I plan to use this USB dongle to setup and monitor the umodule supplies on my board. The board is small and I only plan to support the following signals: I2C_SDA, I2C_CLK, ALERTn, and GND. The supplies will be powered with first sequenced system supply to allow for programming before enabling the umodules. We have no EPROM like on the uModule eval boards, and I will not use GPIOs or remotely enable through the dongle. Any other signals I require to access the uModules for programming and telemetry?
Programming the uModules before bringing up system power is a good idea. In fact, most users will power their uModules directly from the DC1613 dongle while system power is down. This prevents anything bad happening to the power supplies while they are being programmed. To do this use the +3.3V supply (and GND) from the DC1613 connector (pin 5), which can supply up to 100mA. Use a PMOS FET as shown in Figure 5 of the LTM4677 datasheet (for example) as a gate when the board is powered.
The only signals that you need to program the uModules are SDA and SCL and GND. You don't even need ALERT, though it can be helpful if something goes wrong. I suggest the following 4 signals to your board:
SDA : DC1613 pin 2
SCL : DC1613 pin 4
+3.3V : DC1613 pin 5
GND : DC1613 pin 3,10
Is it possible to use FT2232H USB to I2C dongle to access and control registers of LTM4677 instead of using DC1613A? Thanks!
There are many ways to communicate with an I2C bus, on which the LTM4677 communicates. The FT2232H module can, in theory, be used to convert USB communications from a PC into I2C bus traffic using the multi-protocol engine. If you are familiar with programming the FTDI chip then you should be able to cause it to speak I2C on our bus (we do not have the FTDI programming interface to do so). Just make sure that it is 3.3V, and no faster than 400kHz, and you connect the SDA, SCL, and GND pins.
Keep in mind that one of the important features of the DC1613 is that it provides a clean 3.3V supply that the LTC4677 can use for power while programming the EEPROM. This is a safety feature that allows you to keep main board power off while programming the Power supply.
Note also that one of the non-obvious benefits of using the DC1613 is that it provides galvanic isolation between your PC and the LTM4677. This means that it is impossible for your experimental power supply project to accidentally inject ground offsets or other harmful potentials up-stream through the USB connection into your PC. This may not be an issue for you, but keep it in mind as you build your custom interface. One potential solution that you might consider is the "Linduino" DC2026C, which acts just like an Arduino and provides the isolated USB port to the PC.
Thank you for your reply, for some reasons, I am not able to read command code 0x19 correctly using FT2232H, I'm getting 0xFF instead of 0xB0. We are using our own software, so we prefer to stick to FT2232H dongle. Do you mind to send me email directly and help us out?