Rev. 1.40
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BS67F340/BS67F350/BS67F360/BS67F370
Enhanced Touch A/D Flash MCU with LCD Driver
BS67F340/BS67F350/BS67F360/BS67F370
Enhanced Touch A/D Flash MCU with LCD Driver
LCDC1 Register
Bit
7
6
5
4
3
2
1
0
Name
QCT�
QCT1
QCT0
—
PLCD3
PLCD�
PLCD1
PLCD0
R/W
R/W
R/W
R/W
—
R/W
R/W
R/W
R/W
POR
0
0
0
—
0
0
0
0
Bit 7~5
QCT2~QCT0
: R type quick charging time selection
000: 1 t
SUB
001: 2 t
SUB
010: 3 t
SUB
011: 4 t
SUB
100: 5 t
SUB
101: 6 t
SUB
110: 7 t
SUB
111: 8 t
SUB
The t
SUB
is the period of the LCD clock source f
SUB
, i.e., 1/f
SUB
.
Bit 4
Unimplemented, read as “0”
Bit 3~0
PLCD3~PLCD0
: R type bias supply voltage selection for VA
0000: 8/16 × PLCD
0001: 9/16 × PLCD
0010: 10/16 × PLCD
0011: 11/16 × PLCD
0100: 12/16 × PLCD
0101: 13/16 × PLCD
0110: 14/16 × PLCD
0111: 15/16 × PLCD
1xxx: PLCD
Note that the VA voltage level has to be equal to or greater than 2.1V.
LCD Voltage Source and Biasing
The time and amplitude varying signals generated by the LCD Driver function require the generation
of several voltage levels for their operation. The devices can have either R type or C type biasing
selected via a software control bit named RCT. Selecting the C type biasing will enable an internal
charge pump circuitry.
R Type Biasing
For R type biasing an external LCD voltage source must be supplied on pin PLCD to generate the
internal biasing voltages. This could be the microcontroller power supply V
DD
or some other voltage
source equal to or less than V
DD
. For the R type 1/3 bias scheme, four voltage levels V
SS
, V
A
, V
B
and
V
C
are utilised. The voltage V
A
is selected by the PLCD3~PLCD0 bits to be equal to a specific ratio
of V
PLCD
varying from 8/16 V
PLCD
to V
PLCD
. The voltage V
B
is equal to V
A
×2/3 while the voltage V
C
is
equal to V
A
×1/3.
Different values of internal bias resistors can be selected using the RSEL2~RESEL0 bits in the
LCDC0 register. This along with the voltage on pin PLCD will determine the bias current. The
VMAX pin should be connected to the VDD pin since the available maximum voltage applied to the
PLCD pin is equal to V
DD
. Note that no external capacitors or resistors are required to be connected
if R type biasing is used.