Datasheet AD8240 (Analog Devices) - 9

AD8240
As a result, the constant voltage driving/monitoring method is Constant voltage driving/monitoring is a proven method the lowest cost and least-prone-to-failure method for driving already in use in a number of automotive platforms to drive and monitoring LEDs from a system perspective. This is LED tail, running, and turn-indicator lamps. primarily because the number of wires and connections can be minimized. By using a constant voltage driver and measuring The AD8240 LED lamp driver/monitor is designed for use in the current, an LED lamp can be driven and monitored using the body control or related module. When used this way, it is only two wires (power and ground). In many cases, this can be very similar to the method that has been used to control reduced to one wire when the chassis or shared ground return external incandescent lamps. By utilizing the existing lamp is used. This is a similar architecture used with incandescent driving architecture, additional modules are not required to bulbs, which means no changes to the wiring harness are drive the external lamps, which further minimizes the cost. necessary with this LED implementation. It is possible to retrofit existing lamp driving modules with the AD8240 with minimal engineering time required. Most automotive platforms no longer use a switch on the dashboard to directly control the incandescent lamps. These lamps are now controlled and driven by the body control ECU. By using this constant voltage architecture, the control and drive function for the LEDs can remain in the ECU with minimal design modification. Rev. 0 | Page 9 of 12 Document Outline FEATURES GENERAL DESCRIPTION FUNCTIONAL BLOCK DIAGRAM PRODUCT HIGHLIGHTS SPECIFICATIONS ABSOLUTE MAXIMUM RATINGS PRODUCT DESCRIPTION LINEAR REGULATOR (BLOCK A) HIGH-SIDE CURRENT-SENSE AMPLIFIER WITH OPEN LED DETECTION (B COMPARATOR WITH LATCH-OFF OVERCURRENT PROTECTION (BLOCK C) INTELLIGENT DRIVER (BLOCK D) USING/EVALUATING THE AD8240 LED DRIVER MONITOR SETUP Shunt Resistor Selection Circuit Configuration CONTROLLING THE LED LAMP USING/EVALUATING THE VSENSE OUTPUT Using/Evaluating the Short-Circuit Protection Feature ADVANTAGES OF DRIVING LED LAMPS WITH CONSTANT VOLTAGE BACKGROUND MONITORING THE LEDS DRIVING AUTOMOTIVE LEDS Constant Current Constant Voltage OUTLINE DIMENSIONS ORDERING GUIDE