LTC3615 LINER [Linear Technology], LTC3615 Datasheet - Page 26

• Manufacturer Part Number: LTC3615
• Description: Dual 4MHz, 3A Synchronous Step-Down DC/DC Converter
• Manufacturer: LINER [Linear Technology]

LTC3615
applicaTions inForMaTion
C
to satisfy the output voltage ripple requirement and the
bulk capacitance needed for loop stability. For this design,
47µF ceramic capacitors will be used with X5R or X7R
dielectric.
C
Decoupling the PV
for most applications.
Finally, it is possible to define the soft-start up time choos-
ing the proper value for the capacitor and the resistor
connected to TRACK/SS pin. If one sets minimum T
5ms and a resistor of 4.7M, the following equation can
be solved with the maximum SV
The standard value of 10nF and 4.7M guarantees the
minimum soft-start time of 5ms. In Figure 3, channel 1
shows the schematic for this design example.

OUT
IN
I
C
RMS MAX
should be sized for a maximum current rating of:
SS
will be selected based on the ESR that is required
(
=
4 7
.
)
M In
=
I
•
OUT
2
IN

 
1
with two 47µF capacitors is adequate
5
5 5
ms
+
.
I
V
OUT
5 5
2
.
– .
2
V
0 6
=
IN
V
2
A

 
= 5.5V:
RMS
=
9 2
.
nF
SS
=
PC Board Layout Checklist
When laying out the printed circuit board, the following
checklist should be used to ensure proper operation of
the LTC3615:
1. A ground plane is recommended. If a ground plane
2. Connect the (+) terminal of the input capacitors, C
3. Keep the switching nodes, SWx, away from all sensitive
4. Flood all unused areas on all layers with copper. Flooding
5. Connect the V
layer is not used, the signal and power grounds should
be segregated with all small signal components return-
ing to the SGND pin at one point which is then con-
nected to the PGND node at the exposed pad close to
the LTC3615
as close as possible to the PV
minal as close as possible to the exposed pad PGND.
This capacitor provides the AC current into the internal
power MOSFETs.
small signal nodes FBx, ITHx, RTSYNC, SRLIM.
with copper will reduce the temperature rise of power
components. Connect the copper areas to PGND (ex-
posed pad) for best performance.
The resistor divider must be connected between V
and SGND.
FBx
pins directly to the feedback resistors.
INx
pins, and the (–) ter-
OUTx
3615f
IN
,