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bq24070 pin doubts

alberto gonz
Prodigy 50 points
Other Parts Discussed in Thread: BQ24070, TPS63000

Hi,

 

We are designing a product which needs battery backup so we are using BQ24070.

We are not using USB.

The lithium battery has the following specs:

3.6V

2250 mAh

 

We configured the bq24070 with the following:

Preconditioning current: 56mA

Charging Current: 560mA

Charge time: min -> 5.2 hours, max-> 7 hours. depending on min and max values of K(tmr)

Charge Termination: 53mA

DPPM activates at: 4V

Mode: High (not usb)

 

We have the next doubts hope you can help us:

 

1) We want to charge the battery at: 560mA.

    but on page 17 of the datasheet it says: "Charge level during AC mode operation (Mode: HIgh) can be changed by a factor of 2 by setting ISET2 pin high or low."

    So, we dont know how to ISET2. we want to charge the battery at 560 mA so do we need to configure ISET1 to 280mA and then ISET2 on high to double it so it gives us

    the 560mA?, or should we left floating ISET2?. also if we need to connect ISET2 to something (5V or 0V) do we need to connect it via a 100K resistor as in the EVM?

   Im assuming we can connect it to 5V right?

 

2)  How to connect MODE pin?

    We want high, but on the specs on the datasheet it is not clear VIL = 1V, and ViH = VIL + .024 ? so we want it in high, we need a 1.024 V on this pin?

   Can we connect it to 5V directly ? do we need a 100K resistor?, or do we really need the 1.024V?

 

3) CE Input

    We want to chip to be enabled all the time. do we connect it to the 5V Input  via a 100K resistor? or the resistor its not necessary?.

 

4) Design Question

     The rest of the system will be powered by the BQ24070. so the lithium battery will provide voltage from 4.2 V to 3V.

     The system needs 3.3V at 1.5A. 

      Can you recommend me a Buck Boost converter ?

 

This is the schematic of the connection can you check it to see if its ok?:

 

Best Regards,

 

 

 

  • 0
    TI__Mastermind 31120 points

    the data sheet has many examples and refering to the function block diagram would answer most of your questions.

    1) Iset2 high to 5V (greater than the high threshold)

    2) Mode to 5V (greater than the high threshold)

    3) CE high to 5V (greater than the high threshold)

    4) TPS63000

     

     

  • 0 in reply to Charles Mauney
    Prodigy 50 points

    Hi Charles,

     

    1)

    Do I have to connect it via a 100K resistor? or directly?

     

    2) 

    Is it safe to use TPS63000 to power the 3.3V rail of the microcontroller? I read somewhere that its too noisy, and that its much better to have a Linear regulator.

     

  • 0 in reply to alberto gonz
    TI__Mastermind 36110 points

    I think you are misinformed about the TPS63000 noise.  This TPS63000 is a good fit for your application and has very little noise.  It is not noisier than any other switching power supply.  As with all switching power supplies, it will have more noise than a linear regulator, but it will be a good choice to power the 3.3V rail of a microcontroller.

    For the ISET2 pin, please refer to the electrical characteristics table for the requirements to make the pin detect a logic high or logic low.  You can connect to you input without using a resistor.