LTC3810EG LINER [Linear Technology], LTC3810EG Datasheet - Page 33

• Manufacturer Part Number: LTC3810EG
• Description: 100V Current Mode Synchronous Switching Regulator Controller
• Manufacturer: LINER [Linear Technology]

APPLICATIONS INFORMATION
Since power dissipation at V
0.4W, calculate R
always enabled:
So, choose R
C
85°C. The output capacitors are chosen for a low ESR
of 0.018Ω to minimize output voltage changes due to
inductor ripple current and load steps. The ripple voltage
will be only:
However, a 0A to 10A load step will cause an output
change of up to:
An optional 10μF ceramic output capacitor is included
to minimize the effect of ESL in the output ripple. The
complete circuit is shown in Figure 19.
PC Board Layout Checklist
When laying out a PC board follow one of two suggested
approaches. The simple PC board layout requires a dedi-
cated ground plane layer. Also, for higher currents, it is
recommended to use a multilayer board to help with heat
sinking power components.
• The ground plane layer should not have any traces and
• Place C
IN
ΔV
= 72mV
ΔV
= 180mV
it should be as close as possible to the layer with power
MOSFETs.
compact area. It may help to have some components
on the bottom side of the board.
R
is chosen for an RMS current rating of about 5A at
NDRV
OUT(RIPPLE)
OUT(STEP)
IN
, C
36V 10V – 3.5V
NDRV
OUT
= ΔI
= ΔI
270μA
, MOSFETs, D1 and inductor all in one
NDRV(MAX)
= 80.6k.
LOAD
L(MAX)
• ESR = 10A • 0.018Ω
IN(MIN)
• ESR = 4A • 0.018Ω
such that fault timeout is
= 83.3k
= 36V already exceeds
• Use an immediate via to connect the components to
• Use compact plane for switch node (SW) to improve
• Use planes for V
• Flood all unused areas on all layers with copper. Flooding
• Segregate the signal and power grounds. All small-
• Place M2 as close to the controller as possible, keeping
• Connect the input capacitor(s) C
• Keep the high dV/dt SW, BOOST and TG nodes away
• Connect the INTV
• Connect the top driver boost capacitor C
• Connect the bottom driver decoupling capacitor C
When laying out a printed circuit board, without a ground
plane, use the following checklist to ensure proper opera-
tion of the controller.
ground plane including SGND and PGND of LTC3810.
Use several bigger vias for power components.
cooling of the MOSFETs and to keep EMI down.
fi ltering and to keep power losses low.
with copper will reduce the temperature rise of power
component. You can connect the copper areas to any
DC net (V
system).
signal components should return to the SGND pin at
one point which is then tied to the PGND pin close to
the source of M2.
the PGND, BG and SW traces short.
er MOSFETs. This capacitor carries the MOSFET AC
current.
from sensitive small-signal nodes.
to the INTV
the BOOST and SW pins.
closely to the DRV
IN
CC
, V
OUT
and SGND pins.
IN
, GND or to any other DC rail in your
CC
and V
CC
decoupling capacitor C
and BGRTN pins.
OUT
to maintain good voltage
IN
close to the pow-
LTC3810
B
VCC
closely to
33
closely
DRVCC
3810fb