SCT2027 V01_03; Jun/13
16-bit Constant-Current LED Driver with ModelessTM Error Detection
The SCT2027 is a serial interfaced 16 bit constant current sinker with error detection designed for LED
displays and LED lighting applications. In applications, an external resistor is used to adjust the full scale
output current from 5mA up to 90mA. The serial data are shifted into 16 bit shift register by clock signal.
Input data appear at the SDO output 16 clock cycles later to allow cascading of multiple SCT2027s. The
latch enable input, LA/, loads the 16 bits data of shift register into a 16 bit latch to determine which LEDs
are on and off. The output enable input, OE/ gates all 16 outputs on and off, and is fast enough to be
used as PWM input for the LED intensity control.
The SCT2027 combines the SCT2024/6 with ModelessTM technique to detect open load and
shorted load errors while driving the LEDs without mode switching*. With the pin to pin compatible
design, all the LED display or lighting systems can be upgraded to perform the on the fly error detection
functions simply by replacing all the SCT2024/6s with SCT2027s directly. Also, by the ModelessTM
technique, the software and hardware works well without reworks between systems of the SCT2024/6
During operations, the SCT2027 takes only 200ns to generate error status codes after the rising edge of
LA/. The error status codes saved in the shift register can be shifted out via SDO bit by bit along with
CLK, at the same time the new serial data can be shifted into SCT2027 via SDI. By comparing the
display data with error status codes, the system control unit can read the error status to determine
whether or not the LEDs are properly lit. If the input display signals are inconsistent with the
corresponding output status code, the corresponding LEDs are determined to have been stuck open or
Since the high clock frequency can reach up to 25MHz, the SCT2027 satisfies the system requirements
of high volume data transmission to control the LED display. The SCT2027 also guarantees each output
endures up to 7V voltage stress, thus each output can drive multiple LEDs. The ModelessTM SCT2027
combines the error detection mechanism with display signals; hence the control unit does not need to
switch between different modes, and therefore both the hardware costs and the control complexity can
be reduced. In addition, the LED error status codes can be read in real time, and hence the fault status
of the faulty LEDs can be discovered sooner.
*Starchips’ patent protection.