Tcyc of LTC2310-14

Hi

Regarding LTC2310-14 data sheet, Tcyc max is 1msec. Our customer considers that Tconv plus Treadout is about 800nsec. When Tcnvh is close to 1msec, he is warried about Tcyc beyond 1msec. Can LTC2310-14 work at Tcyc > 1msec ? Could you please let me know the concern about working at Tcyc > 1msec ?

One more question regarding the ADC, what does 14-bit + sign mean ?  Why isn't it differential 15-bit ADC ?

Regards,

Hiroyuki

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  • 0
    •  Analog Employees 
    on Jan 2, 2019 4:23 PM over 1 year ago

    Tcyc max is a carryover from parts with 1 cycle of latency where the SCK is used to perform the conversion. I do not believe that is an issue with parts that have the conversion internally clocked.

    There is no difference really between 14-bit + sign and 15-bit ADC. Traditionally, ADCs have an even number of bits, so 14-bit + sign was used for this ADC.

  • Thank you for your reply.

    I don’t understand your reply about Tcyc. Why is Tcyc max decided as 1msec in data sheet ? Tcyc consists of Tcnvh, Tconv and Treadout. Tcyc is defined the time between the rising edge of CNV and the next rising edge of CNV. On the other hand, for example, AD4000 has no specification about Tcyc max. 

    Regarding INL, DNL and BZE, are these specs of LSB defined as 15bit ?

    Regards,

    Hiroyuki

  • 0
    •  Analog Employees 
    on Jan 28, 2019 3:22 PM over 1 year ago in reply to Hiroyuki.D

    Tcyc max is a carryover from ADCs that use the SCK to perform the conversion. If 1/Fsck was too long, the hold capacitor would start to lose charge through leakage and the conversion result would lose accuracy. The LTC2310-14 has an internal clock to perform the conversion, so SCK can be very slow and the ADC will still convert accurately. Tcyc max does not really apply to this part. 

    The data sheet states: The LTC2310-14 digitizes the full-scale voltage of 2 × REFOUT into 2^15 levels, resulting in an LSB size of 250µV with REFOUT = 4.096V. This means that INL, DNL and BZE LSBs are defined as 15bit.

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  • 0
    •  Analog Employees 
    on Jan 28, 2019 3:22 PM over 1 year ago in reply to Hiroyuki.D

    Tcyc max is a carryover from ADCs that use the SCK to perform the conversion. If 1/Fsck was too long, the hold capacitor would start to lose charge through leakage and the conversion result would lose accuracy. The LTC2310-14 has an internal clock to perform the conversion, so SCK can be very slow and the ADC will still convert accurately. Tcyc max does not really apply to this part. 

    The data sheet states: The LTC2310-14 digitizes the full-scale voltage of 2 × REFOUT into 2^15 levels, resulting in an LSB size of 250µV with REFOUT = 4.096V. This means that INL, DNL and BZE LSBs are defined as 15bit.

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