AM3715 Power Rail Decoupling

AndMan said:

We have an application in which we wish to use discrete supplies on the AM3715 instead of a PMIC. Many of the supplies we are investigating require more capacitance output for stable operation than that specified as a maximum in tables 3-6 and 3-7 in the datasheet. What drives these maximum capacitance specifications, and are there situations in which more capacitance can reside on these rails? Note that we will be running all rails at fixed voltages and will not utilize DVFS.

My view on the maximum capacitance indicated in the data manual for the AM3715 is indicative of the tight relationship of the various PMICs appropriate for the AM3715 and the device itself to support such functionality as DVFS (Dynamic Voltage and Frequency Scaling).  In this type of scenario, adding more capacitance would have an effect on the transcient response of the supply rails as they are being modulated from jumping through various OPP (Operating Performance Points).

Beyond this, the AM3715 supports a concept called DPS, or Dynamic Power Switching, which is described in Chapter 3.1 and specifically in Section 3.1.2.3.  With DPS, the system switches dynamically between high and low consumption system power modes during system active time.  For this to be effective, the transition overhead must be minimized which would be affected by power supply transition latencies.  DPS transition latencies need to be small.

Since you have indicated DVFS is not a feature you are concerned with supporting and have a need to drive the AM3715 from a discrete supply design, there is less of a restriction on the maximum capacitance on each rail with the exception of ensuring the power-up and power-down sequencing is maintained.