lt3693 Linear Technology Corporation, lt3693 Datasheet - Page 12

• Manufacturer Part Number: lt3693
• Description: 36v, 3.5a, 2.4mhz Step-down Switching Regulator
• Manufacturer: Linear Technology Corporation

APPLICATIONS INFORMATION
LT3693
When choosing a capacitor, look carefully through the
data sheet to fi nd out what the actual capacitance is under
operating conditions (applied voltage and temperature).
A physically larger capacitor, or one with a higher volt-
age rating, may be required. High performance tantalum
or electrolytic capacitors can be used for the output
capacitor. Low ESR is important, so choose one that is
intended for use in switching regulators. The ESR should
be specifi ed by the supplier, and should be 0.05 or less.
Such a capacitor will be larger than a ceramic capacitor
and will have a larger capacitance, because the capacitor
must be large to achieve low ESR. Table 2 lists several
capacitor vendors.
Catch Diode
The catch diode conducts current only during switch off
time. Average forward current in normal operation can be
calculated from:
12
Table 2. Capacitor Vendors
VENDOR
Panasonic
Kemet
Sanyo
Murata
AVX
Taiyo Yuden
I
D(AVG)
= I
OUT
(V
PHONE
[phone]
[phone]
[phone]
[phone]
[phone]
IN
– V
OUT
)/V
IN
URL
www.panasonic.com
www.kemet.com
www.sanyovideo.com
www.murata.com
www.avxcorp.com
www.taiyo-yuden.com
where I
consider a diode with a larger current rating than necessary
for nominal operation is for the worst-case condition of
shorted output. The diode current will then increase to the
typical peak switch current. Peak reverse voltage is equal
to the regulator input voltage. Use a schottky diode with a
reverse voltage rating greater than the input voltage. Table
3 lists several Schottky diodes and their manufacturers.
Table 3. Diode Vendors
PART NUMBER
On Semiconductor
MBRA340
Diodes Inc.
PDS340
B340A
B340LA
OUT
PART SERIES
Ceramic,
Polymer,
Tantalum
Ceramic,
Tantalum
Ceramic,
Polymer,
Tantalum
Ceramic
Ceramic,
Tantalum
Ceramic
is the output load current. The only reason to
(V)
V
40
40
40
40
R
COMMANDS
EEF Series
T494, T495
POSCAP
TPS Series
I
(A)
AVE
3
3
3
3
V
F
(mV)
500
500
500
450
AT 3A
3693f