DDC112 Datasheet, PDF (23/24 Pages) Burr-Brown (TI) – Dual Current Input 20-Bit ANALOG-TO-DIGITAL CONVERTER

RETRIEVAL: NONCONTINUOUS MODE
Retrieving in noncontinuous mode is slightly different as
compared with the continuous mode. As shown in Figure 27
and described in detail in Application Bulletin AB-131,
DVALID goes LOW in time t₃₀ after the first integration
completes. If T_INT is shorter than this time, all of t₃₁ is
available to retrieve data before the other side’s data is
ready. For T_INT > t₃₀, the first integration’s data is ready
before the second integration completes. Data retrieval must
be delayed until the second integration completes leaving
less time available for retrieval. The time available is
t₃₁ – (T_INT – t₃₀). The second integration’s data must be
retrieved before the next round of integrations begin. This
time is highly dependent on the pattern used to generate
CONV. As with the continuous mode, data retrieval must
halt before and after CONV toggles (t₂₈, t₂₉) and be com-
pleted before new data is ready (t₂₆).
POWER-UP SEQUENCING
Prior to power-up, all digital and analog input pins must be
LOW. At the time of power-up, these signal inputs can be
biased to a voltage other than 0V, however, they should
never exceed AV_DD or DV_DD. The level of CONV at power-
up is used to determine which side (A or B) will be
integrated first. Before integrations can begin though, CONV
must toggle, as shown in Figure 28.
CONV
T_INT
T_INT
DVALID
DXMIT
t₃₀
t₃₁
T_INT
T_INT
DCLK
•••
•••
SYMBOL
t₃₀
t₃₁
DOUT
DESCRIPTION
1st Ncont Mode Data Ready (see AB-131)
2nd Ncont Mode Data Ready (see AB-131)
•••
Side A
Data
•••
Side B
Data
CLK = 10MHz
MIN
TYP
MAX
421.2 ±0.3
454.8
CLK = 15MHz
MIN
TYP
MAX
280.5 ±0.2
302.9
UNITS
µs
µs
FIGURE 27. Readback in Noncontinuous Mode.
CONV
(HIGH at power-up)
CONV
(LOW at power-up)
Release State
Power-Up
Initialization
Start
Integration
t₃₂
t₃₃
Integrate Side A
Integrate Side B
Power Supplies
FIGURE 28. Timing Diagram at Power-Up of the DDC112.
SYMBOL
t₃₂
t₃₃
DESCRIPTION
Power-On Initialization Period
From Release Edge to Integration Start
TABLE XI. Timing for the DDC112 Power-Up Sequence.
23
MIN
TYP
MAX
UNITS
50
µs
50
µs
®
DDC112