DDC112_15 Datasheet, PDF (16/34 Pages) Texas Instruments – Dual Current Input 20-Bit ANALOG-TO-DIGITAL CONVERTER

Ncont Mode
Figure 13 illustrates operation in the ncont mode. The
integrations come in pairs (that is, sides A/B or sides B/A)
followed by a time during which no integrations occur.
During that time, the previous integrations are being mea-
sured, reset and auto-zeroed. Before the DDC112 can
advance to states 3 or 6, both sides A and B must be
finished with the m/r/az cycle which takes time t₁₀. When the
m/r/az cycles are completed, time t₁₁ is needed to prepare
the next side for integration. This time is required for the
ncont mode because the m/r/az cycle of the ncont mode is
slightly different from that of the cont mode. After the first
integration ends, DVALID goes LOW in time t₈. This is the
same time as in the cont mode. The second data will be
ready in time t₉ after the first data is ready. One result of the
naming convention used in this application bulletin is that
when the DDC112 is operating in the ncont mode, it passes
through both ncont mode states and cont mode states. For
example, in Figure 13, the state pattern is 3, 4, 1, 2, 3, 4, 1,
2, 3, 4...where 3 and 4 are cont mode states. Ncont mode
by definition means that for some portion of the time, neither
side A nor B is integrating. States that perform an integration
are labeled cont mode states while those that do not are
called ncont mode states. Since integrations are performed
in the ncont mode, just not continuously, some cont mode
states must be used in an ncont mode state pattern.
CONV
State
Integration
Status
m/r/az
Status
mbsy
DVALID
3
4
1
Int A Int B
23
4
t₁₁
Int A Int B
m/r/az A
m/r/az B
t₁₀
m/r/az A
1
2
m/r/az B
t₉
t₈
Side A
Data
Side B
Data
Side A
Data
Side B
Data
SYMBOL
t₈
t₉
t₁₀
t₁₁
DESCRIPTION
1st ncont mode data ready.
2nd ncont mode data ready.
Ncont mode m/r/az cycle.
Prepare side for integration.
VALUE (CLK = 10MHz)
421.2 ±0.3µs
454.8µs
910.8µs
≥ 24.0µs
FIGURE 13. Non-Continuous Mode Timing.
VALUE (CLK = 15MHz)
280.8 ±0.2µs
303.2µs
607.2µs
≥ 24.0µs
16
DDC112
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SBAS085B