Philips Semiconductors
Universal LCD driver for low
multiplex rates
Product specification
PCF8576D
6.4.2 1 : 2 MULTIPLEX DRIVE MODE
The 1 : 2 multiplex drive mode is used when two backplanes are provided in the LCD. This mode allows fractional LCD
bias voltages of 1⁄2 bias or 1⁄3 bias as shown in Figs 7 and 8.
handbook, full pagewidth
BP0
BP1
Sn
Sn + 1
VLCD
VLCD/2
VSS
VLCD
VLCD/2
VSS
VLCD
VSS
VLCD
VSS
state 1
state 2
VLCD
VLCD/2
0V
−VLCD/2
−VLCD
VLCD
VLCD/2
0V
−VLCD/2
−VLCD
Tframe
LCD segments
state 1
state 2
(a) Waveforms at driver.
(b) Resultant waveforms
at LCD segment.
MGL746
Vstate1(t) = VSn(t) – VBP0(t)
Von(rms) = 0.791VLCD
Vstate2(t) = VSn(t) – VBP1(t)
Voff(rms) = 0.354VLCD
Fig.7 Waveforms for the 1 : 2 multiplex drive mode with 1⁄2 bias.
2004 Dec 22
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