MAX16805 Datasheet, PDF(10/19 Page) Maxim Integrated Products – EEPROM-Programmable, High-Voltage, 350mA LED Drivers with LED Current Foldback

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MAX16805 Datasheet, PDF (10/19 Pages) Maxim Integrated Products – EEPROM-Programmable, High-Voltage, 350mA LED Drivers with LED Current Foldback

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EEPROM-Programmable, High-Voltage, 350mA

LED Drivers with LED Current Foldback

SDA

tBUF

SCL

STOP

START

tLOW

tHD:STA

tHD:DAT

tHIGH

tSU:DAT

tSU:STA

REPEATED

START

tSP

tSU:STO

Figure 1. I2C Serial Interface Timing Diagram

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

MAX16805/MAX16806 feature the I2C interface that

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

I2C interface. See Table 2 for register addresses. Turning

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 âwriteâ command to

the EEPROM Content Transfer register.

The MAX16805/MAX16806âs 5V regulator (V5) provides

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

MAX16806âs 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

Diagram. The MAX16805/MAX16806 offer a program-

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/MAX16806âs 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-

ed through the I2C interface from 50% (typ) to 100% in

real time when VDIM is 1.54V.

The output current duty cycle is adjustable from 0% to

100% (0.21V < VDIM < 3.1V).

Use the following formula to calculate the output cur-

rent duty cycle:

Duty cycle = (VDIM - 0.21V) / VRAMP

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