MAX16833EVKIT+ Maxim Integrated Products, MAX16833EVKIT+ Datasheet - Page 15

• Manufacturer Part Number: MAX16833EVKIT+
• Description: KIT EVAL FOR MAX16833 LED DRIVER
• Manufacturer: Maxim Integrated Products

Specifications of MAX16833EVKIT+

• Current - Output / Channel: 1A
• Outputs And Type: 1, Non-Isolated
• Voltage - Output: 3 ~ 36 V
• Features: Analog Brightness control
• Voltage - Input: 5 ~ 18 V
• Utilized Ic / Part: MAX16833A/B
• Lead Free Status / RoHS Status: Lead free / RoHS Compliant

In the boost converter (see the Typical Operating
Circuits), the average inductor current varies with the
line voltage. The maximum average current occurs at the
lowest line voltage. For the boost converter, the average
inductor current is equal to the input current. Calculate
maximum duty cycle using the following equation:
where V
in volts, V
volts (approximately 0.6V), V
supply voltage in volts, and V
source voltage of the MOSFET Q1 in volts when it is on.
Use an approximate value of 0.2V initially to calculate
D
can be calculated once the power MOSFET is selected
based on the maximum inductor current.
Use the following equations to calculate the maximum
average inductor current IL
tor current ripple DI
amperes:
Allowing the peak-to-peak inductor ripple to be DI
peak inductor current is given by:
The inductance value (L) of inductor L1 in henries (H) is
calculated as:
where f
and V
Choose an inductor that has a minimum inductance
greater than the calculated value. The current rating of
the inductor should be higher than IL
temperature.
In the buck-boost LED driver (see the Typical Operating
Circuits), the average inductor current is equal to the
MAX
. A more accurate value of the maximum duty cycle
FET
SW
LED
are in volts, and DI
D
is the switching frequency in hertz, V
is the forward drop of rectifier diode D1 in
is the forward voltage of the LED string
D
L
MAX
=
______________________________________________________________________________________
(
IL
V
IL
L
INMIN
=
P
, and peak inductor current IL
AVG
V
=
LED
V
IL
LED
f
SW
=
- V
AVG
1- D
+
Buck-Boost Configuration
INMIN
L
FET
FET
AVG
× ∆
+
Integrated High-Side Current Sense
I
V - V
LED
is in amperes.
V - V
D
+
MAX
Inductor Selection
I
D
)
L
is the average drain-to-
, peak-to-peak induc-
∆
×
High-Voltage HB LED Drivers with
2
Boost Configuration
is the minimum input-
I
D
L
INMIN
MAX
FET
P
at the operating
INMIN
L,
P
the
in
input current plus the LED current. Calculate the maxi-
mum duty cycle using the following equation:
where V
in volts, V
(approximately 0.6V) in volts, V
input supply voltage in volts, and V
drain-to-source voltage of the MOSFET Q1 in volts when
it is on. Use an approximate value of 0.2V initially to cal-
culate D
cycle can be calculated once the power MOSFET is
selected based on the maximum inductor current.
Use the equations below to calculate the maximum aver-
age inductor current IL
rent ripple DI
Allowing the peak-to-peak inductor ripple to be DI
where IL
The inductance value (L) of inductor L1 in henries is
calculated as:
where f
and V
inductor that has a minimum inductance greater than the
calculated value.
The value of the switch current-sense resistor R4 for the
boost and buck-boost configurations is calculated as
follows:
where IL
V
SC
is the peak slope compensation voltage.
FET
SW
LED
MAX
P
P
D
are in volts, and DI
is the peak inductor current.
D
is the peak inductor current in amperes and
MAX
is the switching frequency in hertz, V
L
. A more accurate value of maximum duty
is the forward drop of rectifier diode D1
Peak Current-Sense Resistor (R4)
is the forward voltage of the LED string
, and peak inductor current IL
L
=
=
R4
(
IL
V
IL
V
INMIN
=
P
LED
AVG
0.418V - V
=
AVG
IL
f
+
SW
=
- V
AVG
V
V
IL
, peak-to-peak inductor cur-
1- D
D
L
LED
FET
× ∆
P
I
LED
is in amperes. Choose an
+
+
MAX
I
V
)
L
SC
+
INMIN
∆
×
INMIN
2
I
V
D
L
D
Ω
FET
MAX
- V
is the minimum
is the average
FET
P
in amperes:
L:
INMIN
15