ADS7253 datasheet(39/73 Pages) TI2

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SCLK

ADS8353, ADS8354

SDO_A

Sample

N+1

tACQ

tCONV

tTHROUGHPUT

Data From Sample N

5-A

Data From Sample N

B15

B14

SDI

ADS7853, ADS7854

SDO_A

Data From Sample N

ADS7253, ADS7254

SDO_A

4-A

D4-

D3-

D2-

D1-

D0-

5-B

D0-

D1-

D2-

D3-

D4-

3-A

2-A

D2-

D1-

D0-

3-B

D0-

D1-

D2-

1-A

0-A

D0-

1-B

D0-

All Devices

SDO_B

ADS8354, ADS7854, ADS7254

www.ti.com

SBAS556B – OCTOBER 2013 – REVISED AUGUST 2014

8.5.3.2.2

32-CLK, Single-SDO Mode (CFR.B11 = 0, CFR.B10 = 1)

The 32-CLK, single-SDO mode provides the option of using only one SDO pin (SDO_A) to read conversion

results from both ADCs (ADC_A and ADC_B). SDO_B remains in 3-state and can be treated as a no connect

(NC) pin.

This mode can be selected by writing CFR.B11 = 0 and CFR.B10 = 1. Figure 91 shows a detailed timing diagram

for this mode.

Figure 91. 32-CLK, Single-SDO Mode Timing Diagram

A CS falling edge brings the serial data bus out of 3-state and also outputs a 0 on the SDO_A pin. The device

converts the sampled analog input during the conversion time (tCONV). SDO_A reads 0 during this period. After

competing the conversion process, the sample-and-hold circuit goes back into sample mode. The device outputs

the MSB of ADC_A on the SDO_A pin on the 16th SCLK falling edge. The subsequent SCLK falling edges are

used to shift out the conversion result of ADC_A followed by the conversion result of ADC_B on the SDO_A pin,

as shown in Table 13.

Table 13. Data Launch Edge

LAUNCH EDGE

DEVICE

SCLK

↓

↓1

—

↓15

↓16

—

↓27

↓28

↓29

↓30

↓31

↓32

—

↓43

↓44

↓45

↓46

↓47

↓48 ...

↑

ADS8354

SDO-A

—

D15_A

—

D4_A

D3_A

D2_A

D1_A

D0_A

D15_B

—

D4_B

D3_B

D2_B

D1_B

D0_B

0 ...

Hi-Z

ADS7854

SDO-A

—

D13_A

—

D2_A

D1_A

D0_A

—

D2_B

D1_B

D0_B

0 ...

Hi-Z

ADS7254

SDO-A

—

D11_A

—

D0_A

—

D0_B

0 ...

Hi-Z

In this mode, at least 48 SCLK falling edges must be given to validate the read or write frame. A CS rising edge

ends the frame and puts the serial bus into 3-state.

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Product Folder Links: ADS8354 ADS7854 ADS7254

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