Datasheet

CONVST
CONVST
CONVST
#1
#2
#3
EOC#1
(activelow)
CS #2
#3CS
SCLK#1
SCLK#2
SCLK#3
SDO#1
CDI#2
SDO#2
CDI#3
EOS
EOC
EOS
Conversion N
Conversion
fromDevice#2
N
1..............16
ManualTrigger,ReadWhileSampling
(UseinternalCCLK,EOCactivelow,andTAGmodedisabled)
High-Z
High-Z
High-Z
CS #1
t =18CCLK
CONV
t =3CCLKmin
SAMPLE1
t
SU2
t
SU2
High-Z
SDO#3
High-Z
High-Z
1..............16 1..............16
Conversion
fromDevice#3
N
Conversion
fromDevice#1
N
Conversion
fromDevice#1
N
Conversion
fromDevice#2
N Conversion
fromDevice#1
N
SDI#1
SDI#2
SDI#3
Don'tCare Configure
ReadData ReadData
Don'tCare
ADS8331/32
#1
SDI
SDO
SDI
SDO
SDI
SDO
MICROCONTROLLER
SDISDOCS1 CS2 CS3
ProgramDevice#1:CFR_D5= ‘1’
INT
CS
CONVST
CS
CONVST
CS
CONVST
EOC/INT
CDI CDI
ProgramDevices#2and#3:CFR_D5= ‘0’
SCLK
SCLKSCLK SCLK
ADS8331/32
#2
ADS8331/32
#3
ADS8331
ADS8332
SBAS363C –DECEMBER 2009–REVISED MAY 2012 www.ti.com
Figure 46. Multiple Converters Connected Using Daisy-Chain Mode
When multiple converters are used in daisy-chain mode, the first converter is configured in regular mode while
the rest of the converters downstream are configured in daisy-chain mode. When a converter is configured in
daisy-chain mode, the CDI input data go straight to the output register. Therefore, the serial input data passes
through the converter with either a 16 SCLK (if the TAG feature is disabled) or 24 SCLK delay, as long as CS is
active. See Figure 47 for detailed timing. In this timing diagram, the conversion in each converter is performed
simultaneously.
Figure 47. Simplified Dasiy-Chain Mode Timing with Shared CONVST and Continuous CS
The multiple CS signals must be handled with care when the converters are operating in daisy-chain mode. The
different chip select signals must be low for the entire data transfer (in this example, 48 bits for three
conversions). The first 16-bit word after the falling chip select is always the data from the chip that received the
chip select signal.
30 Copyright © 2009–2012, Texas Instruments Incorporated