HD66740 Datasheet, PDF (13/95 Pages) Hitachi Semiconductor – 112 x 80-dot Graphics LCD Controller/Driver

HD66740
Oscillation Circuit (OSC)
The HD66740 can provide R-C oscillation simply through the addition of an external oscillation-resistor
between the OSC1 and OSC2 pins. The appropriate oscillation frequency for operating voltage, display size,
and frame frequency can be obtained by adjusting the external-resistor value. Clock pulses can also be
supplied externally. Since R-C oscillation stops during the standby mode, current consumption can be
reduced. For details, see the Oscillation circuit section.
Liquid Crystal Display Driver Circuit
The liquid crystal display driver circuit consists of 80 common signal drivers (COM1 to COM80) and 112
segment signal drivers (SEG1 to SEG112). When the number of lines are selected by a program, the
required common signal drivers automatically output drive waveforms, while the other common signal
drivers continue to output unselected waveforms.
Graphics data is sent serially through a 112-bit shift register and latched when all needed data has arrived.
The latched data then enables the segment signal drivers to generate drive waveform outputs.
The shift direction of 112-bit data can be changed by the SGS bit. The shift direction for the common driver
can also be changed by the CMS bit by selecting an appropriate direction for the device mounting
configuration.
When display is off, or during the standby or sleep mode, all the above common and segment signal drivers
output the GND level, halting the display.
Booster (DC-DC Converter)
The booster generates triple, quadruple, or five-times voltage input to the Vci pin. With this, both the
internal logic units and LCD drivers can be controlled with a single power supply. Boost output level from
triple to five-times boost can be selected by software. For details, see the Power Supply for Liquid Crystal
Display Drive section.
V-Pin Voltage Follower
A voltage follower for each voltage level (V1 to V5) reduces current consumption by the LCD drive power
supply circuit. No external resistors are required because of the internal bleeder-resistor, which generates
different levels of LCD drive voltage. This internal bleeder-resistor can be software-specified from 1/4 bias
to 1/10 bias, according to the liquid crystal display drive duty value. The voltage followers can be turned off
while multiplexing drive is not being used. For details, see the Power Supply for Liquid Crystal Display
Drive section.
Contrast Adjuster
The contrast adjuster can be used to adjust LCD contrast in 64 steps by varying the LCD drive voltage by
software. This can be used to select an appropriate LCD brightness or to compensate for temperature.
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