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PCF85162T/1,118

P1-P3P4-P6P7-P9P10-P12P13-P15P16-P18P19-P21P22-P24P25-P27P28-P30P31-P33P34-P36P37-P39P40-P42P43-P45P46-P48P49-P51P52-P53
PCF85162 All information provided in this document is subject to legal disclaimers. © NXP Semiconductors N.V. 2014. All rights reserved.
Product data sheet Rev. 5 — 17 December 2014 10 of 53
NXP Semiconductors
PCF85162
32 × 4 universal LCD driver for low multiplex rates
7.3 Possible display configurations
The possible display configurations of the PCF85162 depend on the number of active
backplane outputs required. A selection of display configurations is shown in Table 13
. All
of these configurations can be implemented in the typical system shown in Figure 4
.
[1] 7 segment display has 8 segments/elements including the decimal point.
[2] 14 segment display has 16 segments/elements including decimal point and accent dot.
Fig 3. Example of displays suitable for PCF85162
Table 13. Selection of possible display configurations
Number of
Backplanes Icons Digits/Characters Dot matrix:
segments/
elements
7-segment
[1]
14-segment
[2]
4 128 16 8 128 dots (4 32)
39612696dots (3 32)
2648464dots (2 32)
1324232dots (1 32)
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PCF85162 All information provided in this document is subject to legal disclaimers. © NXP Semiconductors N.V. 2014. All rights reserved.
Product data sheet Rev. 5 — 17 December 2014 11 of 53
NXP Semiconductors
PCF85162
32 × 4 universal LCD driver for low multiplex rates
The host microcontroller maintains the 2-line I
2
C-bus communication channel with the
PCF85162. The internal oscillator is enabled by connecting pin OSC to pin V
SS
. The
appropriate biasing voltages for the multiplexed LCD waveforms are generated internally.
The only other connections required to complete the system are the power supplies (V
DD
,
V
SS
, and V
LCD
) and the LCD panel chosen for the application.
7.3.1 LCD bias generator
Fractional LCD biasing voltages are obtained from an internal voltage divider consisting of
three impedances connected in series between V
LCD
and V
SS
. The center impedance is
bypassed by switch if the
1
⁄
2
bias voltage level for the 1:2 multiplex drive mode
configuration is selected. The LCD voltage can be temperature compensated externally,
using the supply to pin V
LCD
.
7.3.2 Display register
The display register holds the display data while the corresponding multiplex signals are
generated.
7.3.3 LCD voltage selector
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
LCD
and the resulting discrimination ratios (D) are given in Table 14.
Discrimination is a term which is defined as the ratio of the on and off RMS voltage across
a segment. It can be thought of as a measurement of contrast.
The resistance of the power lines must be kept to a minimum.
Fig 4. Typical system configuration
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PCF85162 All information provided in this document is subject to legal disclaimers. © NXP Semiconductors N.V. 2014. All rights reserved.
Product data sheet Rev. 5 — 17 December 2014 12 of 53
NXP Semiconductors
PCF85162
32 × 4 universal LCD driver for low multiplex rates
A practical value for V
LCD
is determined by equating V
off(RMS)
with a defined LCD
threshold voltage (V
th(off)
), typically when the LCD exhibits approximately 10 % contrast. In
the static drive mode a suitable choice is V
LCD
>3V
th(off)
.
Multiplex drive modes of 1:3 and 1:4 with
1
⁄
2
bias are possible but the discrimination and
hence the contrast ratios are smaller.
Bias is calculated by , where the values for a are
a = 1 for
1
⁄
2
bias
a = 2 for
1
⁄
3
bias
The RMS on-state voltage (V
on(RMS)
) for the LCD is calculated with Equation 1:
(1)
where the values for n are
n = 1 for static drive mode
n = 2 for 1:2 multiplex drive mode
n = 3 for 1:3 multiplex drive mode
n = 4 for 1:4 multiplex drive mode
The RMS off-state voltage (V
off(RMS)
) for the LCD is calculated with Equation 2:
(2)
Discrimination is the ratio of V
on(RMS)
to V
off(RMS)
and is determined from Equation 3:
(3)
Using Equation 3
, the discrimination for an LCD drive mode of 1:3 multiplex with
1
⁄
2
bias is and the discrimination for an LCD drive mode of 1:4 multiplex with
1
⁄
2
bias is .
Table 14. Biasing characteristics
LCD drive
mode
Number of: LCD bias
configuration
Backplanes Levels
static 1 2 static 0 1
1:2 multiplex 2 3
1
⁄
2
0.354 0.791 2.236
1:2 multiplex 2 4
1
⁄
3
0.333 0.745 2.236
1:3 multiplex 3 4
1
⁄
3
0.333 0.638 1.915
1:4 multiplex 4 4
1
⁄
3
0.333 0.577 1.732
V
on RMS
V
LCD
------------------------
D
V
on RMS
V
off RMS
-------------------------=
1
1a+
-------------
V
on RMS
a
2
2a n++
n 1a+
2
------------------------------
V
LCD
=
V
off RMS
a
2
2a– n+
n 1a+
2
------------------------------
V
LCD
=
D
V
on RMS
V
off RMS
-----------------------
a
2
2a n++
a
2
2a– n+
---------------------------==
3 1.732=
21
3
---------- 1.528=
P1-P3P4-P6P7-P9P10-P12P13-P15P16-P18P19-P21P22-P24P25-P27P28-P30P31-P33P34-P36P37-P39P40-P42P43-P45P46-P48P49-P51P52-P53

PCF85162T/1,118

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Buy PCF85162T/1,118
Manufacturer:
NXP Semiconductors
Description:
LCD Drivers I2C - LCD Driver
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