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LMR36015-Q1: Quiescent current consumption

Antoine Chapuis1
Expert 4965 points
Part Number: LMR36015-Q1
Other Parts Discussed in Thread: LMR33620

Tool/software:

Hi team,

I would like to clarify a point about LMR36015-Q1 Iq specification: 1st page of DS states an Iq of 26uA, as does section 8.5 (36uA max in PFM variant) and Figure 

But, there is an application curve Figure-50 that shows an Iq > 20mA over Vin range: I see the OPN of the devcie shows its in FPWM mode: is that curve a good proxy to estimate device Iq in FPWM mode? the EC section only specs the PFM variant.

Best regards, Antoine

  • 0
    TI__Mastermind 25630 points

    Hi Antoine,

    This is referring to the input current drawn from the power supply in a closed loop system, not just Iq- so it wouldn't be a good proxy to estimate device Iq. However, if you're operating in FPWM, usually device Iq is not the main concern. 

    Thanks,

    Richard

  • 0 in reply to Richard Fu22
    TI__Expert 4965 points

    Hi Richard,

    I see, so if the device is used in FPWM mode and the average output current decreases below the ripple current divided by 2, then I suppose we are entering a zone where inductor current becomes negative in CCM, and so, you will have a loss in the low-side FET due to this reverse current.

    And in PFM, you are actually using DEM, meaning the low-side FET opens as soon as inductor current becomes 0, so effectively entering DCM.

    Is there a p2p converter that has a 2.2MHz fixed version, AUTO mode, Adj output?

    BR Antoine

  • 0 in reply to Antoine Chapuis1
    TI__Expert 4965 points

    follow up question: figure 50 shows this input supply current is not constant over voltage in FPWM mode: is this because the frequency decreases when Vin gets close to Vout in order to respect min on-time of HS FET and keep regulating, so efficiency gets higher as a result?

    Best regards, Antoine

  • +1 in reply to Antoine Chapuis1
    TI__Mastermind 25630 points

    Hi Antoine,

    We have the LMR33620, which is closest to your spec at 36Vin, 2A output. If you need a higher input voltage, there currently isn't anything with an adjustable output, auto mode, and 2.1MHz, but the closest we have is the non-Q grade version with adjustable output, auto mode, and 1MHz. 

    And the input current changes over input voltage, at low voltages, the frequency reduction occurs to respect the minimum off-time, and as input voltage increases, the switching frequency increases to where it is consistent at the 2.2MHz, which increases current drawn, and then at the high input voltage, the device may enter minimum on-time, so frequency once again reduces, resulting in lower switching frequency and lower current draw.

    Thanks,

    Richard