TLC5618_16 Datasheet, PDF (15/25 Pages) Texas Instruments – PROGRAMMABLE DUAL 12-BIT DIGITAL-TO-ANALOG CONVERTERS

TLC5618, TLC5618A
PROGRAMMABLE DUAL 12-BIT DIGITAL-TO-ANALOG CONVERTERS
APPLICATION INFORMATION
SLAS156G – JULY 1997 – REVISED APRIL 2001
latch B and double-buffer 1 write (D15 = low, D12 = low)
The SIR data are written to both latch B and the double buffer. Latch A is unaffected.
Serial
Interface
Register
Latch A
To DAC A
D12 = Low
D15 = Low
Double
Buffer Latch
Latch B
To DAC B
Figure 20. Latch B and Double-Buffer Write
double-buffer-only write (D15 = low, D12 = high)
The SIR data are written to the double buffer only. Latch A and B contents are unaffected.
Serial
Interface
Register
Latch A
To DAC A
D12 = High
D15 = Low
Double
Buffer
Latch B
To DAC B
Figure 21. Double-Buffer-Only Write
purpose and use of the double buffer
Normally only one DAC output can change after a write. The double buffer allows both DAC outputs to change
after a single write. This is achieved by the two following steps.
1. A double-buffer-only write is executed to store the new DAC B data without changing the DAC A and B
outputs.
2. Following the previous step, a write to latch A is executed. This writes the SIR data to latch A and also
writes the double-buffer contents to latch B. Thus both DACs receive their new data at the same time,
and so both DAC outputs begin to change at the same time.
Unless a double-buffer-only write is issued, the latch B and double-buffer contents are identical. Thus, following
a write to latch A or B with another write to latch A does not change the latch B contents.
operational examples
changing the latch A data from zero to full code
Assuming that latch A starts at zero code (e.g., after power up), the latch can be filled with 1s by writing (bit D15
on the left, D0 on the right)
1X0X 1111 1111 1111
to the serial interface. Bit D14 can be zero to select slow mode or one to select fast mode. The other X can be
zero or one (don’t care).
The latch B contents and the DAC B output are not changed by this write unless the double-buffer contents are
different from the latch B contents. This can only be true if the last write was a double-buffer-only write.
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