lt3479efe-trpbf Linear Technology Corporation, lt3479efe-trpbf Datasheet - Page 8

• Manufacturer Part Number: lt3479efe-trpbf
• Description: 3a, Full Featured Dc/dc Converter With Soft-start And Inrush Current Protection
• Manufacturer: Linear Technology Corporation

APPLICATIO S I FOR ATIO
LT3479
8
2A/DIV
5V/DIV
2A/DIV
5V/DIV
V
V
OUT
OUT
Figure 5. Start-Up with No Soft-Start Capacitor
I
I
L
L
Figure 6. Start-Up with C
TO GND
TO V
TO V
MINIMIZE THE AREA
IN
S
U
OF THIS TRACE
0.2ms/DIV
0.2ms/DIV
U
C
S
W
SS
L1
= 22nF
C
IN
3479 F05
3479 F06
Figure 4. Suggested Board Layout
U
R
T
SW
SW
L
V
V
R
SHDN
S
IN
T
TO SHDN
Switching Frequency
The switching frequency of the LT3479 is set by an
external resistor attached to the R
pin open. A resistor must always be connected for proper
operation. See Table 4 and Figure 7 for resistor values and
corresponding frequencies.
Table 4. Switching Frequency
SWITCHING FREQUENCY (MHz)
D
LT3479
3.5
2.5
1.5
0.5
0.2
V
GND
GND
3
2
1
C
FBN
FBP
REF
PLACE VIAS AROUND EXPOSED PAD
TO ENHANCE THERMAL PERFORMANCE
OUT
SS
V
C
C
R2
SS
R1
C
C
3479 F04
T
TO V
R
C
pin. Do not leave this
OUT
R
T
1.78
2.87
4.32
6.49
10.2
17.8
39.2
113
(kΩ)
3479fa