PCF8531U/2DA/1 View Datasheet(PDF) - NXP Semiconductors.
Part Name
Description
MFG CO.
'PCF8531U/2DA/1' PDF : 51 Pages View PDF
NXP Semiconductors
PCF8531
34 x 128 pixel matrix driver
9.8 LCD bias voltage
Table 9.
Symbol
V1
V2
V3
V4
V5
V6
Intermediate LCD bias voltages
Bias voltage
VLCD
n-----+-----3-
n+4
×
VL
C
D
n-----+-----2-
n+4
×
VL
C
D
-----2------
n+4
×
VLCD
-----1------
n+4
×
VLCD
VSS
Example for 1⁄7 bias
VLCD
6⁄7 × VLCD
5⁄7 × VLCD
2⁄7 × VLCD
1⁄7 × VLCD
VSS
9.9 Set VLCD value
VLCD can be set by software. The voltage at intersection temperature [VLCD (T = Tints)] can
be calculated as: VLCD (Tints) = a + VLCD × b
The generated voltage is dependent on the temperature, programmed Temperature
Coefficient (TC) and the programmed voltage at intersection temperature (Tints).
VLCD = VLCD (Tints) × [1 + TC × (T − Tints)]
The parameter values are given in Table 10. Two overlapping VLCD ranges can be
selected via the command HV-gen control (see Table 10 and Figure 12). The maximum
voltage which can be generated depends on the VDD2 and VDD3 voltages and the display
load current. For multiplex rate 1:34, the optimum VLCD can be calculated as:
VLCD
=
----------1----+---------3---4-----------
2 × ⎝⎛1 – ----1-3---4-⎠⎞
× Vth
=
5.30 × Vth
Where Vth is the threshold voltage of the liquid crystal material used.
The practical value for VLCD is determined by equating Voff(RMS) with a defined LCD
threshold voltage (Vth), typically when the LCD exhibits approximately 10 % contrast.
As the programming range for the internally generated VLCD allows values above the
maximum allowed VLCD, the user must ensure, while setting the VOP register and
selecting the temperature compensation, that the VLCD limit maximum of 9.0 V is never
exceeded under all conditions and including all tolerances.
PCF8531
Product data sheet
All information provided in this document is subject to legal disclaimers.
Rev. 6 — 16 May 2011
© NXP B.V. 2011. All rights reserved.
23 of 51
Share Link: 
