pca8576c NXP Semiconductors, pca8576c Datasheet - Page 7

• Manufacturer Part Number: pca8576c
• Description: Universal Lcd Driver For Low Multiplex Rates
• Manufacturer: NXP Semiconductors

NXP Semiconductors
PCA8576C
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
2a
+
2a
–
1
+
+
+
1
Rev. 1 — 22 July 2010
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
Universal LCD driver for low multiplex rates
⁄
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
------------------------ -
.
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
PCA8576C
Equation
Equation
)
© 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:
(
(
7 of 44
)
(1)
(2)
(3)
)