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For pricing, delivery, and ordering information, please contact Maxim Direct at 1-888-629-4642,

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LED Driver with Integrated MOSFET

for MR16 and Other 12V AC Input Lamps

19-5671; Rev 3; 8/11

General Description

The MAX16840 is an LED driver IC for lighting applica-

tions. It includes all the necessary features to design

low-component-count LED drivers for 12V AC and 24V

AC input (e.g., MR16) light bulbs. A proprietary input-

current control scheme allows LED lamps based on this

device to be compatible with electronic transformers,

and

dimmable with standard trailing-edge dimmers

(where electronic transformers are present).

The IC can be used in buck, boost, and buck-boost

topologies and features. It has an integrated 0.2I (max),

48V switching MOSFET.

The IC uses constant-frequency average current-mode

control. It senses the input current through the voltage

at the FB pin, and regulates its average. An input pin

(REFI) allows the setting of the input-current level. When

the voltage at this pin is set below a certain threshold, the

input current is proportional to this voltage, while when

that voltage is beyond the threshold, the input current is

set at a fixed, predefined level. This nonlinear behavior

of REFI allows its use to achieve thermal foldback, by

connecting it to an NTC resistor.

The IC also features an internal overvoltage protection on

the IN pin to protect the internal switching MOSFET from

damage if the LED string is open or if the voltage on the

LED string is too high.

The IC has a separate EXT pin that can be used to guar-

antee that there is a kick-start of current at turn-on for

low-input voltages for proper operation with electronic

transformers. EXT drives an external npn transistor.

Once the UVLO threshold of 5.5V is crossed on IN, EXT

is pulled to ground and the external npn transistor is

turned off.

The IC is available in a 3mm x 3mm, 10-pin TDFN power

package, and is rated over the -40NC to +125NC operat-

ing temperature range.

Applications

MR16 and Other 12V AC or DC Input LED

Lighting Applications

Features

S

Control_of_the_Average_Input_Current_to_Achieve_

Operation_with_Electronic_Transformers_and_

Dimmability

S

Buck,_Boost,_SEPIC,_and_Buck-Boost_Topologies

S

Integrated_0.2I_(max)_48V_Switching_MOSFET

S

Analog_Dimming_and_Thermal_Foldback

S

Output_Overvoltage_Protection

S

Internal_Overtemperature_Protection

S

-40°C_to_+125°C_Operating_Temperature_Range

S

3mm_x_3mm,_10-Pin_TDFN_Package

Ordering Information

+Denotes a lead(Pb)-free/RoHS-compliant package.

*EP = Exposed pad.

Typical Operating Circuit

EVALUATION

_KIT

AVAILABLE

L1

BD1

C1

C4

R3

L2

D1

C2

LED-

LED+

EXT

COMP

SOURCE

IN

GND

DRAIN

12V AC

REFI

FB

R1

R2

MAX16840

PART

TEMP_RANGE

PIN-PACKAGE

MAX16840ATB+

-40NC to +125NC

10 TDFN-EP*