Aux BMS Architecture

Owned by Former user (Deleted)
Last updated: Dec 28, 2017

Battery Charger: LTC4010

  • for best reliability, input voltage should be (2V*n_cells)+0.3V = ~21V
  • thermistor
    • 10K NTC with beta 3750
    • charging without thermistor not recommended for charging well above or below 1C (voltage termination insufficient)
    • needs off-board thermistor connection to put thermistor on pack


Undervoltage Protection: LT6703-2

  • 1.4-18V voltage comparator with built in reference
  • V- pin exposed, will output a logic 1 if input < reference
  • low current draw, ~6.5uA
  • open collector output, will likely need FET driver


Boost Converter: TPS55330

  • 12V to 21V boost converter
  • 1.5A output current


Load Switch:

  • 2A-5A (higher end of the range is better)
  • battery voltage can be ~14V, so voltage needs to be >14V
  • active high enable
  • WSON package for better power dissipation
  • may need to be a high side MOSFET driver + power MOSFET

Best load switch we could find: http://www.ti.com/product/tps22810

  • 18V max Voltage
  • 3A max Power

  • 79mΩ Ron

Or we can use an NMOS and a Power PMOS in the following manner: 

Here, Q1 will an NMOS that feeds to the gate of Q2.

Suggested power FET for Q2:

  • 5A continuous drain
  • 20V drain to source voltage
  • Ron = 45 mOhm @ 4A, 4.5V

Or we can use an NMOS power FET with a gate driver: 
NMOS: 
https://www.digikey.ca/product-detail/en/vishay-siliconix/SIS412DN-T1-GE3/SIS412DN-T1-GE3DKR-ND/2442463

Gate Driver: 
https://www.digikey.ca/product-detail/en/silego-technology/SLG55021-200010V/1827-1047-1-ND/7562931

OR Gate:

  • actually needs to be a NOR gate (inverted or), since a logic 1 at the output of the OR gate should turn off load switch
  • able to take battery voltage on power supply, or pair with regulator that drops battery voltage to logic voltage
  • 5V or 12V logic compatible (12V preferred)
  • SOT package preferred



System Block Diagram: