pcf8532 NXP Semiconductors, pcf8532 Datasheet - Page 6

• Manufacturer Part Number: pcf8532
• Description: Universal Lcd Driver For Low Multiplex Rates
• Manufacturer: NXP Semiconductors

NXP Semiconductors
Table 5.
PCF8532_1
Product data sheet
LCD drive mode Number of:
static
1:2 multiplex
1:2 multiplex
1:3 multiplex
1:4 multiplex
Preferred LCD drive modes: summary of characteristics
7.3 LCD voltage selector
Backplanes
1
2
2
3
4
V
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
mode-set commands from the command decoder. The biasing configurations that apply to
the preferred modes of operation, together with the biasing characteristics as functions of
V
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 V
The RMS off-state voltage (V
Discrimination is the ratio of V
V
LCD
off RMS
on RMS
a = 1 for
a = 2 for
n = 1 for static mode
n = 2 for 1:2 multiplex
n = 3 for 1:3 multiplex
n = 4 for 1:4 multiplex
and the resulting discrimination ratios (D), are given in
LCD
Bias levels
2
3
4
4
4
=
=
1
1
2
3
V
is the resultant voltage at the LCD segment and where the values for n are
V
bias
bias
LCD
LCD
----------------------------------------------------------- -
1
-- -
n
a
-------------------------------- -
n
2
+
th
–
------------ -
1
), typically when the LCD exhibits approximately 10 % contrast. In
LCD
Rev. 1 — 10 February 2009
1
LCD bias
configuration
static
1
1
1
1
2a
1
+
n 1
2
3
3
3
+
a
–
is determined by equating V
+
a
, where the values for a are
n
n
2
on(RMS)
off(RMS)
on(RMS)
------------ -
1
1
+
) for the LCD is calculated with the equation
) for the LCD is calculated with the equation:
a
to V
V
--------------------------
0
0.354
0.333
0.333
0.333
2
off RMS
V
off(RMS)
1
LCD
Universal LCD driver for low multiplex rates
LCD
2
bias are possible but the discrimination and
3V
and is determined from the equation:
th
.
off(RMS)
1
0.791
0.745
0.638
0.577
V
------------------------ -
on RMS
V
LCD
Table
with a defined LCD
5.
PCF8532
D
2.236
2.236
1.915
1.732
© NXP B.V. 2009. All rights reserved.
=
--------------------------
V
V
off RMS
on RMS
6 of 44
(1)
(2)