RoadTest: Maxim Integrated USB Type-C Autonomous Charger EVK
Author: redcharly
Creation date:
Evaluation Type: Development Boards & Tools
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?:
What were the biggest problems encountered?: The biggest problem I had was doing this roadtest after lui_gough had done his!!!!!
Detailed Review:
Carrying out a roadtest after seeing the work done by Gough Lui is really difficult. The completeness and precision of that work ( Maxim Integrated USB Type-C Autonomous Charger EVK - Review ) made it very difficult to add something to what has already been said.
For this reason, in this roadtest I will use the board in simple applications for educational purposes.
First of all, I want to create an educational application of the board and use it to explain the USB 3.1 C standard to my students. Then I want to use this board as a battery charger.
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The arrival of the package was very eagerly awaited as I was very curious to use this board. The board is made very well and with attention to detail. It allows large currents and also the heat produced is easily dissipated. Another feature that, for my purposes, is very important is the fact that this board has numerous test points that allow you to perform measurements on each part of the board and allow you to test it in all its operating modes.
The purpose of this work is to use the MAX77751 Evaluation Kit board to know the characteristics of the standard USB 3.1 Type-C.
The new USB 3.1 Type-CTM standard is simplifying the way we interconnect and power our electronic devices. This standard utilizes the USB Type-C connector for data and power transfer between any two devices up to 100W. Accordingly, more functionality is required from the battery charging system, which tends to be increasingly smaller and lighter for every new portable device.
USB 3.1 Type-C supports high data rates and increased power delivery between electronic products.
It can deliver 10Gbps of throughput while delivering up to 3A over standard cables and up to 5A over enhanced cables.
The bus voltage can be adjusted up to 20V (60W at 3A with a standard cable or 100W at 5A with an enhanced cable). Many notebook computers today require less than 100W of power, hence new models adopting a Type-C connector can be charged via a USB port the way small devices are charged today.
Before starting a power transfer, the USB-C standard requires that both the USB power supply and the device to be charged must negotiate their respective roles. Only after the power source and the user have been well identified, the system begins to deliver power. This is an innovative aspect of this standard in which there is no fixed role, and the energy source and the user can exchange roles if necessary.
This standard, therefore, seeks to eliminate many different types of power supplies and chargers for small devices characterized by having different plugs and to allow the same power supply to power multiple devices, even very different ones.
Unlike other USB standards, both ends of the USB-C cable are identical and can be connected indifferently to the power source or user.
Configuration Channel Detection (CC) is one of the innovations introduced by this standard. It detects the presence of the USB-C cable, its orientation (the connector is symmetrical and can be inserted in two different ways) and the current carried in the cable. To detect the orientation of the cable, just look at which of the two DC lines, (CC1 and CC2) the potential is lowered.
The board has many test points and makes it easy to measure voltage and current in all its parts.
A simple experience that can be done using the board to deepen the USB-C protocol is to measure the voltage across the terminals CC1 and CC2 with an oscilloscope and check how, based on the direction of insertion, we have different voltages on the two pins. By comparing the value of the two voltages, the direction of insertion of the plug is obtained and therefore the connections can be managed correctly.
In the image, we see how, during normal board operation, one of the two pins CC1 and CC2 is at a high level and the other at a high level. The voltage level on pins CC1 and CC2 will depend on the direction of insertion of the connector into the plug. Thanks to this simple method, it was possible to create a symmetrical connector that can be inserted in both directions without any problem.
One of the problems that characterized some of the previous versions of the USB standard, especially the micro USB format, was the difficulty of recognizing the correct direction of insertion. This often led the user to force the connectors causing damage. Thanks to the USB type-C standard, the connector is now perfectly symmetrical and, as can be seen from the description of the connector pins, there is a mirror arrangement of the connections.
Another innovative and interesting feature of the USB-C standard is that of "cold-plugging". The 5V voltage will be supplied only when a correct recognition and correct configuration of the power supply system has been made. Configuration Channel Detection is therefore essential for applications that use USB-C.
The Max77751 datasheet is very detailed and contains pages of significant measurements and graphs.
The simplified block diagram, shown in the figure, shows how the kit input is the USB Type-C connector. The input voltage is taken from this connector which can range from 4.5V to 13.7V and is used to charge the battery and the DP, DN, CC1, and CC2 terminals are also easily accessible for measurements.
The board supplies the charging current to the battery via the BATT terminal and the maximum deliverable current is 3.15 A.
There are two LEDs on the board that allow you to monitor the situation of the board.
The first LED is the Input Status (INOKB): when a valid input is inserted into the board, or when the Reverse Burst Mode is enabled and the 5V obtained from the battery is on the CHGIN pin, the LED lights up.
The second led is linked to the STAT (Charging Status Output) pin. When there is no active input, it is off. While the battery is being charged the LED flashes at a frequency of 1Hz with a duty cycle of 50%. When the charge is complete, the LED stays on. In the event of a faulty battery, the LED remains off.
From an educational point of view, one of the most important graphs is the one that shows the relationship between the charging current and the voltage across the battery.
It is very interesting to understand how the battery is charged. Charging is carried out with a succession of different modes that are managed in order to optimize the charging process by reducing the time and charging the battery without causing stress.
We can say the Maxim Integrated USB Type-C Autonomous Charger EVK is a great board and does its job beautifully. It manages the batteries with extreme simplicity and chooses the ideal current for each phase of recharging and evaluating the initial conditions of the battery itself.
The documentation is not very rich but the salient features are well described. For those wishing to learn more, I recommend the splendid work done by Gough Lui ( Maxim Integrated USB Type-C Autonomous Charger EVK - Review ).
Carlo Russo
