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ADM1270 for 15A sense

Hi,

I plan to use ADM1270 for to sense 15A. So that i am using 3mR sense resistor. Using PMOSFET TJ30S06M3L,LXHQ on RFEG Pin and gate pin. Ctimer set for 47us(by using 470PF) and Ctimer off set for 200ns(by using 100nf). By using this configuration can i able to sense 15A?

also iam connecting EN pin to my MCU by using a series resistor 10K .10K pull down also using. En pin tied to fault pin. Is there any issue while using this configuration?

How much will be the current consumption of ADM1270?



Extra one queryadded
[edited by: Monisha at 7:09 PM (GMT -4) on 25 May 2021]
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  • Monisha,

    Setting Viset to 1.8V as described on page 17 of the datasheet while using a 3m ohm sense resistor results in a 15A current limit.

    Your timer calculations look good. Note that t_timer_off is 200ms not 200ns for 100nF.

    Your ENABLE pin circuit seems fine if you MCU has an output voltage of at least 2.4V.

    The third line of the "SPECIFICATIONS" section discusses the ADM1270 current.

    Note that the power dissipation of the FET you chose is around 4W. Target closer to 1W in a FET.

    Good Luck!

  • Would it be possible to clarify what the 1 watt FET target suggestion is all about here?

  • The FET heats itself while passing current to the load (Vds x I). 1W is a safe rule of thumb for keeping the FET relatively cool during operation. FET vendors usually specify thermal performance at 25C and soldered to a 1in^2 copper PCB, which is able to dissipate 1W into the ambient air, so you don't want your FET to self-heat to 125C, for example. If you have a heatsink, or substantial airflow over the FET then you could probably get away with 2W or more, but you need to understand where the heat is going before assuming more FET heating is OK. Also, if you use the 1W rule then it is easy to estimate how many FETs you need for a particular load current. Each FET can carry:

    I = 1/sqrt(Rdson).

  • Thank you, I was unclear if this was directed in some way to the soa power up calculations.

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