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TPS65217: The 24V main power supply fails to work properly after re-powering.

Rhea Gao
Expert 2340 points
Part Number: TPS65217
Other Parts Discussed in Thread: AM3359

Hi,

I have a customer using TPS65217CRSLR, there are some problems, please help to support!

1.Functional requirements:

The AC pin of the TPS65217CRSLR connects to a DC5V power supply to generate all power supplies for the AM3359. When the main power is off, the TPS65217CRSLR must maintain power supply for at least 5s to ensure sufficient time for the CPU to store data.

2.The current existing problem:

1) Scheme 1: In the TPS65217CRSLR power supply (AC) input pin to add 1F capacity of the supercapacitor, the time did not increase significantly, the preliminary analysis of the reason is that after the main power failure, due to the large internal resistance of the supercapacitor, the power supply voltage drops below 4.3V, TPS65217CRSLR undervoltage protection.

2)Solution 2: After the supercapacitor is boosted to 5V by DCDC and connected to BAT and BAT_SENSE, the TPS65217CRSLR is also abnormal when the main power supply is powered on again.

3) For Solutions 1 and 2, after adding a supercapacitor and powering on the supercapacitor, the TPS65217CRSLR cannot output normally. After the power of the supercapacitor is basically exhausted, power on the TPS65217CRSLR to output normally.

3. Problems that need to be resolved：
1）How much current does the chip itself consume in normal operating mode?
2）How to solve the problem that the 24V main power supply cannot work properly when AC, USB, and BAT pin power supplies have residual voltage?
Many thanks~
  • 0
    TI__Mastermind 19130 points

    Hi Rhea,

    Can you share the following information:

    • Scope capture showing the issues described above
      • VAC, VUSB, VBAT, VSYS
      • VSYS, PWR_EN, nWAKEUP, VDCDCx

    • Schematic and Layout files if possible (let me know if you need to share these privately)

    The current during normal operation will depend on the load conditions of the application. The current specs for all outputs should be recorded in the datasheet. You would need to measure the current going into the chip during processor function or during idle state to find exact data for your setup.

    I can't make a solid suggestion on the 24V main power issue without fist seeing the abnormal behavior in a scope capture. Can you more clearly describe what part of the power sequence is failing? (See Section 8.4 of the datasheet)

    Regards,

    James