MAX16805_07 Datasheet, PDF (11/19 Pages) Maxim Integrated Products – EEPROM-Programmable, High-Voltage, 350mA LED Drivers with LED Current Foldback

EEPROM-Programmable, High-Voltage, 350mA
LED Drivers with LED Current Foldback
The dimming feature can be used for LED brightness
adjustment (see the Typical Operating Circuits) and
theater dimming. If the external PWM signal is used,
theater dimming can be achieved by varying the PWM
duty cycle. Figure 2 shows a simple circuit that imple-
ments theater dimming with a DC input signal.
Thermal Sensor Inputs/I²C Interface
(TFP/SCL and TFN/SDA)
The MAX16806 features dual-function inputs, TFP/SCL
and TFN/SDA. In programming mode, TFP/SCL and
TFN/SDA serve as the I²C serial communication inter-
face. TFP/SCL and TFN/SDA also serve as inputs for
analog signals generated by an external temperature
sensor such as the MAX6613. When the thermal sensor
is not used, connect TFP/SCL and TFN/SDA through
50kΩ resistors to V5 and GND, respectively.
The MAX16805 does not offer dual-function inputs. SCL
and SDA are used only to communicate with the
MAX16805 through the I²C interface.
Momentary Switch Interface (SW)
The MAX16806 offers a momentary switch (SW) that
overrides the analog dimming signal by latching the
output current to 100% duty cycle. The MAX16806
does not override external PWM signal at DIM or dim-
ming caused by thermal or LED current foldback. To
latch the output current into a 100% duty cycle, press
SW once. To restore the initial duty cycle determined
by the DC level at DIM, press SW again. The
MAX16806 provides a minimum of 1mA of wetting cur-
rent to the momentary switch.
Overtemperature Protection
The MAX16805/MAX16806 enter a thermal shutdown in
the event of overheating. This typically occurs in over-
load or output short-circuit conditions. When the junc-
tion temperature exceeds T_J = +155°C (typ), the
internal thermal protection circuitry turns off the pass
device. The MAX16805/MAX16806 recover from ther-
mal shutdown once the junction temperature drops by
+23°C (typ). This feature allows self-protection by ther-
mally cycling in the event of a short-circuit or overload
condition.
Digital Interface
The MAX16805/MAX16806 feature an I²C, 2-wire serial
interface consisting of a bidirectional serial data line
(SDA) and a serial clock line (SCL). SDA and SCL facili-
tate bidirectional communication between the
MAX16805/MAX16806 and the master device at rates
V_IN
THEATER
DIMMING
SIGNAL
IN
OUT
+5V REG
EN
V5
LEDs
MAX16805
0.1μF
MAX16806
CS+
DIM
CS-
GND
RSENSE
Figure 2. Theater Dimming Light
SDA
SCL
S
P
START
CONDITION
STOP
CONDITION
Figure 3. I²C Communication Start and Stop Conditions
up to 400kHz. The master (typically a microcontroller)
initiates data transfer on the bus and generates SCL.
Start and Stop Conditions
Both SCL and SDA remain high when the interface is
not busy. A master controller signals the beginning of a
transmission with a START condition by transitioning
SDA from high to low while SCL is high. The master
controller issues a STOP condition by transitioning the
SDA from low to high while SCL is high, when it finishes
communicating with the slave. The bus is then free for
another transmission (Figure 3).
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