PCF8820U Philips Semiconductors, PCF8820U Datasheet - Page 25

• Manufacturer Part Number: PCF8820U
• Description: 67 x 101 Grey-scale/ECB colour dot matrix LCD driver
• Manufacturer: Philips Semiconductors

Philips Semiconductors
Table 5 Programming the required bias system
Table 6 Examples of LCD bias voltages
8.1.5
The PCF8820 incorporates a software configurable
voltage multiplier which uses a charge pump circuit
supplied by V
multiplier factor is set to 2 (V
voltage multiplier factors are set by bits S
To reduce high current peaks at voltage multiplier start-up,
it is recommended that the voltage multiplier is switched on
using the following procedure:
1. Set bit DM = 1 and bit PD = 1
2. Set multiplication factor to 2 by setting bits S
3. Set register value V
4. Set bit PD = 0, which switches on the charge pump
2000 Dec 07
67 101 Grey-scale/ECB colour dot matrix
LCD driver
BIAS VOLTAGE
LEVEL ON PAD
BS2
logic 0
bit PRS = 1 and bit HVE = 1
(at multiplication factor 2)
X
0
0
0
0
1
1
1
1
V
LCDOUT
V
H
V
V
V
V
SS1
IGH VOLTAGE GENERATOR CONFIGURATION
2
3
4
5
DD2
BS1
X
0
0
1
1
0
0
1
1
and V
DD3
OP
BS0
X
CALCULATING BIAS
0
1
0
1
0
1
0
1
to the desired value,
. After a reset the voltage
LCDOUT
n
------------ -
n
n
------------ -
n
------------ -
n
------------ -
n
+
+
+
+
2
+
1
+
VOLTAGE
3
4
2
4
4
4
V
BS
V
LCDIN
= 2
0
0
0
0
0
0
0
0
1
SS1
1
V
V
V
V
/
2
LCDIN
LCDIN
LCDIN
LCDIN
2
V
to S
DD2
). Other
n
7
6
5
4
3
2
1
0
0
2
.
2
to S
0
to
BIAS SYSTEM
25
8
7
2
1
1
/
/
/
/
9
9
9
9
/
5. Increment the multiplication factor to the desired value
8.1.6
The PCF8820 has a built-in temperature sensor. At the
end of a temperature measurement, the sensor writes a
temperature value to the status register. The temperature
value is an 8-bit number represented by bits TR
the status register which can be read via the I
To save power, the sensor need only be enabled when a
measurement is required. A measurement is initialized by
setting bit SM = 1 which will be automatically cleared after
5 clock cycles (from internal oscillator or external clock).
The internal oscillator will be initialized and allowed to
warm-up for approximately 2 frame periods, after which a
measurement will be initiated at the start of the next frame
and completing after 2 frames.
9
V
1
1
V
1
1
1
1
1
1
1
/
/
(n = 5)
LCDIN
/
/
/
/
/
/
/
11
10
SS1
9
8
7
6
5
4
2
V
V
V
V
for V
LCDIN
LCDIN
LCDIN
LCDIN
LCDOUT
T
EMPERATURE READ
recommended at multiplex rate 1 : 67
recommended at multiplex rate 1 : 8
allows a lower V
using bits S
BIAS SYSTEM
3
1
1
1
1
/
/
/
/
4
2
2
4
/
4
V
V
(n = 0)
LCDIN
V
V
V
V
SS1
LCDIN
LCDIN
LCDIN
LCDIN
2
-
OUT
to S
COMMENT
LCDIN
0
.
at multiplex rate 1 : 8
Product specification
PCF8820
1
1
1
/
/
/
2
2
2
V
V
(n = 2)
V
V
LCDIN
LCDIN
2
V
SS1
V
SS1
C-bus.
7
LCDIN
LCDIN
to TR
0
in