HD66724 Datasheet, PDF (66/117 Pages) Hitachi Semiconductor – (Graphics LCD Controller/Driver with Key Scan Function)

HD66724/HD66725
Oscillator Circuit
The HD66724/HD66725 can either be supplied with operating pulses externally (external clock mode),
oscillate using an internal CR oscillator with an external oscillator-resistor (external resistor oscillation
mode), or oscillate using an internal oscillator-resistor (internal resistor oscillation mode). Internal
oscillator-resistors fluctuate by ±30% depending on products. Avoid frame frequency fluctuations as these
affect video quality. To prevent these, use an external resistor.
1) External clock mode
Clock
OSC1
(32 kHz)
HD66724
HD66725
2) External resistor oscillation mode
Rf
OSC1
OSC2
HD66724
HD66725
The oscillator frequency can be
adjusted by oscillator resistor
(Rf). If Rf is increased or power
supply voltage is decreased, the
oscillator frequency decreases.
For the relationship between Rf
resistor value and oscillation
frequency, see the Electric
Characteristics Footnote section.
3) Internal resistor oscillation mode
OSC1
R1
Rf 0 (= 650 kΩ/typ.)
R2
Rf 1 (= 350 kΩ/typ.)
R3
Rf 2 (= 100 kΩ/typ.)
OSC2 _HD66724
HD66725
Note that the internal resistors RF0, RF1, and RF2
fluctuate by ±30% depending on products.
i) R1-OSC2 short-circuiting
Rf = Rf0 = 650 kΩ (typ.)
ii) R1-R2 short-circuiting, R3-OSC2 short-circuiting
Rf = Rf0 + Rf2 = 750 kΩ (typ.)
iii) R2-OSC2 short-circuiting
Rf = Rf0 + Rf1 = 800 kΩ (typ.)
iv) R3-OSC2 short-circuiting
Rf = Rf0 + Rf1 + Rf2 = 900 kΩ (typ.)
Figure 34 Oscillator Circuits
Table 36 Multiplexing Duty Ratio and LCD Frame Frequency (fosc = 32 kHz)
Item
Multiplexing duty ratio
Optimum drive bias
(recommended value)
Frame frequency
Segment mode
(NL2/1/0 = 000)
1/2
1/2
80 Hz
1-Line Display
(NL2/1/0 = 001)
1/10
1/4
80 Hz
2-Line Display
(NL2/1/0 = 010)
1/18
1/5
74 Hz
3-Line Display
(NL2/1/0 = 011)
1/26
1/6
77 Hz
66