A8180
AiT Semiconductor Inc.
www.ait-ic.com
LED LIGHTING DRIVER
HIGH BRIGHTNESS LED DRIVER WITH INTERNAL SWITCH
Thermal Shutdown Protection
To ensure the reliability, the A8180 is built with a thermal shutdown (TSD) protection function. The TSD
protests the IC from over temperature (160℃). When the chip temperature decreases (140℃), the IC
recovers again.
Layout Considerations
Careful PCB layout is critical to achieve low switching losses and stable operation. Use a multilayer board
whenever possible for better noise immunity. Minimize ground noise by connecting high-current ground
returns, the input bypass-capacitor ground lead, and the output-filter ground lead to a single point (star ground
configuration).
LX Pin
The LX pin of the device is a fast switching node, so PCB tracks should be kept as short as possible. To
minimize ground 'bounce', the ground pin of the device should be soldered directly to the ground plane.
Coil and Decoupling Capacitors and Current Sense Resistor
It is particularly important to mount the coil and the input decoupling capacitor as close to the device pins as
possible to minimize parasitic resistance and inductance, which will degrade efficiency. It is also important to
minimize any track resistance in series with current sense resistor RS. It’s best to connect VIN directly to one
end of RS and ISENSE directly to the opposite end of RS with no other currents flowing in these tracks. It is
important that the cathode current of the Schottky diode does not flow in a track between RS and VIN as this
may give an apparent higher measure of current than is actually because of track resistance.
ADJ Pin
The ADJ pin is a high impedance input, so when left floating, PCB traces to this pin should be as short as
possible to reduce noise pickup. ADJ pin can also be connected to a voltage between 1.2V~5V. In this case,
the internal circuit will clamp the output current at the value which is set by ADJ=1.2V.
High Voltage Traces
Avoid running any high voltage traces close to the ADJ pin, to reduce the risk of leakage due to board
contamination. Any such leakage may raise the ADJ pin voltage and cause excessive output current. A
ground ring placed around the ADJ pin will minimize changes in output current under these conditions.
REV3.0
- APR 2010 RELEASED, JAN 2017 UPDATED -
- 17 -
AITSEMI [ AiT Semiconductor ]
