TPS546D24A: difference from TPS546C23

Fred Cheng 

It's a VERY long list.  Aside from them both being PMBus configured and controlled fixed frequency, high current switching BUCK regulators, they are different parts.

1) Control Mechanism

TPS546C23 uses externally compensated voltage mode control

TPS546D24A uses internally compensated dual-loop average current mode control

2) Current Handling

TPS546C23 is rated for 35A application current

TPS546D24A is rated for 40A application current

3) Frequency Programming

TPS546C23 uses continuously programmable switching frequency

TPS546D24A uses discrete pin selectable and PMBus programmable switching frequency

4) Output Voltage Setting

TPS546C23's output voltage is set by internal reference (VOUT_COMMAND) and external feedback divider

TPS546D24A's output voltage is set by fully internal feedback divider (VOUT_SCALE_LOOP) and internal reference (VOUT_COMMAND)

5) Stacking Capabilities

TPS546C23 supports stacking to 2-phase with the second phase following the falling edge of SYNC

TPS546D24A supports stack to 2, 3, or 4 phases with additional phases phase-shifted from single frequency SYNC.  Stacked phases can synchronize to rising or falling edge.

In single phase mode, TPS546D24A supports phase selection to 0, 60, 90, 120, 180, 240, and 270 degrees and selectable between rising and falling edges.

6) Pin Programming

TPS546C23 supports 2 pins with 3-bit (8 options) pin programming

TPS546D24A supports 4 pins with 1-bit + 5-bit + 8-bit Plus (274 options) pin programming 

7) PMBus Stacking 

TPS546C23 uses separate addresses and independent telemetry for each phase when stacked

TPS546D24A uses single address with common telemetry, including READ_VIN while allowing independent telemetry through the PHASE command

8) PMBus Command Support 

TPS546C23 supports fewer standard PMBus commands than the TPS546D24A.

Additional commands include: READ_VIN, PHASE, SIMULATE_FAULTS, READ_ALL, STATUS_ALL, Additional USER DATA commands such as MFR_ID, MFR_MODEL, and MFR_REVISION to allow users to store inventory control data into programmed devices, 

9) Security Options

The TPS546D24S, drop-in replacement for the TPS546D24A, supports MFR_SPECIFIC PMBus Commands PASSKEY and EXT_WRITE_PROTECT  for protection against malicious use of PMBus commands.

10) Clock Stretching

The TPS546C23 does not use clock-stretching

The TPS546D24A uses clock-stretching

11) PMBus Clock Frequency

The TPS546C23 supports clock frequencies upto 400kHz with a 4mA rated CLK/DAT pull-down

The TPS546D24A supports clock frequencies upto 1MHz with a 20mA rated CLK/DAT pull-down.

12) Remote Sense Input Impedance

The TPS546C23 has a differential remote sense input impedance of 30kΩ - 100kΩ

The TPS546D24A has a differential remote sense input impedance of 85kΩ - 165kkΩ

There are other differences in their specific details, but those cover the majority of the differences. 

Fred Cheng said:

how about the upgrade ?

What upgrade are you referring to?  The above differences include a wide range of "upgrades" 

Additionally, the TPS546D24A is part of a pin-for-pin compatible family, with lower current 10A (TPS546A24A) and 20A (TPS546B24A) versions optimized for better efficiency at lighter loads.

Fred Cheng said:

how’s the efficiency or transient comparison?

The 40A power stage of the TPS546D24A provides higher efficiency at similar switching frequency or higher switching frequency at similar efficiency to the TPS546C23.

For transient performance, the average current mode control architecture of the TPS546D24A provides similar transient capabilities to the TPS546C23 at the same switching frequency, with improved stack current sharing, especially during transients, and easier tolerance of larger output capacitors.  In addition, the fully internal compensation and output voltage setting of the TPS46D24A provides higher DC accuracy, reduced noise susceptibility, and the ability to adjust the loop parameters without changing external components.

Fred Cheng 

As lead applications support for devices that released more than 20 years ago, I can confidently say that neither the TPS546C23 nor the TPS546D24A should be considered "End of Life" risks.  While the TPS546C23 is built on older fabrication technology than the TPS546D24A, I would not consider that to increase it's End of Life risk as our division of TI has a policy of not ending production of devices while there are any orders during the prior 3 years.

Even devices within our product line which have been moved to "Not Recommended for New Designs" (NRND) because there are pin-for-pin compatible alternatives, remain in production for more than 10 years after being listed as NRND.  End of Life should not be a concern for the customer's medium voltage buck switching regulator products.