EM65570
68COM/ 98SEG 65K Color STN LCD Driver
7.13 LCD Drive Circuit
This drive circuit generates four levels of LCD drive voltage. The circuit has 294
segment outputs and 68 common outputs; and outputs combined display data and
internal signal M. The common drive circuit shifts register and sequentially outputs
common scan signals.
7.14 Oscillator Circuit
The EM65570 has a CR oscillator. The output from this oscillator is used as the signal
timing source of the display and the boosting clock to the booster.
When the external clock is used, feed the clock source to the CK pin.
The duty cycle of the external clock must be 50%.
The resistance ratio of the CR oscillator is programmable. When you change this ratio,
you must also change the display frame frequency.
7.15 Power Supply Circuit
This circuit supplies voltages necessary to drive a LCD. The circuit consists of booster
and voltage converter.
Boosted voltage from the booster is fed to the voltage converter that converts this input
voltage into V0, V1, V2, V3, and V4 which are in turn used to drive the LCD. This
internal power supply should not be used to drive a large LCD panel containing many
pixels. Otherwise, display quality will degrade considerably.
DCON
AMPON
Booster Circuit
ENABLE
Voltage Conversion Circuit
ENABLE
1
1
0
1
0
0
ENABLE
DISABLE
DISABLE
DISABLE
7.16 Booster Circuit
Placing capacitor C1 across CAP1+ and CAP1-, across CAP2+ and CAP2-, across
CAP3+ and CAP1-, across CAP4+ and CAP2-, across CAP5+ and CAP1-, and across
VOUT and VSS will boost the voltage coming from VEE and VSS n times and outputs
the boosted voltage to the VOUT pin. Voltages that are boosted twice, three, four and
five times respectively are output to the VOUT pin by the boost step register set.
(1) To use the voltage that is boosted two times, place C1 only across CAP1+ and
CAP1-; and open CAP2+, CAP2-, CAP3+, CAP1-, CAP4+, CAP2-, CAP5+, &
CAP1-
(2) To use the voltage that is boosted three times, place C1 only across CAP1+ and
CAP1-, across CAP2+ and CAP2-; and open CAP3+, CAP1-, CAP4+, CAP2-,
CAP5+, & CAP1-
36 •
Product Specification (V1.0) 09.05.2005
(This specification is subject to change without further notice)
ELAN [ ELAN MICROELECTRONICS CORP ]
