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TIDA-010030: Schematic check

Chun Lam
Prodigy 10 points
Part Number: TIDA-010030
Other Parts Discussed in Thread: TPS40211, BQ24610, BQ34Z100, , BQ76952, TIDA-010208

Tool/software:

Dear TI,

Could you help me with my design and check the schematics?

The application requires a system voltage of 28V, powered by a 6S1P Li-ion battery, that can be charged in-circuit with USB PD. We need to know the SOC and there must be cell balancing. 

The application expects a USB charger with PD 1.0 profile 3/4 or PD 2.0/3.0 with profile 3/4 using the TPS25730D. The system requires 28V so we boost the input to 28V with TPS40211. This then gets used as the input for the Li-ion charger BQ24610 with Power Path, the BQ34Z100 gas gauge and the BQ7694202 protector/monitor. The cells are connected through P13.

I have included a few questions in the docs but will list them here aswell:

  1. TPS25730D: Does it need an external 3V3 in? I reckon it needs it, otherwise it will always think it is in dead-battery state.
  2. Does the TPS40211 require a pull down on the EN pin? I worry about crosstalk pulling the pin high. 
  3. Does the BQ7694202 BREG/REGIN pin need to be connected, if the system does not use REG1/REG2?
  4. Can the charge gauge and the monitor use the same current sense resistor? 
  5. Are the values of the current sense resistor appropiate? I expect a user activated repetitive 200-600 ms current draw of around 2-3 amps, with an idle current draw of around 0.01 A. 
  6. Does the rest of the system get connected to PACK- or GND? I expect PACK- as otherwise you bypass the current sense resistor of the gas gauge. Should the PD controller and charger not be connected to PACK- then aswell?

Many thanks in advance and kind regards,

Chun Lam

Schematics Review TI.PDF

  • 0
    Prodigy 10 points

    Dear TI,

    Please let me know if the questions need to be broken up, or it is in the wrong forum. Any help would be much appreciated.

    Kind regards,

    Chun Lam

  • 0 in reply to Chun Lam
    TI__Expert 3345 points

    Hi Chun, 

    sorry for the late reply. I believe some of your questions should go to different forum. TIDA-010030 is just a battery pack design without charger or other power design solutions. I will suggest you to create another post specific for power parts. 

    Below are some comments regarding BMS parts: 

    3. REG1 is also used for internal 3.3V pull up, like ALERT, DDSG, DCHG pins, so my suggestion is to reserve BREG/REGIN circuits even REG1 is not used to power any external load. 

    4. Yes. The IC current sensing channel input resistance is very large compared with shunt resistor. It is ok to use one shunt for AFE and gauge current sensing. 

    5. If you are using BQ76952, I recall 1LSB of CC is 7.6uV, you can calculate your shunt based on your current requirements. If you look at TIDA-010208, we achieved +/-10mA-15mA @<2A load at room temperature with well calibrations. The shunt in TIDA-010208 is 1mR. 

    6. We recommend to reference BAT- as GND. It gives smaller common voltage on VC0 pin. But as you mentioned above, if you have a large load and want to monitor the load current to eliminate accumulated SOC error, it would be better to ensure the current flow through the shunt and monitored by AFE.  

    Ryan Tan