MAX16804 Datasheet, PDF (8/11 Pages) Maxim Integrated Products – High-Voltage, 350mA LED Driver with Analog and PWM Dimming Control

High-Voltage, 350mA LED Driver with
Analog and PWM Dimming Control
LED Current Thermal Foldback
With a minimum number of external components, the
MAX16804 provides LED current thermal foldback
using a negative temperature coefficient (NTC) thermis-
tor. Figure 3 shows a thermistor connected to V5 and
the CS+ of the MAX16804. 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
(4)
Other Applications
Figure 4 shows an application circuit with the
MAX16804 using a single BJT to provide high output
current. For proper operation:
V_IN(MIN) > V_CESAT(MAX) + V_FT(MAX) + V_{RSENSE (5)}
where V_CESAT(MAX) is the maximum saturation voltage
of the external BJT.
VIN
IN
OUT
C1
EN
V5
PWM DIMMING
MAX16804
DIM
CS+
GND
CS-
LEDs
C2
RT
R2
R1
Figure 3. LED Current Thermal Foldback Operation with an NTC Thermistor
LEDs
VIN
IN
OUT
C1
EN
V5
C2
MAX16804
PWM DIMMING
DIM
CS+
GND
CS-
Figure 4. Increased Output Current (Amper Range) with a Single BJT
Q1
R_SENSE
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