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Constant current source LM234

Arumugam Chidambaram
Prodigy 120 points
Other Parts Discussed in Thread: LM234, LM334

We are selected constant current source IC LM234. Supply voltage is 12V. Constant current 1mA. We are setting the external resistance 68 Ohm. Our output load variation RL 100 Ohm to 10.5 KOhm. I want to know this 1mA constant current source can support up to 10.5 KOhm. Could you help for this requirement. 

  • 0
    TI__Mastermind 37190 points

    Hi Arumugam,

    We will look into this, and get back to you soon.

    Aaron

  • 0
    TI__Expert 4905 points

    Hi Arumugam,

    With 10.5kohm and 12V power supply the voltage drop across the LM334 will be 12V - (10.5k x 1mA) = 1.5V. The mimum voltage across the LM334 should be 0.9V typical thus is should work since you have 1.5V typical. The only issue is is that the "Average Change in Set Current with Input Voltage" specification has a condition of 1.5V min so if you want to have a specified accuracy for the 1mA you will need to limit the minimum voltage drop across the LM334 to 1.5V. For your conditions it would probably work then. I say probably becuase you need to look at the tolerances of maximum current, maximum resistance and the minimum supply votlage. If the 1mA, 12V and 10.5k include the tolerances then it will work. Key spec here is the 1.5V and max current. Also keep in mind that the set current varies with temperature, see "Temperature Dependence of Set Current" specification and page 7 of the data sheet section "Sensing Teperature".

    Take care,

  • 0 in reply to Emmy Denton
    Prodigy 120 points

    Thanks for your reply.