ADD8701 Просмотр технического описания (PDF) - Analog Devices
Номер в каталоге
Компоненты Описание
производитель
ADD8701 Datasheet PDF : 9 Pages
| |||
70
VDD = 16V
60 VCOM AND BUFFERS 1 TO 9
MARKER SET @ 10kHz
50 MARKER READING = 25.7nV/ Hz
40
30
20
10
0
–10
0
5
10
15
20
25
FREQUENCY – Hz
TPC 28. Voltage Noise Density
vs. Frequency
70
VDD = 16V
60 BUFFERS 10 TO 12
MARKER SET @ 10kHz
50 MARKER READING = 36.6nV/ Hz
40
30
20
10
0
–10
0
5
10
15
20
25
FREQUENCY – Hz
TPC 29. Voltage Noise Density
vs. Frequency
APPLICATIONS
LCD Gamma Reference Buffers
In high resolution TFT-LCD displays, gamma correction must
A12
be performed to correct the nonlinearity in the LCD panel’s
transmission characteristics. A typical TFT-LCD panel consisting
of 256 grayscale levels takes an 8-bit digital word to select an
A11
appropriate gamma reference voltage. An 8-bit source driver may
use 12 analog voltages that match the characteristic gamma curve
for optimum panel picture quality. The ADD8701 is specifically
A10
designed to generate analog reference voltages to meet the gamma
characteristics of an LCD panel used by the source driver. The
gamma reference buffers offer 10 mA drive capability.
The ADD8701 is designed to meet the rail-to-rail capability
A9
needed by the application and yet offers a low cost-per-channel
solution. The design maximizes the die area by offering channels
to swing to the positive and negative rails. It is imperative that
A8
the channels swinging close to the supply rail be used for the
positive gamma references and that the channels swinging close
to GND be used for the negative gamma references. See Figure 2
A7
for an example of the application circuit.
LCD VCOM Buffer
The output of the VCOM buffer is designed to control the voltage
A6
on the back plate of the LCD display. The buffer must be capable
of sinking and sourcing capacitive pulse current. The amplifier
stability is designed for high load capacitance. A high quality
ceramic capacitor is recommended to supply short duration current
A5
pulses at the output. The VCOM buffer of the ADD8701 can
handle up to 35 mA of continuous output current and can drive
up to 1,000 nF of pure capacitive load.
A4
Unused Buffers
Inputs of any unused buffer should be tied to the ground plane.
A3
ADD8701
GMA
GMA
GMA
GMA
GMA
GMA
GMA
GMA
GMA
GMA
A2
GMA
REV. 0
–7–
A1
GMA
ADD8701
LCD SOURCE DRIVER
Figure 2. Application Circuit
Share Link: 