TPS543B20: schematic check

Hi GARETH OU,

1. 1V rail:
   1. Is there a reason the customer wants to use 0.6V reference and have a resistor divider versus using the 1V reference setting (VSEL = open). By using the 1V reference, they will have higher output accuracy since they can tie RSP and RSN sense directly to the output without needing a resistor divider that introduces additional error to the output set point.
   2. If they are keeping the reference as 0.6V and keeping the feedback divider, I would suggest adding a DNP placeholder for a feedforward capacitor Cff in parallel to R3038/R3039. Or they can use the R3039 placeholder for a Cff if needed since it is a DNP component.
   3. Please add a 10-100nF capacitor between pin 25 PVIN and pin 27 GND per datasheet layout recommendations on p. 36.
   4. Otherwise schematic looks fine. I cannot find that inductor part number but assume the R68M suffix means it is a 0.68uH. This same inductor is used on all three rails.
   5. Please check the voltage rating on the input caps, keeping in mind the capacitor derating due to 12V bias on these capacitors.

2. 1.8V rail:
   
   1. I would recommend using RVSEL = 51.1kohm to set VREF = 0.9V. That way feedback divider can be matched 10kohm top (R3024) and 10kohm bottom (R3023) resistors.
   2. Same recommendation as for 1V rail of adding a DNP feedforward capacitor placeholder Cff in parallel to the top feedback resistor R3024. Or they can use the R3025 placeholder for a Cff if needed since it is a DNP component.
   3. Same recommendation as for 1V rail of adding 10-100nF capacitor between pin 25 PVIN and pin 27 GND
   4. Same comment about checking voltage rating on input caps.
3. 3.3V rail:
   
   1. Overall looks fine.
   2. Same recommendation as for 1V rail of adding a DNP feedforward capacitor placeholder Cff in parallel to the top feedback resistor R4415. R4420 can also be stuffed with Cff instead since it is already a DNP component.
   3. Same recommendation as for 1V rail of adding 10-100nF capacitor between pin 25 PVIN and pin 27 GND
   4. Same comment about checking voltage rating on input caps.

Hi GARETH OU,

I just noticed that the 3.3V rail has 5V input. I would recommend reducing the switching frequency of that rail to <=750kHz to give some more margin to the converter's minimum off time of 250ns typical in datasheet. This would require RT=R4424 to change to approximately 26kohm.

Hi Kris

Attached is the customer updated circuit diagram

TI TPS543B20RVFR-20201218.pdf