PCA8534AH-Q900 NXP [NXP Semiconductors], PCA8534AH-Q900 Datasheet - Page 7

• Manufacturer Part Number: PCA8534AH-Q900
• Description: Universal LCD driver for low multiplex rates
• Manufacturer: NXP [NXP Semiconductors]

NXP Semiconductors
PCA8534A_2
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 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 from the command decoder. The biasing configurations that apply to
the preferred modes of operation, together with the biasing characteristics as functions of
V
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
where the values for n are
V
LCD drive
mode
static
1:2 multiplex 2
1:2 multiplex 2
1:3 multiplex 3
1:4 multiplex 4
LCD
•
•
on RMS
a = 1 for
a = 2 for
n = 1 for static drive mode
n = 2 for 1:2 multiplex drive mode
(
The data pointer and the subaddress counter are cleared (set to logic 0)
The display is disabled
and the resulting discrimination ratios (D) are given in
)
=
Biasing characteristics
1
1
⁄
⁄
V
2
3
LCD
Number of:
Backplanes Levels
1
bias
bias
1
All information provided in this document is subject to legal disclaimers.
⁄
2
----------------------------- -
n
a
bias voltage level for the 1:2 multiplex drive mode configuration is
2
×
th
+
(
------------ -
1
), typically when the LCD exhibits approximately 10 % contrast. In
1
LCD
2a
1
+
+
Rev. 02 — 1 June 2010
a
+
a
is determined by equating V
)
, where the values for a are
n
2
3
4
4
4
2
on(RMS)
LCD bias
configuration
static
1
1
1
1
⁄
⁄
⁄
⁄
) for the LCD is calculated with
2
3
3
3
2
C-bus after a power-on for at least 1 ms to allow
1
LCD
Universal LCD driver for low multiplex rates
⁄
LCD
2
bias are possible but the discrimination and
and V
> 3V
th
0
0.354
0.333
0.333
0.333
V
------------------------ -
SS
.
off RMS
V
off(RMS)
. The center resistor is bypassed
LCD
(
Table
)
with a defined LCD
1
0.791
0.745
0.638
0.577
V
----------------------- -
on RMS
V
5.
(
LCD
PCA8534A
Equation
)
© NXP B.V. 2010. All rights reserved.
∞
2.236
2.236
1.915
1.732
D
=
1:
------------------------ -
V
V
off RMS
on RMS
(
(
7 of 44
)
(1)
)