Synchronous Step-Down Converter Evaluation Module - Review

Table of contents

RoadTest: Synchronous Step-Down Converter Evaluation Module

Author: ljakes

Creation date: 28 Jan 2017

Evaluation Type: Evaluation Boards

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?: null

What were the biggest problems encountered?: not having a oscilloscope.

Detailed Review:

Thanks to Element 14 for the opportunity to thoroughly test this product to the best of my capability with the support test equipment and test aids that I have at hand.

This is the product I received:

It is a very sturdy product.  The screw terminals worked very good and the test points were easy to use.

The board is hardwired for 1.2 volts dc out but can be modified to output up to 5 volts dc.

I refereed to the product specifications, http://www.farnell.com/datasheets/2062745.pdf?_ga=1.25390584.436985416.1452100341 , in identifying test points and terminal locations in accomplishing the tests.

I did however note a discrepancy between the board output current maximum and the terminal output current maximum.

While the board is specified as having a maximum current output of 12 Amps, J2 and J4 are specified as having a 10 Amp maximum rating.

I decided to test at as close to 12 Amps as I can get to the best data representation of the board.

These two multimeters were used in collecting the data:

The Cen-Tech P98674 (right) was used for voltage data.

     (DC Voltage Accuracy ± 0.7% of reading + 2 digits)

The Radio Shack 22-168A (left) was used for current data.

     (DC Current Accuracy ± 1.5% of reading + 1 digit)

These resistors in various parallel combinations were used to provide loading for the tests:

10 - 5 watt 1 ohm 5%

1 - 50 watt 3 ohm 3%

1 - .25 watt 470 ohm 1%

1 - .25 watt 150 ohm 1%

1 - .25 watt 47 ohm 1%

1 - .25 watt 10 ohm 1%

In order to provide power I used a 13.8 Volt DC 2 Amp power supply (PHC-412):

adjusted for maximum voltage which turned out to be 18 volts dc.

I fed this into a dc to dc continuously variable buck converter to provide all the necessary voltages to input to the evaluation module:

I used the Cen-Tech infra-red temperature measurement device (Accuracy + 2°) to measure the increase in surface temperature of the TPS56C215 Chip for each test interval:

The following data was collected:

Each column of data is self explanatory.  The temperature column represents the increase in degrees centigrade above the ambient temperature of the room.

The room was at about 22 degrees centigrade.

The following graph shows efficiency vs. output current (A) for the various input dc voltage levels:

The horizontal scale for output current (A) is graphed non-linear to more clearly see the peculiar curve characteristics at around 1 + 0.5 Amps.

It seems as though there is a transition point there where the efficiency starts to decrease or becomes erratic but then continues to increase and maxes out at around 3 Amps.

The following graph is another chart showing efficiency vs. input dc voltage at several output current (A) levels:

The horizontal axis on this chart is also non-linear and demonstrates that the highest efficiency occurs at 5 Volts dc input and the worst efficiency occurs at 17 Volts dc input.

The following graph shows chip surface temperature (°C) increase vs. output current (A) for the various input dc voltage levels:

As expected this graph shows that temperature increases with output current and input voltage with the most drastic increase occurring at 8.5 Amps and higher.

Again the horizontal axis is non-linear for better visualization.

The following graph shows chip surface temperature (°C) increase vs. input dc voltage at various output current (A) levels:

As expected this graph also shows that temperature increases with output current and input voltage with the most drastic increase occurring at 12 Amps at all input voltages between 4.5 to 17 volts dc.

Again the horizontal axis is non-linear for better visualization.

The following graph shows output voltage load regulation at input voltage of 5 Volts dc.  All input voltages behaved the same so only 5 Volts dc is shown:

On the whole, the load regulation is very tight with the worst of only 0.17% occurring at 12 Amps.

Again the horizontal axis is non-linear for better visualization.

Notice the change from a negative error to positive error at that peculiar transition point of around 1 Amp mentioned previously.

I could not measure an discernible line voltage error with respect to input voltage swing so it is not graphed here.

Also, I do not have an oscilloscope so could not measure any ripple characteristics.

CONCLUSION:

This board is very sturdy and performed extremely well. It held an output of 1.2 Volts DC to within an impressive margin with heavy load and varying input voltages.

It can be used in many applications that require a steady low voltage supply while obtaining power from a widely varying source.  I was thinking of possibly modifying the board for 5 VDC output by replacing R7 and powering a Raspberry PI in an automotive application where the voltage input can vary between 11.5 to 14.5 volts DC.  I would definitely recommend adding some heat sinks if you plan on drawing more than 7 Amps load.