STLED316S_08 Datasheet, PDF (12/33 Pages) STMicroelectronics – Serial-interfaced 6-digit LED controller with keyscan

STLED316S functional description
STLED316S
3.8
LED drivers
The constant current capability is up to 40 mA per output segment and is set for all the
outputs using a single external resistor. When acting as digit drivers, the outputs source
current to the display anodes. When acting as segment drivers, the LED outputs sink current
from the display cathodes. The outputs are high impedance when not being used as digit or
segment drivers.
Each port configured as a LED digit driver behaves as a digitally-controlled constant current
sink. The LED drivers are suitable for both discrete LEDs and common anode (CA) numeric
LED digits. When fully configured as a LED driver, the STLED316S controls up to 8 LED
segments in a single digit with 8-step logarithmic brightness control for the digits. A single
resistor sets the maximum segment current for all the segments, with a maximum of 40mA
per segment. The STLED316S drives any combination of discrete LEDs and CA digits for
numeric displays.
The recommended value of R_SET is the minimum allowed value, since it sets the display
driver to the maximum allowed segment current. R_SET can be a higher value to set the
segment current to a lower maximum value where desired. The user must also ensure that
the maximum current specifications of the LEDs connected to the drivers are not exceeded.
The brightness of the individual digits in the display panel can be controlled separately.
3.9
Interrupt
The device includes an active low level IRQ_N pin to the microprocessor. The STLED316S
generates an interrupt when a key is pressed.
3.10
Operating the device with 3.3 V interface voltages
The device can detect the input voltage levels reference to 3.3 V from the main controller
chip as long as the V_IL and V_IH specifications of the STLED316S are met. If the input
voltage to STLED316S is greater than 2.9 V, the STLED316S will recognize the signal level
as a valid high and if the input voltage is lower than 1.75 V, it will be recognized as a valid
low level.
For the output signals from the device like DOUT and IRQ_N, the signal level depends on
the external supply to which the external pull up resistor is connected to. Thus this
eliminates the use of any level shifter between the main controller and the STLED316S.
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