PD16640C_15 Datasheet, PDF (9/18 Pages) Renesas Technology Corp – 300/309-OUTPUT TFT-LCD SOURCE DRIVER (64 GRAY SCALE)

µ PD16640C
4.1 γ-corrected Power Circuit
The reference power supply of the D/A converter consists of a ladder circuit with a total of 64 resistors, and
resistance Σri between γ-corrected power pins differs depending on each pair of γ-corrected power pins. One pair of
γ-corrected power pins consists of seven or eight series resistors, and resistance Σri in the figure below is indicated
as the sum of the seven or eight resistors. The resistance ratio between the γ-corrected power pins (Σri ratio) is
designed to be a value relatively close to the ratio of the γ-corrected voltages V1 to V9 (gray-scale voltages in 8 steps)
used in an actual LCD panel. Under ideal conditions where there is no difference between the two, therefore, there is
no voltage difference between the voltage of the γ-corrected power supplies and the gray-scale voltages in 8 steps of
the resistor ladder circuits of the µPD16640C, and no current flows into the γ-corrected power pins V1 to V9. As a
result, a voltage-follower circuit is not necessary.
Figure 4-2. γ -corrected Power Circuit
γ-corrected power pin
γ-corrected resistor
µPD16640C
−
V0
i0
+
R0 = 2.39 kΩ
−
V1
i1
+
7
R1 = Σ ri = 4.45 kΩ
i=1
−
V2
i2
+
8
R2 = Σ ri = 6.19 kΩ
Sum of eight
i=1
−
V3
i3
γ-corrected resistors
+
8
R3 = Σ ri = 3.58 kΩ
i=1
−
V4
i4
+
8
R4 = Σ ri = 2.15 kΩ
i=1
−
V5
i5
+
8
R5 = Σ ri = 2.03 kΩ
i=1
−
V6
i6
+
8
R6 = Σ ri = 1.61 kΩ
i=1
−
V7
i7
+
8
R7 = Σ ri = 2.03 kΩ
i=1
−
V8
i8
+
7
R8 = Σ ri = 3.39 kΩ
i=1
−
V9
i9
+
R9 = 2.55 kΩ
−
V10
i10
+
Data Sheet S11269EJ1V1DS00
7