參數(shù)資料
型號： BUF08821AIPWPR
廠商： TEXAS INSTRUMENTS INC
元件分類： 時(shí)鐘產(chǎn)生/分配
英文描述： VIDEO CLOCK GENERATOR, PDSO20
封裝： GREEN, PLASTIC, HTSSOP-20
文件頁數(shù)： 27/27頁
文件大小： 654K
代理商： BUF08821AIPWPR
V
=V
OUT
S
CODE
10
1024
www.ti.com ................................................................................................................................................. SBOS438C – AUGUST 2008 – REVISED AUGUST 2009
GENERAL-CALL RESET AND POWER-UP
NONVOLATILE MEMORY
The BUF08821 responds to a General-Call Reset,
BKSEL Pin
which is an address byte of 00h (0000 0000) followed
by a data byte of 06h (0000 0110). The BUF08821
The BUF08821 has 16x rewrite capability for each
acknowledges
both
bytes.
provides
a
word in the nonvolatile memory. The BUF08821 has
reference for the General-Call Reset command code.
the ability to store two distinct gamma curves in two
Upon receiving a General-Call Reset, the BUF08821
different nonvolatile memory banks, each of which
performs a full internal reset, as though it had been
has 16x rewrite capability. To facilitate fast switching
powered off and then on. It always acknowledges the
between the two distinct gamma curves, two storage
General-Call address byte of 00h (0000 0000), but
registers are implemented for each DAC channel so
does not acknowledge any General-Call data bytes
that there is no delay as a result of reading the
other than 06h (0000 0110).
nonvolatile memory when the banks are switched.
One of the two available banks is selected using the
When the BUF08821 powers up, it automatically
external input pin, BKSEL. When this pin is LOW,
performs a reset. As part of the reset, the BUF08821
BANK0 is selected; when this pin is HIGH, BANK1 is
is configured for all outputs to change to the last
selected.
programmed
nonvolatile
memory
values,
or
1000000000 if the nonvolatile memory values have
When the BKSEL pin changes state, the BUF08821
not been programmed.
switches all DAC channels simultaneously from the
values in the storage registers for the previously
selected bank to the values in the storage registers
for the new bank. The storage registers are not
OUTPUT VOLTAGE
updated from the nonvolatile memory. This switching
occurs within 5
μs of the BKSEL pin state change,
Buffer output values are determined by the analog
and the outputs settle in less than 5
μs. The total time
supply voltage (VS) and the decimal value of the
to switch from one gamma curve to the other gamma
binary input code used to program that buffer. The
curve is less than 10
μs. This fast switching allows for
value is calculated using Equation 1:
the
easy
implementation
of
dynamic
gamma
correction using the BUF08821.
(1)
Data from the nonvolatile memory may be fed into the
storage registers by commands issued by the I2C
The BUF08821 outputs are capable of a full-scale
master. The bank to be acquired by the command
voltage
output
change
in
typically
5
μs;
no
from the I2C master depends on the state of the
intermediate steps are required.
BKSEL pin. At power-on, the BUF08821 reads the
values from the nonvolatile memory into the storage
UPDATING THE DAC OUTPUT VOLTAGES
registers. If the I2C interface is used to update the
Because the BUF08821 features a double-buffered
storage registers through write operations, these
register
structure,
updating
the
digital-to-analog
values remain in the storage registers until the device
converter (DAC) and/or the VCOM register is not the
powers off, they are overwritten by a write command
same as updating the DAC and/or VCOM output
on the I2C interface, or a memory acquire command
voltage. There are two methods for updating the
is issued on the I2C interface. This architecture allows
DAC/VCOM output voltages.
a controller to update the storage registers with two
new gamma curves (one in each bank) without
Method 1: Method 1 is used when it is desirable to
updating the nonvolatile memory, and continue to
have
the
DAC/VCOM
output
voltage
change
change quickly between the two new gamma curves
immediately after writing to a DAC register. For each
by using the BKSEL pin.
write transaction, the master sets data bit 15 to a '1'.
The DAC/VCOM output voltage update occurs after
General Acquire Command
receiving the 16th data bit for the currently-written
register.
A general acquire command is used to update all
registers
and
DAC/VCOM
outputs
to
the
last
Method 2: Method 2 is used when it is desirable to
programmed values stored in nonvolatile memory for
have all DAC/VCOM output voltages change at the
the
selected
bank.
A
single-channel
acquire
same time. First, the master writes to the desired
command updates only the register and DAC/VCOM
DAC/VCOM channels with data bit 15 a '0'. Then,
output of the DAC/VCOM that corresponds to the
when writing the last desired DAC/VCOM channel, the
DAC/VCOM address used in the single-channel
master sets data bit 15 to a '1'. All DAC/VCOM
acquire command.
channels are updated at the same time after
receiving the 16th data bit.
Copyright 2008–2009, Texas Instruments Incorporated
9
Product Folder Link(s): BUF08821
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參數(shù)描述
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BUF08821B 制造商:TI 制造商全稱:Texas Instruments 功能描述:Programmable Gamma-Voltage Generator and VCOM Calibrator with Integrated Two-Bank Memory
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