Philips Semiconductors
Universal LCD driver for low multiplex
rates
Product specification
PCF8576C
6.4.2 1 : 2 MULTIPLEX DRIVE MODE
When two backplanes are provided in the LCD, the 1 : 2 multiplex mode applies. The PCF8576C allows use of 1⁄2bias or
1⁄3bias in this mode as shown in Figs 6 and 7.
VDD
BP0 (VDD VLCD )/2
VLCD
VDD
BP1 (VDD VLCD )/2
VLCD
VDD
Sn
VLCD
Sn 1
VDD
VLCD
Vop
Vop /2
state 1
0
Vop /2
Vop
Vop
Vop /2
state 2
0
Vop /2
Vop
T frame
LCD segments
state 1
state 2
(a) waveforms at driver
(b) resultant waveforms
at LCD segment
MBE540
Vstate1(t) = VSn(t) – VBP0(t)
Von(rms) = 0.791Vop
Vstate2(t) = VSn(t) – VBP1(t)
Voff(rms) = 0.354Vop
Fig.6 Waveforms for the 1 : 2 multiplex drive mode with 1⁄2bias (Vop = VDD − VLCD).
1998 Jul 30
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