MAX16807EVKIT+ Maxim Integrated Products, MAX16807EVKIT+ Datasheet - Page 6

• Manufacturer Part Number: MAX16807EVKIT+
• Description: EVAL KIT FOR MAX16807
• Manufacturer: Maxim Integrated Products

Specifications of MAX16807EVKIT+

• Current - Output / Channel: 50mA
• Outputs And Type: 8, Non-Isolated
• Voltage - Output: 32V
• Features: Dimmable
• Voltage - Input: 9 ~ 16V
• Utilized Ic / Part: MAX16807
• Lead Free Status / RoHS Status: Lead free / RoHS Compliant

maximum current-sense voltage due to the addition of
slope compensation. Check this factor and adjust after
the slope compensation is calculated. Slope compensation
is explained in detail in a later section.
The saturation current limit of the selected inductor
(IL
following equation. Selecting an inductor with 10%
higher IL
Calculate the output capacitor C
tion of C1, C2, and C15) 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 output
capacitance based on the compensation requirements.
Calculate the input capacitor C
of C9, C10, and C11) using the following equation:
where VIN
This equation assumes that input capacitors supply
most of the input ripple current.
The switching MOSFET (N1) should have a voltage rat-
ing sufficient to withstand the maximum output voltage
together with the diode drop of D1, and any possible
overshoot due to ringing caused by parasitic inductances
and capacitances. Use a MOSFET with voltage rating
higher than that calculated by the following equation:
where the factor of 1.3 provides a 30% safety margin.
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 equation
below. The MOSFET must be mounted on a board, as
per manufacturer specifications, to dissipate the heat.
MAX16807 Evaluation Kit
6
SAT
_______________________________________________________________________________________
) should be greater than the value given by the
SAT
Selection of Power Semiconductors
PP
rating is a good choice.
PP
is the peak-to-peak input ripple voltage.
ID
C
is the peak-to-peak ripple in the LED
V
C
RMS
OUT
DS
IL
IN
SAT
=
=
=
=
(
8
VLED V
⎛
⎜
⎜
⎝
=
VLED
×
D
IL
F
IL
MAX
SW
D
PEAK
IL
AVG
MAX
+
PP
PP
×
×
IN
D
VIN
2
OUT
×
I
OUT
× 1 1 .
)
F
⎞
⎟
⎟
⎠
(parallel combination
×1 3 .
SW
PP
×
1 3 .
(parallel combina-
The MOSFET will dissipate 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 MAX16807 EV kit uses a Schottky diode as the
boost-converter rectifier (D1). 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
When the boost converter operates in CCM with more
than 50% duty cycle, subharmonic oscillations will
occur if slope compensation is not implemented.
Subharmonic oscillations do not allow the PWM duty
cycle to settle to a peak current value set by the volt-
age feedback loop. The duty cycle oscillates back and
forth about the required value (usually at half the
switching frequency). Subharmonic oscillations will die
out if a sufficient negative slope is added to the inductor
peak current. This means that for any peak current set
GD
P
SW
is the gate-to-drain MOSFET capacitance. Choose
=
GON
IL
AVG
ON
D
and I
P
is the on-state drain-source resistance of
×
in the following equation:
COND
VLED
I
D
P
GS
TOT
=
GOFF
⎛
⎜
⎜
⎝
equal to the threshold voltage)
2
=
2
=
1
IL
×
IL
D
−
P
C
are the gate currents of the
AVG
MAX
COND
AVG
D
GD
MAX
Slope Compensation
2
2
×
×
F
+
⎞
⎟
⎟
⎠
SW
RDS
P
×
SW
1 2 .
×
ON
⎛
⎜
⎝
I
GON
1
+
I
GOFF
1
⎞
⎟
⎠