The MAX16831 features a differential high-side level

shifter to drive an external n-channel MOSFET for dim-

ming. Wide contrast “pulsed” dimming (1000:1) is pos-

sible by applying either a low-frequency PWM input

signal or a DC voltage to the dimming input (DIM).

Protection features include peak current limiting,

HICCUP mode current limiting, output overvoltage pro-

tection, short-circuit protection, and thermal shutdown.

The HICCUP current-limit circuitry reduces the power

delivered to the load during severe fault conditions.

Nonlatching overvoltage protection limits the voltage on

conditions in the LED string. During continuous opera-

tion at high input voltages, the power dissipation of the

MAX16831 could exceed the maximum rating and an

internal thermal shutdown circuitry safely turns off the

MAX16831 when the device junction temperature

exceeds +165°C. When the junction temperature drops

below the hysteresis temperature, the MAX16831 auto-

matically re-initiates startup.

Undervoltage Lockout/Enable

The MAX16831 features a dual-purpose adjustable

through a resistive voltage-divider to set the undervolt-

age lockout (UVLO) threshold. The MAX16831 is

enabled when the UVEN exceeds the 1.244V (typ)

threshold. Drive UVEN to ground to disable the output.

Setting the UVLO Threshold

The MAX16831 features a programmable UVLO thresh-

through a resistive voltage-divider to select a UVLO

threshold (Figure 1). Calculate resistor values as follows:

at the UVLO threshold due to line impedance drops

during power-up and dimming. If the undervoltage set-

ting is very close to the required minimum operating

during dimming, which may cause the MAX16831 to

turn on and off when the dimming signal transitions

large enough to limit the ripple on UVEN to less than

the 100mV (min) UVEN hysteresis so that the device

does not turn off under these circumstances.

Soft-Start

The MAX16831 includes a factory-set 4ms (typ) soft-

start delay that allows the load current to ramp up in a

controlled manner, minimizing output overshoot. Soft-

exceeds the UVLO threshold. Soft-start circuitry slowly

in a controlled rise of the load current. Signals applied

to DIM are ignored until the soft-start duration is com-

plete and a successive delay of 200µs has elapsed.

Internal Regulators

The MAX16831 includes a fixed 5V voltage regulator

REG1, a 7V voltage regulator REG2, and an internal 8V

exceeds the UVLO threshold. REG1 supplies power to

internal circuitry and remains on during PWM dimming.

It is capable of driving external loads up to 2mA.

REG2 is capable of delivering up to 20mA of current.

Connect REG2 to DRI to generate the supply voltage

for the primary switching MOSFET driver, DRV.

CLMP is powered by HI and supplies power to the cur-

rent-sense amplifier (CSA). CSA is enabled when

also provides power to the dimming MOSFET control

circuitry. CLMP is the output of the CLMP regulator. Do

not use CLMP to power external circuitry. Bypass

CLMP to LO with a 0.1µF ceramic capacitor. A larger

capacitor will result in overshoots of the load current.

RR

V

VV

UV

UV

UVEN

UVLO

UVEN

12

=×

⎛

⎝⎜

⎞

⎠⎟

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High-Voltage, High-Power LED Driver with

Analog and PWM Dimming Control

10

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MAX16831

UVEN

QGND

Figure 1. Setting the UVLO Threshold