Thermally enhanced Low VFB Step-Down LED Driver
APPLICATION INFORMATION (continued)
ADT6780
Thermal Management
The ADT6780 contains an internal thermal sensor that limits the total power dissipation in the device and
protects it in the event of an extended thermal fault condition. When the die temperature exceeds +145°C
typically, the thermal sensor shuts down the device, turning off the DC-DC converter to allow the die to
cool. After the die temperature falls by 10°C typically, the device automatically restarts, using the soft-start
sequence.
The ADT6780 is available in a thermally enhanced SOP package and can dissipate up to 1.25W at Ta=50°C
(TJ=125°C). The exposed pad should be connected to GND externally, preferably soldered to a large ground
plane to maximize thermal performance. Maximum available power dissipation should be de-rated by
17mW/℃ above Ta=25℃ not to damage the device.
PCB Layout Consideration
PCB layout is very important to achieve clean and stable operation. It is highly recommended to follow
below guidelines for good PCB layout.
1. Input capacitor (C1) should be placed as near as possible to the IC and connected with direct traces.
2. Keep the high current paths as short and wide as possible.
3. Keep the switching current path short and minimize the loop area, formed by SW, the output capacitors
and the input capacitors.
4. Route high-speed switching nodes (such as SW and BST) away from sensitive analog areas (such as FB
and COMP).
5. Ensure all feedback connections are short and direct. Place the current sense resistor and compensation
components as close as possible to the IC.
6. Exposed pad of device must be connected to GND with solder. For single layer, do not solder exposed
pad of the IC.
* This specifications are subject to be changed without notice
http://www.ad-tech.co.kr
Jul. 12. 2012 / Preliminary
12/13
ADTECH [ ADTECH ]
