PCF8534A(2008) データシートの表示（PDF） - NXP Semiconductors.
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PCF8534A Datasheet PDF : 44 Pages
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NXP Semiconductors
PCF8534A
Universal LCD driver for low multiplex rates
Table 5 shows the biasing configurations applicable to the preferred operating modes
together with the biasing characteristics as functions of Voper and the resulting
discrimination ratios (D).
A practical value for Voper is determined by equating Voff(RMS) with a defined LCD
threshold voltage (Vth), typically when the LCD exhibits approximately 10 % contrast. In
the static drive mode a suitable choice is Voper > 3Vth.
Multiplex drive ratios of 1:3 and 1:4 with 1⁄2 bias are possible but the discrimination and
hence the contrast ratios are smaller e.g.:
3
=
1.732
for
1:3
multiplex
or
-----2---1-
3
=
1.528
for 1:4 multiplex
The advantage of these modes is the reduction of the LCD full-scale voltage Voper as
follows:
• 1:3 multiplex (1⁄2 bias): V oper = 6 × V off (RMS) = 2.449V off (RMS)
• 1:4 multiplex (1⁄2 bias): V oper =
(---4----×---------3----)
3
= 2.309V off (RMS)
These compare with Voper = 3Voff(RMS) when 1⁄3 bias is used. It should be noted that
Voper = VLCD.
Table 5. Preferred LCD drive modes: summary of characteristics
LCD drive Number of
mode
Backplanes Levels
LCD bias
configuration
V-----o---f-f---(-R----M----S---)
Voper
V-----o---n--(--R---M-----S--)
Voper
static
1
2
static
0
1
1:2
2
1:2
2
1:3
3
1:4
4
3
1⁄2
4
1⁄3
4
1⁄3
4
1⁄3
0.354
0.333
0.333
0.333
0.791
0.745
0.638
0.577
D = -V----o---n---(--R---M----S---)-
Voff (RMS)
∞
2.234
2.237
1.915
1.732
PCF8534A_3
Product data sheet
Rev. 03 — 10 November 2008
© NXP B.V. 2008. All rights reserved.
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