4554 Datasheet, PDF (50/138 Pages) Renesas Technology Corp – SINGLE-CHIP 4-BIT CMOS MICROCOMPUTER

4554 Group
(5) LCD power supply circuit
• Internal dividing resistor
The 4554 Group has the internal dividing resistor for LCD power
supply.
When bit 0 of register L2 is set to “0”, the internal dividing resis-
tor is valid. However, when the LCD is turned off by setting bit 2
of register L1 to “0”, the internal dividing resistor is turned off.
The same six resistor (r) is prepared for the internal dividing re-
sistor. According to the setting value of bit 3 of register L1 and
using bias condition, the resistor is prepared as follows;
• L13 = “0”, 1/3 bias used: 2r ✕ 3 = 6r
• L13 = “0”, 1/2 bias used: 2r ✕ 2 = 4r
• L13 = “1”, 1/3 bias used: r ✕ 3 = 3r
• L13 = “1”, 1/2 bias used: r ✕ 2 = 2r
• VLC3/SEG0 pin
The selection of VLC3/SEG0 pin function is controlled with the bit
3 of register L2.
When the VLC3 pin function is selected, apply voltage of VLC3 <
VDD to the pin externally.
When the SEG0 pin function is selected, VLC3 is connected to
VDD internally.
• VLC2/SEG1, VLC1/SEG2 pin
The selection of VLC2/SEG1 pin function is controlled with the bit
2 of register L2.
The selection of VLC1/SEG2 pin function is controlled with the bit
1 of register L2.
When the VLC2 pin and VLC1 pin functions are selected and the
internal dividing resistor is not used, apply voltage of
0<VLC1<VLC2<VLC3 to these pins. Short the VLC2 pin and VLC1
pin at 1/2 bias.
When the VLC2 pin and VLC1 pin functions are selected and the
internal dividing resistor is used, the dividing voltage value gener-
ated internally is output from the VLC1 pin and VLC2 pin. The VLC2
pin and VLC1 pin has the same electric potential at 1/2 bias.
When SEG1 and SEG2 pin function is selected, use the internal
dividing resistor. In this time, VLC2 and VLC1 are connected to the
generated dividingg voltage.
Rev.3.00 Aug 06, 2004 page 50 of 136
REJ03B0043-0300Z