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AD9122 power-up and settling time

Question asked by omkarpradhan on Apr 21, 2015
Latest reply on May 6, 2015 by Biao.H



I'm trying to figure out the smallest pulse duration that I can achieve with an FMCOMMS1+zedboard setup for a pulsed radar. I have questions regarding two possible ways to do this.


AD9122 used to pulse the signal.

1) I was planning to use the  I DAC sleep and Q DAC sleep (IDAC control and QDAC control registers-i.e. 0x41 and 0x45) . These seem to be fast wake-up modes. But don't see any info on exactly how fast. Is there any numbers on how soon after 'fast wake-up' can I expect a clean signal i.e. 0.5% of LSB? (Would this then simply be the settling time of 20ns?).

2) Is it possible to pulse i.e. switch the DAC o/p on /off by enabling/disabling the clock dividers (PLL, external clocks) instead?



AD4351 used to pulse the signal

2) If the VCO AD4351 was instead used to pulse the carrier RF, does the software power down and power up (using DB5 bit in register 2) need the same band select+PLL settling time as when the VCO is first powered up?