pcf8535 NXP Semiconductors, pcf8535 Datasheet - Page 11

• Manufacturer Part Number: pcf8535
• Description: 65 X 133 Pixel Matrix Driver
• Manufacturer: NXP Semiconductors

Philips Semiconductors
7.9
The PCF8535 can be used to drive displays of varying
sizes. The selected multiplex rate controls which rows are
used. In all cases, the last row is always driven and is
intended for icons. If Top Row Swap (TRS) is at logic 1,
then the icon row will be output on pad R48. M[2:0] selects
the multiplex rate (see Table 2).
Table 2 Multiplex rates
7.10
7.10.1
The bias voltage levels are set in the ratio of
R
different factors n. This is programmed by BS[2:0]. For
optimum bias values, n can be calculated from:
Changing the bias system from the optimum values will
have a consequence on the contrast and viewing angle.
One reason to come away from the optimum would be to
reduce the required V
and V
Table 3 Programming the required bias system
2001 Nov 07
n
BS2 BS1 BS0
M2
0
0
0
0
1
1
1
:
65
=
0
0
0
0
1
1
1
1
R
OP
M1
Mux rate 3
Set multiplex rate
Bias system
0
0
1
1
0
0
1
:
nR
S
must be found for any particular application.
0
0
1
1
0
0
1
1
133 pixel matrix driver
ET BIAS SYSTEM
M0
0
1
0
1
0
1
1
:
R
0
1
0
1
0
1
0
1
–
R. Different multiplex rates require
MULTIPLEX
do not use
do not use
OP
n
7
6
5
4
3
2
1
0
RATE
1 : 17
1 : 26
1 : 34
1 : 49
1 : 65
. A compromise between contrast
:
MODE
BIAS
1
1
1
1
1
1
1
1
/
/
/
/
/
/
/
/
11
10
9
8
7
6
5
4
R0 to R15 and R64
R0 to R24 and R64
R0 to R32 and R64
R0 to R47 and R64
ACTIVE ROWS
TYPICAL MUX
R0 to R64
RATES
1 : 100
1 : 80
1 : 65
1 : 49
1 : 34
1 : 26
1 : 17
1 : 9
:
11
Table 4 Example of LCD bias voltage for
7.11
7.11.1
The PCF8535 has an in-built temperature sensor.
For power saving, the sensor should only be enabled
when a measurement is required. It will not operate in the
Power-down mode. The temperature read back requires a
clock to operate. Normally the internal clock is used but, if
the device is operating from an external clock, then this
clock must be present for the measurement to work.
V
initialized by setting the SM bit. Once started the SM bit will
be automatically cleared. An internal oscillator will be
initialized and allowed to warm-up for approximately
2 frame periods. After this the measurement starts and
lasts for a maximum of 2 frame periods.
Temperature data is returned via a status register. During
the measurement the register will contain zero. Once the
measurement is completed the register will be updated
with the current temperature (non zero value). Because
the I
measurement, read back prior to the end of the
measurement is not guaranteed. If this mode is required
the register should be read twice to validate the data.
The ideal temperature read-out can be calculated as
follows:
where T is the on-chip temperature in C and c is the
conversion constant: c = 1.17 C/lsb.
It should be noted that the temperature read-out is only
valid when TC0 is selected. If another TC is used, the
read-out function will generate a non-linear result.
To improve the accuracy of the temperature measurement
a calibration is recommended during the assembly of the
final product.
DD2
TR
2
SYMBOL
ideal
C-bus interface is asynchronous to the temperature
and V
Temperature measurement
V1
V2
V3
V4
V5
V6
T
=
(n = 3)
EMPERATURE READ BACK
DD3
128
must also be applied. A measurement is
+
T 27
–
1
-- -
c
BIAS VOLTAGE
6
5
2
1
/
/
/
/
7
7
7
7
V
V
Product specification
LCD
SS
V
V
V
V
LCD
LCD
LCD
LCD
PCF8535
1
/
7
bias mode
(1)