DC1812A-B: PCB trace current rating

Hi, 

I require some information on the current rating of the traces used in the DC1812A-B (specifically that of the traces used for the Rsense resistor). Reason being, I aim to charge a 50Ah, 24V Lithium Iron Phosphate battery with 10A, but I can find neither the current rating of the DC1812A-B board (using LTC2944 chip) nor the trace current rating. I would appreciate if anyone can guide me accordingly. Thanks in advance. 

Kind regards,

Vernarda  

  • +1
    •  Analog Employees 
    on Sep 13, 2021 9:03 PM

    From the DC1812A user manual - "Up to 500mA supplied to the battery can be measured with the board default 100mΩ sense resistor present on the DC1812A-A and DC1812A-B. The DC1812A-C can support currents of up to 1A with its integrated 50mΩ sense resistor. Use SENSE+ and SENSE– test points to read voltage across the sense resistor".

    So to measure more current, you'll need to change your sense resistor first.  for a maximum measured current of 10A, you would need 50mv=10*R, or a 5mOhm shunt.  Up to 300mV difference is safe on the sense inputs, but accuracy is not guaranteed.  I'm not sure of the exact rating on the trace, but it looks to be 150mil which typically can only handle 6A for 10C rise.  You will likely want to either use an external shunt (preferred) or reinforce it.

    See page 11 of the LTC2944 datasheet, section "Choosing RSENSE" for more details as well as the required register changes to account for the difference. 

  • Thank you for your swift response. I will investigate the use of the external shunt for my application.