Datasheet

V
PP-RMS
= V
PP-C
2
+ V
PP-ESR
2
V
OUT
=
V
PP-ESR
= I
PP
* R
ESR
V
PP-C
=
f*8*C
I
PP
LM3670
www.ti.com SNVS250E –NOVEMBER 2004–REVISED FEBRUARY 2013
Table 1. Suggested Inductors and Their Suppliers
Model Vendor Phone FAX
IDC2512NB100M Vishay 408-727-2500 408-330-4098
DO1608C-103 Coilcraft 847-639-6400 847-639-1469
ELL6RH100M Panasonic 714-373-7366 714-373-7323
CDRH5D18-100 Sumida 847-956-0666 847-956-0702
Output Capacitor Selection
The output filter capacitor smoothes out current flow from the inductor to the load, maintaining 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 to perform these functions.
The output ripple current can be calculated as:
Voltage peak-to-peak ripple due to capacitance =
Voltage peak-to-peak ripple due to ESR =
Voltage peak-to-peak ripple, root mean squared =
Note that the output ripple is dependent on the current ripple and the equivalent series resistance of the output
capacitor (R
ESR
).
Because these two components are out of phase the rms value is used. The R
ESR
is frequency dependent (as
well as temperature dependent); make sure the frequency of the R
ESR
given is the same order of magnitude as
the switching frequency.
Table 2. Suggested Capacitors and Their Suppliers
Model Type Vendor Phone FAX
10 µF for C
OUT
VJ1812V106MXJAT Ceramic2 Vishay3 408-727-25004 408-330-4098 5
LMK432BJ106MM Ceramic Taiyo-Yuden 847-925-0888 847-925-0899
JMK325BJ106MM Ceramic Taiyo-Yuden 847-925-0888 847-925-0899
4.7 µF for C
IN
VJ1812V475MXJAT Ceramic Vishay 408-727-2500 408-330-4098
EMK325BJ475MN Ceramic Taiyo-Yuden 847-925-0888 847-925-0899
C3216X5R0J475M Ceramic TDK 847-803-6100 847-803-6296
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