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AM62L 系列：Only the power supply requirements during the RTC Only Low-Power Mode

JUNZHI LIN
Prodigy 130 points
Part Number: AM62L

Tool/software:

Hello, I have a few questions regarding the RTC Only Low-Power Mode of AM62L that I would like to ask you.

1.According to the reference manual, in the low-power real-time clock mode only, the power supply of VDDS_RTC and VDD_RTC needs to be maintained. If an independent power supply design is adopted and the customer desires to keep the internal RTC timing function even after the device is powered off, is it sufficient to merely maintain the power supply of VDDS_RTC and VDD_RTC?

2. What is the approximate power consumption in the RTC Only Low-Power mode? Are there any available reference power consumption data?

3. Based on the first point, if only the power supply states of VDDS_RTC and VDD_RTC need to be maintained, can we use a battery pack or a button battery to continuously supply power to VDDS_RTC and VDD_RTC? Will this design affect the subsequent power-on sequence?

Thank you!

  • 0
    TI__Mastermind 22366 points

    Hi,

    Thanks for reaching out. To support "RTC only" low power mode, VDDS_RTC and VDD_RTC must be connected to always-ON regulators. These regulators should integrate a power-good signal that can drive the RTC reset signal (RTC_PORz). The expected power consumption of the RTC domain is very low (in the micro-watts). Refer to the AM62L max current ratings in the product folder for supply sizing. 

    Here is the link to the AM62L power supply implementation which explains how the power solution can be scalable based on the application current and low power mode requirements. To support RTC only mode, refer to PDN#3: https://www.ti.com/lit/pdf/slvafw3. 

    Thanks,

    Brenda

  • 0 in reply to Brenda Diaz
    Prodigy 130 points

    Hello! In the RTC Only Low-Power Mode, does the RTC_PORz signal have to conform to this waveform? Can it be controlled without the PG signal? Can we directly pull up to VDDS_RTC without using the PG control?

  • 0 in reply to JUNZHI LIN
    TI__Mastermind 22366 points

    Hi,

    RTC_PORz must follow the timing/slew rate and sequencing requirements specified in the datasheet. To accomplish this, the RTC regulators must integrate "power-good" signal or a discrete supervisor must be added to monitor the RTC supplies and drive the corresponding reset signal.  Having a pull-up to VDDS_RTC is not recommended. Here are some of the reasons:

    • uncontrolled slew rate
    • it does not guarantee the RTC_PORz signal will only go high after both RTC supplies (RTC CORE and RTC IO) have a valid voltage level.
    • it does not guarantee proper reset handling. RTC_PORz must be pulled low as soon as either VDDS_RTC or VDD_RTC are out of regulation (and outside of the SoC operating conditions).  

    Thanks,

    Brenda