AAT1301 Advanced Analog Technology, Inc., AAT1301 Datasheet - Page 8

• Manufacturer Part Number: AAT1301
• Description: Programmable Vcom Buffer
• Manufacturer: Advanced Analog Technology, Inc.

DESIGN PROCEDURE
One of many important functions of AAT1301 is to
minimize flicker in TFT-LCD panels by adjusting VCOM
voltage. AAT1301 is attached to an external resistive
voltage-driver to sink a programmable current (IOUT),
which determines the VCOM voltage. Eq. 1 and Eq.2
can be used to calculate the output current (IOUT) and
output voltage (VCOM).
Table 1 shows calculated value of VCOM under
following condition:
AVDD = 10V, R1 = 200k , R2 = 243k ,
and R
IOUT
VCOM VDDA *
=
=
SET
(SETTING 1)
= 24.9k .
128
Figure 3. Application Circuit
R1 R2
R2
+
+
*




20(R
1
VDDA
Advanced Analog Technology, Inc.
−
(SETTING 1)
SET
)
128
. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
+
*
20(R
R1
SET
–
)




… …
–
Advanced Analog Technology, Inc . –
台 灣 類 比 科 技 股 份 有 限 公 司
E q. 2
E q. 1
Version 1.00
Page 8 of 11
SETTING VALUE
–
Table 1. VCOM Setting Value
100
110
127
10
20
30
40
50
60
70
80
90
0
VCOM(V)
AAT1301
5.4681
5.2960
5.1239
4.9518
4.7797
4.6076
4.4355
4.2634
4.0913
3.9192
3.7471
3.5750
3.2824
October 2009