STLED316S functional description

STLED316S

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STLED316S functional description

The STLED316S is a common-anode LED driver controller which can be used to drive red,

green or blue LEDs as the current is adjustable through the external resistor. In the common

anode configuration, the segment outputs sink the current from the cathodes while the digit

outputs source the current to the anodes. The configurable output current can be used to

drive LEDs with different current ratings (red, green or blue). The brightness of the whole

display can be controlled through the serial interface as described later. The outputs can be

connected together in parallel to drive a single LED. In this case, two parallel current

sources of equal value drive a single LED. The external resistor value can be set accordingly

to determine the desired output current thus controlling the display brightness.

Soft-start limits the inrush current during power-up. The display is blanked (LEDs are turned

off or in high-Z state) on power-up.

3.1

Low power mode of operation

Upon initial power up or when not configured or when not used, the STLED316S will be in

low power mode of operation wherein the current consumption drops to less than 1mA.

During this mode, the data configured is maintained as long as the supply voltage is still

present (the contents of the internal RAM need the supply voltage to be present). Port

configuration and output levels are restored when the STLED316S resumes normal

operation. For minimum supply current in shutdown mode, logic inputs should be at GND or

3.2

Serial interface

The interface is used to write configuration and display data to the STLED316S. The serial

interface comprises of a shift register into which DIN is clocked on the rising edge of the

CLK when STB is low. When STB is low, falling transitions on CLK clock the data from the

device to the microcontroller. The 8-bit data is decoded to determine and execute the

command.

STB indicates to the device the start of communication when it goes low. DIN/DOUT pin is

bi-directional. The data will be validated during positive pulse of the clock in both write/read

modes. If the STB signal goes high before completing the data byte write to the device, the

preceding data bits are ignored and the previous configuration remains intact.

3.3

Initial power up

On initial power-up, all control registers are reset, the display is blanked and the

STLED316S is in the low power mode. All the outputs are in high-impedance state at initial

power-up. The DIN/DOUT is pulled high by an external pull-up resistor. The display driver

has to be configured before the display can be used.