• State
  • Locked Locked
  • Replies 1 reply
  • Subscribers 63 subscribers
  • Views 720 views
  • Users 0 members are here
Support feedback
Options
Options
Related

This thread has been locked.

If you have a related question, please click the "Ask a related question" button in the top right corner. The newly created question will be automatically linked to this question.

TPS71533 and TPS70933 Ground Current question

Brian Antheunisse
Expert 5305 points

Hi LDO teams,

I have a customer who is doing some tests on the TPS71533 and TPS70933.

1. The datasheet for TPS71533 says it has a quiescent current of 3.2uA and later specifies it as a ground current.

I measured the input current to a TPS71533 and found:

Iin = 3.54uA with no load on the output

Iin = 4.2uA with ~160nA load on the output

Question: why would it increase by 700nA when the load only increased 160nA? Does this have something to do with the leakage null control circuit?

2. The datasheet for TPS70933 says it has a quiescent current of 1uA on page 1.  Page 6 shows it as 1.3uA typ 2.05uA max

I measured the input current to a TPS70933 and found:

Iin = 1.6uA with no load on the output
Iin = 2.4uA with ~180nA load on the output

(Question: why would it increase by 800nA when the load only increased 180nA)

Iin = 20uA if Vin=3V (output cannot regulate to 3.3V at this point)

Question: why does Iq get 10X larger when the regulator falls out of regulation? Isn't ground current going to be input current minus output current?

Thanks,

Brian 

  • 0
    TI__Guru 55940 points
    Hi Brian,

    Quiescent current (Iq) is a specific case of ground current (Ignd). By definition, Iq is an unloaded condition.

    In order to accurately measure Ignd on the bench, place an electronic load from the output to the input of the LDO and measure the current from the input supply. This allows the output load to circulate back through the device and isolate the ground current.

    Ignd for many LDOs increases when close to the dropout region. This is because the device burns current attempting to regulate the output.

    Ignd will increase as the load increases as the LDO burns more current in order to drive the pass element harder.

    Very Respectfully,
    Ryan