RoadTest: Seeking a Power Engineer to Evaluate the ROHM LogiCoA™ BUCK Converter
Author: venkat01
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?: On one end of the spectrum are fully digital controllers, like Texas Instruments' C2000 DSPs, which offer unmatched flexibility but demand significant development effort and consume more power. In contrast, the LogiCoA™ solution provides a simpler path to high performance by retaining a fast analog control loop, making it a more efficient choice for many applications. On the other end are high-end analog controllers with PMBus interfaces from companies like Analog Devices, which excel at system-level configuration and monitoring. While excellent, they lack the deep programmability of the LogiCoA™ MCU, which can be programmed to execute custom logic and intelligent behaviors. Finally, it can be compared to other specialized power-control MCUs from brands like Microchip. While these MCUs provide a powerful toolkit for building digital loops, ROHM's hybrid approach simplifies development by handling the critical, high-speed loop in analog hardware, freeing the developer to focus on supervision and features rather than complex loop stabilization.
What were the biggest problems encountered?: The biggest challenge I faced was not a problem with the board itself, but rather a limitation in exploring its full potential. One of the most exciting features of the LogiCoA™ platform is that ROHM provides the complete development environment, including the LEXIDE-Ω IDE and the full RMOS source code for the board. This opens the door to deep customization, allowing a developer to modify the control logic, create custom protection schemes, or add new features. However, to actually compile this code and flash it onto the microcontroller, you need the EASE1000 V2 On-Chip Emulator, which is a separate purchase.This creates a barrier between the initial evaluation and the next logical step of custom development. It would be a fantastic improvement and add tremendous value if the EASE1000 V2 On-Chip Emulator was provided along with the evaluation kit. Bundling the emulator would instantly transform this product from an "evaluation kit" into a true, all-in-one "development platform."
Detailed Review:
Have you ever thought about the tiny power supplies inside almost every electronic device you own? Their job is to take the power from a battery or a wall outlet and turn it into the perfect, stable voltage that the delicate computer chips inside need to work. For a long time, the companies that design these power supplies had to make a big choice.
They could use an "old-school" analog design, which is like a simple, super-fast reflex. It's great at handling sudden changes, but it's not very smart or flexible. Or, they could use a "new-school" digital design, which is like a tiny, powerful computer. It's very smart and can be programmed to do cool things, but it can be a little slower to react and more expensive.
But what if you could have both? What if you could have the instant reflexes of the old-school way combined with the intelligence of the new-school way?
That's the exciting idea behind a new piece of technology from a company called ROHM. I got my hands on their brand-new evaluation board, the LogiCoA001-EVK-001, to see this "hybrid" technology, thanks to the sponsor [ ROHM ] and element14 RoadTest Team. The LogiCoA001-EVK-001 promises to be a game-changer by mixing the best of both worlds (Analog and Digital) to create a power supply that is fast, efficient, and smart.
References / Useful Docs
1. Quick Start Guide for LogiCoA001-EVK-001
2. Evaluation Board's User's Guide for LogiCoA001-EVK-001
3. ML62Q2033/2035/2043/2045 Datasheet
4. ML62Q2033/2035/2043/2045 User’s Manual
5. Operating system for switching power control MCU “RMOS”
6. LogiCoA001-EVK-001 Schematic
7. LogiCoA Buck Converter GUI (Excel file)
8. Serial communication of RMOS and GUI Manual
9. LogiCoA Solution Buck Converter Reference Program
In this road-test review, I’m going to take you on a journey with me. We'll start by unboxing this cool piece of tech, take a close-up tour of all the parts on the board, and then I'll share my results from putting it to the test to see if it really is the future of power for our gadgets. Let's dive in.
When the LogiCoA001-EVK-001 arrived, the first thing I noticed was its simple but sturdy cardboard box. As I opened it, I could immediately tell that ROHM had been very careful about protecting the board inside.
The evaluation board itself was sealed in a black anti-static bag, which is important for keeping sensitive electronics safe from static damage. To protect it from any bumps during its journey, the board was snuggled tightly between two thick, grey foam pads—one on top and one on the bottom.
Inside the box, I also found two very helpful information sheets. I appreciated that both of these were written in English on one side and Japanese on the other.
The first sheet was a list of Precautions. It gave me important warnings and tips on what to be careful about when handling the board, which is always good to review before starting.
The second sheet was a Getting Started guide, and I found this to be extremely useful. It had several QR codes printed on it. Instead of having to type out long web addresses, I just used my phone to scan the codes. This instantly took me to the exact webpages where I could download the user guide, the software, and everything else I needed. This was a great touch that made finding all the necessary files incredibly fast and easy, letting me get straight to get started with the EVK.
Now that the board is out of the box, let's look at the hardware up close. The first thing I did was just a simple visual check of the whole kit.
Here's the top side of the board.
Note: The board I received has "Rev. A" and "PCB0340" printed on it, which is the PCB revision and board number of the EVK.
Here's the bottom side of the board.
Note: The serial number is on the back of the EVK's PCB which is necessary to access the development resources.
The first thing I thought when I held the board was that it felt very well-made. The board's edges are smooth, and it feels solid. It measures 80mm x 60mm, which is a nice, compact size.
ROHM used a 4-layer PCB for this design. Using four layers is a sign of a good quality board because the extra inner layers help it perform better and create less electrical noise. The copper paths on the board are 1oz thick, which is strong enough to handle the 5 amps of current this board is made for without getting too hot.
I also noticed a few other smart design details:
1. Mounting Holes: The four holes for mounting the board have plenty of empty space around them. This is good because it means I can use metal screws or standoffs to mount the board without worrying about them touching any of the electronics and causing a short circuit.
2. Helpful Little Holes (Vias): I saw lots of tiny, metal-plated holes all over the board. These are called "vias." Some of them are placed in a way that helps block electrical interference, making the board run cleaner. Others are placed right under the main IC’s to help pull heat away from them, which keeps the parts cool and running well.
3. Clear Labels: Even though there are a lot of small parts packed together on the board, every single one of them has a clear label printed next to it. This was very helpful when I needed to find a specific part mentioned in the user guide.
Note : I did see a few empty spots where components could go. On the top of my board, the spot for capacitor C16 was empty. On the bottom, the spots for resistors R39 and R41 were also empty
I also screwed four metal spacers into the mounting holes to lift the board off my workbench. This is an important step to protect the small surface-mount components on the bottom of the PCB and to ensure the board remains stable when probes and wires are connected.
Before I started my tests, I wanted to understand what makes this board different from a regular power supply. I found a great explanation in the EVK's User's Guide that breaks down ROHM's "LogiCoA Power Solution" into three main ingredients.
Block #1: The Special "Brain" (The LogiCoA Microcontroller)
At the very center of the board is a special "brain," which is a microcontroller from their ML62Q20xx family. On my board, the specific brain is the ML62Q2035. This isn't a general-purpose computer chip; it was designed from the ground up to be an expert at managing power supplies. It has all the right tools built-in to handle the special mix of fast analog signals and smart digital control.
Block #2: The "Expert" Operating System (RMOS)
Every computer needs an operating system, and this board's brain is no different. It runs a special, lightweight operating system called RMOS (Real-time Micro Operating System). Think of RMOS as an expert assistant for the brain. It's designed to handle multiple tasks at once and react to things in real-time, which is incredibly important for a power supply that needs to make thousands of decisions every second to keep the voltage perfectly stable.
Block #3: The "Muscle" and Support Team (The Power Supply Application)
This is everything else on the board—all the physical parts that actually handle the electricity. This includes the powerful switches (MOSFETs), the big energy-storing inductor, the gate driver that tells the switches what to do, and all the other support components. For my board, this whole "application" is set up as a synchronous buck converter, which is just a very efficient way to turn a higher voltage into a lower one.
Before diving into my own tests, I check out the the User's Guide to understand the board's specifications. This is what the spec sheet told me to expect.
First, I looked at the main power capabilities. The guide says the board is incredibly flexible, designed to take an input voltage anywhere from 7.5V all the way up to 38V. Right out of the box, it's set to deliver a steady 5V output, and it has the muscle to supply up to a full 5A of current, which is quite a lot for a board this size. I also noted that for advanced users, this output isn't fixed; it can be reprogrammed to be anywhere from 1V to 8V.
Next, I checked out its performance numbers. The internal switches are incredibly fast, turning on and off 160,000 times per second (160 kHz). The guide promises a fantastic efficiency of 92%, which means very little energy should be wasted as heat, so I expected the board to run without any need for heatsinks. It also has a gentle 5-millisecond soft-start, which means when I turn it on, the power will ramp up smoothly instead of slamming on instantly, which is much safer for the electronics I'll connect to it.
I also looked at how the board decides when to turn on and off. It's programmed with some smart rules: it won't even try to start until the input voltage reaches 9V, and it will safely shut down if the input ever drops below 8V. After it decides to start, it waits for a full 1 second before it begins the power-up sequence, adding another layer of stability.
Finally, I was most impressed with the built-in safety features, which act like a personal bodyguard for the board and my project. If the input voltage ever goes over 38V, it will protect itself. If I try to draw too much current—more than 6A—it will shut down to prevent overheating. And to protect whatever I have connected to it, the board will also shut off if the output voltage ever spikes above 6V or drops below 3V. After reading all this, I felt confident that the board was not only powerful but also very well-protected.
The below block diagram of the EVK serves as the definitive blueprint for the board's hybrid control methodology, showing interplay between its high-speed analog core and its intelligent digital supervisor.
At the very heart of this system is the MCU (Microcontroller), which functions as the central "brain." It is not a passive processor but an active supervisor, constantly gathering real-time data from its surroundings. It utilizes a VIN Monitor to assess the input voltage for valid startup and shutdown conditions, a VO Monitor to ensure the output voltage remains within safe operational limits, and an Idrain Monitor to track the load current for over-current protection. This continuous stream of data enables the MCU to execute proactive and intelligent control over the entire power conversion process. While the MCU manages high-level logic, there is a separate, self-contained loop responsible for the instantaneous, cycle-by-cycle regulation. This is the "analog reflex" engine. The feedback path begins by sampling the output voltage and feeding it to an Error Amp, which continuously compares this signal against a precise reference voltage. Any deviation generates an immediate "error signal" that is then fed into a high-speed PWM Comparator. Here, the error signal is compared against a triangle Wave, and the precise intersection of these two analog signals dictates the PWM duty cycle in real-time. This continuous-time comparison process is free of digital latency, which is the key to the board's exceptional transient response. The role of the MCU, then, is to act as the conductor of this analog control system. Its most critical tool is an internal DAC (Digital-to-Analog Converter), which generates the reference voltage for the Error Amplifier. By writing a new digital value to the DAC, the MCU can precisely command the entire analog loop to regulate to a new output voltage target. Furthermore, the MCU controls the Soft Start sequence for a controlled, monotonic power-up and sends the final PWM command to the Gate Driver. This driver then provides the necessary current gain to effectively switch the main high-side and low-side FETs.
Now let's look into the individual blocks in the above block diagram.
1. Microcontroller Unit : The the brain of this board is a MCU called the ML62Q2035. It's the boss of the whole operation.
It gets its power from a clean 5-volt supply on the board. Once it gets power and the voltage is high enough (over 4.1V), it wakes up and starts running its software to manage everything. The user guide also has a table (shown below) that shows what each of the chip's little connector pins does, which is very helpful for advanced users.
2.Control Block Power Supply (5V) : Just like our brain needs a steady supply of energy, so does the MCU. On the board, a chip called the BD950N1WG-C acts as a dedicated power supply for the control circuits. This component is an LDO (Low-Dropout Regulator), and its only job is to take the main input voltage (which could be messy or vary) and create an ultra-clean and stable 5-volt supply. This ensures the brain and its sensitive support circuits can think clearly without being disturbed by electrical noise.
3. Driver Block Power Supply (12V): The main power switches (the MOSFETs) are like heavy doors that need a strong push to open and close quickly. The guide explains that another dedicated power supply chip, the BD900N1WG-C, is used to provide this "push." It creates a strong and stable 12-volt supply specifically for the gate driver chip, ensuring the MOSFETs switch with maximum speed and efficiency.
4. RC Switch : The board features a physical switch labeled SW_RC.
This switch is connected to an input pin on the MCU. My insight here is that this isn't just a simple power switch cutting off electricity. It's a "logic" switch. When I flip it, it sends a simple high or low signal to the MCU. The MCU's software then interprets this signal and decides whether to gracefully start up the main power output or put it into a low-power standby mode.
5. Error Amplifier and Reference Voltage (The Watcher and the Target) : This is the heart of the "fast reflex" loop. A dedicated op-amp chip, the BU7481SG, acts as the "watcher" or Error Amplifier. Its job is to constantly watch the 5V output.
The MCU provides the "target" for the watcher to aim for using its internal Digital-to-Analog Converter (DAC). The watcher instantly compares the real voltage to the target. If it's even a tiny bit off, it sends an error signal to the pulse creator. This instant feedback loop is what makes the board's output voltage so incredibly stable.
6. Soft Start : To prevent a sudden jolt of power when the board turns on, the MCU manages a soft-start sequence. The transistor (TR1, a 2SA2029) is used to control the feedback loop at startup. The MCU sends a slowly rising signal to this transistor, which allows the output voltage to ramp up gently over a few milliseconds. This is a great example of the MCU precisely controlling the analog muscle for a safe and controlled start.
7. Triangle Waveform Generator and PWM Comparator: The actual on-off pulses are created by two parts working together inside the MCU itself. A specialized Operational Timer is programmed by the MCU to generate a constant, repeating "heartbeat"—a triangle-shaped wave. This heartbeat signal and the error signal from the "watcher" (the BU7481SG) are both fed into one of the MCU's built-in Analog Comparators. This comparator is the final decision-maker. It looks at both signals and outputs a high pulse whenever the error signal is higher than the heartbeat. This stream of pulses is the PWM signal that will control the main switches.
8. The Output Stage : This is the final "muscle" section. The PWM signal from the brain is still too weak to drive the main switches directly. So, it's first sent to the BD2320EFJ-LA Gate Driver. This chip acts as an amplifier, turning the small logic signal into a powerful pulse. These powerful pulses are then sent to the two main power switches, the RS6L090BGTB1 MOSFETs. As these FETs switch on and off, they deliver power to the large 15µH Inductor (L1) and the output capacitors, which smooth everything out to create the final, clean 5-volt output.
9. Input Voltage Detection Block : The MCU needs to know the voltage at the main input. A pair of resistors (R6 and R7) are used to divide this voltage down to a safe, small level. This sample is then fed into an Analog-to-Digital Converter (ADC) inside the MCU. The ADC turns the voltage into a number, which the software then uses to check if the input is within the safe range (between 9V and 38V) for operation.
10. Output Voltage Detection Block : Similarly, the MCU needs to watch its own output. Another pair of resistors (R32 and R33) create a small sample of the 5V output, which is fed into another ADC inside the MCU. The software constantly checks this number. If it ever sees the output go too high (above 6V) or too low (below 3V), it knows a fault has occurred and will trigger the safety shutdown procedures.
11. Drain Current Detection Block : To measure the current, a very low-value but precise resistor (R5, a 20mΩ sense resistor) is placed in the path of the main current flow. As current rushes through it, it creates a very small voltage. This tiny voltage is then fed into the MCU. Inside the MCU, a fast Analog Comparator watches this signal. If the voltage suddenly spikes (meaning a huge rush of current), it can instantly turn off the MOSFETs for that one cycle. At the same time, an ADC also measures the voltage to give the brain a more precise reading of the average current being used.
For advanced testing, the board includes a small potentiometer, VR1.
By removing the JP_Loop jumper, we can disconnect the automatic "watcher" circuit. In this "open loop" mode, turning the VR1 knob directly changes the input to the PWM comparator. This allows us to manually set the pulse width, which is an incredibly useful for debugging the power stage without the feedback loop interfering.
To prepare the LogiCoA001-EVK-001 for performance evaluation, I followed the explicit "Operation Procedure" outlined in the Quick Start Guide. This checklist ensures the board is correctly configured for its intended use as a closed-loop synchronous buck converter.
First, the onboard jumpers were configured for standard operation. This involved shorting the JP_LDO and JP_12V jumpers to enable the onboard LDOs that power the control and driver circuitry, respectively. Critically, the JP_Loop jumper was set to connect pins 2 and 3, which places the error amplifier's feedback path into its normal closed-loop configuration. The JP_REG jumper was left open as instructed. Additionally, the SW_RC remote control switch was toggled to the "ON" position (connecting pins 1 and 2), enabling the microcontroller to start the DC-DC conversion upon power-up.
With the board configured, I proceeded to connect the external equipment. Adhering to the guide's safety note regarding the lack of hot-plugging protection, both the main DC power supply and the electronic load were in an "off" state during this process. The DC power supply's (of 12.04V) ground and positive terminals were connected to pins 2 and 1 of the J1 input connector, respectively. For accurate output voltage monitoring, a digital multimeter was connected directly to the dedicated Mon_Vo and Mon_GND test points provided on the PCB. The below picture shows the output voltage without load, next we will establish a serial connection between the EVK and computer to configure the output voltage.
The above picture shows the output voltage without load measured as 5.018V when the input voltage is 12.04V ( just using the default configuration) and now we have checked the EVK is functional without any issues by following the standard Operating Procedure, next we will establish a serial connection between the EVK and computer to configure the output voltage.
For the PC (I'll be using Windows PC) to communicate with the LogiCoA001-EVK-001, they follow a specific set of rules, or a protocol, that is managed by the RMOS software running on the board's microcontroller. This protocol defines everything from the low-level electrical signals to the high-level structure of the command messages.
UART Configuration between the EVK and PC : The communication is built on a standard UART (Universal Asynchronous Receiver-Transmitter) interface, which is the hardware that physically connects the PC and the microcontroller.
Note : The specific settings for this hardware are defined in a file within the RMOS project called 10S70_UART_Set.s.
The UART Settings are as follows :
1.Baud Rate: The speed of the communication is set to 9600 bps (bits per second).
2.Data Format: Each piece of data is sent in a frame with 8 Data Bits, Even Parity for error checking, and 1 Stop Bit.
3.Bit Order: Data is transmitted LSB-first (Least Significant Bit first).
These settings are used by the on-board FT234x USB-to-UART converter to manage the connection.
UART Packet Structure : On top of the basic UART rules, the RMOS software uses a special protocol that groups data into messages called packets. The software processes 6 smaller "frames" of data to create a single, complete packet. Every command sent from the PC and every response from the board is formatted into one of these fixed-length packets.
This packet configuration is what enables a single PC to control up to 32 different power supplies at once.
There are two methods to structure the information within a packet: TX16 and TX32. For this EVK, the simpler and more flexible TX16 method is used in this test.
Here’s a breakdown of how a TX16 packet (sent from the PC to the board) is structured. This entire 42-bit packet is assembled by the software as described in the 93H010_InfoTxRx_Header.s file:
ADR (Address - 5 bits): This is the destination address of the board. The protocol supports up to 32 unique addresses. For this EVK, the default address is 31.
Decision Bit (1 bit): This is the 6th bit in the packet and it tells the board which method is being used. For the TX16 method, this bit is always set to 0.
CmdGr (Command Group - 8 bits): This field specifies the category of the command. For this EVK, command groups from 0 to 15 are used. For example, Command Group 4 is for all "Set" commands.
CmdNo (Command Number - 8 bits): This field defines the specific command within that group. For this EVK, command numbers from 0 to 31 are used. For example, a CmdNo of 0 means "Set the Output Voltage."
Data (Data Payload - 16 bits): This is the actual value that goes with the command, such as the value 101 which corresponds to 5V.
chksum (Checksum - 4 bits): This is a final error-checking field at the end of the packet. The PC calculates this value, and the board verifies it. If the check passes, the board knows the message is valid and will execute the command. If not, the message is ignored.
When the board replies, it also sends back a packet containing the requested information. The entire system is designed to be robust and allows for complex communication using simple, well-defined packets.
Now, I'll connect the EVK to PC using the USB cable to configure it via the Excel GUI File provided by RHOM.
The most exciting feature of the LogiCoA platform is the ability to talk directly to the board's MCU from my computer via the USB-UART bridge. The "Serial communication of RMOS and GUI developing manual" gives a detailed guide on how to do this using a special Excel file that acts as a control panel. I followed these steps exactly, and the process was surprisingly straightforward.
Here's my walkthrough of how to set up and use the Excel GUI.
First, I needed to download the Excel GUI File zip, and open the excel file which is named RMOS_CommunicationControl_LogiCoA001-EVK-001_v_1_0_2.xls.
I opened the file in Microsoft Excel. The first thing I saw was a red "SECURITY RISK" banner at the top as shown below.
To make it work, I had to select the "Unblock" on the properties of the Excel file and then click on apply.
4. This is a normal security feature in Excel. The file contains special code (VBA macros) that allows it to communicate with the board through the USB port. To make it work, I had to click the "Enable Content" button on that banner.
5. Next, I had to make sure the "Developer" tab was visible in Excel's main ribbon. It wasn't there for me, so I followed the simple instructions in the guide:
I went to File > Options > Customize Ribbon.
On the right side of the window, I found the "Developer" checkbox and ticked it.
I clicked "OK." Now the Developer tab was visible, which confirms that Excel is ready to run the communication macros.
With the software ready, it was time to connect the hardware.
I connected the LogiCoA EVK board to my computer using a standard Micro-USB cable.
To find out which "doorway" (COM Port) my computer assigned to the board, I opened the Windows Device Manager.
I looked under the "Ports (COM & LPT)" section and saw a new device named "USB Serial Port (COM6)". This told me the magic number was 6.
Back in the Excel file, I navigated to the "TxRxInterface" sheet. This sheet is the main "engine room" for all communication. In cell H3, there is a button labeled "Port Read."
I clicked the "Port Read" button. A moment later, the number 6 automatically appeared in the cell next to it. This confirmed that the Excel file had successfully found the board.
The TxRxInterface sheet is the most powerful part of the GUI, as it gives you full control over every bit of the communication packet. I decided to send a command to change the board's output voltage.
Here’s the 4-step process I followed:
Input Command Group (CmdGr): First, I needed to tell the board what category of command I was sending. The documentation's "Communication Commands List" shows that changing the DAC (which controls the output voltage) is in Command Group 4. So, I typed the number 4 into cell D10.
Input Command Number (CmdNo): Next, I needed the specific command action. The list shows that the command number for setting the DAC is 0. So, I typed the number 0 into cell F10.
Input Setting Value (DATA): This is the actual value I wanted to send. I calculated from the formula (D/A code = Vo / 0.04929) that the D/A code for 3 V is 61. So, I typed 61 into cell J10.
Click "Send16": Finally, with all the parts of my command ready, I clicked the "Send16" button. This tells the Excel macro to assemble all my inputs into a perfect 42-bit packet and transmit it to the board through the COM port.Then the change in output voltage is reflected on the EVK as shown below.
While the TxRxInterface sheet is like the "engine room" of the communication system—powerful but very technical—the Excel file also includes a much friendlier tab called the TinyGUI. I found this to be the easiest and most fun way to interact with the board. It hides all the complicated packet information and just gives you simple buttons to perform the most common tasks. These buttons are powered by special code in the background (called VBA macros) that automatically does all the hard work of building and sending the commands.
Before we look at the buttons, there's one important thing to understand. The board's brain (the MCU) doesn't understand "5 volts" or "3.3 volts." It only understands numbers. So, to tell the board what voltage we want, we have to send it a special D/A code (a number between 0 and 255).So use the below formula to convert the Vo to D/A code, round off to nearest integer before entering the value into the sheet.
D/A code = Vo / 0.04929
The TinyGUI has four main buttons that let you do everything you need for basic testing:
Button #4: Read_Vo (The "What's your status?" button)
This is the first button I always press. When you click it, it sends a command to the board asking, "What is your current D/A code setting?" A moment later, the board's answer appears in the "Setting value reception" box. It’s the perfect way to check the board's current state.
Button #1: Set_Vo (The "Do this now!" button)
This is the main "Go" button. You type the D/A code you want (like 101 for 5V) into the "Setting value transmission" box, and then you click Set_Vo. This instantly sends the command to the board, and the output voltage will change to your new target.
Button #3 & #2: Up and Down (The "Fine-tuning" buttons)
These were my favorite buttons for experimenting. Next to the D/A code box, there is a small box labeled "Step." If you put the number 1 in the step box, every time you click the Up button, the D/A code increases by one. Every time you click Down, it decreases by one. This is fantastic for slowly and precisely adjusting the voltage up and down to see how it reacts
Here's exactly how I used this friendly control panel to test the board:
First, I clicked the Read_Vo button. The number 101 appeared in the reception box, confirming that the board was correctly set to its default of 5V.
Next, I wanted to change the output to 3.31V. I typed the magic number 67 into the transmission box.
I clicked the Set_Vo button. I was watching my multimeter at the same time, and I saw the output voltage on the board smoothly drop from 5V down to nearly 3.31V. It worked perfectly!
Just for fun, I set the "Step" box to 5. Then I clicked the Up button three times. The D/A code in the box went from 67 up to 81, and I watched the voltage on my multimeter increase in three small, perfect steps.
This TinyGUI sheet is a fantastic feature. It makes testing and interacting with the board incredibly simple and intuitive, even if you don't know anything about the complex communication protocol working behind the scenes.
Note : While I used the Excel GUI to communicate with the board, it's worth noting that the LogiCoA platform is a full development environment. The primary method for an engineer to write and debug their own custom software is by using a special hardware tool called the EASE1000 V2 On-Chip Emulator. This tool connects the development software on a PC directly to the board's microcontroller, allowing for deep programming and troubleshooting.
A key feature of the LogiCoA001-EVK-001 is its comprehensive suite of safety protections. These features are managed by the onboard microcontroller and act as an intelligent safeguard for both the evaluation board and any external electronics connected to it. There are three critical layers of this system: Low Voltage, Over Voltage, and Overcurrent Protection.
First is the Low Voltage Protection (LVP), which is designed to guard against conditions like a brownout or a short circuit. The board's MCU constantly monitors the output, and if the voltage drops below a preset 3.0V threshold, it initiates a 500-millisecond timer. This "mask time" is a clever feature that prevents nuisance trips from brief, harmless voltage dips. If the fault condition persists for the full half-second, the MCU identifies it as a genuine problem, shuts down the power supply completely, and latches off until it is manually reset. This timed response ensures the board only reacts to sustained, legitimate faults.
Arguably the most critical safeguard for downstream components is the Over Voltage Protection (OVP). This feature protects sensitive electronics from being damaged by a potentially destructive voltage spike. The MCU's trip point is set to 6.0V, and unlike the LVP, its response is nearly instantaneous, with only a brief 250-microsecond mask time to filter out noise. If the output ever exceeds this ceiling, the MCU immediately shuts down the power supply and latches off. This rapid, decisive action is the electronic equivalent of an emergency brake, preventing catastrophic damage to any connected devices.
Finally, the Overcurrent Protection (OCP) employs a sophisticated two-stage hybrid approach to handle excessive current draw. The first stage is a lightning-fast "reflex" managed by an internal analog comparator, which provides pulse-by-pulse protection. If the current in any single switching cycle exceeds the 6.0A threshold, this comparator instantly terminates that pulse, preventing immediate damage from a sudden short or overload. The second stage is the "intelligent" response from the MCU's software. After the initial reflex, the brain is notified of the event. If the overload condition continues, the firmware can then make a higher-level decision, such as initiating a complete shutdown and latching off.
One of the most important tests for any power supply is its efficiency. An efficient board runs cool and wastes very little energy. To test this, I powered the board with a steady 12V input and measured its performance as I increased the output current from a light load all the way to its 5A maximum. The results, shown in the graph below, were very impressive.
The curve on this graph describes the performance in three parts:
1. The Light Load Region (from 0A to about 1.5A):At the very beginning, with almost no load, the efficiency starts low but climbs incredibly fast. This is normal. Think of it like a big truck's engine—it uses a fair bit of fuel just to idle. But as soon as you start moving and delivering a real load, that idling energy becomes a tiny fraction of the total work being done. This graph shows the board gets very efficient very quickly. By the time it's delivering just 1 amp, it's already approaching 90% efficiency.
2. The Peak Performance "Sweet Spot" (from 1.5A to 3.5A):In the middle of the graph, the curve flattens out, hitting its peak performance. This is the board's "highway cruising" mode, where it's at its absolute best. I measured a peak efficiency of around 92%, which is an outstanding result and matches the promise in the User's Guide. This is the ideal operating range where the board delivers power with the least amount of waste heat.
3. The High Load Region (from 3.5A to 5A):As I pushed the board to its maximum rated current of 5 amps, the efficiency started to drop off just a little bit, down to about 92%. This is also completely normal and a sign of a good design. When the components are working their hardest, they naturally create a bit more "friction" and waste a little more energy as heat. The important thing here is that the drop is very small and graceful. The board handled its maximum load without struggling.
What this graph tells me: The LogiCoA001-EVK-001 is a highly efficient power supply across its entire useful operating range. Its excellent performance, especially in the 2-to-4-amp sweet spot, means it can power demanding projects without getting too hot, showing that the EVK design is both powerful and very well-engineered.
To quantify the converter's stability against input voltage variations, I performed a line regulation test. This metric is a crucial indicator of a power supply's ability to maintain a constant output voltage despite changes in its input source. The evaluation was conducted under two separate conditions: no-load (Io = 0A) and full-load (Io = 5A). For each condition, the input voltage (Vin) was swept across the specified operational range, from 7.5V to 38V, while the output voltage (Vo) was precisely monitored.
The results, as plotted in the provided graph, demonstrate exceptional line regulation performance. The output voltage remains remarkably stable across the entire input sweep for both no-load and full-load scenarios. At full load (the orange line), the output measured approximately 5.02V at Vin=7.5V and drooped to only 5.01V at Vin=38V. This represents a total deviation of a mere 10mV, which corresponds to a line regulation of approximately 0.2%. This high level of performance indicates a robust control loop with an excellent Power Supply Rejection Ratio (PSRR). The results confirm that the LogiCoA001-EVK-001 can reliably power sensitive electronics from a wide variety of input sources, including those that may exhibit significant voltage fluctuations, without passing those disturbances on to the load.
To assess the converter's ability to maintain a stable output voltage under varying load conditions, a load regulation test was performed. This is a critical metric that demonstrates the stability and low output impedance of the power supply's control loop. For this evaluation, the board was powered with a fixed 12V input. The output current (Io) was then swept from a no-load condition (0A) to the converter's maximum rated capacity (5A), while the output voltage (Vo) was precisely monitored at the board's test points.
The results, as plotted in the graph, reveal exceptional load regulation performance. As shown by the blue line, the output voltage remains virtually flat across the entire load range. At the 12V input, the no-load voltage measured approximately 5.022V, which drooped to only 5.002V under a full 5A load. This represents a total deviation of just 20mV, corresponding to a load regulation of approximately 0.4%. This minimal voltage droop under a heavy load is indicative of a well-compensated control loop with a fast transient response and a low effective output impedance. The results confirm that the LogiCoA001-EVK-001 can power dynamic loads that exhibit significant changes in current draw without experiencing problematic voltage sag.
After spending considerable time exploring the ROHM LogiCoA001-EVK-001, from its high-quality construction to its real-world performance, I can say with confidence that this evaluation kit is a success. It masterfully delivers on its core promise: to erase the long-standing divide between analog and digital power control. The board is a powerful demonstration that you no longer have to choose between the instantaneous response of an analog loop and the intelligence of a digital supervisor. With the LogiCoA platform, you truly get the best of both worlds.
The performance of the board is, in a word, exceptional. My tests confirmed that the high-speed analog core provides rock-solid line and load regulation, keeping the output voltage incredibly stable under all conditions. The efficiency curve is equally impressive, hitting a peak of around 93% and proving that this is a cool-running and well-engineered power stage.
But the real magic happens when you interact with the board's MCU. The Excel-based GUI is a fantastic and surprisingly powerful tool. It makes it incredibly simple to monitor the board's status in real-time and, more importantly, to send commands that change its behavior on the fly. Being able to adjust the output voltage with the click of a button is a powerful feature that showcases the immense flexibility of this hybrid approach.
Exceptional Electrical Performance: The board delivers top-tier results with high efficiency, virtually flat line and load regulation, and what I anticipate would be an excellent transient response due to its analog core.
Intelligent Hybrid Control in Action: The ability to communicate with the board, read its status, and change its settings via the Excel GUI is a game-changer. The configurable and robust safety protections provide peace of mind.
Outstanding Build Quality and Design: The 4-layer PCB is engineered to a very high standard, with a smart layout, clear labeling, and excellent thermal design that contribute directly to its performance.
Excellent Documentation: The User's Guide, Application Notes, and Quick Start Guide are all comprehensive, clear, and provide all the information needed to get started and understand the technology.
Based on the road-test, I can highly recommend the LogiCoA001-EVK-001 to a few key groups:
Professional Power and Embedded Engineers: For anyone designing smart, efficient power supplies, this is an ideal platform for prototyping and for learning how to integrate intelligent power management into a larger system.
Students and Educators: For universities and schools teaching power electronics, this is a premium, safe, and incredibly well-documented tool for demonstrating modern control concepts.
Serious Hobbyists and Makers: For the advanced maker who wants to move beyond simple power modules and work with a professional-grade, configurable power solution, this board is a fantastic choice.
