hd66740 Renesas Electronics Corporation., hd66740 Datasheet - Page 42

• Manufacturer Part Number: hd66740
• Description: 112 X 80-dot Graphics Lcd Controller/driver - Hitachi Semiconductor
• Manufacturer: Renesas Electronics Corporation.

HD66740
Oscillation Circuit
The HD66740 can either be supplied with operating pulses externally (external clock mode) or oscillate
using an internal R-C oscillator with an external oscillator-resistor (external resistor oscillation mode).
Note that in R-C oscillation, the oscillation frequency is changed according to the internal capacitance
value, the external resistance value, or operating power-supply voltage.
of about 1.5k to prevent malfunctions caused by over-shoot or under-shoot noise in the external clock
mode.
Table 17
LCD Drive
Multiplexing
duty ratio
Drive bias
(recommend-
ed value)
Frame
frequency
One-frame
frequency
Note: If the frame frequency is low and the display flickers, increase the oscillation frequency (fosc).
Clock
1) External clock mode
(80 kHz)
Insert the dumping resistance.
1.5 k
Particularly in the 9-line display and 10-line display modes, note that the frame frequency is
lowered.
Relationship between Drive Duty Ratio and Frame Frequency (fosc = 75 kHz)
OSC1
Display mode
1-line
Dis-
play
Set value for NL3–0
0000
1/8
1/4
73 Hz
1,024
HD66740
2-line
Dis-
play
0001
1/16
1/5
73 Hz
1,024
3-line
Dis-
play
0010
1/24
1/6
73 Hz
1,032
Figure 19
2) External resistor oscillation mode
Rf
4-line
Dis-
play
0011
1/32
1/6
73 Hz
1,024
Oscillation Circuits
42
5-line
Dis-
play
0100
1/40
1/7
72 Hz
1,040
OSC1
OSC2
HD66740
6-line
Dis-
play
0101
1/48
1/8
74 Hz
1,008
7-line
Dis-
play
0110
1/56
1/8
74 Hz
1,008
The oscillator frequency can be
adjusted by oscillator resistor
(Rf). If Rf is increased or power
supply voltage is decreased, the
oscillation frequency decreases.
For the relationship between Rf
resistor value and oscillation
frequency, see the Electric
Characteristics Notes section.
Insert the dumping registance
8-line
Dis-
play
0111
1/64
1/9
73 Hz
1,024
9-line
Dis-
play
1000
1/72
1/9.5
65 Hz
1,152
10-line
Dis-
play
1001
1/80
1/10
59 Hz
1,280