ADS1294CZXGR datasheet(52/114 Pages) TI2

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SCLK

DOUT

MSB

MSB-1

DRDY

MSB-2

Analog

Input

DRDY

Input Transient

START

4 x tDR

ADS1294, ADS1294R, ADS1296, ADS1296R, ADS1298, ADS1298R

SBAS459K – JANUARY 2010 – REVISED AUGUST 2015

www.ti.com

When the START pin is held high and there is a step change in the input signal, 3 × tDR conversion cycles are

required for the filter to settle to the new value, as shown in Figure 58. Settled data are available on the fourth

DRDY pulse. This settling time must be considered when trying to measure narrow pace pulses for pace

detection. Data are available to read at each DRDY high-to-low transition, but can be ignored.

Figure 58. Settling Time for Input Transient

9.4.1.2 Data Ready Pin (DRDY)

DRDY is an output. When DRDY transitions low, new conversion data are ready. The CS signal has no effect on

the data ready signal. Regardless of the status of the CS signal, a rising edge on SCLK pulls DRDY high. Thus,

when using multiple devices in the SPI bus, gate SCLK with CS. The behavior of DRDY depends on if the device

is in RDATAC mode or if the RDATA command is being used to read data on demand. See the RDATAC: Read

Data Continuous and RDATA: Read Data sections for further details.

When reading data with the RDATA command, the read operation can overlap the occurrence of the next DRDY

without data corruption.

Use the START pin or the START command to place the device either in normal data capture mode or pulse

data capture mode.

Figure 59 shows the relationship among DRDY, DOUT, and SCLK during data retrieval (in the case of an

ADS129x with a selected data rate that gives 24-bit resolution). DOUT latches at the rising edge of SCLK. The

device pulls DRDY high at the first falling edge of SCLK, regardless of whether data are being retrieved from the

device or a command is being sent through the DIN pin. The data starts from the MSB of the status word and

then proceeds to the ADC channel data in sequential order (that is, channel 1, channel 2, ..., channel x).

Channels that are powered down still have a position in the data stream; however, the data are not valid and can

be ignored.

Figure 59. DRDY with Data Retrieval (CS = 0)

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ADS1294CZXGR Datasheet(PDF) 52 Page - Texas Instruments