Tool/software:
Hello,
At the maximum, up to how many ADS127L11s can be connected in a daisy-chain configuration?
How about ADS127L21? At the maximum, up to how many ADS127L21s can be connected in a daisy-chain configuration?
Best regards,
K.Hirano
Hello K.Hirano,
The maximum number of devices in daisy-chain depends on the data rate, frame size, and SCLK frequency.
Frame size ranges from 16b up to 40b. Maximum data rate is 1067ksps (ADS127L11) and 1365ksps (ADS127L21), but at this data rate, daisy-chain is not possible.
Maximum SCLK frequency is 16.5MHz with IOVDD=1.8V, and 20MHz with IOVDD=2V or greater for both ADS127L11 and ADS127L21 in daisy-chain.
Details can be found in the below application note:
ADS127L11 in Simultaneous-Sampling Systems
ADS127L11 Maximum number:
IOVDD=3.3V
fSCLK=20MHz
fDATA=200ksps
bits per frame = 24 (24b data, no STATUS byte or CRC)
Max Number in daisy-chain = floor[fSCLK/(fDATA*bits per frame)] = floor [20000000/(200000*24)] = 4
ADS127L21 Maximum number:
IOVDD=3.3V
fSCLK=20MHz
fDATA=256ksps
bits per frame = 24 (24b data, no STATUS byte or CRC)
Max Number in daisy-chain = floor[fSCLK/(fDATA*bits per frame)] = floor [20000000/(256000*24)] = 3
Regards,
Keith Nicholas
Precision ADC Applications
