MAX16809EVKIT+ Maxim Integrated Products, MAX16809EVKIT+ Datasheet - Page 5

• Manufacturer Part Number: MAX16809EVKIT+
• Description: Power Management Modules & Development Tools EVAL KIT FOR MAX16809
• Manufacturer: Maxim Integrated Products

Specifications of MAX16809EVKIT+

• Lead Free Status / RoHS Status: Lead free / RoHS Compliant

The saturation current limit of the selected inductor
(IL
equation below. Selecting an inductor with 10% higher
IL
Calculate the output capacitor C
tion of C16, C17, C18, and C24) using the following
equation:
where VLED
supply voltage. The value of the calculated output
capacitance will be much lower than what is actually
necessary for feedback loop compensation. See the
Feedback Compensation section to calculate the out-
put capacitance based on the compensation require-
ments.
Calculate the input capacitor C
of C12, C13, C14, and C5) using the following equation:
where VIN
This equation assumes that input capacitors supply
most of the input ripple current.
The switching MOSFET (Q2) should have a voltage rat-
ing sufficient to withstand the maximum output voltage,
together with the diode drop of D2, and any possible
overshoot due to ringing caused by parasitic induc-
tances and capacitances. Use a MOSFET with voltage
rating higher than that calculated by the following
equation:
The factor of 1.3 provides a 30% safety margin.
SAT
SAT
rating is a good choice:
) should be greater than the value given by the
Selection of Power Semiconductors
PP
PP
is the peak-to-peak input ripple voltage.
C
is the peak-to-peak ripple in the LED
C
V
IL
OUT
IN
DS
_______________________________________________________________________________________
SAT
=
=
=
8
(
=
VLED V
×
VLED
1 1 .
D
F
MAX
SW
IL
×
+
PP
PP
×
IL
×
IN
VIN
OUT
D
×
I
PEAK
OUT
)
F
(parallel combination
×1 3 .
SW
PP
(parallel combina-
MAX16809 Evaluation Kit
The continuous drain-current rating of the selected
MOSFET when the case temperature is at +70°C should
be greater than that calculated by the following equation.
The MOSFET must be mounted on a board, as per
manufacturer specifications, to dissipate the heat:
The MOSFET dissipates power due to both switching
losses, as well as conduction losses. Use the following
equation to calculate the conduction losses in the
MOSFET:
where RDS
the MOSFET with an assumed junction temperature of
100°C.
Use the following equation to calculate the switching
losses in the MOSFET:
where I
MOSFET (with V
when it is turned on and turned off, respectively, and
C
a MOSFET that has a higher power rating than that cal-
culated by the following equation when the MOSFET
case temperature is at +70°C:
The MAX16809 EV kit uses a Schottky diode as the
boost-converter rectifier (D2). A Schottky rectifier diode
produces less forward drop and puts the least burden
on the MOSFET during reverse recovery. If a diode with
considerable reverse-recovery time is used, it should be
considered in the MOSFET switching-loss calculation.
The Schottky diode selected should have a voltage rat-
ing 20% above the maximum boost-converter output
voltage. The current rating of the diode should be
greater than I
P
GD
SW
is the gate-to-drain MOSFET capacitance. Choose
=
IL
GON
AVG
ON
D
and I
×
ID
is the on-state drain-source resistance of
P
in the following equation:
VLED
COND
I
RMS
D
P
GS
=
TOT
GOFF
⎛
⎜
⎜
⎝
2
=
2
equal to the threshold voltage)
=
⎛
⎜
⎜
⎝
1
×
=
IL
IL
−
C
P
D
are the gate currents of the
IL
AVG
COND
D
AVG
GD
D
MAX
MAX
AVG
MAX
×
2
2
F
2
×
+
SW
⎞
⎟
⎟
⎠
⎞
⎟
⎟
⎠
RDS
P
×
SW
×
1 2 .
×
1 3 .
⎛
⎜
⎝
ON
I
GON
1
+
I
GOFF
1
⎞
⎟
⎠
5