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MSP430 Battery backed RTC

Andrew Harwood
Intellectual 355 points
Other Parts Discussed in Thread: TPS3613-01, MSP430F2274, MSP430F169, BQ32000, MSP430F5524

Does anyone know if there is an MSP430 that has a battery backup input for the onboard RTC and Static RAM?  If not is there going to be one in the near future?

  • 0
    Intellectual 645 points

    nope jujst keep the voltage above the ram requirements (usually 1.8v).. The msps are so low in power that you usually just brindge in a voltage source with a diode (the ideal diodes from linear are great.. look at the ltc4413 as an example

  • 0
    TI__Mastermind 23415 points

    Andrew Harwood said:

    Does anyone know if there is an MSP430 that has a battery backup input for the onboard RTC and Static RAM?  If not is there going to be one in the near future?

    You would need an external battery-backup supervisor. I am going to recommend you TPS3613-01 part. This part allows you to put your 2 AA battery and the VOUT will track the input battery until it goes below Vsense and it will switch over to your backup battery.

    The Vsense is an external voltage divider that the customer would need to design and it should be designed to meet the specification of VCC vs MCLK of the MSP430.

    If both the main and backup batteries goes below 1.6V, the supervisor will shut-down completely.


    Please also see this link for a battery backup circuit that some of our customers have used with the MSP430. It has a battery (BT1) and a regular line power (+3V3).

  • 0
    TI__Mastermind 26380 points

    Andrew,

    The first MSP430 device with a backup battery input for RTC will be in the F66xx family (sampled in May 2010).

    The battery backup system provides the possibility to operate a real-time clock (RTC_A) together with retaining some (very limited) bytes in a backup RAM and with monitoring some input pins from a backup source when the primary supply fails.

    Regards,

    Priya

  • 0 in reply to Priya Thanigai
    Intellectual 975 points

    Hi Priya,

                   I am finding hard to interface RTC rx8025 using I2C on MSP430F2274 please take a look at my posts if u have time please help me

  • 0 in reply to Priya Thanigai
    Intellectual 355 points

    Priya,

    Can you tell me how much battery backed up SRAM will be available?  We need about 48 bytes.

    Kind Regards,

    Andrew.

  • 0 in reply to SRIHK
    Intellectual 305 points

    Hi!

     

    I have done interfaceing of MSP430F169 with BQ32000 if need help let me know.

     

    Regards

     

    Aseem

  • 0 in reply to Andrew Harwood
    TI__Mastermind 26380 points

    Andrew,

    Unfortunately the SRAM we save with the backup RAM is only 8 bytes (4 word registers).

    The intent was to store a few bytes of data with a CRC byte that the user can use to see if the RAM data was corrupted during backup operation.

    Regards,

    Priya

  • 0 in reply to Priya Thanigai
    Guru 227245 points

    Wouldn't be an 'NVRam module' suited better for this purpose? No need for a battery backup at all.

    But to the original question: the simplest way would be a goldcap parallel to the processor an both sourced through a diode. (maybe a resistor in line with the goldcap to reduce initial current). And there your 'online UPS' is ready. Use a port pin and a voltage divider on the other side of the diode to detect low power condition and set the MSP into a low power mode then (waking up when power comes back through the port pin interrupt) and depending on the size of the goldcap you can hibernate the system for weeks. Including the RTC, if needed.

    No need for a separate backup input.

     

  • 0 in reply to Aseem Gupta
    Prodigy 10 points

    I'm offering you learn about communication with pq3200 msp430. if you do it yourself application code as well as sharing experiences with them are not. thank you much

  • 0 in reply to Priya Thanigai
    Prodigy 10 points

    Hello Priya,

    We're using a MSP430F5524 in one of our products and use the RTC. 

    The user guide ("MSP430x5xx and MSP430x6xx Family User Guide" - SLAU208N) mentions  the possibility to plug a backup battery supply to allow RTC_B to be running when the main power is down. In this document, I see no special note regarding the fact that this would not be available for all MSP430 products (at least not for all that are concerned by this document). 

    However, I can see no VBAT pin on the MSP430F5524 (cf. SLAS590L); and, when reading your post, I can understand that not all msp430s have this capacity.

    -> Do you confirm that I have no possibility to properly retain RTC clock with the MSP430F5524 ?

    Thanks in advance for your answers.

    Veranith

  • 0 in reply to V��ranith LY
    TI__Mastermind 26380 points

    Yes, you are correct in that the RTC is not supported by the backup battery on the F5524 device.

    The best way to figure out which devices support this feature is by checking the product brochure.

    Download this from the overview page:

    http://www.ti.com/lsds/ti/microcontrollers_16-bit_32-bit/msp/overview.page

    And perform a search for "battery backup".

    This is mainly available in the F663x/563x families.

    Regards,

    Priya

  • 0 in reply to V��ranith LY
    Guru 227245 points

    Also, devices with an auxiliary supply module (AUX) have a separate supply input that powers the RTC and the crystal XT1. Including a charger mechanism to charge this supply when VCC is applied. However, the AUX module does not provide backup ram.
    You can (ab)use the RTC alarm registers as backup ram when you don’t need them for an alarm. :)

  • 0 in reply to Brandon08
    Expert 2225 points
    Hi Brandon,

    Link for a battery backup circuit shows invalid URL.
    Will you please share new link?

    thanks

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