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TPS65400 Initial Programming

Tudor Gherman
Prodigy 20 points
Other Parts Discussed in Thread: TPS65400

Hello,

We are using TPS65400 on an FPGA board and we are facing some problems with the initial configuration. The TPS65400 datasheet states in section  8.3.14:

The recommended method of configuring the TPS65400 the first time is through an external programmer through a separate I2C programming header (as shown in Figure 19). The programming header needs to connect to the SCL, SDA, CE, VDDD, and DGND lines, and can be done using a USB-to-I2C tool. This enables the user to tailor the settings of the TPS65400 for each PCB specifically after PCB assembly, before the first power-up of the

board.

And in section 8.5.1.2.4:

After CE is asserted and VDDD has reached 3.3 V, there is approximately a 320 μs delay before the PMBus interface is active. During this time the TPS65400 is restoring its configuration from the EEPROM.

We deduced that VDDD needs to be supplied by an external power supply. By doing so, the PMBus was not active. It turned out that VIN must be present in order to program the device, but if ENSW1 is obtained from VIN this also enables the power on sequence. To disable the output channels while programming we have tried pulling RST_N low, but the PMBus was not functional.

Is there any way that the TPS65400 can be programmed without enabling the output channels? Why does the datasheet mention that VDDD should be connected to the programming header if it needs to be generated internally by the TPS65400?


Thank you,

Tudor

 

  • 0
    TI__Intellectual 2590 points

    VDD is powered up by our internal LDO, don't need to add external power supply. PMbus and I2C will be active after VDD and CE is on.

    Put VIN, VDDD, CE, is on, put RST_N is low, you can programm TPS65400 without output channels.

    VDDD doesn't need to cennect to programming header, it is pull up power for SDA, SCL, PGOOD,I2CALERT.

    Thanks!

  • 0 in reply to Eric Guo1
    Prodigy 10 points
    Hi Eric,

    I tried this on the TPS65400EVM. Just pulling RST_N low and TPS65400 does not response to any command, even an ACK is not present after I call its address. There is no way I can access and program it. It just like that RST_N has the same function as CE.

    I found there is two ways to program TPS65400 without output.

    The first one is to power VIN while leave PVIN float. Since in my application, the VIN and PVINs are tied together, this method is not practicable.

    It seems the only choice for me is to power VIN and PVINs while pulling all four ENSWx low, since the factory default enable all the ENSWxs.