RoadTest: Richtek EVB_RT7275GQW Evaluation Board
Author: Robert Peter Oakes
Creation date:
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?: TI Buck converters as used on the Battery Booster pack
What were the biggest problems encountered?: null
Detailed Review:
To Clarify, there is no "Not Applicable" setting for some of the scoring so in order to not mess the overall score I chose top rating for those items (There is no demo software and I'm currently not aware of the price), the remaining scores are valid
The Richtek evaluation board is a board a couple of inches square, most of the board is ground plane that doubles as a heat sink (Not that it needed it for most of the test so far)
The board is basically a tiny buck converter chip and a huge (relative to the chip) inductor, a few smoothing caps on input and output and a divider feedback network to set the voltage out
Schematic for the board is not provided with the product but easily retrieved from the internet using the links provided on the road test intro, the schematic is provided for the board and is clear and easy to follow (There is not much to this evaluation board)
My first tests involved DC load characteristics, Did it deliver to the stated AMPS, was the output stable across the full current range and Voltage input swing
The default output volts is nominally 1.05V, not sure why this voltage but there is is and the chip has a continuous output current of 3A, lest see how it performs
These are the captured results of the current range test, also plotted for power conversion efficiency, mA are across the bottom and efficiency up the side
This test was with the recommended 12V input and keeping the default output V which as you will see is just below the stated 1.05V but still well within the expected tolerance
As you can see the efficiency did not get above ~83% but that is still quite respectable for such a simple circuit
this chart captures the performance keeping the output the same and sweeping the input from minimal Vin to MAX Vin (4 - 18V) to see how well the output remained at set point (It did better than advertised 
)
This time input volts across the bottom and output volts up the side
The board claims to have good transient response performance so the next tests will be hooking up my DC load (Still in development for the PSU project) to my Agilent signal generator to give the board a heart attack on load variations..
In the above video I evaluate the boards ability to deliver a stable output voltage with various dynamic load conditions driven by a selection of different waveforms from my signal generator into my DC Load. As it happens the converter performed very well, I used Square, Sine, Triangle, Noise, Pulse and other waveforms to switch the load from 1A to 3A (Its MAX rated output current) and with varying frequency up to 300Khz. It stood up to all the punishment I threw at it... Nice
I would consider this chip for my projects, it has a small BOM, and seems to be able to easily meet its stated specifications
If your interested, this is the DC load circuit I used in the testing, It is the same circuit I have been working on for my DC load, int he evaluation I was using 1R0 sense resistors but as this board is set to output 1.05V, this sense resistor had to be reduced to 0r1 Iin ordedr to draw the MAX current the chip can deliver (3A)
This basically completes this road test, its a device with a single function with no knobs or Displays to play with so rather limited to make it exciting. I will look at following up with a brief video on upping the output voltage to something useful though. 1.05V is not exactly good for anything I can immediately think of. so upping the output to say 3V3 or 5V would be more beneficial, Ill see what I can do, stay tuned.
