MAX16803_09 Datasheet, PDF (8/11 Pages) Maxim Integrated Products – High-Voltage, 350mA, High-Brightness LED Driver with PWM Dimming and 5V Regulator

High-Voltage, 350mA, High-Brightness LED
Driver with PWM Dimming and 5V Regulator
Two Brightness Levels for
TAIL/STOP Lights
Figure 4 shows PWM dimming operation for the
MAX16803 with an ICM7555 timer. The ICM7555 pro-
vides adjustable duty cycle using two external resistors
and a capacitor. In TAIL operation, the output of the
ICM7555 feeds into DIM and lights up the LEDs. The
LED’s brightness depends on the duty cycle of the
ICM7555. When V_STOP is present, DIM is pulled up to
V_STOP. The PWM dimming operation is disabled and
the LEDs light up to full brightness. See the ICM7555
data sheet for formulas to calculate the dimming fre-
quency and the duty cycle.
D1
STOP
D2
TAIL
R1
R2
C1
D3
IN
D4
DIS
OUT
ICM7555
R3
TH
TRG
GND
C3
LED Current Thermal Foldback
With a minimum number of external components, the
MAX16803 provides LED current thermal foldback
using a negative temperature coefficient (NTC) thermis-
tor. Figure 5 shows a thermistor connected to V5 and
the CS+ of the MAX16803. As the temperature increas-
es, the voltage drop across R2 increases causing the
LED current to decrease.
I_LED = [V_SENSE - [R2 / (R2 + RT)] x V5] / R1
IN
OUT
EN _MAX16803
+5V REG
V5
LEDs
C2
DIM
CS+
R_SENSE
GND
CS-
Figure 4. PWM Dimming Operation with ICM7555 Timer
VIN
C1
PWM DIMMING
IN
OUT
EN
V5
MAX16803
DIM
CS+
GND
CS-
LEDs
C2
RT
R2
R1
Figure 5. LED Current Thermal Foldback with an NTC Thermistor
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