Datasheet

Application information STVM100
12/28 DocID13236 Rev 9
3 Application information
The STVM100 is a programmable V
COM
calibrator to remove flickers in TFT-LCDs or to
avoid the “ghosting effect” (residual pixels during refresh) in e-paper and e-books. It
provides a digital I
2
C interface to control the sink current output. This output drives an
external resistive voltage divider, which can then be applied to an external V
COM
buffer.
The highest and lowest V
COM
value is determined by three resistors, R
1
, R
2
, and R
SET
. The
connection is shown in Figure 8.
The sink current from the STVM100 OUT pin is given in Equation 1. This current then flows
through R
SET
. This current must be less than 120 µA (see I
SET
value in Table 7 on page 16).
Figure 8. R
1
, R
2
, and R
SET
connection
Note: In order to choose an appropriate device to buffer the output of STVM100, please see our
operational amplifier product portfolio available at:
http://www.st.com/stonline/products/families/amplifiers_comparators/amplifiers_comparators.htm
Equation 1
Note: “D” is a user-selected value, an integer ranging from 0 to 127.
The V
COM
value can be obtained in Equation 2.
Equation 2
AV
DD
I
OUT
V
COM
AV
DD
R
SET
R1
R2
SET
STVM100
+
–
AV
DD
OUT
AI12933
I
OUT
D1+
128
--------------
AV
DD
20 R
SET
()
--------------------------
⋅=
V
COM
R
2
R
1
R
2
+
--------------------
AV
DD
1
D1+
128
--------------
R
1
20 R
SET
()
--------------------------
⋅–


⋅=