MAX16832AASASLASHV datasheet(7/10 Pages) MAXIM

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Undervoltage Lockout (UVLO)

The MAX16832A/MAX16832C include a UVLO with

500mV hysteresis. The internal MOSFET turns off when

VIN falls below 5.5V to 6.0V.

DIM Input

LED dimming is achieved by applying a PWM signal at

DIM. A logic level below 0.6V at DIM forces the

MAX16832A/MAX16832Cs’ output low, thus turning off

the LED current. To turn the LED current on, the logic

level at DIM must be greater than 2.8V.

Thermal Shutdown

The MAX16832A/MAX16832C thermal-shutdown feature

turns off the LX driver when the junction temperature

exceeds +165°C. The LX driver turns back on when the

junction temperature drops 10°C below the shutdown

temperature threshold.

Analog Dimming

The MAX16832A/MAX16832C offer an analog-dimming

feature that reduces the output current when the volt-

age at TEMP_I is below the internal 2V threshold volt-

age. The MAX16832A/MAX16832C achieve analog

dimming by either an external DC voltage source con-

nected between TEMP_I and ground or by a voltage on

a resistor connected across TEMP_I and ground

induced by an internal current source of 25µA. When

the voltage at TEMP_I is below the internal 2V threshold

limit, the MAX16832A/MAX16832C reduce the LED cur-

rent. Use the following formula to set the analog dim-

ming current:

where VTFB_ON = 2V and FBSLOPE = 0.75 are obtained

from the

Electrical Characteristics table and VAD is the

voltage at TEMP_I.

Thermal Foldback

The MAX16832A/MAX16832C include a thermal-fold-

back feature that reduces the output current when the

temperature of the LED string exceeds a specified tem-

perature point. These devices enter thermal-foldback

mode when the voltage drop on the NTC thermistor,

thermally attached to the LEDs and electrically con-

nected between TEMP_I and ground, drops below the

internal 2V threshold limit.

Applications Information

Selecting RSENSE to Set LED Current

The LED current is programmed with a current-sense

resistor connected between IN and CS. Use the follow-

ing equation to calculate the value of this resistor:

where VSNSHI is the sense voltage threshold high and

VSNSLO is the sense voltage threshold low (see the

Electrical Characteristics table for values).

Current-Regulator Operation

The MAX16832A/MAX16832C regulate the LED current

using a comparator with hysteresis (see Figure 2). As

the current through the inductor ramps up and the volt-

age across the sense resistor reaches the upper

threshold, the internal MOSFET turns off. The internal

MOSFET turns on again when the inductor current

ramps down through the freewheeling diode until the

voltage across the sense resistor equals the lower

threshold. Use the following equation to determine the

operating frequency:

where n is the number of LEDs, VLED is the forward

voltage drop of 1 LED, and

∆V = (VSNSHI - VSNSLO).

Inductor Selection

The MAX16832A/MAX16832C operate up to a switch-

ing frequency of 2MHz. For space-sensitive applica-

tions, the high switching frequency allows the size of

the inductor to be reduced. Use the following formula to

calculate an approximate inductor value and use the

closest standard value:

For component selection, use the MAX16832A/C Design

Tool available at: www.maxim-ic.com/MAX16832-

software.

L approx

VnV

VV f

LED

SENSE

(.)

()

××

−

∆

VnV

VV L

LED

SENSE

××

−

()

∆

SENSE

SNSHI

SNSLO

LED

()

()( )

()

Ω=

LED

SLOPE

TFB ON

()

( )

=×

⎛

⎝⎜

⎞

⎠⎟

()

⎡

⎣

⎢

⎤

⎦

⎥

−−

2MHz, High-Brightness LED Drivers with

Integrated MOSFET and High-Side Current Sense

MAX16832AASA/V Datasheet(PDF) 7 Page - Maxim Integrated Products

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