AD6645ASVZ-105 Digital Output Current & driver condition

Hi all,

In the AD6645 Rev. E datasheet,

Absolute Maximum Ratings @ page 7,

Digital Output Current : 4 mA

We think this is continuous currents.

Is it rating of total pin or each pin ?

Is it true ?

Digital Outputs @ page 18,

10 mA (10 pF × 1 V ÷ 1 ns)

140 mA (14 bits ×10 mA/bit)

CLOAD = 10 pF. Capacitive loads < 10 pF ; recommended condition.

These are switching currents, then it does not equal to 4mA continuous current.

Is it true ?

Best regards,

sss



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[edited by: sss@jpn at 2:09 AM (GMT 0) on 21 Dec 2018]
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  • +1
    •  Analog Employees 
    on Feb 5, 2020 9:13 PM

    Hi sss,

    Your inquiry apparently got misrouted in our system. Sorry for the delayed response. To address your inquiry:

    Yes, the 4mA AMR spec on pg 7 is the max steady state source/sink current the output drivers illustrated in Fig 35 can sustain without potential damage.

    Yes, the 10mA/bit "example" on pg 18 reflects a worse case dynamic source/sink switching current when no series slew damping resistors are present in the output lines. The output drivers can tolerate these higher dynamic switching currents but they may contribute unwanted parasitic digital switching noise/transients that can couple back into your analog signal path, degrading performance. These unnecessarily high switching currents can easily be reduced by inserting the recommended series slew damping resistors between the ADC outputs and your receiver logic.

    Best Regards,

    TonyM

Reply
  • +1
    •  Analog Employees 
    on Feb 5, 2020 9:13 PM

    Hi sss,

    Your inquiry apparently got misrouted in our system. Sorry for the delayed response. To address your inquiry:

    Yes, the 4mA AMR spec on pg 7 is the max steady state source/sink current the output drivers illustrated in Fig 35 can sustain without potential damage.

    Yes, the 10mA/bit "example" on pg 18 reflects a worse case dynamic source/sink switching current when no series slew damping resistors are present in the output lines. The output drivers can tolerate these higher dynamic switching currents but they may contribute unwanted parasitic digital switching noise/transients that can couple back into your analog signal path, degrading performance. These unnecessarily high switching currents can easily be reduced by inserting the recommended series slew damping resistors between the ADC outputs and your receiver logic.

    Best Regards,

    TonyM

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