AD7277ARMZ datasheet(25/29 Pages) AD

25 / 29 page

AD7276/AD7277/AD7278

Rev. C | Page 24 of 28

AD7278 IN A 10 SCLK CYCLE SERIAL INTERFACE

For the AD7278, if CS is brought high during the 10

th rising

edge after the two leading zeros and eight bits of the conversion

are provided, then the part can achieve a 4 MSPS throughput

rate. For the AD7278, the track-and-hold goes back into track

mode on the ninth rising edge. In this case, a fSCLK = 48 MHz and

throughput of 4 MSPS result in a cycle time of t2 + 8.5(1/fSCLK) +

tACQ = 250 ns, where t2 = 6 ns minimum and tACQ = 67 ns. This

satisfies the requirement of 60 ns for tACQ.

shows that

tACQ comprises 0.5(1/fSCLK) + t8 + tQUIET, where t8 = 14 ns max.

This allows a value of 43 ns for tQUIET, satisfying the minimum

requirement of 4 ns.

Figure 35

MICROPROCESSOR INTERFACING

AD7276/AD7277/AD7278-to-ADSP-BF53x

The ADSP-BF53x family of DSPs interfaces directly to the

AD7276/AD7277/AD7278 without requiring glue logic. The

SPORT0 Receive Configuration 1 Register should be set up as

outlined in Table 9.

AD7276/

AD7277/

AD7278*

ADSP-BF53x*

SCLK

RCLK0

SPORT0

DR0PRI

RFS0

DT0

DOUT

DIN

*ADDITIONAL PINS OMITTED FOR CLARITY

Figure 36. Interfacing with ADSP-BF53x

Table 9. The SPORT0 Receive Configuration 1 Register

(SPORT0_RCR1)

Setting

Description

RCKFE = 1

Sample data with falling edge of RSCLK

LRFS = 1

Active low frame signal

RFSR = 1

Frame every word

IRFS = 1

Internal RFS used

RLSBIT = 0

Receive MSB first

RDTYPE = 00

Zero fill

IRCLK = 1

Internal receive clock

RSPEN = 1

Receive enabled

SLEN = 1111

16-bit data-word (or can be set to 1101 for

14-bit data-word)

TFSR = RFSR = 1

To implement the power-down modes, SLEN should be set to

1001 to issue an 8-bit SCLK burst.

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