Richtek Synch. Step-Down Converter EVB_RT6204GSP - Review

Table of contents

RoadTest: Richtek Synch. Step-Down Converter EVB_RT6204GSP

Author: ljakes

Creation date: 19 May 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?: null

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:

The board is sturdy and contains enough test points with posts and oscilloscope clips for complete bench testing of all aspects.  It also contains 4 nice mounting holes at each corner. The board is hardwired for 5 VDC output.  Specifications described in http://www.richtek.com/assets/product_file/RT6204/DS6204-00.pdf indicate that the output is adjustable from 0.8v to 50v by replacing feedback resistors R1 and R2.  Also the Pulse Wave Modulation frequency is fixed at 350 kHz.  The input voltage range is 5.2 VDC to 60 VDC.  The maximum current draw is 500 mA.

I also received the Load Transient Tool, http://www.richtek.com/design%20support/reference%20design/rd0004  as fully described by Richtek Synch. Step-Down Converter EVB_RT6204GSP - Review by hlipka .  I wiil use the 10 ohm variable load from this tool to provide the max 500 mA current draw in my tests.  I'm sure I will be using this tool more for future roadtests.

Since hlipka has already provided a magnificent bench test using the Load Transient Tool, I will concentrate on performing efficiency, temperature loading and regulation at an input voltage range from 6.2 VDC to 60 VDC and output current range of 0 to 500 mA at 5 VDC output.

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:

1 - .25 watt 5100 ohm 1%

1 - .25 watt 1000 ohm 1%

1 - .25 watt 510 ohm 1%

2 - .25 watt 200 ohm 1% (in parallel to provide better power handling)

1 - 50 watt 50 ohm variable rheostat

1 - 20 watt 10 ohm variable rheostat

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 the necessary <18v voltages to input to the evaluation module:

I fed this into a dc to dc continuously variable boost converter to provide the necessary >18v 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 RT6204 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 100 miliAmps.

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 500 milliAmps.  As to be expected the highest efficiencies occur where the is a smaller difference between input and output voltage.

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

The horizontal axis on this chart is also non-linear and demonstrates that the highest efficiency occurs at less than 12 Volts dc input and at the highest currents toward 500 mA .  The worst efficiency occurs at greater than 12 Volts dc input.  Overall the chip is quite inefficient at high input voltages.

The following graph shows chip surface temperature (°C) increase vs. output current (mA) 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 above 200 milliAmps 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 (mA) levels:

As expected this graph also shows that temperature increases with output current and input voltage with the most drastic increase occurring at input voltages of 36 volts and above and currents above 200 milliamps.  Again the horizontal axis is non-linear for better visualization.

Overall the chip runs cool and there is no need for a heat sink, but then again the chip is limited to only a maximum of 500 mA draw.

The following graph shows output voltage load regulation at input voltage of 5 Volts dc.  All input voltages behaved the same so only 35 Volts dc is shown:

On the whole, the load regulation is good with the worst of only 1.6% occurring at the peculiar 100 mA point. It is best at around 10 mA and 200 mA.  Again the horizontal axis is non-linear for better visualization.

CONCLUSION:

This board is sturdy and performed well. It held an output of 5.0 Volts DC to within an acceptable margin with varying load and input voltages throughout its specified ranges.  It can be used in many applications that require a steady voltage supply with a widely varying input voltage.  Efficiency seems to be the biggest negative.  Also, this device can only be used in low power applications since the maximum current draw is 500 mA.  This device is best suited for automotive applications where low current is desired.  For example, powering a Raspberry PI in an automotive application would work good since the PI would be protected from high voltage surges coming from the vehicle's alternator.  No heat sink is require since the device runs relatively cool.