點晶科技股份有限公司
ST2225A
SILICON TOUCH TECHNOLOGY INC.
Operating Ratings
Supply Voltage (VDD – VSS) ..............................+4.75V to 11V
Ambient Temperature Range (T )..................-40℃ to +85℃
A
Functional Description
The ST2225A display driver can drive either 4- or 5-digit alphanumeric LED displays. One of
its advantages is its minimal interface requirement with the display or data source.
Data transfer is accomplished by sending clock and serial data signals, without any need of an
external load signal. This method provides a non-multiplexed, direct drive to the LED display. The
data transfer format uses a leading “1” followed by 35 data bits. These 35 data bits are latched after
the 36th has been transferred. In this way, data output (refers to the currently displayed characters)
changes only if the serial data bits differ from those previously transferred.
Display brightness is controlled by the output current for LED displays. A 1nF capacitor should
be connected to brightness control pin to prevent oscillations.
Figure 1 shows the block diagram of this driver. The output current is set via an external
variable resistor, and is typically 27 times greater than the current in brightness control pin.
Input data format, as in Figure 4, shows a leading “1” followed by 35 data bits. When the 36th is
transferred, a LOAD signal is generated synchronously with the clock high state, thus, the 35 bits of
data are loaded into the latches. The low state of the clock is used to generate a RESET signal to
clear all shift registers for the next set of data. To allow continuous operation, all shift registers are
static master-slaves, with no clear for the master portion of the first register.
LED Display Driver
-6-
Version：A.025
SITI [ SILICON TOUCH TECHNOLOGY INC. ]
