pcf8562 NXP Semiconductors, pcf8562 Datasheet - Page 7

• Manufacturer Part Number: pcf8562
• Description: Universal Lcd Driver For Low Multiplex Rates
• Manufacturer: NXP Semiconductors

NXP Semiconductors
PCF8562_2
Product data sheet
6.3.1 LCD bias formulae
-------------- -
V
Bias is calculated by the formula
where for
The LCD on voltage (V
The LCD off voltage (V
where V
1 = static, 2 = 1 : 2, 3 = 1 : 3, 4 = 1 : 4.
Discrimination is the ratio of V
Using
and the discrimination for an LCD drive mode of 1 : 4 with
The advantage of these LCD drive modes is a reduction of the LCD full-scale voltage V
as follows:
These compare with V
V
•
•
OFF
3
ON
1 : 3 multiplex (
1 : 4 multiplex (
= 1.732
Equation 1
=
op
1
is the resultant voltage at the LCD segment; N is the LCD drive mode:
--------------------------------------------- -
2
a
a 1
bias, a = 1; for
+
–
1
2
2
the discrimination for an LCD drive mode of 1 : 3 with
+
+
1
1
2
2
Rev. 02 — 22 January 2007
N
N
bias): V
bias): V
LCD
on
off
–
–
) is calculated using the formula:
) is calculated using the formula:
1
1
= 3 V
1
3
on
LCD
LCD
bias, a = 2.
off(rms)
to V
----------- -
1
=
=
1
+
-------------------- -
off
a
4
6 V
, and is determined by the formula:
when
3
3
Universal LCD driver for low multiplex rates
off rms
1
= 2.309 V
3
bias is used.
= 2.449 V
off(rms)
V
V
1
2
op
op
off(rms)
bias is
----
N
---------------------------------------------------------------
a
---------------------------------- -
1
N
2
+
–
----------
2a
1
3
21
N
PCF8562
© NXP B.V. 2007. All rights reserved.
+
1
–
+
2
a
= 1.528.
1
N
bias is:
N
2
------------ -
1
1
+
a
7 of 36
LCD
(1)
2
.