PCF8813 View Datasheet(PDF) - Philips Electronics
Part Name
Description
MFG CO.
'PCF8813' PDF : 72 Pages View PDF
Philips Semiconductors
(67 + 1) × 102 pixels matrix LCD driver
Product speciï¬cation
PCF8813
11.11 Set HV generator stages
The PCF8813 incorporates a software-configurable
voltage multiplier. After reset (RES) the voltage multiplier
is set to 2 × VDD2. Other voltage multiplier factors are set
via the set HVgen stages command bits S[1:0].
11.12 Bias system
The bias voltage levels are set in the ratio of
R - R - nR - R - R giving a 1/(n + 4) bias system. Different
multiplex rates require different n factors. This is
programmed by BS[2:0] (see Table 15).
For multiplex rates of 1 : 68 the optimum bias value n is
given by: n = 68 – 3 = 5.246 = 5 resulting in 1/9 bias.
Changing the bias system from the optimum value will
have a consequence for the contrast and viewing angle.
One reason to depart from the optimum would be to
reduce the required operating voltage. A compromise
between contrast and operating voltage must be found for
any particular application.
Table 15 Bias system programming
BS[2] BS[1] BS[0] n
RECOMMENDED
MULTIPLEX RATES
0
0
0
7 1 : 100
0
0
1
6 1 : 80
0
1
0
5 1 : 65 or 1 : 67
0
1
1
4 1 : 48
1
0
0
3 1 : 34 or 1 : 40
1
0
1
2 1 : 24
1
1
0
1 1 : 18 or 1 : 16
1
1
1
0 1 : 10, 1 : 9 or 1 : 8
Table 16 LCD bias voltage
SYMBOL
V1
V2
V3
V4(1)
V5(2)
V6
BIAS VOLTAGES
VLCD
((---nn-----++-----34----))
((---nn-----++-----24----))
(---n-----+2-----4----)
(---n-----+1-----4----)
VSS
BIAS
VOLTAGES
FOR 1/9 BIAS
VLCD
8/9 × VLCD
7/9 × VLCD
2/9 × VLCD
1/9 × VLCD
VSS
Notes
1. Operation of bias level V4 is given for
V4 > VSS + 0.9 V. For higher multiplex rates, VLCD has
to be selected accordingly.
2. For multiplex rates equal to or lower than 1 : 24 (n = 2)
operation of the bias level V5 is limited to voltages
V5 < VDD2,3 − 1.1 V. VLCD has to be selected
accordingly.
The operating voltage can be set by software through the
interface. The binary number VOP representing the
operating voltage can be set according to the following
formula:
VOP = VCAL[4:0] + VPR∗
Where:
VOP is an 8-bit unsigned number used internally for
generation of the LCD supply voltage VLCD
VCAL is a 5-bit twos complement number set by the
module maker; see Table 17
VPR is an 8-bit unsigned number composed of PRS and
VPR* set by an interface command.
The corresponding voltage at the reference temperature,
TCUT, can be calculated as:
VLCD(Tcut) = (a + VOP × b)
2004 Mar 05
36
Share Link: 
