NXP Semiconductors
PCF8534A
Universal LCD driver for low multiplex rates
7.4.2 1:2 Multiplex drive mode
When two backplanes are provided in the LCD, the 1:2 multiplex mode applies. The
PCF8534A allows the use of 1⁄2 bias or 1⁄3 bias in this mode as shown in Figure 6 and
Figure 7.
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
Tfr
LCD segments
state 1
state 2
(a) Waveforms at driver.
(b) Resultant waveforms
at LCD segment.
mgl746
Fig 6.
Vstate1(t) = VSn(t) − VBP0(t).
Von(RMS) = 0.791VLCD.
Vstate2(t) = VSn(t) − VBP1(t).
Voff(RMS) = 0.354VLCD.
Waveforms for the 1:2 multiplex drive mode with 1⁄2 bias
PCF8534A_3
Product data sheet
Rev. 03 — 10 November 2008
© NXP B.V. 2008. All rights reserved.
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