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TPS65910: How to connect the different kinds of GND

Part Number: TPS65910
Other Parts Discussed in Thread: TMS320C6742, OMAP-L137

Hi,

I have several questions about TPS65910. 

Figure 1-1:

1 Does DGND/AGND/AGND2/GND3 connect inside the TPS65910, and then connect with GNDP?

2 GNDA and REFGND does not connect with GNDP. How to connect GNDA, REFGND and GNDP in design or on the PCB?

The recommended connection between TPS65910 and C6748 is as Figure 2 below.

3 There are three kinds of GND: REFGND, POWERPAD and Unknown GND. If this design is recommended, how to connect the three kinds of GND.

4 In this design, the button of PWRON must be pressed to power up. How to avoid this button in design so that the TPS65910 could power up immediately when VBAT is on.

Best Regards,

Kevin Clooney

  • Kevin,

    Yes, all of the grounds are connected internally as shown in the Functional Block Diagram of the device. Technically speaking, all pins should be referenced to the ground pin named in Table 4-1. Signal Descriptions in the Supplies column.

    In the User's Guide you are referring to (www.ti.com/.../swcu071b.pdf):
    1) Regular GND = Power GND, connected to PowerPad and all input/output capacitors. This GND is directly connected to your main GND plane.
    2) REFGND should connect directly from the the VREF cap to the REFGND pin, just as the other side of the VREF cap should connect directly to the VREF pin. Ideally, your REFGND net should not connect to any other GND on the PCB, but it is not critical to operation.
    3) Unknown GND = connected to VFB3 pin. I do not see any significance to this GND when looking at the TPS65910EVM-583. It appears to me this is a warning that you may want to isolate this GND from others due to the fact that it is a Boost converter and may be noisy compared to other buck converters or LDOs.

    Regarding the push-button: it must be used. The PWRON pin relies on a Hi-Lo-Hi toggle on this pin to turn on the system. There is no way around this requirement except with circuitry that would mimic a physical push-button.
  • Hi Brian,

    Thanks for your reply.

    Now i have another question. Sometimes we need that the device could power on without pushing any button. As the Figure 6-1, if i leave PWRON unconnected and connect PWRHOLD to VCC input ( 5v), it will generate a rising edge with VCC input. Under this situation, could the TPS65910 achieve power on.

    Best Regards,

    Kevin Clooney

  • Kevin,

    There are many OTP spins of the TPS65910, and each of these OTP spins has a corresponding User's Guide.

    For the OMAP-L137/8 and TMS320C6742/6/8, the corresponding part number is the TPS65910A1RSL and the User's Guide is here: www.ti.com/.../swcu071

    This User's Guide states clearly "To power on the system, the user must press and release the PWRON switch (generating a negative pulse)."
    Figure 3. Power-Up Timing Diagram also clearly shows that the PWRON signal must toggle low to initiate the Power-on sequence for this device.

    The TPS65910 datasheet describes (1) the TPS65910 generically, and (2) the cases when (a) BOOT1 = 0, BOOT0 = 0 and (b) BOOT1 = 0, BOOT0 = 1.

    When BOOT1 = 1 and BOOT0 = 0, the TPS65910 devices behave according to the EEPROM for each use case and the User's Guide supersedes the datasheet. The logic in Figure 6-1 does not apply in this situation. More appropriately, some of the signals in the logic circuit may be ignored and the User's Guide is the only accurate representation of how to use the device.

    Thanks & Best Regards,
    Brian