AD7468BRT-R datasheet(10/28 Pages) AD

10 / 28 page

AD7466/AD7467/AD7468

Rev. C | Page 10 of 28

TIMING EXAMPLES

Figure 3 shows some of the timing parameters from Table 4 in

the Timing Specifications section.

Timing Example 1

As shown in Figure 3, fSCLK = 3.4 MHz and a throughput of

100 kSPS gives a cycle time of tCONVERT + t8 + tQUIET = 10 μs.

Assuming VDD = 1.8 V, tCONVERT = t2 + 15(1/fSCLK) = 55 ns +

4.41 μs = 4.46 μs, and t8 = 60 ns maximum, then tQUIET = 5.48 μs,

which satisfies the requirement of 10 ns for tQUIET. The part is

fully powered up and the signal is fully acquired at Point A.

This means that the acquisition/power-up time is t2 + 2(1/fSCLK)

= 55 ns + 588 ns = 643 ns, satisfying the maximum requirement

of 640 ns for the power-up time.

Timing Example 2

The AD7466 can also operate with slower clock frequencies.

As shown in Figure 3, assuming VDD = 1.8 V, fSCLK = 2 MHz,

and a throughput of 50 kSPS gives a cycle time of tCONVERT + t8 +

tQUIET = 20 μs. With tCONVERT = t2 + 15(1/fSCLK) = 55 ns + 7.5 μs =

7.55 μs, and t8 = 60 ns maximum, this leaves tQUIET to be 12.39

μs, which satisfies the requirement of 10 ns for tQUIET. The part is

fully powered up and the signal is fully acquired at Point A,

which means the acquisition/power-up time is t2 + 2(1/fSCLK) =

55 ns + 1 μs = 1.05 μs, satisfying the maximum requirement of

640 ns for the power-up time. In this example and with other

slower clock values, the part is fully powered up and the signal

already acquired before the third SCLK falling edge; however,

the track-and-hold does not go into hold mode until that point.

In this example, the part can be powered up and the signal can

be fully acquired at approximately Point B in Figure 3.

SCLK

tCONVERT

tQUIET

1/THROUGHPUT

AUTOMATIC

POWER-DOWN

TRACK-AND-HOLD IN HOLD

TRACK-AND-HOLD

IN TRACK

ACQUISITION TIME

POINT A: THE PART IF FULLY POWERED UP WITH VIN FULLY ACQUIRED.

Figure 3. AD7466 Serial Interface Timing Diagram Example

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