LH155BA datasheet(21/51 Pages) SHARP

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LH155BA

2.15. LCD Drive Circuit

This drive circuit generates 4 levels of LCD drive

voltage. The circuit has 128 segment outputs and

64 common outputs and outputs combined display

data and M signal. A common drive circuit that has

a shift register sequentially outputs common scan

signals.

2.16. Oscillation Circuit

The frequency of this CR oscillator is controlled by

the feedback resistor RF.

The output from this oscillator is used as the timing

signal source of the display and the boosting clock

to the booster circuit. This is valid only in the

master operation mode.

During the slave operation mode, maintain OSCI

pin at VSS and OSCO pin open (NC).

When in the master operation mode and if external

clock is used, maintain OSCI pin at VSS and OSCO

pin open (NC), and feed the clock to CK pin. The

duty cycle of the external clock must be 50%.

The CKS pin selects either internal oscillation circuit

or external clock.

2.17. Power Supply Circuit

This circuit supplies voltages necessary to drive an

LCD panel. This circuit is valid only in the master

operation mode. The circuit consists of booster

circuit and voltage converter.

Boosted voltage from the booster circuit is fed to the

voltage converter which converts this high input

voltage into V0, V1, V2, V3 and V4 which are used

for graphic display. This internal power supply

should not be used to drive a large LCD panel

containing many pixels or a large LCD panel that

has large capacity consisting of more than one chip.

Otherwise, display quality will degrade considerably.

Instead, use an external power supply.

This internal power supply is controlled by the

power supply circuit ON/OFF command (PON).

When the internal power supply is turned off, the

booster circuit and voltage converter are also

turned off.

When using the external power supply, turn off the

internal power supply, disconnect pins CAP+,

CAP–, VEE2, VEE3, VOUT, VEE, VR1 and VR2, and

keep PMODE pin at VSS. Then, feed external LCD

drive voltages to pins V0, V1, V2, V3, and V4.

This circuit can be changed by the state of PMODE

pin.

NOTES :

1. Because the booster circuit and voltage converter are

not functioning, disconnect pins CAP+, CAP–, VEE2,

VEE3, VOUT, VEE, VR1 and VR2.

Apply external LCD drive voltages to corresponding pins.

2. Because the booster circuit is not functioning, disconnect

pins CAP+, CAP–, VEE2, VEE3 and VEE. Derive the

voltage source to be supplied to the voltage converter

from VOUT pin and then output LCD drive voltage to VR1

and VR2 pins. The voltage level at VR1 and VR2 pins

must be VR2 ≤ VR1 ≤ VOUT.

CKS

MASTER MODE

OSC

External

Clock (CK)

OSC

External

Clock (CK)

Enabled

Disabled

Enabled

Disabled

SLAVE MODE

PON PMODE

BOOSTER

CIRCUIT

VOLTAGE

CONVERTER

EXTERNAL

VOLTAGE INPUT

NOTE

Disabled Disabled V0, V1, V2, V3, V4

Enabled

–

Disabled

Enabled

VOUT, VR1, VR2

LH155BA Datasheet(PDF) 21 Page - Sharp Corporation

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