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TPS 61200 High quiescent at very low load

Jason Parmenter
Intellectual 410 points
Other Parts Discussed in Thread: TPS61200

Looking for some words of wisdom on this product.  We are planning on using the TPS61200 regulator to boost a super cap voltage (.5 to 2.7 V) to and operating voltage of 3.6V.  We have designed our first pcb prototype but have notice an unusually high quiescent current at virtually no load(.1uA).  Here are the some measured values for two cases:  

1) Vin = 1; Vout = 3.6V; IQ = 16 mA.

2) Vin = 2; Vout = 3.6V; IQ = 14 mA.

We were expecting something around 50 uA!  This circuit that we are designing has various load conditions ranging from 1uA to 150mA.  However, 98% of the time is spent in a sleeping mode where we would like to achieve much lower sleeping currents.  We connected the PS mode pin to VCC.  All the functionality of the circuit works great other than the high sleeping current due to the regulator.  My main question is, with a range of load currents such as (1uA to 150 mA), what would be a good recommendation for connecting the PS (power save mode).  I understand from other posts that pulling this pin low aids in efficiency at low levels,  But could this hurt us when we need the high current draw (150mA)?  Any Ides, on how to get the high efficiency quiescent current and still be able to provide the burst of 120mA occasionally.

Below is an attached schematic of our power supply.

https://www.dropbox.com/s/fnsmnknriy7sl62/Screenshot%202014-07-30%2023.58.18.png

Thanks, 

Jason

  • 0
    TI__Intellectual 1305 points

    Hi Jason,

    I suggest using the Power Save mode in your application if there is not much concern about audio problem. Actually, using Power Save mode doesn't influence the max output load. From the datasheet Fig.4, which is similar to your condition, this device can still work well at about 250mA output current before it reaches current limit. So it's fairly enough in your application. The only problem is that if using Power Save mode, what is your transient time requirement (for example, from nearly 0 to 120mA)? 

    So please using PS mode and measure the IQ to see if it can be reduced and tell me if you have any concern about transient time.

    BR

    Gene

  • 0 in reply to Gene Lu
    Intellectual 410 points

    Gene,

    I have modified the board such that the "Power Save" pin is tied to ground.  It appears that everything is working fine and our quiescent current is much much lower (200 uA vs. 14 mA) from before!  Still seems a bit high but that is with feeding the regulator only 1.8 volts and making the regulator spit out 3.7 volts.  Transient time shouldn't be a problem for us as our ramp up is programmable.

    Thank you for your quick and helpful response!

    Sincerely,

    Jason

  • 0 in reply to Jason Parmenter
    TI__Intellectual 1305 points

    Hi Jason,

    The 200uA current should be the "no load current", which is a little different from quiescent current (quiescent current means there is no switching of the IC).

    Our team is cuirious about your application of TPS61200 in super cap. In order to support you better and more quickly, would you please tell me more information about your application environment? You can reach me by gene-lu@ti.com.

    Thanks a lot!

    BR

    Gene