BUF16821_1 Datasheet, PDF (11/30 Pages) Texas Instruments – Programmable Gamma-Voltage Generator and VCOM Calibrator with Integrated Two-Bank Memory

BUF16821
www.ti.com ............................................................................................................................................................... SBOS428B – JULY 2008 – REVISED MAY 2009
When the BKSEL pin changes state, the BUF16821
acquires the last programmed DAC/V_COM values from
the nonvolatile memory associated with this newly
chosen bank. At power-up, the state of the BKSEL
pin determines which memory bank is selected.
The I²C master also has the ability to update
(acquire) the DAC registers with the last programmed
nonvolatile memory values using software control.
The bank to be acquired depends on the state of
BKSEL.
General Acquire Command
A general acquire command is used to update all
registers and DAC/V_COM outputs to the last
programmed values stored in nonvolatile memory. A
single-channel acquire command updates only the
register and DAC/V_COM output of the DAC/V_COM
corresponding to the DAC/V_COM address used in the
single-channel acquire command.
These are the steps of the sequence to initiate a
general channel acquire:
1. Be sure BKSEL is in its desired state and has
been stable for at least 1ms.
2. Send a START condition on the bus.
3. Send the appropriate device address (based on
A0) and the read/write bit = LOW. The BUF16821
acknowledges this byte.
4. Send a DAC/V_COM pointer address byte. Set bit
D7 = 1 and D6 = 0. Bits D5–D0 are any valid
DAC/V_COM address. Although the BUF16821
acknowledges 000000 through 010111, it stores
and returns data only from these addresses:
– 000000 through 001111
– 010010 and 010011
It returns 0000 for reads from 010000 and
010001, and 010100 through 010111. See
Table 4 for valid DAC/V_COM addresses.
5. Send a STOP condition on the bus.
Approximately 750µs (±80µs) after issuing this
command, all DAC/V_COM registers and DAC/V_COM
output voltages change to the respective, appropriate
nonvolatile memory values.
xxx
xxx
Single-Channel Acquire Command
These are the steps to initiate a single-channel
acquire:
1. Be sure BKSEL is in its desired state and has
been stable for at least 1ms.
2. Send a START condition on the bus.
3. Send the device address (based on A0) and
read/write bit = LOW. The BUF16821
acknowledges this byte.
4. Send a DAC/V_COM pointer address byte using the
DAC/V_COM address corresponding to the output
and register to update with the OTP memory
value. Set bit D7 = 0 and D6 = 1. Bits D5–D0 are
the DAC/V_COM address. Although the BUF16821
acknowledges 000000 through 010111, it stores
and returns data only from these addresses:
– 000000 through 001111
– 010010 and 010011
It returns 0000 reads from 010000 and 010001,
and 010100 through 010111. See Table 4 for
valid DAC/V_COM addresses.
5. Send a STOP condition on the bus.
Approximately 36µs (±4µs) after issuing this
command, the specified DAC/V_COM register and
DAC/V_COM output voltage change to the appropriate
OTP memory value.
MaxBank
The BUF16821 can provide the user with the number
of times the nonvolatile memory of a particular
DAC/V_COM channel nonvolatile memory has been
written to for the current memory bank. This
information is provided by reading the register at
pointer address 111111.
There are two ways to update the MaxBank register:
1. After initiating a single acquire command, the
BUF16821 updates the MaxBank register with a
code corresponding to how many times that
particular channel memory has been written to.
2. Following a general acquire command, the
BUF16821 updates the MaxBank register with a
code corresponding to the maximum number of
times the most used channel (OUT1–16 and
V_COMs) has been written to.
MaxBank is a read-only register and is only updated
by performing a general- or single-channel acquire.
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