ST2226A SiTi, ST2226A Datasheet - Page 11

• Manufacturer Part Number: ST2226A
• Description: PWM-Controlled Constant Current Driver
• Manufacturer: SiTi

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2) LED Emitting Time and Current
The luminance data (D
independently for each LED. The relationship between Iout, luminance data, and emitting
time is shown in Figure 2.
3) Phase Relationship of DCLK and GCLK
there is a certain length of delay between the rising edge of DCLK and of GCLK, the
command “LED Emitting“& “LED Disable” will not be correctly recognized, which will then
cause the display data loss. It is safe to keep both of GCLK and DCLK rising at the same
time, so that the frequencies of DCLK and GCLK have an integer multiple relationship.
GCLK & DCLK, e.g. the display controller is built by FPGAs, this clock phase problem is
unlikely to happen. However, if it dose happen, try to control the clock phase, e.g. invert
GCLK, to solve this problem. On the contrary, for the design which can not control the
clock phase, e.g. the display controller is built by microprocessors, the following sequential
modification on “Emitting” & “Disable” commands is preferred to be employed in the
design:
ST2226A adjusts the LED luminance using PWM (pulse width modulation) technique.
Matching ST2226A’s GCLK and DCLK is an important step in the system design. If
For the design which has a fixed, corresponding clock phase relationship between
ST2226A
1.
2.
3.
點晶科技股份有限公司
點晶科技股份有限公司
SILICON TOUCH TECHNOLOGY INC.
點晶科技股份有限公司
點晶科技股份有限公司
Gate GCLK.
Issue “Emitting” or “Disable” command.
Let go of GCLK.
Iout
2 x GCLK
Current
V
) has a resolution of 10 bits (1024steps) and can be set
“LED Emitting” command issued
Figure 2. PWM Current Output
D
V
x T
Version ： ： ： ： A.010
GCLK
1024 x T
GCLK
Page ： ： ： ： 10
Time
ST2226A