AD8240
Rev. 0 | Page 9 of 12
As a result, the constant voltage driving/monitoring method is
the lowest cost and least-prone-to-failure method for driving
and monitoring LEDs from a system perspective. This is
primarily because the number of wires and connections can be
minimized. By using a constant voltage driver and measuring
the current, an LED lamp can be driven
and monitored using
only two wires (power and ground). In many cases, this can be
reduced to one wire when the chassis or shared ground return
is used. This is a similar architecture used with incandescent
bulbs, which means no changes to the wiring harness are
necessary with this LED implementation.
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.
Constant voltage driving/monitoring is a proven method
already in use in a number of automotive platforms to drive
LED tail, running, and turn-indicator lamps.
The AD8240 LED lamp driver/monitor is designed for use in
the body control or related module. When used this way, it is
very similar to the method that has been used to control
external incandescent lamps. By utilizing the existing lamp
driving architecture, additional modules are not required to
drive the external lamps, which further minimizes the cost.
It is possible to retrofit existing lamp driving modules with
the AD8240 with minimal engineering time required.
