Datasheet

DocID13236 Rev 9 13/28
STVM100 Application information
27
If the user-selected value is 0 (zero scale), the minimum current is sunk. The maximum
V
COM
value is obtained in Equation 3.
Equation 3
If the user-selected value is 127 (full scale), the maximum current is sunk and the minimum
V
COM
value is obtained in Equation 4.
Equation 4
During operation, the V
COM(max)
and V
COM(min)
range is set, based on different TFT-LCD
processes.The R1 value is given based on the acceptable power loss from the AV
DD
supply
rail. Using Equation 3 and Equation 4, the R
2
and R
SET
values can be calculated. If R
SET
is
put into Equation 1 on page 12 and maximum I
OUT
≥ 120 µA, then R
1
should be increased.
V
COM max()
R
2
R
1
R
2
+
--------------------
AV
DD
1
1
128
----------
R
1
20 R
SET
()
--------------------------
⋅–


⋅=
V
COM min()
R
2
R
1
R
2
+
--------------------
AV
DD
1
R
1
20 R
SET
()
--------------------------
–


⋅=