Datasheet

START
DRDY
CS
SCLK
DIN
DOUT
ADS1198
(Device0)
START
DRDY
CS
SCLK
DIN
DOUT
ADS1194
(Device1)
START
(1)
a)StandardConfiguration
CLK
CLK
INT
GPO0
GPO1
SCLK
MOSI
HostProcessor
MISO
CLK
START
DRDY
CS
SCLK
DIN
DOUT
0
ADS1198
(Device0)
START
DRDY
CS
SCLK
DIN
DAISY_IN
1
ADS1194
(Device1)
START
(1)
b)Daisy-ChainConfiguration
CLK
CLK
INT
GPO
SCLK
MOSI
HostProcessor
MISO
CLK
0
DOUT
1
DAISY_IN
0
ADS1194, ADS1196
ADS1198
www.ti.com SBAS471C –APRIL 2010– REVISED NOVEMBER 2011
Standard Mode
Figure 36a shows a configuration with two devices cascaded together. One of the devices is an ADS1198
(eight-channel) and the other is an ADS1194 (four-channel). Together, they create a system with 12 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. This configuration method is suitable for the majority of
applications.
DAISY-CHAIN MODE
Daisy-chain mode is enabled by setting the DAISY_EN bit in the CONFIG1 register. Figure 36b shows the
daisy-chain configuration. In this mode SCLK, DIN, and CS are shared across multiple devices. The DOUT of
one device is hooked up to the DAISY_IN of the other device, thereby creating a chain. One extra SCLK must be
issued in between each data set. Also, when using daisy-chain mode the multiple readback feature is not
available. Short the DAISY_IN pin to digital ground if not used. Figure 2 (Daisy-Chain Interface Timing) describes
the required timing for the ADS1198 shown in Figure 36. Data from the ADS1198 appear first on DOUT, followed
by a don’t care bit, and finally by the status and data words from the ADS1194.
(1) To reduce pin count, set the START pin low and use the START serial command to synchronize and start conversions.
Figure 36. Multiple Device Configurations
In a case where all devices in the chain operate in the same register setting, DIN can be shared as well and
thereby reduce the SPI communication signals to four, regardless of the number of devices. However, because
the individual devices cannot be programmed, the RLD driver cannot be shared among the multiple devices.
Furthermore, an external clock must be used.
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Product Folder Link(s): ADS1194 ADS1196 ADS1198