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BQ24070: help with device regulation design.

Jose Valencia
Prodigy 80 points
Part Number: BQ24070
Other Parts Discussed in Thread: TPS630250, BQ25180, BQ24079, LMR51430, BQ25181, BQ25180EVM

Hello Texas Instruments community!

I am redesigning a device and would like your help.

These are the requirements:
10Vdc – 30 Vdc input voltage (for vehicle use)
Voltage outputs 3.3v (1A) and 3.8v (2A).

I require the use of a 3.7v 250mA (max 1000mA) backup battery, so far I have used the bq24070 regulator (but if you have a better option I would appreciate seeing the recommendations)

The current design makes use of many regulators for its operation, and I would like to reduce the number of components that the regulation stage has, in addition to making use of components that are currently in stock on the market.

This is the current design.

The LMR2360 is used as the main regulator, with which the output is regulated at 5v. This regulator is currently out of stock.
1. I would like to get a replacement for another regulator with a smaller size to use as the main regulator.

The BQ24070 is used as a battery charger and backup system. This regulator requires many components, and I understand that it is designed for batteries with a higher capacity than the one currently being used.

2. Do you have any recommendations to replace this component?

I use the TPS360250 regulator to generate the 3.3v that the system requires, because the microcontroller that feeds it only supports a voltage of 3.3v - 3.6v.

I also use a voltage supervisor (TPS3899DL30DSER) to sense the battery and disable the TPS630250 regulator. but i also get a problem: when the supervisor cuts off the voltage because it is below the limit, the battery runs out of charge and the voltage rises, which causes the supervisor to enable the regulator and turns the microcontroller back on (and repeats this cycle until the battery is fully discharged).

3. Do you have any recommendations to treat this problem? I don't want the battery to fully discharge, is 3 volts too low a voltage for the battery?


4. Lastly, which scheme is more effective (recommended) the one currently being used or the one attached below.

Thank you for your time and I look forward to your comments.

  • 0
    TI__Mastermind 23340 points

    Hi,

    I'll be able to answer the questions regarding the BQ24070. For the other devices, you may need to repost the thread with the specific device questions. Please refrain from posting questions about multiple devices in a post. 

    If the desire is to minimize the number of components, I highly recommend the BQ25180. It only requires capacitors and is configured through I2C.

    Jose Valencia said:
    hen the supervisor cuts off the voltage because it is below the limit, the battery runs out of charge and the voltage rises

    I'm not too sure I understand, if the supervisor cuts off the voltage, how is the battery being drained?

    Best Regards,

    Anthony Pham

  • 0 in reply to Anthony P Pham
    Prodigy 80 points

    Hi Anthony,

    thanks for your answer,

    I will take into account your suggestion to make a different post for each component.

    I am going to review the regulator that you are recommending.

    Regarding the voltage supervisor, I think I did not express myself well.

    when the power is disconnected, the BQ24070 regulator takes the battery voltage begins to decrease, when it drops below 3v the supervisor cuts the power to the load (microcontroller and sensors), the problem is that when disconnecting the battery load, the battery voltage rises again (because it now has no charge) and the supervisor reconnects the charge to the battery.

  • 0 in reply to Jose Valencia
    TI__Mastermind 23340 points

    Hi Jose,

    Ah I see! It sounds like you're attempting to implement what's called Battery Undervoltage Lock Out (BUVLO). This is actually already a feature we've implemented in B BQ25180. Would this help you or would you rather use a voltage supervisor still? If a charger is desired that is configured by resistors, you can take a look at the BQ2075 or BQ24079 that has the SYSOFF pin though you may need. It may be possible with a microcontroller to turn off the load without it relaxing and turning it on.

    It wouldn't seem like a voltage supervisor would be the only component needed to implement BUVLO. Would it be ok if you needed to add components to your current system?

    Best Regards,

    Anthony Pham

  • 0 in reply to Anthony P Pham
    Prodigy 80 points

    Hi  Anthony,

    Anthony P Pham said:
    Would this help you or would you rather use a voltage supervisor still?

    If the regulator has this function, it would not need to use the supervisor.


    the table: Table 8-15. CHARGECTRL1 Register Field Descriptions, do the settings of bits 5 - 3 refer to the voltage at which the protection is activated?

    Anthony P Pham said:
    Would it be ok if you needed to add components to your current system?

    I have no impediment to add more components, I am following the recommendation you gave me to use the LMR51430 regulator (this would go before the BQ25180 battery regulator).

    I am also reviewing documentation to add before the LMR51430 an ideal diode (LM74722 or LM74721 or maybe 74700) but this is the subject of another thread.

    another question.

    Could I replace the BQ25180 with the BQ25181? this in case of having problems with the package of the BQ25180 (it is very small)

  • 0 in reply to Jose Valencia
    Prodigy 80 points

    Hi Anthony,

    good day,

    I have another question, regarding the BQ25180, I was reviewing the characteristics of the i2c interface, according to the datasheet in the "7.5 Electrical Characteristics" table, in the "2C INTERFACE" section, it indicates that the i2c operating voltage is 1.8v. but in the datasheet of the evaluation board "BQ25180EVM" in "Table 2-1. Jumper Descriptions" It says that J1 "Provides the I2C Pins a pull-up to 3p3V". then in "Figure 6-2. BQ25180EVM Jumper Connectors" I find that J1 connects the voltage from the i2c pullups to VIO, and VIO connects to 3.3v through a 0 ohm resistor.

    So, can you confirm if the BQ25180 can work with i2c logic level in 3.3v? or should i use a level converter to work on 1.8v?

  • 0 in reply to Jose Valencia
    TI__Mastermind 23340 points

    Hi Jose,

    You might have this thread confused with another one, it may be that someone else gave you the LMR51430 as a recommendation?

    Yes, you could replace the BQ25180 with the BQ25181.

    Best Regards,

    Anthony Pham

  • 0 in reply to Jose Valencia
    TI__Mastermind 23340 points

    Hi Jose,

    Yes, the BQ25180 will work with the I2C logic level of 1.8V. 

    Best Regards,

    Anthony Pham

  • 0 in reply to Anthony P Pham
    Prodigy 80 points

    Hi Anthony,
    You are right, I was wrong, I took the recommendation of LMR51430 from another post.

  • 0 in reply to Anthony P Pham
    Prodigy 80 points
    Anthony P Pham said:
    Yes, the BQ25180 will work with the I2C logic level of 1.8V. 

    I understand, although I still have the question of why the evaluation board uses the i2c in 3.3v.

    Can you confirm if the BQ235181 / BQ25180 can work with 3.3v i2c?

  • +1 in reply to Jose Valencia
    TI__Mastermind 23340 points

    Hi Jose,

    The EVM board uses 3.3V as we did not want to limit the evaluation when used in parallel with other i2c devices that may only work with 3.3V logic levels. 

    The BQ25180 and BQ25181 have a low logic level of 0.4 V and a high threshold level of 1.3V so both 3.3V and 1.8V will work.

    Best Regards,

    Anthony Pham

  • 0 in reply to Anthony P Pham
    Prodigy 80 points

    Perfect, thank you very much for your help.