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AD8240:  LED Driver/Monitor

Product Details


The AD8240 LED driver/monitor, in combination with an external transistor, supplies a constant 12 V to drive LED lamps. This allows cost-effective LED lamp monitoring and short-circuit protection. The output is regulated at 12 V when the supply voltage is between 12.5 V and 27 V.

A CMOS compatible, level-dependent, digital input can be used for PWM control of the LED brightness. VO is turned on when the PWM input is high and turned off when the input is low. The AD8240 is designed to work with a PWM frequency up to 500 Hz, and a typical PWM range from 5% to 95%.

Open LED detection is accomplished by measuring the change in LED lamp current caused by an open LED(s) through the use of an internal high-side current-sense amplifier that amplifies the voltage across an external current shunt. The voltage across the shunt resistor is amplified to a level that can be measured by a microcontroller A/D converter or a comparator. The ability to measure the change in LED lamp current is the key benefit of constant-voltage LED lamp driving.

The output is current-limited by latching off the output voltage when the current reaches a preset level. The current limit is set by selecting the value of the external current shunt that causes the output of the sense amplifier to slightly exceed the 5 V reference level when the current exceeds a maximum level. When the sense amplifier output exceeds 5 V, it trips an internal comparator that causes the driver to latch off the output voltage. The latch is reset during the next PWM cycle. The overcurrent condition can also be detected by a microcontroller or external comparator by measuring the sense amplifier output.

FEATURES and BENEFITS

  • PWM input for LED Brightness Control
  • Open LED Detection
  • Latch-off Overcurrent Protection
  • Constant Voltage Regulated Output
  • Regulated Voltage Range: 12.5V to 27V
  • Supply range: 9V to 27 V
  • Operating current: 300 µA
  • Shutdown current: 10 µA
  • Temperature range -40°C to +125°C
  • 8-lead MSOP package

Functional Block Diagram for AD8240

Documentation

Title Content Type File Type
AD8240:  LED Driver/Monitor Data Sheet (Rev. 0, 4/2004) (Rev 0, 04/2004) (pdf, 217 kB) Data Sheets PDF
AN-669: Effectively Applying the AD628 Precision Gain Block  (pdf, 193 kB) Application Notes PDF
A Designer's Guide to Instrumentation Amplifiers (3rd Edition) Design Handbooks HTML
Auto-Zero Amplifiers  (doc, 75 kB)
A wide variety of electronic applications, especially those involving very small input signals, require signal paths with very low offset voltage and offset voltage drift over time and temperature.
Technical Articles DOC
Current Measurement in Solenoids for Automotive Control Systems  (pdf)
by Scott Beversdorf and Charles Whiting, Analog Devices, Inc. (Analog Dialogue 38-04, April 2004)
Technical Articles PDF
High-performance Adder Uses Instrumentation Amplifiers
Make an adder circuit using instrumentation amplifiers to increase input impedance.
(EDN, 9/3/2009)
Technical Articles HTML
Innovative Power Reduction Techniques Enable Handset Manufacturers to Provide Media Rich Devices
The demand for mobile devices with high-end features has been rapidly increasing. Features like text messaging, gaming, GPS navigation, web browsing and video playback on high resolution color displays are becoming the norm in today’s portable consumer electronics market.
(LED Journal, August/September 2009)
Technical Articles HTML
Applying Instrumentation Amplifiers Effectively: The Importance of an Input Ground Return  (pdf, 508 kB) Technical Documentation PDF
Leading Inside Advertorials: Applying Instrumentation Amplifiers Effectively–The Importance of an Input Ground Return  (pdf, 121 kB) Overview PDF
Power System Management (Spring 2007)  (pdf, 1170 kB) Overview PDF
RAQs index Rarely Asked Questions HTML
Glossary of EE Terms Glossary HTML

Evaluation Kits & Symbols & Footprints

Symbols and Footprints— Analog Devices offers Symbols & Footprints which are compatible with a large set of today’s CAD systems for broader and easier support.

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Price, packaging, availability

AD8240 Model Options
Model Package Pins Temp.
Range
Packing,
Qty
Price*(100-499) Price*1000 pcs RoHS View PCN/ PDN Check Inventory/
Purchase/Sample
AD8240YRMZ Status: Production 8 ld MSOP 8 Ind Tube, 50 $1.38 $1.29 Y  Material Info PCN Purchase
AD8240YRMZ-R7 Status: Production 8 ld MSOP 8 Ind Reel, 1000 - $1.29 Y  Material Info PCN Purchase
AD8240YRMZ-RL Status: Production 8 ld MSOP 8 Ind Reel, 3000 - $1.29 Y  Material Info PCN Purchase
Price Table Help

The USA list pricing shown is for BUDGETARY USE ONLY, shown in United States dollars (FOB USA per unit for the stated volume), and is subject to change. International prices may differ due to local duties, taxes, fees and exchange rates. For volume-specific price or delivery quotes, please contact your local Analog Devices, Inc. sales office or authorized distributor. Pricing displayed for Evaluation Boards and Kits is based on 1-piece pricing.


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