TLC32040C Datasheet, PDF (14/33 Pages) Texas Instruments – ANALOG INTERFACE CIRCUITS

TLC32040C, TLC32040I, TLC32041C, TLC32041I
ANALOG INTERFACE CIRCUITS
SLAS014E – SEPTEMBER 1987 – REVISED MAY 1995
improper operation due to conversion times being too close together
If the difference between two successive D/A conversion frame syncs is less than 1/19.2 kHz, the AIC operates
improperly. In this situation, the second D/A conversion frame sync occurs too quickly and there is not enough
time for the ongoing conversion to be completed. This situation can occur if the A and B registers are improperly
programmed or if the A + A’ register or A – A’ register result is too small. When incrementally adjusting the
conversion period via the A + A’ register options, the designer should be very careful not to violate this
requirement (see following diagram).
t1
t2
Frame Sync
FSX or FSR
 t2 – t1 1/19.2 kHz
Ongoing Conversion
asynchronous operation — more than one receive frame sync occurring between two transmit
frame syncs
When incrementally adjusting the conversion period via the A + A’ or A – A’ register options, a specific protocol
is followed. The command to use the incremental conversion period adjust option is sent to the AIC during a
FSX frame sync. The ongoing conversion period is then adjusted. However, either receive conversion period
A or B may be adjusted. For both transmit and receive conversion periods, the incremental conversion period
adjustment is performed near the end of the conversion period. Therefore, if there is sufficient time between
t₁ and t₂, the receive conversion period adjustment is performed during receive conversion period A. Otherwise,
the adjustment is performed during receive conversion period B. The adjustment command only adjusts one
transmit conversion period and one receive conversion period. To adjust another pair of transmit and receive
conversion periods, another command must be issued during a subsequent FSX frame (see figure below).
t1
FSX
FSR
Transmit Conversion Period
t2
Receive
Conversion
Period A
Receive
Conversion
Period B
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