BUF08630_14 Datasheet, PDF (13/35 Pages) Texas Instruments – Programmable Gamma-Voltage Generator and High Slew Rate VCOM

BUF08630
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GENERAL-CALL RESET AND POWER-UP
The BUF08630 responds to a General-Call Reset,
which is an address byte of 00h (0000 0000) followed
by a data byte of 06h (0000 0110). The BUF08630
acknowledges both bytes. Table 2 provides a
reference for the General-Call Reset command code.
Upon receiving a General-Call Reset, the BUF08630
performs a full internal reset, as though it had been
powered off and then on. It always acknowledges the
General-Call address byte of 00h (0000 0000), but
does not acknowledge any General-Call data bytes
other than 06h (0000 0110).
When the BUF08630 powers up, it automatically
performs a reset. As part of the reset, the BUF08630
is configured for all outputs to change to the last
programmed nonvolatile memory values, or
1000000000 if the nonvolatile memory values have
not been programmed.
Upon power-up or general-call reset, the DAC
registers for channels 1 though 8 are set to 200
(default) that corresponds to mid-scale output for a
10-bit DAC. The high and low limit registers are set to
3FF and 000 respectively. Therefore, the limits are
transparent if not programmed. Reset typically
requires approximately 1ms.
OUTPUT VOLTAGE
Buffer output values are determined by the analog
supply voltage (V_S) and the decimal value of the
binary input code used to program that buffer. The
value is calculated using Equation 1:
V_OUT = V_S ´
Code
1024
Where Code = 0 to 1023.
(1)
The BUF08630 outputs are capable of a full-scale
voltage output change in typically 5 μs; no
intermediate steps are required.
SBOS515A – OCTOBER 2010 – REVISED AUGUST 2012
UPDATING THE DAC OUTPUT VOLTAGES
Because the BUF08630 features a double-buffered
register structure, updating the digital-to-analog
converter (DAC) and/or the V_COM register is not the
same as updating the DAC and/or V_COM output
voltage. There are two methods for updating the
DAC/V_COM output voltages.
Method 1: Method 1 is used when it is desirable to
have the DAC/V_COM output voltage change
immediately after writing to a DAC register. For each
write transaction, the master sets data bit 15 to a '1'.
The DAC/V_COM output voltage update occurs after
receiving the 16th data bit for the currently-written
register.
Method 2: Method 2 is used when it is desirable to
have all DAC/V_COM output voltages change at the
same time. First, the master writes to the desired
DAC/V_COM channels with data bit 15 a '0'. Then,
when writing the last desired DAC/V_COM channel, the
master sets data bit 15 to a '1'. All DAC/V_COM
channels are updated at the same time after
receiving the 16th data bit.
NONVOLATILE MEMORY
BKSEL Pin
The BUF08630 has 16x rewrite capability of the
nonvolatile memory. Additionally, the BUF08630 has
the ability to store two distinct gamma curves in two
different nonvolatile memory banks, each of which
has 16x rewrite capability. One of the two available
banks is selected using the external input pin,
BKSEL. When this pin is low, BANK0 is selected;
when this pin is high, BANK1 is selected.
When the BKSEL pin changes state, the BUF08630
loads values from the DAC registers to the DAC
outputs for the newly chosen bank. At power-up, the
state of the BKSEL pin determines which memory
bank is selected.
The two-wire 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.
Copyright © 2010–2012, Texas Instruments Incorporated
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