Data Sheet S11269EJ1V1DS00

7

µµµµ PD16640C

4.1

γγγγ-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.

γγγγ -corrected Power Circuit

V0

V1

V2

V3

V4

V5

V6

V7

V8

V9

V10

i0

R0 = 2.39 k

Ω

PD16640C

R1 =

Σ ri = 4.45 kΩ

i1

i2

i3

i4

i5

i6

i7

i8

i9

i10

7

i = 1

R2 =

Σ ri = 6.19 kΩ

8

i = 1

R3 =

Σ ri = 3.58 kΩ

8

i = 1

R4 =

Σ ri = 2.15 kΩ

8

i = 1

R5 =

Σ ri = 2.03 kΩ

8

i = 1

R6 =

Σ ri = 1.61 kΩ

8

i = 1

R7 =

Σ ri = 2.03 kΩ

8

i = 1

R8 =

Σ ri = 3.39 kΩ

7

i = 1

R9 = 2.55 k

Ω

µ

γ-corrected power pin

γ-corrected resistor

Sum of eight

γ-corrected resistors

−

+

−

+

−

+

−

+

−

+

−

+

−

+

−

+

−

+

−

+

−

+