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MAX1512ETA+T

P1-P3P4-P6P7-P9P10-P12P13-P13
MAX1512
EEPROM-Programmable TFT VCOM Calibrator
_______________________________________________________________________________________ 7
Setting the VCOM
Adjustment Range (R
SET
)
The external resistive voltage-divider sets the maximum
value of the VCOM adjustment range. R
SET
sets the
full-scale sink current, I
OUT
, which determines the mini-
mum value of the VCOM adjustment range. Large R
SET
values increase resolution but decrease the VCOM
adjustment range. Calculate R1, R2, and R
SET
using
the following procedure:
1) Choose the maximum VCOM level (V
MAX
), the mini-
mum VCOM level (V
MIN
), and the AVDD supply
voltage (V
AVDD
).
2) Calculate the R1 / R2 ratio:
3) Calculate the R1 / R
SET
ratio:
4) Choose R
SET
according to the limits shown in the
Electrical Characteristics section and calculate the
values for R1 and R2.
5) The resulting resolution is:
A complete design example is given below:
1) V
MAX
= 5V, V
MIN
= 3V, V
AVDD
= 10V
4) If R
SET
= 24.9kΩ, then R1 = 200kΩ and R2 =
200kΩ
5) Resolution = 15.75mV
3
1
20
53
5
8)
R
R
SET
=×
()
=
-
2
1
2
10
5
1)
R
R
≅=-1
Re
solution
V
=
()
MAX MIN
-V
127
R
R
V
V
SET MAX
1
20
≅
()
×
MAX MIN
-V
R
R
V
V
AVDD
MAX
1
2
1 ≅ -
CE
R
CTL
7
7
CTL
AVDD
R
SET
OUT
R2
R1
19R
DAC
EEPROM
VCOM
SET
GND
V
DD
V
DD
AVDD
MAX1512
CONTROL
INTERFACE
Figure 2. Simplified Functional Diagram
MAX1512
Translating Existing
Potentiometer Circuits
Existing VCOM adjustment circuits using conventional
mechanical potentiometers can be translated into
MAX1512 circuits. Figures 3 and 4 show two common
adjustment circuits and their equivalent MAX1512 circuits.
Interface Enable/Disable (CE)
The MAX1512 control interface can be disabled to
reduce the V
DD
supply current. Connect CE to GND to
reduce the typical supply current from 32µA to 12µA.
Connect CE to V
DD
to enable the control interface.
EEPROM-Programmable TFT VCOM Calibrator
8 _______________________________________________________________________________________
AVDD
R
SET
R
SET
=
OUT
R2
R1
R1 = Ra
R2 = Rb + Rc
Ra × (Rb + Rc)
20 × Rb
VCOM
SET
AVDD
MAX1512
Rb
Ra
VCOM
AVDD
Rc
MECHANICAL
POTENTIOMETER
MAX1512
EQUIVALENT CIRCUIT
Figure 3. Replacement of Mechanical/Potentiometer Circuit
AVDD
R
SET
R
SET
=
OUT
R2
R1
R1 = Rd
R2 = Rf
Rd × (Rd + Re + Rf)
20 × Re
VCOM
SET
AVDD
MAX1512
Re
Rd
VCOM
AVDD
Rf
MECHANICAL
POTENTIOMETER
MAX1512
EQUIVALENT CIRCUIT
Figure 4. Replacement of Mechanical/Potentiometer Circuit
The programming circuit in Figure 5 drives CE high to
enable the CTL input when it is connected. When the
programming circuit is not connected, CE is pulled low
through resistor R
CE
, which disables the CTL input. The
CTL input is relatively immune to noise and brief volt-
age transients. It can be safely left continuously
enabled if higher supply current is acceptable.
VCOM Adjustment (CTL)
Pulse CTL low for more than 200µs to increment the DAC
setting, which increases the OUT sink current and lowers
the VCOM level by 1 least-significant bit (LSB) (Figure 6).
Similarly, pulse CTL high for more than 200µs to decre-
ment the DAC setting, which decreases the OUT sink cur-
rent and increases the VCOM level by 1 LSB.
MAX1512
EEPROM-Programmable TFT VCOM Calibrator
_______________________________________________________________________________________ 9
CE
CTL
GND
MAX1512
PROGRAMMING
CIRCUIT
R
CE
V
DD
Figure 5. Optional Circuit to Drive CE
>1ms >200µs >200µs >200µs >10µs <20µs <20µs>200µs
CTL HIGH
V
DD
/2
CTL LOW
CTL
DAC SETTING
CE / V
DD
VCOM
CTL
ENABLED
64 65 64 63
UNDEFINED
FIRST
COUNT
IGNORED
SHORT
COUNTS
IGNORED
VCOM UP
VCOM DOWN
Figure 6. VCOM Adjustment
P1-P3P4-P6P7-P9P10-P12P13-P13

MAX1512ETA+T

Mfr. #:
Buy MAX1512ETA+T
Manufacturer:
Maxim Integrated
Description:
LCD Gamma Buffers EEPROM-Prog TFT VCOM Calibrator
Lifecycle:
New from this manufacturer.
Delivery:
DHL FedEx Ups TNT EMS
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