DC EVM LM3242TM-EV/NOPB LM3242TM-EV/NOPB Datenbogen
Produktcode
LM3242TM-EV/NOPB
SNOSB48D – OCTOBER 2011 – REVISED MARCH 2013
Method 2:
A more conservative and recommended approach is to choose an inductor that can handle the maximum current
limit of 1600 mA.
limit of 1600 mA.
The inductor’s resistance should be less than around 0.1
Ω
for good efficiency.
lists suggested inductors
and suppliers.
Table 2. Suggested Inductors
Model
Size (W x L x H) (mm)
Vendor
MIPSZ2012D0R5
2.0 x 1.2 x 1.0
FDK
LQM21PNR54MG0
2.0 x 1.25 x 0.9
Murata
LQM2MPNR47NG0
2.0 x 1.6 x 0.9
Murata
CIG21LR47M
2.0 x 1.25 x 1.0
Samsung
CKP2012NR47M
2.0 x 1.25 x 1.0
Taiyo Yuden
Capacitor Selection
The LM3242 is designed for use with ceramic capacitors for its input and output filters. Use a 10 µF ceramic
capacitor for input and a sum total of 4.7 µF ceramic capacitors for the output. They should maintain at least 50%
capacitance at DC bias and temperature conditions. Ceramic capacitors types such as X5R, X7R, and B are
recommended for both filters. These provide an optimal balance between small size, cost, reliability and
performance for cell phones and similar applications.
capacitor for input and a sum total of 4.7 µF ceramic capacitors for the output. They should maintain at least 50%
capacitance at DC bias and temperature conditions. Ceramic capacitors types such as X5R, X7R, and B are
recommended for both filters. These provide an optimal balance between small size, cost, reliability and
performance for cell phones and similar applications.
lists some suggested part numbers and suppliers.
DC bias characteristics of the capacitors must be considered when selecting the voltage rating and case size of
the capacitor. If it is necessary to choose a 0603 (1608) size capacitor for V
the capacitor. If it is necessary to choose a 0603 (1608) size capacitor for V
IN
and 0402 (1005) size capacitor for
V
OUT
, the operation of the LM3242 should be carefully evaluated on the system board. Use of a 2.2 µF capacitor
in conjunction with multiple 0.47 µF or 1.0 µF capacitors in parallel may also be considered when connecting to
power amplifier devices that require local decoupling.
power amplifier devices that require local decoupling.
Table 3. Suggested Capacitors and Their Suppliers
Capacitance
Model
Size (Wx L) (mm)
Vendor
2.2 µF
GRM155R60J225M
1.0 x 0.5
Murata
2.2 µF
C1005X5R0J225M
1.0 x 0.5
TDK
2.2 µF
CL05A225MQ5NSNC
1.0 x 0.5
Samsung
4.7 µF
C1608JB0J475M
1.6 x 0.8
TDK
4.7 µF
C1005X5R0J475M
1.0 x 0.5
TDK
4.7 µF
CL05A475MQ5NRNC
1.0 x 0.5
Samsung
10 µF
C1608X5R0J106M
1.6 x 0.8
TDK
10 µF
GRM155R60J106M
1.0 x 0.5
Murata
10 µF
CL05A106MQ5NUNC
1.0 x 0.5
Samsung
The input filter capacitor supplies AC current drawn by the PFET switch of the LM3242 in the first part of each
cycle and reduces the voltage ripple imposed on the input power source. The output filter capacitor absorbs the
AC inductor current, helps maintain a steady output voltage during transient load changes and reduces output
voltage ripple. These capacitors must be selected with sufficient capacitance and sufficiently low ESR
(Equivalent Series Resistance) to perform these functions. The ESR of the filter capacitors is generally a major
factor in voltage ripple.
cycle and reduces the voltage ripple imposed on the input power source. The output filter capacitor absorbs the
AC inductor current, helps maintain a steady output voltage during transient load changes and reduces output
voltage ripple. These capacitors must be selected with sufficient capacitance and sufficiently low ESR
(Equivalent Series Resistance) to perform these functions. The ESR of the filter capacitors is generally a major
factor in voltage ripple.
DSBGA Package Assembly and Use
Use of the DSBGA package requires specialized board layout, precision mounting and careful re-flow
techniques, as detailed in Texas Instruments Application Note 1112. Refer to the section Surface Mount
Assembly Considerations. For best results in assembly, alignment ordinals on the PC board should be used to
facilitate placement of the device. The pad style used with DSBGA 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.
techniques, as detailed in Texas Instruments Application Note 1112. Refer to the section Surface Mount
Assembly Considerations. For best results in assembly, alignment ordinals on the PC board should be used to
facilitate placement of the device. The pad style used with DSBGA 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.
16
Copyright © 2011–2013, Texas Instruments Incorporated
Product Folder Links: