Application information

STLA01

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6

Application information

The STLA01 is a single LED driver using a constant-current topology. It can deliver up to 80

mA of output current.

If a 1% program resistor is connect from the PROG pin to the GND pin and the EN pin is

higher than 0.92 V, the device will supply the LED with the programmed constant current.

Putting the EN pin below 0.80 V results in no current flow into the LED diode.

6.1

6.2

EN pin

The enable input pin is used to shut down the device when the value of the pin is below

0.80 V. In shutdown condition, the device has less than 10 µA supply current. The enable pin

6.3

Programming charge current

The LED current is programmed using a single resistor from the PROG pin to ground. The

LED current is 100 times the current out of the PROG pin. The program resistor and the led

current are calculated using, in first approximation, the following equations:

6.4

Power dissipation

A good thermal PCB layout is very important to maximize the available output current. The

thermal path for the heat generated by the IC is from the die to the copper lead frame

through the package leads and exposed pad to the PC board copper. The PC board copper

acts as the heat sink. The copper pad footprints should be as wide as possible and expand

to larger copper areas in order to spread and dissipate the heat to the surrounding ambient.

Feed-through vias to inner or backside copper layers are also useful in improving the overall

thermal performance of the device. Other heat sources on the board, not related to the

device, must also be considered when designing a PC board layout because they will affect

overall temperature rise and the maximum output current.