![](http://datasheet.mmic.net.cn/Maxim-Integrated-Products/MAX8738EUA-T_datasheet_105673/MAX8738EUA-T_9.png)
1) Choose the maximum VCOM level (VMAX), the mini-
mum VCOM level (VMIN), and the AVDD supply
voltage (VAVDD).
2) Select R1 between 10k
and 500k based on the
acceptable power loss from the AVDD supply rail.
3) Calculate R2:
4) Calculate RSET:
5) Verify that ISET(MAX) does not exceed 120A:
6) If ISET exceeds 120A, return to step 2 and choose
a larger value for R1.
7) The resulting resolution is:
A complete design example is given below:
1) VMAX = 5V, VMIN = 3V, VAVDD = 10V.
2) If R1 = 200k
, then R2 = 200k and
RSET = 24.9k
.
3) ISET(MAX) = 20A.
4) Resolution = 15.75mV.
Translating Existing Potentiometer
Circuits
Existing VCOM adjustment circuits using conventional
mechanical potentiometers can be translated into
MAX8738 circuits. Figures 4 and 5 show two common
adjustment circuits and their equivalent MAX8738 circuits.
(
)
VV
MAX
MIN
127
I
V
R
A
SET MAX
AVDD
SET
() =
×
≤
20
120
R
V
VV
R
SET
MAX
MIN
(
)
=
×
20
1
R
V
VV
R
MAX
AVDD
MAX
21
(
)
×
MAX8738
EEPROM-Programmable TFT VCOM
Calibrator with I2C Interface
_______________________________________________________________________________________
9
MAX8738
AVDD
RSET
R2
R1
VCOM
SET
GND
AVDD
OUT
MAX8738
EQUIVALENT CIRCUIT
MECHANICAL
POTENTIOMETER
RA
RB
RC
R1 = RA
R2 = RB + RC
RSET =
RA x (RB + RC)
20 x RB
Figure 4. Replacement of Mechanical Potentiometer Circuit