pca85232 NXP Semiconductors, pca85232 Datasheet - Page 8

• Manufacturer Part Number: pca85232
• Description: Pca85232 Lcd Driver For Low Multiplex Rates
• Manufacturer: NXP Semiconductors

NXP Semiconductors
PCA85232
Product data sheet
7.3 LCD voltage selector
The LCD voltage selector coordinates the multiplexing of the LCD in accordance with the
selected LCD drive configuration. The operation of the voltage selector is controlled by the
mode-set command from the command decoder. The biasing configurations that apply to
the preferred modes of operation, together with the biasing characteristics as functions of
V
Table 5.
A practical value for V
threshold voltage (V
the static drive mode a suitable choice is V
Multiplex drive modes of 1:3 and 1:4 with
hence the contrast ratios are smaller.
Bias is calculated by
The RMS on-state voltage (V
where the values for n are
The RMS off-state voltage (V
Discrimination is the ratio of V
V
V
D
LCD drive
mode
static
1:2 multiplex 2
1:2 multiplex 2
1:3 multiplex 3
1:4 multiplex 4
LCD
on RMS
off RMS
a = 1 for
a = 2 for
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
=
(
(
---------------------- -
V
and the resulting discrimination ratios (D) are given in
V
off RMS
on RMS
)
)
(
(
=
=
Biasing characteristics
1
1
⁄
⁄
V
2
3
V
LCD
LCD
)
)
Number of:
Backplanes Levels
1
bias
bias
=
All information provided in this document is subject to legal disclaimers.
----------------------------- -
n
----------------------------- -
n
a
a
2
×
×
2
(
------------------------------------------- -
(
th
+
a
a 1
–
(
(
------------ -
1
), typically when the LCD exhibits approximately 10 % contrast. In
1
1
LCD
Rev. 1 — 8 December 2010
2a
+
2a
–
1
+
+
+
1
a
+
+
a
)
a
)
is determined by equating V
2
2
)
, where the values for a are
n
)
n
2
3
4
4
4
2
2
+
+
on(RMS)
off(RMS)
(
(
on(RMS)
n 1
n 1
–
–
LCD bias
configuration
static
1
1
1
1
)
)
) for the LCD is calculated with
⁄
⁄
⁄
⁄
) for the LCD is calculated with
2
3
3
3
to V
off(RMS)
1
⁄
LCD
2
bias are possible but the discrimination and
> 3V
and is determined from
th
0
0.354
0.333
0.333
0.333
V
------------------------ -
.
LCD driver for low multiplex rates
off RMS
V
off(RMS)
LCD
(
Table
)
with a defined LCD
1
0.791
0.745
0.638
0.577
V
----------------------- -
on RMS
V
5.
(
LCD
Equation
Equation
PCA85232
)
© NXP B.V. 2010. All rights reserved.
Equation
∞
2.236
2.236
1.915
1.732
D
=
2:
1:
------------------------ -
V
V
off RMS
on RMS
3:
(
(
8 of 54
)
(1)
(2)
(3)
)