OM6208 NXP Semiconductors, OM6208 Datasheet - Page 33

• Manufacturer Part Number: OM6208
• Description: Om6208 65 X 96 Pixels Matrix Grey-scale Lcd Driver
• Manufacturer: NXP Semiconductors

Philips Semiconductors
11.10.2 T
The temperature measurement is repeated every
10 seconds. The measured value is provided as a 7-bit
digital value TD[6:0] which can be read back via the
interface. The temperature can be determined from
TD[6:0] using the equation
11.10.3 T
Due to the temperature dependency of the liquid crystal’s
viscosity, the LCD controlling voltage V
adjusted at different temperatures to maintain optimal
contrast.
Internal temperature compensation may be enabled via
the ‘temperature compensation enable’ instruction. When
the internal temperature compensation is applied (TCE bit
is set to 1) then according to Equation (4) the V
depends also on V
component defined in Table 16), otherwise V
considered to be 0 V.
After the reset, the V
register that is reset to zero. The MMVOPCAL is also set
to zero because this comes from the registers of OTP that
are not refreshed yet, also V
because the temperature measurement block supplies a
TD value that is the default value stored in the register
after the reset.
The four temperature coefficients MA, MB, MC and MD
correspond to four equally spaced temperature regions.
Each coefficient can be selected from a choice of eight
different slopes, or multiplication factors. Each one of
these coefficients may be independently selected by the
user via the ‘temperature compensation enable’
instruction. The default for each slope register can be
stored in OTP.
Table 16 Temperature compensation equations
2003 feb 10
65 x 96 pixels matrix grey-scale LCD driver
TEMPERATURE RANGE ( C)
EMPERATURE MEASUREMENT
EMPERATURE COMPENSATION
T
40 to 11
10 to 19
20 to 49
50 to 79
=
T
1.875 TD 40
(the temperature compensation
LCD
is fixed because the V
T
is evaluated after the reset
–
LCD
C
may have to be
T
is
PR
LCD
is a
TD RANGE
(6)
16 to 31
32 to 47
48 to 63
0 to 15
33
Table 15 Temperature coefficients
Slopes of V
and Table 16.
Temperature compensation is implemented by adding an
offset V
calibration offset MMVOPCAL).
The final result for V
number as shown in equations (4) and (5). Care must be
taken by the user to ensure that the ranges of V
MMVOPCAL and V
undesired results. The adder stages will not permit
overflow or underflow and will clamp results to either end
of the range.
The temperature read-out generates a 7-bit result,
TD[6:0]. For temperatures below 40 C, the value of TD
is zero. For temperatures above 79 C, the value of TD is
higher than 63, but for V
used.
The offset value V
effect on V
value with the value of b (from Table 14).
For example, if T = 10 C, TD = 16 and MB = 1.25 then
V
SLA, SLB, SLC
LCDoffset
and SLD
111
110
101
100
011
010
001
000
T
to the V
= 30 mV
LCD
LCD
can be calculated by multiplying the offset
are calculated from equations (4), (5), (6)
PR
T
V
V
V
V
T
may be calculated from Table 16. The
value (additionally to the OTP
LCD
T
T
T
T
(32
do not cause clipping and hence
= (16
= (32
= (TD
= (16
MA, MB, MC
calculation is an 8-bit positive
T
and MD
calibration the value TD = 63 is
16)
3.00
2.00
1.25
1.00
0.75
0.50
0.25
0.00
MB) + MA
TD)
MC) + MD
32)
EQUATION
1.25 = 600 mV.
MB
Product specification
MC
OM6208
(16
(TD
SLOPE
(mV/K)
48
32
20
16
12
0
PR
8
4
TD)
,
48)