MAX16814ATP+T Maxim Integrated Products, MAX16814ATP+T Datasheet - Page 17

• Manufacturer Part Number: MAX16814ATP+T
• Description: LED Drivers Integrated 4-Channel High-Brightness LED
• Manufacturer: Maxim Integrated Products

Specifications of MAX16814ATP+T

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

The factor 1.1 provides a 10% margin to account for the
converter losses:
Assuming the peak-to-peak inductor ripple DIL is Q30%
of the average inductor current:
and:
and:
Calculate the minimum inductance values L1
L2
the maximum value as follows:
where 0.3V is the peak current-sense voltage. Choose
inductors that have a minimum inductance greater than
the calculated L1
greater than IL1
mended saturation current limit of the selected inductor
is 10% higher than the inductor peak current:
MIN
in henries with the inductor current ripples set to
L1
L2
MIN
MIN
Integrated, 4-Channel, High-Brightness LED
=
=
Driver with High-Voltage DC-DC Controller
(VIN
∆
P
IL2
(VIN
∆
IL1
______________________________________________________________________________________
IL2 IL2
IL1 IL1
MIN
and IL2
P
P
IL2
MIN
MIN
=
=
=
=
IL1
and L2
IL2
AVG
−
−
AVG
AVG
AVG
f
f
V
AVG
SW
P
V
SW
DS
, respectively. The recom-
DS
I =
×
× ∆
LED
+
×
× ∆
MIN
−
+
−
0.3 2
0.3 2
∆
0.3V) D
0.3V) D
∆
IL1
IL2
IL1
2
IL2
2
×
×
and current rating
×
×
MAX
MAX
MIN
and
For simplifying further calculations, consider L1 and
L2 as a single inductor with L1 and L2 connected in
parallel. The combined inductance value and current is
calculated as follows:
and:
where IL
both the inductors together for SEPIC configuration. Use
these values in the calculations for SEPIC configuration
in the following sections.
Select coupling capacitor C
ripple on it is less than 2% of the minimum input sup-
ply voltage. This ensures that the second-order effects
created by the series resonant circuit comprising L1,
C
converter. Use the following equation to calculate the
minimum value of C
where C
in farads, I
factor 0.02 accounts for 2% ripple.
The MAX16814 generates a current ramp for slope com-
pensation. This ramp current is in sync with the switch-
ing frequency and starts from zero at the beginning of
every clock cycle and rises linearly to reach 50FA at the
end of the clock cycle. The slope-compensating resistor,
R
source of the external MOSFET. This adds a program-
mable ramp voltage to the CS input voltage to provide
slope compensation.
SCOMP
S
, and L2 does not affect the normal operation of the
S
AVG
, is connected between the CS input and the
is the minimum value of the coupling capacitor
LED
represents the total average current through
IL
C
is the LED current in amperes, and the
L
S
AVG
MIN
≥
S
:
V
=
IN_MIN
=
IL1
L1
L1
I
LED
AVG
MIN
MIN
S
×
×
so that the peak-to-peak
×
+
0.02 f
D
+
L2
L2
MAX
IL2
Slope Compensation
MIN
MIN
×
AVG
SW
17