AN3981 datasheet(10/54 Pages) STMICROELECTRONICS

10 / 54 page

8-bit LED array drivers

AN3981

10/54

Doc ID 022217 Rev 1

The “Control logic” block decodes the signal sequence provided to the LE and

pin for

entering and ending the error detection, performed by the block “Open/Short-Circuit

Detector”.

The Thermal shutdown block monitors the junction temperature and switches the current

generators off if this temperature goes over the thermal shutdown threshold (typically

170 °C), independent to the actual status of the generators. The generators go back to the

previous status if the junction temperature falls, typically 15-20 °C, below the thermal

shutdown threshold.

Figure 7.

8-bit LED array driver block diagram

2.4

SPI data sending

Figure 8 shows a typical timing diagram of an 8-bit LED driver.

The LE pulse latches the last 8 bits loaded into the shift register through the SDI pin and

sampled by the last 8 clock rising edges.

As long as the

pin is high, all current generators are not active. Once

is set low, the

current generators are enabled and their status is determined by the data latched by the last

LE pulse.

AN3981 Datasheet(PDF) 10 Page - STMicroelectronics