EEPROM-Programmable, High-Voltage, 350mA

LED Drivers with LED Current Foldback

10

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SDA

SCL

REPEATED

START

STOP

START

P

Detailed Description

The MAX16805/MAX16806 are constant-current regu-

lators that provide up to 350mA of current to one or

more strings of high-brightness LEDs. A wide operat-

ing input voltage range of 5.5V to 40V makes the

devices ideal for automotive applications. The

allows communication with the internal dynamic regis-

ters and EEPROM.

Dynamic registers control the MAX16805/MAX16806

functions and can be updated in real time through the

off the input voltage clears the dynamic register contents.

To save settings, store them into the EEPROM. The

MAX16805/MAX16806 load the stored settings into the

dynamic registers at power-up. In addition, during nor-

mal operation a write command to the EEPROM Content

Transfer register loads the stored settings into the

dynamic register. Information stored can be transferred

into dynamic registers after issuing a “write” command to

the EEPROM Content Transfer register.

The MAX16805/MAX16806’s 5V regulator (V5) provides

up to 2mA of current to external circuitry. However, the

MAX16806’s 5V regulator can deliver 2mA of output cur-

rent only when the momentary switch is not used. When

the momentary switch is active, the MAX16806 achieves

up

to

0.5mA

of

current.

In

addition,

the

MAX16805/MAX16806 feature thermal and output short-

circuit protection. The wide operating voltage range

helps protect the device against large transients up to

45V such as those found in load dump situations.

The MAX16805/MAX16806 use a feedback loop to

control the output current. The differential voltage

across the sense resistor is compared to a fixed refer-

ence voltage and the error is amplified to serve as the

drive to the internal pass device, see the

Functional

mable LED current reference using the Binning

Adjustment register.

These devices are current controllers internally opti-

mized for driving the impedance range expected from

1 to 10 (or more) high-brightness LEDs.

Dimming Input (DIM)

The MAX16805/MAX16806’s dimming input operates

with either an analog or PWM control signal. If the

pulse detector detects three edges of a PWM signal

with a frequency range between 80Hz to 2kHz, the

MAX16805/MAX16806 synchronize to external PWM

input signal and pulse-width-modulate the LED current.

If an analog control signal is applied to DIM, the

MAX16805/MAX16806 compare the DC input to an

internally generated 200Hz ramp to pulse-width-modu-

late the LED current. The maximum peak value of the

200Hz ramp can be programmed using the Ramp

Peak register. This allows the LED current to be adjust-

The output current duty cycle is adjustable from 0% to

Use the following formula to calculate the output cur-

rent duty cycle: