Recommended Sequency to change channels over I2C

Question I can't change channels on the AD7998, I get the same value 8 times. Can you give a recommended sequence to change channels over I2C? Answer START Write Address ACK by AD7993 Command mode byte 0x30 (set command bits to 0011 and address pointer bits to 0000) On the 5th SCL rising edge of the command/pointer byte the ADC will power up and convert on ch1 ADC ACK Repeated Start (ensure this is not a stop condition) Read address (part power up and converts on ch2) ACK by AD7993 MSB byte of conversion result ch1 ACK by master LSB byte of conversion result ch1 ACK by master (part powers up and converts on ch1 again) MSB byte of conversion result ch2 ACK by master LSB byte of conversion result ch2 NACK by master STOP Once the command bits are set in the command/address pointer byte the ADC starts to operate in mode 2. When ever the part receives a STOP or NACK condition it will no longer operate in mode 2 until the command bits are again programmed to do so.

Why is it recommended to use a dedicated voltage reference IC for the REF_IN pin of the AD7998 instead of a regular power supply?

Answer: AD7998 does not have an internal voltage reference, it is recommended to provide an external reference via REF_IN. To achieve accurate and stable ADC performance, it's recommended to use a dedicated voltage reference IC instead of a regular power supply, as voltage references offer better stability, lower noise, and tighter tolerance.

AD7998: Unused control pin

Question I do not intend to use AD7998 pin 16 (CONVST) for control. Do I tie this pin high-low or leave floating. Intend to use Mode 2 only for conversions. Answer The CONVST pin should be tied low for all other modes of operation. I do not intend to use AD7998 pin 16 (CONVST) for control. Do I tie this pin high-low or leave floating. Intend to use Mode 2 only for conversions, have no spare I/O on processor chip.

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AD7998 Production
The AD7997Â / AD7998 are 8-channel, 10- and 12-bit, low power, successive approximation ADCs with an I2C-compatible interface. The parts operate from a...
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AD7998 on Analog.com