MAX16834 Datasheet, PDF (13/23 Pages) Maxim Integrated Products – High-Power LED Driver with Integrated High-Side LED Current Sense and PWM Dimming MOSFET Driver

High-Power LED Driver with Integrated High-Side LED
Current Sense and PWM Dimming MOSFET Driver
VIN
C1
L1
R1
D1
LED+
LV
HV
IN
NDRV
Q1
UVEN
CS
C2
SC MAX16834
ON
LEDs
C3
R4
R3
PWMDIM
OFF
RT/SYNC
LED-
C5
Q2
R2
V_CC
DIMOUT
C4
REF
SENSE+
R6
R5
REFI
OVP+
CLV
FLT
SGND
COMP
PGND
R8
C7
C6
R7
R9
R10
VIN
Figure 3. Buck-Boost LED Driver (V_LED+ < 28V)
ESR and the bulk capacitance are equal, allowing 50%
of the ripple for the bulk capacitance. The capacitance
is given by:
C_OUT
≥
I_LED × 2 × D_MAX
∆V_OUTRIPPLE × f_SW
where I_LED is in amperes, C_OUT is in farads, f_SW is in
hertz, and ∆V_OUTRIPPLE is in volts. The remaining 50%
of allowable ripple is for the ESR of the output capaci-
tor. Based on this, the ESR of the output capacitor is
given by:
ESR _COUT
<
∆V_OUTRIPPLE (Ω)
(IL_P × 2)
where IL_P is the peak inductor current in amperes.
Use the below equation to calculate the RMS current
rating of the output capacitor:
I_COUT(RMS) =
(IL _AVG × (1 - D_MAX ))² × D_MAX
+(IL _AVG × D_MAX )² × (1 - D_MAX )
Input 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 configuration, the input current is the
same as the inductor current. For buck-boost
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