TPS546C20A: What's the difference between TPS546C20 and TPS546C20A?

Jacky Wang(QD) 

There are a number of differences between the TPS546C20 and TPS546C20A.  They are not designed to be interoperable and TI does not recommend replacing a TPS546C20A with a TPS546C20.

1) Default function of Pin 32 (PGD/RESET)

The TPS546C20 defaults Pin 32 to the RESET function and does not have Power Good by default.

The TPS546C20A defaults Pin 32 to the PGOOD function for start-up sequencing.

2) TON_RISE when SS pin pulled to BP3

The TPS546C20 defaults TON_RISE to 7ms when pulled to BP3

The TPS546C20A default the TON_RISE to select the NVM programmed TON_RISE, allowing users to change the TON_RISE and store that value to NVM.

3) IOUT_WARN_LIMIT and IOUT_OC_FAULT_LIMIT default and maximum programmable value

The TPS546C20 has a default Warning of 35A and Fault of 40A with maximum programmable range of 39.5A and 40A respectively.  The TPS546C20A extends the defaults to 37A Warning and 42A fault with meximum programmable values of 50 and 52A respectively.

4) The TPS546C20A offers tighter specifications for:  Switching Frequency, Remote Sense Amplifier Offset, Over-Voltage Fault and Under Voltage Fault thresholds

5) Default OV-Fault Response.

The TPS546C20 default the VOUT_OV_FAULT_RESPONSE to Ignore while the TPS546C20A defaults the OV Fault Response to shutdown and restart

6) Output Voltage when VOUT_COMMAND received during TON_RISE (Soft-start)

The TPS546C20 can experience a VOUT_COMMAND counter fault condition if a new VOUT_COMMAND value lower than the current output voltage is received during the TON_RISE period.  When this occurs, VOUT will continue to rise past the original VOUT_COMMAND value until the FB voltage rises to 1.5V, then the reference will reset to 0V and continue to rise until VOUT reaches the programmed VOUT_COMMAND value.

The TPS546C20 will not exceed the previous programmed VOUT_COMMAND and will drop to the newly updated VOUT_COMMAND value.

7) VOUT_TRIM readback error when negative values

The TPS546C20 does not correctly support negative read-back for the VOUT_COMMAND value.

8) MEM error in STATUS_CML and SMBALERT assertion.

The TPS546C20 can report a MEM error in STATUS_CML and ALERT assertion when STORE_USER_ALL PMBus values to NVM in Follower (second device in 2-phase stack) when VOUT_COMMAND is not equal to 0.95V

9) Programmed VOUT_COMMAND following power-up with VSEL fault

The TPS546C20 will power up to the VOUT_COMMAND stored in NVM following a power-up with a convergence fault on VSEL pin.

The TPS546C20A will prevent output enable following a power-up with a convergence fault on the VSEL pin to prevent power-up with the wrong VOUT.