uc1682 ETC-unknow, uc1682 Datasheet - Page 31

• Manufacturer Part Number: uc1682
• Description: 80 X 104rgb C-stn Lcd Controller-driver W/ 32-shade Per Dot, 12-bit Per Rgb
• Manufacturer: ETC-unknow

LCD V
M
Multiplex Rate is completely software
programmable in UC1682 via registers CEN,
DST, DEN, and partial display control LC[9:8].
Combined with low power partial display mode
and a low bias ratio of 5, UC1682 can support
wide variety of display control options. For
example, when a system goes into stand-by
mode, a large portion of LCD screen can be
turned off to conserve power.
B
Bias Ratio (BR) is defined as the ratio between
V
The theoretical optimum Bias Ratio can be
estimated by
lower/higher than the optimum value calculated
above will not cause significant visible change in
image quality.
Due to the nature of STN operation, an LCD
designed for good gray-shade performance at
high Mux Rate (e.g. MR=80), can generally
perform very well as a black and white display, at
lower Mux Rate. However, it is also true that such
technique generally can not maintain LCD’s
quality of gray shade performance, since the
contrast of the LCD will increase as Mux Rate
decreases, and the shades near the two ends of
the spectrum will start to lose visibility.
UC1682 supports four BR as listed below. BR
can be selected by software program.
T
Four (4) different temperature compensation
coefficients can be selected via software. The
four coefficients are given below:
Revision 0.6
where V
EMPERATURE
LCD
IAS
ULTIPLEX
% per
R
and V
Bias Ratio
Table 2: Temperature Compensation
ATIO
TC
BR
BIAS
OLTAGE
BR = V
o
R
BIAS
S
C
ATES
ELECTION
= V
C
, i.e.
Table 1: Bias Ratios
Mux
OMPENSATION
-0.05
B1+
LCD
0
S
0
5
– V

/V
ETTING
1
BIAS
. BR of value 15~20%
B1–
-0.10
,
1
= V
1
7
B0+
-0.15
– V
2
8
2
B0–
.
-0.20
3
9
3
V
V
pump or by external power supply. The source of
V
reliability, it is recommended to keep V
12V over the entire operating range.
When V
level of V
registers: BR (Bias Ratio), PM (Potentiometer),
and TC (Temperature Compensation), with the
following relationship:
where
V
Gray shade and color STN LCD is sensitive to
even a 1% mismatch between IC driving voltage
and the V
LCD makers to guarantee such high precision
matching of parts from different venders. It is
therefore necessary to adjust V
actual V
For the best results, software or
adjustment
fine tuning.
For applications where mechanical manual fine
tuning of V
may be used with an external trim pot to fine tune
the V
L
The power supply circuit of UC1682 is designed
to handle LCD panels with load capacitance up to
~20nF when V
use higher V
20nF is also the recommended limit for LCD
panel size for COG applications.
V
OAD
LCD
LCD
LCD
LCD
LCD
C
depends on the setting of BR register, as
illustrated in the table on the next page,
PM is the numerical value of PM register,
T is the ambient temperature in
C
coefficient as selected by TC register.
V0
T
G
may be supplied either by internal charge
is controlled by PC[3:2]. For good product
F
LCD
D
is the temperature compensation
INE
ENERATION
and C
RIVING
(
LCD
OP
.
C
LCD
OP
T
V
LCD
of the LCD.
0
UNING
is generated internally, the voltage
is the recommended method for V
of LCD. However, it is difficult for
DD
is determined by three control

PM
S
becomes necessary, then V
DD2
C
TRENGTH
and COF packaging.
are two constants, whose value
PM
80x104RGB CSTN Controller-Driver
= 2.5V. For larger LCD panels
u
PM
)
u
1 (

LCD
OTP based V
(
T
to match the
O

C, and
UC1682
25
LCD
)
u
under
BIAS
C
T
LCD
LCD
pin
%)
29