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TPS65720: Please explain these Iq numbers in the datasheet

Daraius Hathiram
Prodigy 130 points
Part Number: TPS65720
Other Parts Discussed in Thread: TPS65217, TPS65218D0

There are 2 Iq numbers here...

1) the 36/45uA numbers implies that the LDO1 is off.  only DCDC1

2) the 33/50uA numbers implies that both are on.  with 13uA being the Iq of the LDO

SO... The Typical numbers are lower if both are enabled ? 

Further - the 13uA into VINLDO1... is that not included in the total of 33uA into the BAT pin ?  And if so, shouldn't turning off LDO1 yield a savings of 13uA ??

Looks like something is wrong here, or at least not clear to me.

Thanks - Daraius

TenX Precision


  • 0
    TI__Expert 8780 points
    Daraius,
    I have forwarded your question to the product specialist for clarification. You should get a response soon.
  • 0 in reply to Gordon Varney
    Prodigy 130 points

    Thanks.

    These are significant numbers for the small wearable product we are designing.  

    Daraius

  • 0
    TI__Mastermind 30260 points
    Daraius,

    I apologize, it looks like this thread was not answered.

    The reason for the confusing specification is because DCDC1 is always provided power directly from SYS, while LDO1 can be powered in two ways:
    VIN_LDO1 may be supplied by SYS or DCDC1.

    Indeed, when VINLDO1 is disabled, you should save approximately 13uA, and that when DCDC1 and LDO1 are enabled the two values are summed (33+13 = 46uA typical, 50+18 = 68uA max).

    My only concern regarding the numbers is that IQ1 (top-line) and IQ2 (top-line) both say only DCDC1 is enabled in PFM mode and sound the same. My understanding is the IQ1 spec means AC is the supply and DCDC1 is enabled while BAT is not consuming power, whereas IQ2 means BAT is the supply and AC is not applied. This would account for the 3-5uA differential because the PowerPath will consume some power when AC is the only supply.

    I agree that the current consumption appears to be high, but the PMIC must consume some current to prevent power from being consumed and be able to wake up the system when required. The <10uA nominal number is consistent with even the newest PMICs in the portfolio, and this IOFF or ISD for shipping/storing new products is enough for ~1yr of shelf life in many portable systems. For, example the TPS65217 and TPS65218D0 both have IOFF specified around 5-6uA typical.
  • 0 in reply to Brian Berner
    Prodigy 130 points

    Thanks for the follow up Brian.

    I managed to get what I needed using the Eval board and made measurements on it.

    Just FYI - all numbers in uA running on a battery (~3.8V)

    LDO fed from VSYS.

    - Only DCDC1 32.3
    - DCDC+LDO 55.8
    - LDO Only 56.6
    - Both off (powerup) 5.5
    - Both off (later) 14

    These were somewhat higher than I expected, but in the ballpark of the datasheet.

     

  • 0 in reply to Daraius Hathiram
    TI__Mastermind 30260 points
    Thanks for confirming Daraius! It is quite interesting that the "LDO Only" value would be marginally higher than "DCDC+LDO", unless some other variable were tweaked but not listed. On the other hand, I agree this data is remarkably consistent with the datasheet.