PD16721_15 Datasheet, PDF (8/30 Pages) Renesas Technology Corp – 384-OUTPUT TFT-LCD SOURCE DRIVER (COMPATIBLE WITH 256-GRAY SCALES)

µPD16721
5. RELATIONSHIP BETWEEN INPUT DATA AND OUTPUT VOLTAGE VALUE
The µPD16721 incorporates a 8-bit D/A converter whose odd output pins and even output pins output respectively
gray scale voltages of differing polarity with respect to the LCD’s counter electrode voltage. The D/A converter
consists of ladder resistors and switches.
The ladder resistors (r0 to r253) are designed so that the ratio of LCD panel (γ -compensated voltages to V0’ to V255’
and V0” to V255” is almost equivalent as shown in Figure 5-2 and 5-3. For the 2 sets of eight γ -compensated power
supplies, V0 to V7 and V8 to V15, respectively, input gray scale voltages of the same polarity with respect to the 0.5
VDD2.
Figure 5-1 shows the relationship between the driving voltages such as liquid-crystal driving voltages VDD2, VSS2 and
0.5 VDD2, and γ -corrected voltages V0 to V15 and the input data. Be sure to maintain the voltage relationships below.
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VDD2–0.2 V ≥ V0 > V1 > V2 > V3 > V4 > V5 > V6 > V7 ≥ 0.5 VDD2+0.5 V
0.5 VDD2–0.5 V ≥ V8 > V9 > V10 > V11 > V12 > V13 > V14 > V15 ≥ 0.5 VSS2+0.2 V
Also, V6 to V7 and V8 to V9 are left open in the LSI. Be sure to input the gray scale level power supply at a constant
level to the all pins, as V0 to V15.
Figures 5-2 and 5-3 show the relationship between the input data and the output voltage and the resistance values
of the resistor strings.
Figure 5-1. Relationship between Input Data and γ -corrected Power Supplies
0.2 V
VDD2
V0
V1
V2
V3
V4
V5
V6
V7
0.5 VDD2
V8
V9
V10
V11
V12
0.5 V
0.5 V
V13
V14
V15
0.2 V
VSS2
00 01
20
40
80
C0
F0 FF
Input Data (HEX)
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DataSheet S14791EJ1V0DS