ADS7881

SLAS400 − SEPTEMBER 2003

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11

Sample N

Conversion N

Data For Conversion N−1

(Data read Without Latency)

CONVST

BUSY

D11−D0

t(conv) + td11

tw4

tw3

t(acq)

t0 = 250 ns for 4 MSPS Operation

th1

CS

td12

Figure 8. Back-To-Back operation With CS Toggling and RD Low

NAP MODE

The device can be put in nap mode following the sequences shown in Figure 9. This provides substantial power

saving while operating at lower sampling rates.

While operating the device at throughput rates lower than 3.2 MSPS, A_PWD can be held low (see Figure 9).

In this condition, the device goes into the nap state immediately after BUSY goes low and remains in that state

requirements section.

acquires data at the maximum conversion speed for some period of time (back-to-back conversion) and it does

not acquire data for some time while the acquired data is being processed. During this period, the device can

being low and sampling has not started. The minimum acquisition time for the first sampling after the nap state

A_PWD

(Held Low)

BUSY

SAMPLE

(Internal)

NAP

(Internal Active High)

t(acq) + 60 ns

NOTE: The SAMPLE (Internal) signal is generated as described in the Sampling and Conversion

Start section.

Figure 9. Device Operation While A_PWD is Held Low