Overview
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
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.
Product Categories
Product Lifecycle
Last Time Buy
All products in this family will be obsolete soon. Please contact ADI Sales or Distributors to arrange for final purchases and read our Obsolescence Information to review the time periods for placing final orders and receiving final shipments.
Documentation & Resources
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Auto-Zero Amplifiers3/1/2010
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Automobile Tail Lamp and Brake Lamp Controller12/1/2009 Analog Dialogue
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High-performance Adder Uses Instrumentation Amplifiers9/3/2009
Design Resources
ADI has always placed the highest emphasis on delivering products that meet the maximum levels of quality and reliability. We achieve this by incorporating quality and reliability checks in every scope of product and process design, and in the manufacturing process as well. "Zero defects" for shipped products is always our goal.View our quality and reliability program and certifications for more information.
| Part Number | Material Declaration | Reliability Data | Pin/Package Drawing | CAD Symbols, Footprints & 3D Models |
|---|---|---|---|---|
| AD8240YRMZ | Material Declaration | Reliability Data | 8-Lead MSOP | |
| AD8240YRMZ-R7 | Material Declaration | Reliability Data | 8-Lead MSOP | |
| AD8240YRMZ-RL | Material Declaration | Reliability Data | 8-Lead MSOP | |
| Wafer Fabrication Data |
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