Rev.3.01
REJ03B0158-0301
Aug 08, 2007
Page 53 of 134
38D5 Group
Voltage Multiplier
The voltage multiplier performs threefold boosting. This circuit
inputs a reference voltage for boosting from LCD power input
pin V
L1
. Set each bit of the segment output disable registers and
the LCD mode registers in the following order for operating the
voltage multiplier.
(1) Set the segment output disable bits (bits 0 to 19) of the
segment output disable registers (SEG0, 1, 2) to “0” or “1”.
(2) Set the duty ratio selection bits (bits 0 to 2), the bias control
bit (bit 3), the LCD circuit divider division ratio selection
bits (bits 5 and 6), and the LCDCK count source selection
bit (bit 7) of the LCD mode register 1 to “0” or “1”.
(3) Set the V
L3
connection bit (bit 1 of the LCD mode register 2
(LM2)) to “1”.
(4) Set the voltage multiplier control bit (bit0) of the LCD mode
register 2 to “1”.
When voltage is input to the V
L1
pin during operating the voltage
multiplier, voltage that is twice as large as V
L1
occurs at the V
L2
pin, and voltage that is three times as large as V
L1
occurs at the
V
L3
pin.
The voltage multiplier is controlled by the voltage multiplier
control bit (bit 0 of the LCD mode register 2).
In addition, when the voltage multiplier is used, set the voltage
multiplier control bit to “1” (voltage multiplier enabled) after the
voltage 1.3 V or more and 2.1 V or less.
When the voltage multiplier is not used, set the V
L3
connection
bit to “1” (open), and apply the suitable voltage for the power
supply input pins for LCD (V
L1
-V
L3
).
When V
L3
connection bit is set to be open, V
L3
pin is in a high
impedance state.
When the voltage multiplier is used, set the LCDCK frequency to
100 Hz or more. The on-chip oscillator cannot be used for
LCDCK.
In a system where the multiplier circuit is used (a multiplier
capacitor is externally connected between the C
1
and C
2
pins),
set the voltage multiplier circuit control bit to “1” (voltage
multiplier circuit enabled) before executing the STP or WIT
instruction.
Bias Control and Applied Voltage to LCD Power Input
Pins
Apply the voltage value shown in Table 13 according to the bias
value to the LCD power input pins. Apply the voltage value
shown in Table 13 according to the bias value by setting to V
L3
connection bit (bit 1 of LCD mode register 1) to “1”, when the
voltage multiplier is not used.
Select a bias value by the bias control bit (bit 3 of the LCD mode
register 1).
NOTE:
1. V
LCD
is the maximum value of supplied voltage for the LCD
panel.
Common Pin and Duty Ratio Control
The common pins (COM
0
COM
7
) to be used are determined by
duty ratio. Select duty ratio by the duty ratio selection bits (bits 0,
1 and 2 of the LCD mode register1). When reset is released, V
CC
voltage is output from the common pin.
NOTE:
1. Unused common pin outputs the unselected waveform.
Segment Signal Output Pin
The segment signal output pins (SEG
0
SEG
31
) are shared with
ports P0
P3. When these pins are used as the segment signal
output pins, set the direction registers of the corresponding pins
to “1”, and set the segment output disable register to “0”.
Also, these pins are set to the input port after reset, the V
CC
voltage is output by the pull-up resistor.
Fig. 45 Example of circuit at each bias (at external power supply input)
Table 13
Bias control and applied voltage to V
L1
V
L3
Bias value
Voltage value
1/3 bias
V
L3
= V
LCD
V
L2
= 2/3 V
LCD
V
L1
= 1/3 V
LCD
V
L3
= V
LCD
V
L2
= V
L1
= 1/2 V
LCD
1/2 bias
Table 14
Duty ratio control and common pins used
Duty
ratio
1
2
3
4
8
Duty ratio selection bits
Bit 2
Bit 1
0
0
0
0
0
1
0
1
1
1
Common pins used
Bit 0
0
1
0
1
1
COM
0
COM
0
, COM
1
COM
0
COM
2
COM
0
COM
3
COM
0
COM
7
R4
R5
R4 = R5
1/2 bias
Contrast adjust
R1
R2
R3
1/3 bias
Voltage multiplier is not used.
V
L1
V
L3
V
L2
*
*
P7
1
/INT
11
P7
0
/INT
0
1
V
L1
V
L3
V
L2
*
*
P7
1
/INT
11
P7
0
/INT
0
1
1/3 bias: R1 = R2 = R3
1/3 bias
Voltage multiplier is used.
V
L1
V
L3
V
L2
C
2
C
1
1/1 bias (static)
V
L1
V
L3
V
L2
Contrast adjust
*
: When the voltage muitiplier is not used, the C
1
and C
2
pins function as input ports
P7
0
/INT
01
,
P7
1
/INT
11.