ADS1291_14 Datasheet, PDF (34/75 Pages) Texas Instruments – Power, 2-Channel, 24-Bit Analog Front-End for Biopotential Measurements

ADS1291
ADS1292
ADS1292R
SBAS502B – DECEMBER 2011 – REVISED SEPTEMBER 2012
www.ti.com
When using multiple devices, the devices can be synchronized with the START signal. The delay from START to
the DRDY signal is fixed for a fixed data rate (see the START subsection of the SPI Interface section for more
details on the settling times). Figure 41 shows the behavior of two devices when synchronized with the START
signal.
START
CLK
Device₁
START₁
DRDY
CLK
DRDY₁
Device₂
START₂
DRDY
CLK
DRDY₂
CLK
START
Note 1
DRDY₁
DRDY₂
Note 2
(1) Start pulse must be at least one t_MOD cycle wide.
(2) Settling time number uncertainty is one t_MOD cycle.
Figure 41. Synchronizing Multiple Converters
Standard Mode
Figure 42 shows a configuration with two devices cascaded together. One of the devices is an ADS1292R (two-
channel with RESP) and the other is an ADS1292 (two-channel). Together, they create a system with four
channels. DOUT, SCLK, and DIN are shared. Each device has its own chip select. When a device is not selected
by the corresponding CS being driven to logic 1, the DOUT of this device is high-impedance. This structure
allows the other device to take control of the DOUT bus.
START⁽¹⁾
CLK
START
CLK
DRDY
CS
ADS1292
(Device 0)
SCLK
DIN
DOUT
START
CLK
ADS1292R
(Device 1)
DRDY
CS
SCLK
DIN
DOUT
INT
GPO0
GPO1
SCLK
MOSI
MISO
Host Processor
Figure 42. Multiple Device Configurations
34
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