TI SWIFT™ Power Module EVM - Review

Table of contents

RoadTest: TI SWIFT™ Power Module EVM

Author: snidhi

Creation date: 1 Apr 2018

Evaluation Type: Power Supplies

Did you receive all parts the manufacturer stated would be included in the package?: True

What other parts do you consider comparable to this product?: PTH04T241W,TPSM84A22,LMZ31710,PTH04T240F

What were the biggest problems encountered?: 1. No external solder point for VADJ was provided in the evaluation board to connect Rdac resistor for dynamic voltage control. 2. Footprint for R1 resistor was too small and too close to the device hence was unsolderable. 3. No external pad to measure the switching frequency of the DC DC converter.

Detailed Review:

Road Test Review of TPSM84A21 Power Module

I applied for this Road test as currently dipping my hands into the power side of analog seems about right. The high current output TPSM84A21 is an excellent candidate for this purpose. Being a new member of the element14 community, this is my first Road Test Review. I would like to thank the organizers for their trust in the newbies.

My review is divided in four parts:

1. Introduction to TPSM84A21 SWIFT Power Module
   
   1. Unboxing of the Evaluation Board
   2. Circuit Diagram Analysis at the Evaluation Board
   3. Simulation Support for TPSM84A21 device.
2. Test Setup Description
   1. Devices used in the setup
   2. Home-made cables for the setup
3. Analog tests of the Power Module
   1. Output voltage ripple measurements (with and without external capacitors)
   2. Tests at high output current with external load
   3. The Vin, Vout and PGOOD start up waveforms
   4. The Vin, Vout and PGOOD shutdown waveforms
4. Dynamically adjust the output voltage using external DAC
   1. ZedBoard Zynq-7000 FPGA Development Board
   2. AMS101 plug in board using AD5065 DAC.
   3. Integrate the AMS DAC output with the TPSM8421 module.
   4. Write a simple FPGA code to control the VADJ pin on TPSM8421 through Rdac resister. 
5. Road Test Summary

Introduction to TPSM84A21 SWIFT Power Module

The TPSM84A21 is a high current low voltage output DC/DC synchronous step down buck converter with integrated capacitors and allows small footprint and fast design on the PCB. This device can be integrated to a power design schematic without investing much time in the circuit design part.

Unboxing the Evaluation Board

The process was rather simple. I received a well-insulated package from Element 14. I will not go in the details here as other road testers have already focused on it.

Unboxing of the Power Module

Circuit Diagram Analysis of the Evaluation Board

Brief Description: A simple circuit diagram explanation has been presented below. The footprints marked with Cross were not present on the board and should be externally soldered. Many test points and GND points were present. There are two different GNDs on-board: AGND and PGND.

Since I had already downloaded the TPSM84A21 10A SWIFT™ Power Module Evaluation Module Evaluation guide I was ready to roll.

Reference: TPSM84A21EVM-808 10-A, SWIFT™ Power Module Evaluation Module User Guide

Circuit diagram of the Evaluation Board

Simulation Support: I am always interested in looking for parts with simulation models. It gives you a good rough idea if you want to proceed further with this IC or not. WEB Bench Designer Simulation Window also allows you to download .xlsx format files to look into the exact simulation points for the IC which is so great.

Simulation Models for Altium, Cadence Orcad or TINA TI formats can be downloaded from the WEBENCH designer. It also auto-generates reports for the simulation as pdfs. Refer to webench_design_4903046_2_546518393.pdf I have uploaded here. I also downloaded the 3D CAD model to add it to my PCB and schematic in Mentor. 

WEB Bench Designer Simulation Window for TPSM84A21

Its no secret that TI has a lot of simulation support for its devices. TPSM84A21 is also fully supported with TINA TI and in PSpice simulation model. I downloaded the TINA TI model and gave it a quick run on my PC. Such models ease the task and allow fast design progress. Its also fun to compare the simulation outputs with the real evaluation board. The TINA TI circuit was more basic and different from the evaluation board schematic.

TINA TI Simulation Model

Road Test Summary

In Conclusion, the device TPSM84A21 lives upto its promise to deliver high stable currents at low input voltage. Although there are still some mysteries to be solved such as why the deviation from measured to calculated current values starts to become wider at larger currents  although with the same setup.

As for the TPSM84A21 EVM board, it could have been better designed with more test points for DAC control, resistor place holders to solder Rdac, and a separate test point for AGND pin as it is used in dyanmic voltage control.

Would I integrate and use this device in my future work:       Yes

Is the TPSM84A21 device well supported by TI:                    Yes 

Does the TPSM84A21 allow faster schematic design

and uses less pcb board space:                                            Yes

And this device definately has some good competion in the market with its brothers like LMZ31710. They offer smaller footprint and almost similar efficiency.

Read here to check out: Comparison between LMZ31710 and TPSM84A21

References:

TPSM84A21 Datasheet

Deciding Between DC-DC Modules or Discretes When Facing a Space Jam

Simplify low EMI design with power modules

....Posts in Progress..........

TI SWIFT™Power Module EVM Review: Part 4 Dynamically adjust the output voltage using external DAC