TPS659037: TPS659036/7 VS TPS659038/9

Hi Iwasaki-san,

> TPS6590378 and 9 were added LDOLN from 500us to 1000us. Why was it added?
To more closely align with the AM572x sequence requirements, we wanted to make sure DDR ramps down before VDDS18V. So we did two changes:

1. Move DDR supply from slot 3 to slot 2
2. Increase slot 2 -> slot 3 delay from 500us to 1000us

The reason for the delay increase is because DDR typically has a lot of capacitance on the supply rail (more than VDDS18V), so its ramp down will be slower. So we increased the time to make sure that DDR can discharge before VDDS18V starts its discharge.

> How does a custome select TPS65906/7 or TPS659038/9?
If your customer is already using TPS6590376/7, they can continue using it. If they are starting a new design, or have the opportunity to change the PMIC, we recommend that they use TPS6590378/9.

If they are trying to choose between TPS6590378 and TPS6590379, they should choose this based on the performance needed. TPS6590378 combined DSPEVE/GPU/IVA on to SMPS45 with 4A capability, and leaves SMPS7 and SMPS9 unused so they can save on inductors / capacitors, or use these for external loads. TPS6590379 has an individual supply for DSPEVE, GPU, and IVA, so it can reach higher performance points.

> The sequence of TPS659038/9 were inserted GPIO2. Is that for a FAN?
This was added in case we needed to add an external discharge FET to DDR supply to make it discharge even faster. Then GPIO_2 could be used with an inverter to drive an NMOS from VDD_DDR to GND. Based on our testing, this is not required to meet the timing requirements between DDR and VDDS18V, but it was added in the sequence as a backup in case it was needed.

Regards,
Karl