pcf85162 NXP Semiconductors, pcf85162 Datasheet - Page 6

• Manufacturer Part Number: pcf85162
• Description: Universal Lcd Driver For Low Multiplex Rates
• Manufacturer: NXP Semiconductors

NXP Semiconductors
PCF85162_1
Product data sheet
7.2 LCD bias generator
7.3 LCD voltage selector
Remark: Do not transfer data on the I
the reset action to complete.
Fractional LCD biasing voltages are obtained from an internal voltage divider consisting of
three resistors connected in series between V
bypassed by switch if the
configuration is selected. The LCD voltage can be temperature compensated externally
using the supply to pin 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 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 data pointer and the subaddress counter are cleared (set to logic 0)
Display is disabled
5.
)
=
Biasing characteristics
1
1
⁄
⁄
V
2
3
LCD
Number of:
Backplanes Levels
1
bias
bias
----------------------------- -
n
a
2
×
th
+
(
------------ -
1
), typically when the LCD exhibits approximately 10 % contrast. In
1
LCD
2a
Rev. 01 — 7 January 2010
1
+
+
LCD
a
+
a
1
Table
is determined by equating V
⁄
)
, where the values for a are
n
2
2
3
4
4
4
2
.
bias voltage level for the 1:2 multiplex drive mode
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
1
Universal LCD driver for low multiplex rates
⁄
LCD
2
bias are possible but the discrimination and
LCD
> 3V
and V
th
0
0.354
0.333
0.333
0.333
V
------------------------ -
.
off RMS
V
off(RMS)
LCD
(
SS
. The center resistor is
)
with a defined LCD
1
0.791
0.745
0.638
0.577
V
----------------------- -
on RMS
V
(
LCD
Equation
PCF85162
)
© NXP B.V. 2010. All rights reserved.
∞
2.236
2.236
1.915
1.732
D
=
1:
------------------------ -
V
V
off RMS
on RMS
(
(
6 of 39
)
(1)
)