PCF8576C Philips Semiconductors, PCF8576C Datasheet - Page 9

• Manufacturer Part Number: PCF8576C
• Description: Universal LCD driver for low multiplex rates
• Manufacturer: Philips Semiconductors

Philips Semiconductors
6.1
At power-on the PCF8576C resets to a starting condition
as follows:
1. All backplane outputs are set to V
2. All segment outputs are set to V
3. The drive mode ‘1 : 4 multiplex with
4. Blinking is switched off.
5. Input and output bank selectors are reset (as defined
6. The I
7. The data pointer and the subaddress counter are
Data transfers on the I
following power-on to allow completion of the reset action.
6.2
The full-scale LCD voltage (V
V
compensated externally through the V
Fractional LCD biasing voltages are obtained from an
internal voltage divider of the three series resistors
connected between V
be switched out of the circuit to provide a
level for the 1 : 2 multiplex configuration.
Table 2 Preferred LCD drive modes: summary of characteristics
1998 Jul 30
DD
Universal LCD driver for low multiplex
rates
LCD DRIVE MODE
in Table 5).
cleared.
V
Power-on reset
LCD bias generator
LCD
2
C-bus interface is initialized.
static
1 : 2
1 : 2
1 : 3
1 : 4
. The LCD voltage may be temperature
DD
2
C-bus should be avoided for 1 ms
and V
BACKPLANES
op
LCD
) is obtained from
. The centre resistor can
NUMBER OF
1
2
2
3
4
DD
LCD
DD
.
1
.
3
supply to pin 12.
bias’ is selected.
1
2
bias voltage
LEVELS
2
3
4
4
4
CONFIGURATION
9
6.3
The LCD voltage selector co-ordinates 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
resulting discrimination ratios (D), are given in Table 2.
A practical value for V
with a defined LCD threshold voltage (V
the LCD exhibits approximately 10% contrast. In the static
drive mode a suitable choice is V
Multiplex drive ratios of 1 : 3 and 1 : 4 with
possible but the discrimination and hence the contrast
ratios are smaller (
The advantage of these modes is a reduction of the LCD
full-scale voltage V
These compare with V
----------
LCD BIAS
3
21
1 : 3 multiplex (
V
1 : 4 multiplex (
V
op
op
static
1
1
1
1
= 1.528 for 1 : 4 multiplex).
=
=
2
3
3
3
LCD voltage selector
----------------------- -
6 V
4
3
off rms
3
1
1
op
2
2
V
-------------------- -
bias):
bias):
3
= 2.309 V
off(rms)
0.354
0.333
0.333
0.333
op
as follows:
V
op
= 1.732 for 1 : 3 multiplex or
op
0
= 2.449 V
is determined by equating V
= 3 V
off(rms)
off(rms)
V
-------------------- -
op
on(rms)
0.791
0.745
0.638
0.577
V
op
off(rms)
= V
op
1
> 3V
Product specification
when
DD
PCF8576C
th
th
), typically when
D
approximately.
V
1
1
3
LCD
2
=
bias are
bias is used.
2.236
2.236
1.915
1.732
V
-------------------- -
V
and the
on(rms)
off(rms)
off(rms)