LTC3836 LINER [Linear Technology], LTC3836 Datasheet - Page 23

• Manufacturer Part Number: LTC3836
• Description: Dual 2-Phase, No RSENSETM Low VIN Synchronous Controller
• Manufacturer: LINER [Linear Technology]

APPLICATIONS INFORMATION
PC Board Layout Checklist
When laying out the printed circuit board, the following
checklist should be used to ensure proper operation of the
LTC3836. These items are illustrated in the layout diagram of
Figure 13. Figure 14 depicts the current waveforms present
in the various branches of the 2-phase dual regulator.
1) The power loop (input capacitor, MOSFETs, inductor,
2) The signal and power grounds should be kept separate.
output capacitor) of each channel should be as small
as possible and isolated as much as possible from the
power loop of the other channel. Ideally, the main and
synchronous FETs should be connected close to one
another with an input capacitor placed right at the FETs.
It is better to have two separate, smaller valued input
capacitors (e.g., two 10μF —one for each channel) than
it is to have a single larger valued capacitor (e.g., 22μF)
that the channels share with a common connection.
The signal ground consists of the feedback resistor divid-
ers, I
The power grounds consist of the (–) terminal of the
input and output capacitors and the source of the
synchronous N-channel MOSFET. Each channel should
have its own power ground for its power loop (as de-
TH
compensation networks and the SGND pin.
BOLD LINES INDICATE HIGH CURRENT PATHS
10
11
12
13
Figure 13. LTC3836 Layout Diagram
1
2
3
4
5
6
7
8
9
SW1
N/C
IPRG1
V
I
IPRG2
PLLLPF
SGND
V
TRACK/SS2
V
I
PGOOD
TH1
TH2
FB1
IN
FB2
LTC3836EGN
SYNC/FCB
SENSE1
SENSE2
BOOST1
BOOST2
RUN/SS
PGND
PGND
PGND
SW2
BG1
TG1
TG2
BG2
N/C
+
+
28
27
26
25
24
23
22
21
20
19
18
17
16
15
14
3) Put the feedback resistors close to the V
4) The current sense traces (SENSE
5) Keep the switch nodes (SW1, SW2) and the gate driver
6) Connect the boost capacitors to the switch nodes, not to
scribed above in item 1). The power grounds for the
two channels should connect together at a common
point. It is most important to keep the ground paths
with high switching currents away from each other.
The PGND pins on the LTC3836 should be shorted
together and connected to the common power ground
connection (away from the switching currents).
trace connecting the top feedback resistor (R
the output capacitor should be a Kelvin trace. The I
compensation components should also be very close
to the LTC3836.
Kelvin connections right at the main N-channel MOSFET
drains and sources.
nodes (TG1, TG2, BG1, BG2) away from the small-
signal components, especially the opposite channel’s
feedback resistors, I
the current sense pins (SENSE
the small signal nodes SWn. Connect the boost diodes
to the positive terminal of the input capacitor.
D
C
D
B2
B2
B1
C
B1
C
C
OUT2
OUT1
C
C
C
VIN1
VIN2
M1
M3
VIN
+
+
3836 F13
L1
L2
TH
M2
M4
V
V
OUT1
OUT2
compensation components, and
V
IN
+
and SW).
+
and SW) should be
LTC3836
FB
pins. The
23
B
) to
3836fa
TH