MAX16816 Datasheet, PDF(15/33 Page) Maxim Integrated Products – Programmable Switch-Mode LED Driver with Analog-Controlled PWM Dimming

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MAX16816 Datasheet, PDF (15/33 Pages) Maxim Integrated Products – Programmable Switch-Mode LED Driver with Analog-Controlled PWM Dimming

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Programmable Switch-Mode LED Driver

with Analog-Controlled PWM Dimming

Detailed Description

The MAX16816 is a current-mode PWM LED driver for

use in driving HB LEDs. An output current accuracy of

5% is achievable using two current regulation loops:

one current regulation loop controls the external switch-

ing MOSFET peak current through a sense resistor,

RSENSE, from SNS+ to SNS- while the other current reg-

ulation loop controls the average LED string current

through the sense resistor, RCS, in series with the

LEDs. The wide operating supply range of 5.9V/5.4V

(ON/OFF) to 76V makes the MAX16816 ideal in auto-

motive applications.

The MAX16816 provides LED binning through one pro-

grammable on-chip nonvolatile EEPROM. The LED cur-

rent can be scaled up to a factor of 1.6. This feature is

used to offset factory LED luminance variations and

allows the system to achieve overall luminance accuracy.

A programmable undervoltage lockout (UVEN) ensures

predictable operation during brownout conditions. The

UVEN input circuitry monitors the supply voltage, VCC,

and turns the driver off when VCC drops below the

UVLO threshold. Connect UVEN to VCC to use the 5.7V

(typ) default UVLO threshold. The MAX16816 includes

a cycle-by-cycle current limit that turns off the gate

drive to the external switching MOSFET (QS) during an

overcurrent condition and a programmable oscillator

that simplifies and optimizes the design of external

magnetics.

The MAX16816 is capable of synchronizing to an

external clock or operating in a stand-alone mode. A

single resistor, RT, can be used to adjust the switching

frequency from 125kHz to 500kHz for stand-alone

operation. To synchronize the device with an external

clock, apply a clock signal directly to the RTSYNC

input. A buffered clock output, CLKOUT, is available to

configure the MAX16816 for multichannel applications.

The external RT oscillator can be disabled by setting

EEPROM register RTOF to â1â.

The MAX16816 provides wide contrast pulsed dimming

(up to 1000:1) utilizing a separate dimming input. Apply

either a DC level voltage or low-frequency PWM signal

to the dimming input. DC level input results in a 200Hz

fixed dimming frequency.

The MAX16816 provides configurable on-chip non-

volatile EEPROM features including a programmable

soft-start, load current, external MOSFET gate-driver

supply voltage, blanking time, and slope compensation.

Protection features include peak current limiting, HICCUP

mode current limiting, output overvoltage protection,

short-circuit protection, and thermal shutdown. The

HICCUP current-limit circuitry reduces the power deliv-

ered to the load during severe fault conditions. A non-

latching overvoltage protection limits the voltage on the

external switching MOSFET (QS) under open-circuit

conditions in the LED string. During continuous opera-

tion at high input voltages, the power dissipation of the

MAX16816 could exceed the maximum rating and the

internal thermal shutdown circuitry safely turns off the

MAX16816 when the device junction temperature

exceeds +165Â°C. When the junction temperature drops

below the hysteresis temperature, the MAX16816 auto-

matically reinitiates startup.

Undervoltage Lockout/Enable (UVEN)

The MAX16816 features a dual-purpose adjustable

undervoltage lockout input and enable function

(UVEN). Connect UVEN to VCC through a resistive volt-

age-divider to set the undervoltage lockout (UVLO)

threshold. The device is enabled when the voltage at

UVEN exceeds the 1.244V (typ) threshold. Drive UVEN

to ground to disable the output.

Setting the UVLO Threshold

Connect UVEN directly to VCC to select the default 5.7V

(typ) UVLO threshold. Connect UVEN to VCC through a

resistive voltage-divider to select a UVLO threshold

(Figure 1). Select the desired UVLO threshold voltage,

VUVLO, and calculate resistor values using the following

equation:

R UV1

R UV2

ââ

VUVEN

VUVLO - VUVEN

â â

UVEN threshold voltage.

VIN

RUV2

CUVEN

RUV1

VCC

UVEN

MAX16816

QGND

Figure 1. Setting the UVLO Threshold

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