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TLV2401 Exhibits High Current Draw

Phil Lizzi
Intellectual 2605 points
Other Parts Discussed in Thread: TLV2401

Customer is designing low current / speed light sensitive diode product using the TLV2410 as very low current TIA for 3VDC long life battery operation (> 7 years).

Candidate circuits (attached a TINA schematic entries ... not as actual simulation attempts) show initial design (diagram 1) with equivalent idle operation (as diagram 2). Actual operation draws 10x the datasheet current indicated (around 10uA vs. ~1uA). Note the operation is single supply 3VDC with a switchable offset voltage at the plus input of ~200mV (not the Vcc/2 on the datasheet).

Circuit in digram 3 shows a circuit which approached the datasheet current, but required an undesired bias idle current of 1uA (compared to 0.7uA opamp draw).

Questions are:

1.  What mechanism is causing the 10x current draw in the TLV2401 for this circuit (are there additional test plots available indicating a change in current draw vs. input voltage)?

2.  Why does circuit in diagram 3 cause the datasheet spec'd current draw (for 3k feedback resistor) but much higher draw for a 300k feedback resistor?

3. What recommendations / circuit configurations could be made to allow for a low current draw circuit for this application (target is ~1uA total ... including bias)?

The atttached TINA schematics include additional explanatory notes.

Thanks,

Phil

TLV2401 Circuit.zip
  • 0
    TI__Guru* 93105 points

    Hi Paul,

    Unless the TLV2401 is driving additional current into a load the operating current should not change significantly over the TIA input current range. The circuit looks pretty straightforward which makes me question if the devices are drawing excessive operating current - independent of the application. Here are some things to try:

    • Monitor the output of the TLV2401 with a wideband oscilloscope using a 10x probe. Probe the point at the output pin; before the output RC network. Check for any evidence of oscillation. Do this with the feedback resistor set to each of the two values.
    • Connect the TLV2401 as a simple buffer and check the operating current. Make sure that it isn't oscillating. Is the operating current still too high?
    • Collect the lot and date code information off of the devices, or better from the reel or packing documentation. We have to be on the lookout for counterfeit product.

    Please let me know what you find.

    Thanks, Thomas

     

    Thomas Kuehl

    Senior Applications Engineer - HPA Linear products

    Texas Instruments - Tucson