lt1913 Linear Technology Corporation, lt1913 Datasheet - Page 13

• Manufacturer Part Number: lt1913
• Description: 25v, 3.5a, 2.4mhz Step-down Switching Regulator
• Manufacturer: Linear Technology Corporation

APPLICATIONS INFORMATION
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 speci-
fi 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:
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
Table 2. Capacitor Vendors
VENDOR
Panasonic
Kemet
Sanyo
Murata
AVX
Taiyo Yuden
I
D(AVG)
OUT
= I
is the output load current. The only reason to
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
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.
B330
B320
Frequency Compensation
The LT1913 uses current mode control to regulate the
output. This simplifi es loop compensation. In particular, the
LT1913 does not require the ESR of the output capacitor
for stability, so you are free to use ceramic capacitors to
achieve low output ripple and small circuit size. Frequency
compensation is provided by the components tied to the
PART SERIES
Ceramic,
Polymer,
Tantalum
Ceramic,
Tantalum
Ceramic,
Polymer,
Tantalum
Ceramic
Ceramic,
Tantalum
Ceramic
(V)
V
40
30
20
R
COMMANDS
EEF Series
T494, T495
POSCAP
TPS Series
I
(A)
AVE
3
3
3
LT1913
V
F
(mV)
500
500
450
13
AT 3A
1913f