STLED316S
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Due to the extremely competitive market, today’s consumer
electronics or home appliance producers, are under constant pressure
to reduce costs. ST has recently introduced the STLED316S, an integrated
LED driver to help designers achieve a more efficient and simplified
design for front panels, such as those found on set-top boxes, DVD
players, washing machines, dryers and microwave ovens.
The STLED316 is an integrated LED driver which controls front-panel
activities. A typical front panel consists of a key-pad, an LED
display panel and various discrete LEDs. The device employs a unique
timemultiplexing scheme to drive displays together with key-scans
with a limited number of I/Os.
The combination of display driving and key-scanning allows a single
device like STLED316S
for the complete front panel solution eliminating the use of sub-CPU
and other logics plus discrete devices, reducing BOM count and lowering
the final cost.
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Common anode LED driver
Drives 56 outputs (7 grids and 8 segments)
Drive capability of up to 40 mA per output
Capable of driving red, green and blue LEDs
Maximum segment current for the display can be set through one external
resistor
Continuous key-scanning up to 16 keys
3-wire serial SPI interface to MCU
8-step dimming capability for each digit
Drives additional 8 LEDs with dimming control
Available in pin-count optimized SO-24 package
STLED316S application diagram
Interrupt output to main CPU upon key-press does not need the CPU
to poll the device continuously
Low power consumption during standby
Flexibility means that devices can be connected in parallel when
more digits/segments are needed
Minimizes the peripheral component count
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The current solutions implemented by most customers consist of two
main architectures:
Shift register logic device with a main MCU
Sub-CPU and darlington current array
There are certain drawbacks to these solutions. The precious I/Os
of the MCU need to be used for key-scan and for driving interfaces.
These methods increase the BOM cost and also complicate the PCB
routing. In home appliances where a main board is far from the front
panel, the cost of the cable for wiring increases reliability risk
and cost.
STLED316S block diagram
This device can be used in a variety of applications where a front
panel interface is present with LED display and key-scanning. The
applications range from white goods such as washers, dryers, microwave
ovens, refrigerators to consumer devices like DVD players and set-top
boxes to gaming machines and even industrial equipment and instrumentation. |
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