PC85133-1 データシートの表示（PDF） - NXP Semiconductors.
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PC85133-1 Datasheet PDF : 53 Pages
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NXP Semiconductors
PCF85133
Universal LCD driver for low multiplex rates
VLCD and the resulting discrimination ratios (D) are given in Table 6.
Discrimination is a term which is defined as the ratio of the on and off RMS voltage across
a segment. It can be thought of as a measurement of contrast.
Table 6. Biasing characteristics
LCD drive
mode
Number of:
LCD bias
Backplanes Levels configuration
static
1
1:2 multiplex 2
1:2 multiplex 2
1:3 multiplex 3
1:4 multiplex 4
2
static
3
1⁄2
4
1⁄3
4
1⁄3
4
1⁄3
V-----o--f--f----R---M-----S---
VLCD
0
0.354
0.333
0.333
0.333
V-----o--n-----R----M----S---
VLCD
1
0.791
0.745
0.638
0.577
D = -V----o---n----R----M----S----
VoffRMS
2.236
2.236
1.915
1.732
A practical value for VLCD is determined by equating Voff(RMS) with a defined LCD
threshold voltage (Vth(off)), typically when the LCD exhibits approximately 10 % contrast. In
the static drive mode a suitable choice is VLCD > 3Vth(off).
Multiplex drive modes of 1:3 and 1:4 with 1⁄2 bias are possible but the discrimination and
hence the contrast ratios are smaller.
Bias is calculated by -----1------- , where the values for a are
1+a
a = 1 for 1⁄2 bias
a = 2 for 1⁄3 bias
The RMS on-state voltage (Von(RMS)) for the LCD is calculated with Equation 1:
VonRMS
=
VLCD
--a---2----+-----2---a----+-----n---
n 1 + a2
(1)
where the values for n are
n = 1 for static drive mode
n = 2 for 1:2 multiplex drive mode
n = 3 for 1:3 multiplex drive mode
n = 4 for 1:4 multiplex drive mode
The RMS off-state voltage (Voff(RMS)) for the LCD is calculated with Equation 2:
VoffRMS
=
VLCD
--a---2----–----2----a----+-----n---
n 1 + a2
(2)
Discrimination is the ratio of Von(RMS) to Voff(RMS) and is determined from Equation 3:
D = -V----o---n----R---M----S--- = a----2---+-----2----a----+-----n--
(3)
VoffRMS
a2 – 2a + n
PCF85133
Product data sheet
All information provided in this document is subject to legal disclaimers.
Rev. 3 — 4 July 2014
© NXP Semiconductors N.V. 2014. All rights reserved.
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