7
LT1300
COMPONENT
PART NUMBER
VENDOR
L (
µ
H)
DCR (
Ω
)
I
LIM
PIN
50mA LOAD
200mA LOAD
HEIGHT (mm)
PHONE NUMBER
DO1608-103
Coilcraft
10
0.11
Float
83
83
3.5
(708) 639–6400
DO3316-223
Coilcraft
22
0.050
Float
85
85
5.5
DO1608-223
Coilcraft
22
0.31
Ground
85
—
3.5
CTX10-1
Coiltronics
10
0.038
Float
85
85
4.2
(407) 241–7876
CTX20-1
Coiltronics
20
0.175
Ground
86
—
4.2
LQH3C2204K0M00
Murata-Frie
22
0.7
Ground
81
—
2.0
(404) 436–1300
CD54-100M
Sumida
10
0.11
Float
85
85
4.5
(708) 956–0666
CDRH62-220M
Sumida
22
0.38
Ground
84
—
3.0
CDRH62-100M
Sumida
10
0.17
Float
81
82
3.0
GA10-102K
Gowanda
10
0.038
Float
85
86
6.6 Through-Hole
(716) 532–2234
APPLICATIO
N
S I
N
FOR
M
ATIO
N
W
U
U
U
Table 1. Recommended Inductors
Inductor Selection
For full output power, the inductor should have a satura-
tion current rating of 1.25A for worst-case current limit,
although it is acceptable to bias an inductor 20% or more
into saturation. Smaller inductors can be used in conjunc-
tion with the I
LIM
pin. Efficiency is significantly affected by
inductor DCR. For best efficiency limit the DCR to 0.03
Ω
or less. Toroidal types are preferred in some cases due to
their closed design and inherent EMI/RFI superiority.
Recommended inductors are listed in Table 1.
Capacitor Selection
Low ESR capacitors are required for both input and output
of the LT1300. ESR directly affects ripple voltage and
efficiency. For surface mount applications AVX TPS series
tantalum capacitors are recommended. These have been
specially designed for SMPS and have low ESR along with
high surge current ratings. For through-hole application
Sanyo OS-CON capacitors offer extremely low ESR in a
small size. Again, if peak switch current is reduced using
the I
LIM
pin, capacitor requirements can be relaxed and
smaller, higher ESR units can be used. Low frequency
output ripple can be reduced by adding multiple output
capacitors. If capacitance is reduced, output ripple will
increase. Suggested capacitor sources are listed in Table 2.
Table 2. Recommended Capacitors
VENDOR
SERIES
TYPE
PHONE#
AVX
TPS
Surface Mount
(803)448–9411
Sanyo
OS-CON
Through-Hole
(619) 661–6835
Panasonic
HFQ
Through-Hole
(201) 348–5200
Diode Selection
Best performance is obtained with a Schottky rectifier
diode such as the 1N5817. Phillips Components makes
this in surface mount as the PRLL5817. Motorola makes
the MBRS130LT3 which is slightly better and also in
surface mount. For lower output power a 1N4148 can be
used although efficiency will suffer substantially.
Layout Considerations
The LT1300 is a high speed, high current device. The input
capacitor must be no more than 0.2" from V
IN
(pin 6) and
ground. Connect the PGND and GND (pins 8 and 1)
together under the package. Place the inductor adjacent to
SW (pin 7) and make the switch pin trace as short as
possible. This keeps radiated noise to a minimum.
EFFICIENCY 2.5V
IN
, 5V
OUT
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.
