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Original question:

ADC128S052-Q1: Current consumption

REF3440: Extension of current capability by using a parallel resistor

Martin Maier
Prodigy 20 points
Part Number: REF3440
Other Parts Discussed in Thread: REF2041, , ADC128S052-Q1

As stated in the datasheet, the REF3440-Q1 can deliver 10 mA at 4.096 V output. In my application, I need some mA additional current. As the REF3440-Q1 can also sink 10 mA, the idea is to apply a parallel resistor from input to output of REF3440-Q1 (Pin 4 to pin 6). In discussion are values of 680 Ohm or even 150 Ohm, the input voltage of REF3440-Q1 being 5.0 V (regulated). The intention is to extend the current capability to 11.5 or even 15 mA.

How do you think about this kind of solution? From the datasheet, there is the fact that accuracy of the output voltage is compromised when sinking current, my design will be checked if it can deal with that. Are there any other known problems with this kind of solution that I could not anticipate from the datasheet (e. g. when being run near the sink/source transition region)

best regards

Martin

  • 0
    TI__Expert 4530 points

    Hi Martin,

    There are ways to increase the current output that are somewhat application dependent. I would be interested to know more details of your application so I can accurately address your question:

    1. What is your accuracy spec?

    2. I noticed that the reason you need more than 10mA of current is so that you can maximize the current consumption of the analog path. Why is this important for your application? 

    3. What is the "external circuitry" that REF34 would also be supplying current to? Additionally, what is the reason for selecting the 4.1V voltage level?

    4. We have a device available that can source/sink up to 20mA called REF2041. Have you considered this device? 

    https://www.ti.com/product/REF2041

    Thanks,

    Jackson

  • 0 in reply to Jackson Wightman
    Prodigy 20 points

    1) For the REF3440, my worst case analysis resulted in 4.096 V +/- 7 mV over tolerance, temperature drift and load regulation. This accuracy is required to fulfil customer requirements.

    2), 3) The REF3440 supplies the analogue part of an ADC128S052-Q1 (see also related thread) and three voltage dividers for temperature measurement by an NTC. This means that the current consumption is highly temperature dependent and varies from almost 0 to maximum, with the ADC128S052-Q1 as a constant load of max. 2.6 mA.

    4) The REF2041-Q1 is interesting as it would solve my problems in a favourable way. In fact, we do not need the sensing inputs of the REF3440, while the feature of 1/2 of the reference voltage may be useful in other applications.

    Thank you for that suggestion, most probably we will change REF3440 to REF2041 to get our problems solved.