BUF12840_15 Datasheet, PDF (9/31 Pages) Texas Instruments – Programmable Gamma-Voltage Generator

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DAC VOLTAGE OUTPUT CODE
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:
CODE
V_OUT = V_S ´ ₁₀₂₄
Where:
CODE can vary from 0 to 1023.
(1)
The BUF12840 outputs are capable of a full-scale
voltage output change in typically 5μs, see Figure 9;
no intermediate steps are required. The outputs are
also capable of a full-scale output change using the
BKSEL or LD pin in typically 7µs, see Figure 8.
SOFTWARE DAC OUTPUT UPDATE
Because the BUF12840 features a double-buffered
register structure, updating the digital-to-analog
converter (DAC) register is not the same as updating
the DAC output voltage. There are two methods for
updating the DAC output voltages.
Method 1: Method 1 is used when it is desirable to
have the DAC 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 output voltage update occurs after receiving the
16th data bit for the currently-written register, as
shown in Figure 11.
Method 2: Method 2 is used when it is desirable to
have all DAC output voltages change at the same
time. First, the master writes to the desired DAC
channels with data bit 15 a '0'. Then, when writing the
last desired DAC channel, the master sets data bit 15
to a '1'. All DAC channels are updated at the same
time after receiving the 16th data bit.
BUF12840
SBOS519A – OCTOBER 2010 – REVISED JULY 2011
Figure 11. Write DAC_OUT Register Timing
Copyright © 2010–2011, Texas Instruments Incorporated
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