MAX16833EVKIT+ Maxim Integrated Products, MAX16833EVKIT+ Datasheet - Page 17

• 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

where I
hertz, and V
allowable ripple is for the ESR of the output capacitor.
Based on this, the ESR of the output capacitor is given by:
where IL
the equation below to calculate the RMS current rating of
the output capacitor:
The input-filter capacitor bypasses the ripple current
drawn by the converter and reduces the amplitude of
high-frequency current conducted to the input supply.
The ESR, ESL, and the bulk capacitance of the input
capacitor contribute to the input ripple. Use a low-ESR
input capacitor that can handle the maximum input RMS
ripple current from the converter. For the boost con-
figuration, the input current is the same as the inductor
current. For buck-boost configuration, the input current
is the inductor current minus the LED current. However,
for both configurations, the ripple current that the input
filter capacitor has to supply is the same as the induc-
tor ripple current with the condition that the output filter
capacitor should be connected to ground for buck-boost
configuration. This reduces the size of the input capaci-
tor, as the input current is continuous with maximum
QDI
calculation of the input capacitor for boost, as well as
buck-boost configurations is the same.
Neglecting the effect of the ESL, the ESR, and the bulk
capacitance at the input contribute to the input-voltage
ripple. For simplicity, assume that the contributions from
the ESR and the bulk capacitance are equal. This allows
50% of the ripple for the bulk capacitance. The capaci-
tance is given by:
where DIL is in amperes, C
and DV
ripple is for the ESR of the input capacitor. Based on this,
the ESR of the input capacitor is given by:
L
/2. Neglecting the effect of LED current ripple, the
LED
IN
I
P
COUT(RMS)
is the peak-inductor current in amperes. Use
is in volts. The remaining 50% of allowable
OUTRIPPLE
is in amperes, C
ESR
______________________________________________________________________________________
COUT
C
IN
=
≥
is in volts. The remaining 50% of
<
IL
4
V
AVG
× ∆
IN
OUTRIPPLE
(IL
V
OUT
∆
is in farads, f
Integrated High-Side Current Sense
2
IN
I
P
D
L
×
MAX
×
High-Voltage HB LED Drivers with
f
is in farads, f
SW
2)
Input Capacitor
(
1 D
( )
−
Ω
SW
MAX
is in hertz,
)
SW
is in
where DI
is in volts. Use the equation below to calculate the RMS
current rating of the input capacitor:
The switching MOSFET (Q1) should have a voltage rat-
ing sufficient to withstand the maximum output voltage
together with the diode drop of rectifier diode D1 and
any possible overshoot due to ringing caused by parasit-
ic inductances and capacitances. Use a MOSFET with a
drain-to-source voltage rating higher than that calculated
by the following equations.
where V
is the forward drop of rectifier diode D1. The factor of 1.2
provides a 20% safety margin.
where V
is the forward drop of rectifier diode D1. The factor of 1.2
provides a 20% safety margin.
The RMS current rating of the switching MOSFET Q1 is cal-
culated as follows for boost and buck-boost configurations:
where ID
amperes.
The MOSFET Q1 dissipates power due to both switching
losses, as well as conduction losses. The conduction
losses in the MOSFET are calculated as follows:
where R
is in watts, and IL
ing equations to calculate the switching losses in the
MOSFET.
DS
DS
DSON
L
RMS
P
I
Selection of Power Semiconductors
V
DRMS
is in amperes, ESR
COND
is the drain-to-source voltage in volts and V
is the drain-to-source voltage in volts and V
DS
is the MOSFET Q1’s drain RMS current in
is the on-resistance of Q1 in ohms, P
= (V
V
DS
= (IL
=
AVG
ESR
I
LED
CIN
= (V
1.3 ( (IL
AVG
(RMS)
CIN
+ V
×
is in amperes. Use the follow-
LED
)
2
INMAX
<
Buck-Boost Configuration
x D
+ V
∆ ×
=
CIN
AVG
∆
I
L
V
2 3
MAX
∆
D
IN
I
) x 1.2
+ V
L
Boost Configuration
)
is in ohms, and DV
2
2
Switching MOSFET
×
x R
D
D
) x 1.2
MAX
DSON
)
COND
17
IN
D
D