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OPT3101: Deep Sleep Current Consumption

Toom Yantek
Prodigy 20 points
Part Number: OPT3101

We have been created a prototype board with the OPT3101 in hopes of creating a battery powered detector.  We have followed the schematic suggestions in the datasheet to split the power between 3.3 and 1.8.  We are configuring the device to go into monoshot mode by setting register 0x27 to 0x26AC07u to select MONOSHOT_FZ_CLKCNT 0x26AC (9900) default, MONOSHOT_NUMFRAME = 1 and MONOSHOT_MODE = 3 in attempts to set up the OPT3101 to give us the minimum current draw.  We are then using the RST_MS pin to trigger a monoshot sampling every 250 ms.

However, when using our power analyzer we do NOT see the idle current in the uA as the data sheet mentions for deep sleep, but we are seeing between 2 and 3 mA.  The analyzer allows us to see the current spikes for the transmission according to our 250 ms timing.  In addition, we can use an IR camera to see the LEDs also pulsing at our interval.  Thus, we can know the OPT3101 is operating on the timing we expected (and not transmitting more often than we expect), but the current draw is much higher than expected.

We have examined the datasheet and don't see anything else required to put the OPT3101 into the deep sleep mode and reduce the current draw.  Is there something that we are missing?

Thanks,

Tom

  • 0
    TI__Mastermind 25895 points

    Hi Tom,

    How much current do you read if you force the OPT3101 into power down mode? Are there any other circuits or passives that could be accounting for extra current?

    Best,

    Alex

  • 0 in reply to Alex Bhandari-Young
    Prodigy 20 points

    Hi Alex,

    Thanks for the quick response. When you say "force" into power down mode, do you mean hold the RST_MS pin low?  If so, we see something even stranger when we tried that as the current jumps to over 25 mA.  This really confused us.  Perhaps this may be a clue to another underlying issue?

    As for other circuits, the 2 to 3 mA is applied to the OPT3101 and its circuitry.  The rest of our circuits consume around and additional .6 to .8 mA, which is just the MCU, power conditioning and some few IO which we have completely disabled in efforts to debug the situation.  We have several samples and on one of the sample we removed the OPT3101 to determine this.

    One other question we have is that in sbau305b.pdf - 4.8.1.1 Only 1.8V Supply Available, it mentions this is the best mode for power consumption.  However, we noticed that there is not much mention of this in the actual datasheet.  Do we need to be running in this configuration to obtain the low deep sleep numbers?

    Thanks,

    Tom

  • 0 in reply to Toom Yantek
    TI__Mastermind 25895 points

    Hi Tom,

    Please see the PDN_GLOBAL register for forcing power down mode.

    The datasheet provides current for both modes, see POWER (DEEP SLEEP MODE) and POWER (DEEP SLEEP MODE), INTERNAL LDO MODE

    Best,

    Alex

  • 0 in reply to Alex Bhandari-Young
    Prodigy 20 points

    Hi Alex,

    Thanks for the tip, that helped me find the issue.

    The problem was that we were disabling a few of the power down items in the 0x76 register as we saw some example code on the web doing that and figured that those few items needed to remain powered.  But it looks like everything is re-powered after the OP3101 receives the RST_MS signal as our device will function and detect. 

    From the DMM on my desk we went from 6.15 mA average to 2.75 mA average with the OPT3101 functioning.  I also did a test where I only forced the OPT3101 into power down (as you suggested) and never obtained measurements.  The current for this test was 0.99 mA, which also makes sense as we were determined our board drew between .6 to .8 mA itself.  Also note, that I was using a DMM at home and we will go into the office next week to use the power analyzer to get true measurements.

    Thanks for all your help!

    Tom