MAX16806 데이터 시트보기 (PDF) - Maxim Integrated

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MAX16806

EEPROM-Programmable, High-Voltage, 350mA LED Drivers with LED Current Foldback

Maxim Integrated 

MAX16805/MAX16806

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 the-

ater 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 implements 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 interface.

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 out-

put current to 100% duty cycle. The MAX16806 does not

override external PWM signal at DIM or dimming 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 current 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 junction

temperature exceeds TJ = +155°C (typ), the internal

thermal protection circuitry turns off the pass device. The

MAX16805/MAX16806 recover from thermal shutdown

once the junction temperature drops by +23°C (typ). This

feature allows self-protection by thermally 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 up to 400kHz.

VIN

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

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 trans-

mission 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 transmis-

sion (Figure 3).

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