DDC232 Datasheet, PDF (22/28 Pages) Burr-Brown (TI) – 32-Channel, Current-Input Analog-to-Digital Converter

DDC232
SBAS331C – AUGUST 2004 – REVISED SEPTEMBER 2006
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)τ_DCLK is used for FORMAT = 0,
where t_DCLK is the period of the data clock. For
example, if t_INT = 1000µs 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
Table 11. Timing for Readback
SYMBOL DESCRIPTION
t_SDCV Data Retrieval Shutdown Before or After Edge of CONV
CLK = 5MHz, Clk_4x = 0
MIN
TYP
MAX
10
UNITS
µs
22
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