PCF8534 Просмотр технического описания (PDF) - Philips Electronics
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PCF8534 Datasheet PDF : 40 Pages
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NXP Semiconductors
PCF8534
Universal LCD driver for low multiplex rates
A practical value for VOP 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 VOP > 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 a reduction of the LCD full-scale voltage VOP as follows:
• 1:3 multiplex (1⁄2 bias): VOP = 6 × VOFF(rms) = 2.449VOFF(rms)
• 1:4 multiplex (1⁄2 bias): VOP =
(---4----×---------3----)
3
= 2.309VOFF(rms)
These compare with VOP = 3 x VOFF(rms) when 1⁄3 bias is used. Note: VOP = VLCD.
Table 5. Preferred LCD drive modes: summary of characteristics
LCD drive
mode
Number of:
Backplanes Levels
LCD bias
configuration
V----O----F---F----(-m----s--)
VOP
static
1
2
static
0
1:2
2
3
1:2
2
4
1:3
3
4
1:4
4
4
1⁄2
0.354
1⁄3
0.333
1⁄3
0.333
1⁄3
0.333
V----O----N----(--m---s--)
VOP
1
0.791
0.745
0.638
0.577
D = --V----O----N---(--m----s--)-
VOFF(ms)
∞
2.236
2.236
1.915
1.732
PCF8534_0
Preliminary datasheet
Rev. 00.05 — 20 February 2007
© NXP B.V. 2007. All rights reserved.
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