PCF85134HL-1 NXP [NXP Semiconductors], PCF85134HL-1 Datasheet - Page 7

• Manufacturer Part Number: PCF85134HL-1
• Description: Universal LCD driver for low multiplex rates
• Manufacturer: NXP [NXP Semiconductors]

NXP Semiconductors
PCF85134_1
Product data sheet
7.2 LCD bias generator
7.3 LCD voltage selector
Remark: Do not transfer data on the I
reset action to complete.
Fractional LCD biasing voltages are obtained from an internal voltage divider of three
series resistors connected between pins V
by switch if the
selected.
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 (see
configurations that apply to the preferred modes of operation, together with the biasing
characteristics as functions of V
Table
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
V
LCD drive
mode
static
1:2 multiplex 2
1:2 multiplex 2
1:3 multiplex 3
1:4 multiplex 4
•
•
•
on RMS
a = 1 for
a = 2 for
The I
The data pointer and the subaddress counter are cleared (set to logic 0)
The display is disabled
5.
2
=
C-bus interface is initialized
Biasing characteristics
1
1
V
2
3
LCD
Number of:
Backplanes Levels
1
bias
bias
1
2
----------------------------- -
n
a
bias voltage level for the 1:2 multiplex drive mode configuration is
2
th
+
Rev. 01 — 17 December 2009
------------ -
1
), typically when the LCD exhibits approximately 10 % contrast. In
1
LCD
2a
1
+
+
a
+
a
Table
is determined by equating V
, where the values for a are
2
3
4
4
4
n
2
on(RMS)
10) from the command decoder. The biasing
LCD
LCD bias
configuration
static
1
1
1
1
and the resulting discrimination ratios (D) are given in
) for the LCD is calculated with
2
3
3
3
2
C-bus for at least 1 ms after a power-on to allow the
1
LCD
Universal LCD driver for low multiplex rates
LCD
2
bias are possible but the discrimination and
and V
> 3V
th
V
--------------------------
0
0.354
0.333
0.333
0.333
SS
.
off RMS
V
off(RMS)
. The center resistor is bypassed
LCD
with a defined LCD
1
0.791
0.745
0.638
0.577
V
------------------------ - D
on RMS
V
LCD
Equation
PCF85134
© NXP B.V. 2009. All rights reserved.
2.236
2.236
1.915
1.732
=
1:
--------------------------
V
V
off RMS
on RMS
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