Rainbow Electronics MAX15034 - Manual (Page 24)

MAX15034
In practical applications, pick the crossover frequency
(f
C ) in the range of:
First calculate R
CF
in equation 2 above. Calculate C
CF
so that:
where C CF is C10 and C12 in Figure 6.
Calculate C
CFF
so that:
where C CFF is C11 and C13 in Figure 6.
Applications Information
Independent Turn-On and Turn-Off
The MAX15034 can be used to regulate two outputs
from one controller. Each of the two outputs can be
turned on and off independently of one another by con-
trolling the enable input of each phase (EN1 and EN2).
A logic-low on each enable pin shuts down the
MOSFET drivers for that phase. When the voltage on the
enable pin exceeds 1.2V, the drivers are turned on and
the output can come up to regulation. This method of
turning on the outputs allows the MAX15034 to be used
for power sequencing.
PCB Layout Guidelines
Careful PCB layout is critical to achieve low losses, low
output noise, and clean and stable operation. This is
especially true for dual-phase converters where one
channel can affect the other. Use the following guide-
lines for PCB layout:
1) Place the V
DD
, REG, and the BST1 and BST2 bypass
capacitors close to the MAX15034.
2) Minimize all high-current switching loops.
3) Keep the power traces and load connections short.
This practice is essential for high efficiency. Use
thick copper PCBs (2oz or higher) to enhance effi-
ciency and minimize trace inductance and resis-
tance.
4) Run the current-sense lines CSP_ and CSN_ very
close to each other to minimize loop areas. Do not
cross these critical signal lines through power cir-
cuitry. Sense the current right at the pads of the
current-sense resistors.
5) Place the bank of output capacitors close to the
load.
6) Isolate the power components on the top side from
the analog components on the bottom side with a
ground plane in between.
7) Provide enough copper area around the switching
MOSFETs, inductors, and sense resistors to aid in
thermal dissipation and reducing resistance.
8) Distribute the power components evenly across the
top side for proper heat dissipation.
9) Keep AGND and PGND isolated and connect them
at one single point close to the IC. Do not connect
them together anywhere else.
10) Place all input bypass capacitors for each input as
close to each other as is practical.
C
f R
CFF
C CF
=
Ч Ч Ч Ч
1
2 10 π
C
f R
CF
C CF
=
Ч Ч Ч
10
2 π
f
f
f
SW
C
SW
10 2
< <
Configurable, Single-/Dual-Output, Synchronous
Buck Controller for High-Current Applications
24 ______________________________________________________________________________________