7
DEMO MANUAL DC059
Components Manufacturer
Besides those components that are used on the demon-
stration board, other components may also be used.
Below is a partial list of the manufacturers whose compo-
nents you can use for the switching regulator. Using
components, other than the ones on the demonstration
board, require re-characterizing the circuit for efficiency.
Table 1. Inductor Manufacturer
MANUFACTURER PART NUMBERS
Coilcraft DT3316 Series
1102 Silver Lake Road
Cary, Illinois
(Phone) 708-639-6400
(Fax) 708-639-1469
Coiltronics International Econo-Pac
6000 Park of Commerce Blvd Octa-Pac
Boca Raton, FL 33487
(Phone) 407-241-7876
(Fax) 407-241-9339
Dale Electronics Inc. LPT4545
E. Highway 50
P.0. Box 180
Yankton, SD 57078-0180
(Phone) 605-665-9301
(Fax) 605-665-1627
Sumida Electric Co. Ltd. CD 54 Series
5999 New Wilke Rd., Suite #110 CDR 74H Series
Rolling Meadows, IL 60008
(Phone) 708-956-0666
(Fax) 708-956-0702
Table 2. Capacitor Manufacturers
MANUFACTURER PART NUMBERS
AVX Corporation TPS Series
P.O. Box 887
Myrtle Beach, SC 29578
(Phone) 803-448-9411
(Fax) 803-448-1943
Sanyo Video Components OS-CON Series
2001 Sanyo Avenue
San Diego, CA 92071
(Phone) 619-661-6322
(Fax) 619-661-1055
Sprague 593D Series
678 Main Street
Sanford, ME 04073
(Phone) 207-324-4140
(Fax) 207-324-7223
Capacitors
The most common component uncertainty with switching
power supplies involves capacitors. In this circuit (refer
to Figure 1) C1 and C2 are all specially developed low
ESR, high ripple-current tantalum capacitors specifically
designed for use in switching power supplies. ESR is the
parasitic series resistance in the capacitor. Very often this
resistance is the limiting element in reducing ripple at the
output or input of the supply. Standard wet electrolytics
may cause the feedback loop to be unstable (this means
your power supply becomes an oscillator). They may also
cause poor transient response or have a limited operating
life. Standard parts normally do not have an ESR specifi-
cation at high frequencies (100kHz) so, although you may
find a part that works to your satisfaction in a prototype,
the same part may not work consistently in production.
Furthermore, surface mount versions of wet electrolytics
are not space efficient, and they may have high ESR and
limited lifetimes.
Normal tantalums are not recommended for use in these
applications (most notably the low cost ones) as they do
not have the ability to take the large peak currents that are
required for the application. Tantalums have a failure
mechanism whereby they become a low value resistance
or short. Wet electrolytics rarely short; they usually fail by
going high impedance if over stressed. Very few tantalum
manufacturers have the ability to make capacitors for
power applications.
There are some tantalums, such as those used in
this design, that are specifically designed for switching
power supplies. They are much smaller than wet electro-
lytic capacitors and are surface mountable but they do
cost more.
One other choice that fits between wet electrolytics
and tantalums is organic semiconductor type capacitors
(OS-CON) that are specifically made for power supply
applications. They are very low ESR and are 1/2 the size of
an equivalent wet electrolytic.
OPERATIO
U
Information furnished by Linear Technology Corporation is believed to be accurate and reliable.
However, no responsibility is assumed for its use. Linear Technology Corporation makes no represen-
tation that the interconnection of its circuits as described herein will not infringe on existing patent rights.
