HD66717 Datasheet, PDF (49/90 Pages) Hitachi Semiconductor – (Low-Power Dot-Matrix Liquid Crystal Display Controller/Driver)

HD66717
Oscillator Circuit
The HD66717 can either be supplied with operating clock pulses externally (external clock mode) or
oscillate using an internal R-C oscillator and an external oscillator-resistor (internal oscillation mode), as
shown in Figure 28. An appropriate oscillator-resistor must be used to obtain the optimum clock
frequency according to the number of display lines (Table 18). Instruction execution times change in
proportion to the operating clock frequency or R-C oscillation frequency; MPU data transfer rate must be
appropriately adjusted (see Table 17, Instruction List). Figure 29 shows a sample LCD drive output
waveform, where 4-lines are displayed with 1/34 multiplexing duty ratio.
1) When an external clock is used 2) When an internal oscillator is used
Clock
OSC1
HD66717
OSC1
Rf
OSC2
HD66717
The oscillator frequency can be
adjusted by oscillator resistance
(Rf). If Rf is increased or power
supply voltage is decreased, the
oscillator frequency decreases.
Figure 28 Oscillator Circuit
Table 19 Oscillation Frequency and LCD Frame Frequency
Item
Multiplexing duty ratio
Oscillator resistance (R_f)
CR oscillator frequency
Frame frequency
V_CC = 3V
1-Line Display 2-Line Display 3-Line Display 4-Line Display
NL1, NL0 = 00 NL1, NL0 = 01 NL1, NL0 = 10 NL1, NL0 = 11
1/10
1/18
1/26
1/34
620 kΩ
300 kΩ
200 kΩ
150 kΩ
40 kHz
85 kHz
120 kHz
160 kHz
67 Hz
79 Hz
77 Hz
78Hz
501