MAX16834 Maxim Integrated Products, MAX16834 Datasheet - Page 11

• Manufacturer Part Number: MAX16834
• Description: High-Power LED Driver
• Manufacturer: Maxim Integrated Products

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Figure 2. Boost LED Driver
The LED current is programmed using the voltage on
REFI and the LED current-sense resistor R10 (see
Figure 2). The current is given by:
where V
are in ohms. The regulation voltage on the LED current-
sense resistor must not exceed 0.3V to prevent activa-
tion of the LED short-circuit protection circuit.
In the boost converter (Figure 2), the average inductor
current varies with the line voltage. The maximum aver-
age current occurs at the lowest line voltage. For the
boost converter, the average inductor current is equal
to the input current.
High-Power LED Driver with Integrated High-Side LED
Current Sense and PWM Dimming MOSFET Driver
V
IN
REF
R1
R2
I
is 3.7V and the resistors R5, R6, and R10
LED
Programming the LED Current
=
______________________________________________________________________________________
R
10
×
V
C1
(
REF
R
6
R5
R3
C4
C2
C5
+
Boost Configuration
×
R
R
5
5
)
×
R6
9 9
.
( )
IN
UVEN
HV
SC
RT/SYNC
V
REFI
SGND
A
LV
REF
CC
MAX16834
PWMDIM
DIMOUT
SENSE+
COMP
NDRV
OVP+
PGND
CLV
FLT
CS
Calculate maximum duty cycle using the below equation.
where V
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
cycle 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
current ripple ∆I
amperes:
MAX
. A more accurate value of the maximum duty
D
ON
LED
is the forward drop of the rectifier diode D1 in
R7
C7
is the forward voltage of the LED string in
OFF
D
Q1
MAX
C6
L
, and the peak inductor current IL
=
L1
R8
V
D1
V
LED
LED
+
AVG
INMIN
+
FET
R4
R9
V
V
D
Q2
D
, peak-to-peak inductor
−
is the average drain to
−
V
is the minimum input
V
INMIN
FET
C3
R10
LED+
LED-
LEDs
P
11
in