DDC232_15 Datasheet, PDF (22/34 Pages) Texas Instruments – 32-Channel, Current-Input Analog-to-Digital Converter

DDC232
SBAS331D – AUGUST 2004 – REVISED APRIL 2010
RETRIEVAL BEFORE CONV TOGGLES
(CONTINUOUS MODE)
Data retrieval before CONV toggles is the most
straightforward method. Data retrieval begins soon
after DVALID goes low and finishes before CONV
toggles, as shown in Figure 20. For best
performance, data retrieval must stop t_SDCV before
CONV toggles. This method is most appropriate for
longer integration times. The maximum time available
for readback is t_INT – t_CMDR – t_SDCV.
For DCLK = 10MHz and CLK = 5MHz, the maximum
number of DDC232s that can be daisy-chained
together (Format = 1) is calculated by Equation 1:
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t_INT * ^ǒt_CMDR ) t_SDCV^Ǔ
(20 32)t_DCLK
(1)
NOTE: (16 × 32)t_DCLK is used for Format = 0, where
t_DCLK is the period of the data clock. For example, if
t_INT = 1000ms and DCLK = 10MHz, the maximum
number of DDC232s with Format = 1 is shown in
Equation 2:
1000ms * 286.8ms
(640)(100ns)
+
11.14
³
11
DDC232
(2)
(or 13 for Format = 0)
CONV
DVALID
DCLK
DOUT
t_CMDR
t_INT
t_SDCV
…
…
Side B
Data
t_INT
…
…
Side A
Data
Figure 20. Readback Before CONV Toggles
SYMBOL
t_SDCV
Table 15. Timing Characteristics for Readback
DESCRIPTION
Data Retrieval Shutdown Before or After Edge of CONV
MIN
TYP
10
MAX
UNITS
ms
22
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