em65567 ELAN Microelectronics Corp, em65567 Datasheet - Page 36

• Manufacturer Part Number: em65567
• Description: Com/ Color Driver
• Manufacturer: ELAN Microelectronics Corp

EM65567
66 COM/ 96 SEG 256 Color STN LCD Driver
7.23 Electronic volume
The voltage conversion circuit has built-in an electronic volume, which allows the LCD drive voltage level V0 to be
controlled with DV register setting and allows the tone of LCD to be controlled. The DV registers are 7-bits, so can select
128 voltage values for the LCD drive voltage V0.
7.24 Voltage Regulator
The EM65567 has built-in reference voltage regulator, which generate the voltage amplified by input voltage from VREF pin.
The generated voltage is output at the VREG pin. Even if the boosted voltage level fluctuates, VREG remains stable so far as
VOUT is higher than VREG Stable power supply can be obtained using this constant voltage, even if the load fluctuates. The
EM65567 uses the generated VREG level for the reference level of the electronic volume to generate LCD drive voltage. In
order to stabilize the output voltage at the VREG pin, connect the capacitor C3 as appropriate by choosing its value.
7.25 LCD Drive Voltage Generation Circuit
The voltage converter contains the voltage generation circuit. The LCD drive voltages other than V0, that is, V1, V2, V3 and
V4 are obtained by dividing V0 through a resistor network. The LCD drive voltage from EM65567 is biased at 1/5, 1/6, 1/7,
1/8 or 1/9. When using the internal power supply, connect a stabilizing capacitor C2 to each of pins V0 to V4. The
capacitance of C2 should be determined while observing the LCD panel to be used. When using the external power supply,
apply external LCD drive voltages to V0, V1, V2, V3, V4, disconnect pins CAP1+, CAP-, CAP2+, CAP2-, CAP3+, CAP3-,
VOUT, VEE, VREF and VREG. When using only the voltage conversion circuit, turn off the internal booster circuit,
disconnect pins CAP1+, CAP1-, CAP2+, CAP2-, CAP3+, CAP3- and VEE. Derive the voltage source to be supplied to the
voltage converter from VOUT pin and then input the reference voltage to VREF pin.
* This specification is subject to be changed without notice.
36
2003/1/9 (V0.1)