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ADC12DJ5200RF: ADC12DJ5200RF power supply recommendation

Prodigy 30 points

Replies: 4

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Part Number: ADC12DJ5200RF

Our question is about power sequencing of ADC12DJ5200RF. In data sheet (page 154) there is recommendation to use common 1.1VDC regulator for analog voltage VA11 and digital voltage VD11. Sometimes it’s not convenient because VD11 power consumption can be significantly bigger compare with analog voltage VA11 (for example, Power mode 5, VA11 has current consumption 845mA, VD11 2672 mA). The digital power can creates noise on analog voltage even choke isolation.
How critical is the requirement to use common voltage regulator? How big can be difference between VD11 and VA11 during power up/down procedure?
In eval board for ADC12DJ5200RF TI use different approach: switching regulator for VD11 and switching regulator with following LDO for VA11. This solution reduce power consumption on VD11 but probably has difference between this two voltages during power up/down.