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TPS54227: TPS54227 quiescent current at no load (input current)

Part Number: TPS54227
Other Parts Discussed in Thread: TPS54228, TPS62903, TPS562200

Hello, I would like to ask if TPS54227 quiescent current at no load of ~12 mA is correct for this chip?

In the datasheet there is mentioned only "Operating - non-switching supply current" of 0.8-1.2 mA.

The input voltage in my case is 12.0 V, output voltage is 3.5 V.

Thank you in advance


  • Hello Adrian,

    The no-load non-switching current in the datasheet is what is the quiescent current for this part. If you are measuring 12mA, you need to check if the part is switching at the time. Also, any connections from VIN like EN divider needs to be removed else the measured current will be higher.


  • Hello Jose, thank you for your answer,
    my current consumption was measured when IC is enabled (EN pulled high as on schematic) and output voltage is present (switching is present). There is no other load than output voltage divider and caps perhaps. I just want to know why it takes 12 mA of current from 12 V with no other load.

    If I unsolder R1 resistor, the current consumption goes down to 2.2 uA (Shutdown supply current from datasheet I guess). Reducing output capacitance to 22 uF does not seem to affect the consumption. The output voltage waveform is:

    As far as I remember, under higher load, output voltage is much more stable with noise at oscilloscope level. 

    Switching waveform is:

    Output divider has total resistance of 46 kOhm, so it is ~0.7 mA of current at 3.5 V. EN pin has resistance to ground of min 220 kOhm, so with my 10k it is 0.05 mA at 12 V. Far from my consumption.

    When condition of "Operating - non-switching supply current" will happen? 

    Thank you in advice


  • Hello Adrian,

    What you are measuring is not quiescent current but input current. For input current, higher values like 12mA look reasonable with no load at output. With higher load current, this input current will be higher. 

    This app note clearly mentions the difference between input current and quiescent current.


    For quiescent current, the user will need to refer to the datasheet.


  • Thank you Jose for clarification on the terminology, I should use term input current.

    For input current, higher values like 12mA look reasonable with no load at output.

    Thank you also for that, do you have any tips or advices in reducing this value for TPS54227? Is my ~10 mA input current consumption a result of ~1 mA quiescent current (plus parasitics like EN, voltage divider) divided by the light-load efficency (~13%)?

    I found that there is TPS54228DRCT with better light-load efficency (30% vs 13%) so can I expect lower input current from TPS54228DRCT?

    / Adrian

  • Hello Adrian,

    Ic = C * (delta V / delta T)

    Where Ic is the current used to charge the output capacitance during start-up

    IIN ~= D (ILOAD + Ic)

    The above Equation can be used to estimate converter input current in a buck converter where D is the duty ratio. For a buck converter, the duty ratio is VOUT/VIN. If many converters are supplied from the same intermediate bus, the current demand on the bus converter can be large if they all start up simultaneously. A technique commonly used to address this issue is to sequence the start-up intervals of the converters. This spreads out the current demanded on the bus converter and avoids hitting its current limit.

    Also, IIN = PIN / VIN

    As, one can see, increasing Vin or reducing the output voltage, reduces the input current. This might not be suitable for your application.

    You can try reducing the soft-start time by decreasing the capacitor at pin SS, so just use a smaller capacitor value for faster start-up. 

    Faster start-up, decreases the input current.

    I found that there is TPS54228DRCT with better light-load efficency (30% vs 13%) so can I expect lower input current from TPS54228DRCT? 

    Better efficiency will result in a slightly smaller input current, this might not be the best approach.

    Hope this helps!


  • Thank you Jose for your next response,

    as far as I can understand the formulas and logic behind your sentences, I have trouble understanding why we started to talk about soft-start. My problem is not the input current during start of SMPS, but the input current during normal switching operation under no additional load.

    I tried to change SS capacitor from 100 nF to 560 pF and 10 pF and it had no effect on my issue.

  •  Hello Adrian, 

    Sorry, I did not catch input current during normal switching operation in your previous reply.

    Note: The TPS54227, when it works under the PWM mode, the no load current is very big based on the different Vin, Vout because of the drive loss, switching loss.... at no load.

    I found that there is TPS54228DRCT with better light-load efficency (30% vs 13%) so can I expect lower input current from TPS54228DRCT? 

    Yes, you can use the TPS54228.

    Going back to Note: 

    If you are open to other devices and if you want high efficiency at low currents, the TPS62903 could be much better. You can set it work under the PFM mode, the no load current will be smaller.

    The TPS62903 has a typical quiescent  current of 5uA. Please find below pictures of the TPS62903 where you can see high efficiency at light-load current and very low IQ.


  • Thank you Jose for whole help,

    I think this sums up this thread and I will investigate TPS54228DRCT as drop-in replacement, as well as other TI chips, better suited to this application (my first other solution was TPS562200, but I need to spend some more time digging into the detals, unfortunately the first requirement is off shelf availability).

    Have a great day and thank you again,


  • If some is interested in TPS54228DRCT performance, today I measured input current at no load of 0.7 mA with my schematic, which is huge improvement over TPS54227 - my problem was resolved completely.

  • Hello Adrian,

    I am glad you could solve your problem. Thank you for choosing TI. If you have another question, please don't hesitate to ask in