AN3114 datasheet(9/43 Pages) STMICROELECTRONICS

Part #	AN3114

Description	This application note describes techniques for connecting

PDF	43 Pages

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Manufacturer	STMICROELECTRONICS [STMicroelectronics]

Direct Link	http://www.st.com

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9 / 43 page

AN3114

LCD controller drive signals

Doc ID 16829 Rev 3

9/43

LCD controller drive signals

2.1

Single backplane LCD drive

In a single backplane drive, each LCD segment is connected to a segment line (Sx) and to a

backplane (common line) common to all the segment lines. A display using S LCD

segments is driven with S+1 MCU output lines (S segments + 1common). The backplane is

driven with a COM signal between 0 and VDD with a duty cycle of 50%.

When switching on an LCD segment, a signal with opposite polarity to COM is sent to the

corresponding Segment line. When the non-inverted COM signal-to-segment signal is sent

to the Segment line, the LCD segment is off. Using an MCU, the I/O operates in output

mode at either logic 0 or 1.

Figure 3.

LCD signals for direct drive

COM

MS19737V1

+VDD

S1 = COM – S

OFF

+VDD

S1 = COM – S

–VDD

Odd

frame

Even

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Odd

frame

Even

frame

Odd

frame

Even

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Odd

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Even

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Odd

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