PCF8820 Datasheet, PDF (25/60 Pages) NXP Semiconductors – 67 x 101 Grey-scale/ECB colour dot matrix LCD driver

Philips Semiconductors
67 × 101 Grey-scale/ECB colour dot matrix
LCD driver
Product specification
PCF8820
Table 5 Programming the required bias system
BS2
BS1
BS0 BS¹/₂
n
0
0
0
0
7
0
0
1
0
6
0
1
0
0
5
0
1
1
0
4
1
0
0
0
3
1
0
1
0
2
1
1
0
0
1
1
1
1
0
0
X
X
X
1
−2
Table 6 Examples of LCD bias voltages
BIAS VOLTAGE
LEVEL ON PAD
V_LCDOUT
V₂
V₃
V₄
V₅
V_SS1
CALCULATING BIAS
VOLTAGE
V_LCDIN
nn-----++_{-----34-- × VLCDIN}
nn-----++_{-----24-- × VLCDIN}
n-----+^{2-----4-- × VLCDIN}
n-----+^{1-----4-- × VLCDIN}
V_SS1
BIAS SYSTEM
1_/11
1_/10
1_/9
1_/8
1_/7
1_/6
1_/5
1_/4
1_/2
COMMENT
recommended at multiplex rate 1 : 67
recommended at multiplex rate 1 : 8
allows a lower V_LCDIN at multiplex rate 1 : 8
1_{/9 (n = 5)}
V_LCDIN
8_{/9 × VLCDIN}
7_{/9 × VLCDIN}
2_{/9 × VLCDIN}
1_{/9 × VLCDIN}
V_SS1
BIAS SYSTEM
1_{/4 (n = 0)}
V_LCDIN
3_{/4 × VLCDIN}
1_{/2 × VLCDIN}
1_{/2 × VLCDIN}
1_{/4 × VLCDIN}
V_SS1
1_{/2 (n = −2)}
V_LCDIN
1_{/2 × VLCDIN}
V_SS1
V_LCDIN
1_{/2 × VLCDIN}
V_SS1
8.1.5 HIGH VOLTAGE GENERATOR CONFIGURATION
The PCF8820 incorporates a software configurable
voltage multiplier which uses a charge pump circuit
supplied by V_DD2 and V_DD3. After a reset the voltage
multiplier factor is set to 2 (V_LCDOUT = 2 × V_DD2). Other
voltage multiplier factors are set by bits S₂ to S₀.
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 S₂ to S₀ to
logic 0
3. Set register value V_OP to the desired value,
bit PRS = 1 and bit HVE = 1
4. Set bit PD = 0, which switches on the charge pump
(at multiplication factor 2)
5. Increment the multiplication factor to the desired value
for V_LCDOUT using bits S₂ to S₀.
8.1.6 TEMPERATURE READ-OUT
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 TR₇ to TR₀ in
the status register which can be read via the I²C-bus.
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.
2000 Dec 07
25