Datasheet

MAX16804
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.
High-Voltage, 350mA LED Driver with
Analog and PWM Dimming Control
8 _______________________________________________________________________________________
IN
EN
DIM
CS-
CS+
OUT
GND
R1
LEDs
V
IN
V5
R2
RT
PWM DIMMING
MAX16804
C2
C1
Figure 3. LED Current Thermal Foldback Operation with an NTC Thermistor
IN
EN
DIM
CS-
CS+
OUT
GND
R
SENSE
LEDs
Q1
V
IN
V5
PWM DIMMING
MAX16804
C2
C1
Figure 4. Increased Output Current (Ampere Range) with a Single BJT