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TPS62140: Inverting back boost with over 6Vout

Hirokazu Takahashi
Expert 8420 points
Part Number: TPS62140
Other Parts Discussed in Thread: TINA-TI, TPS62147, TPS62148, , TPS62136

Dear Support team,

Could you please let me confirm some points when using this TPS63140 as a inverting back boost converter discribing in Application Report SLVA469C.
We assume that the converter will be used under the following conditions.
Conditions :
* Vin: 5V ~ 9V
* Vo: -6.02V (or -6.4V)
* Io = 10mA (Inrush: 90mA)
* Tj: -10 ℃ ~ 75 ℃

* Is it possible to use TPS63140 as inverting back boost with this condition as like description in SLA469C?
* Behavior when using beyond the output voltage range
The recommended operating range on the data sheet is -6V as Vout (max), but can it be used at -6.02 to -6.4V? Will it affect performance? (Absolute max rating is defined as 7V)
* Output voltage accuracy
Since the voltage setting method is the same as that for the step-down converter, can the output voltage accuracy be considered the same?
* Can the Discharge function be used?
* When I tried to simulate the inverting buck-boost circuit in datasheet p.27 with TINA-TI, no output voltage was obtained.
Is such a simulation impossible?

Best Regards,
Hirokazu Takahashi

  • 0
    TI__Prodigy 450 points

    Hi Takahashi-san,

    Question 1-3: For your application, I would recommend you to use TPS62147 family which can support higher Vout.  

    Question 4:  Discharge function can still be used in TPS62148. 

    Question 5: TINA simulation doesn't support inverting buck boost config for this device because most models including TPS62140 has GND tired to 0V, that's why you cannot simulate the output correctly.  Please refer to this FAQ link for more information.

    https://e2e.ti.com/support/tools/sim-hw-system-design/f/234/t/692602?tisearch=e2e-quicksearch&keymatch=floating%20ground

    Regards,

    jenson

  • 0 in reply to Jenson Lam
    TI__Expert 8420 points

    Hello Jenson-san

    Thanks for your support.
    Let me confirm below.

    Q1. Can TPS62147/8 support the inverting back boost like TPS62140? If possible, do you have any application note or reference circuit?
    Q2. Is it possible to make inrush current limit to less than 90mA at inverting back boost?
    Q3. Can TINA-TI model of TPS62147/8 support inverting output?

    Best Regards,
    Hirokazu Takahashi

  • 0 in reply to Hirokazu Takahashi
    TI__Prodigy 450 points

    Hi Takahashi-san,

    I will get back to you tomorrow.

    Regards,

    jenson

  • 0 in reply to Jenson Lam
    TI__Expert 8420 points

    Hello Jenson-san

    I have one more question.
    Q4. Can TPS62140 at inverting back boost support -6.02V or -6.4V output? I guess it won't violate the absolute max rating 7V. If it can't support, how issue will be happened at -6.02V or -6.4V?

    Best Regards,
    Hirokazu Takahashi

  • 0 in reply to Hirokazu Takahashi
    TI__Guru**** 191445 points

    Takahashi-san,

    I generally do not recommend operating above the recommend operating conditions.  I would not worry about -6.02 V, but I think -6.4 V has risk.

    First order approximation of inrush current is the current required to charge the output capacitors to the regulated voltage during the chosen SS time plus the load current during slow start.   You can select the SS cap to limit the inrush.

  • 0 in reply to JohnTucker
    TI__Expert 8420 points

    Hello John-san

    I want the clarified answer regarding below previous my question also.

    Q1. Can TPS62147/8 support the inverting back boost like TPS62140? If possible, do you have any application note or reference circuit?
    Q3. Can TINA-TI model of TPS62147/8 support inverting output?

    And regarding question at my first post also,
    * Output voltage accuracy at inverting back boost application
    Since the voltage setting method is the same as that for the step-down converter, can the output voltage accuracy be considered the same? for both of TPS62140 and TPS62147/8.
    * Can the Discharge function be used at inverting back boost application? for both of TPS62140 and TPS62147/8.

    Best Regards,
    Hirokazu Takahashi

  • 0 in reply to Hirokazu Takahashi
    TI__Prodigy 450 points

    Hi Takahashi-san,

    Q1. Yes, TPS62147/8 can support inverting buck boost like TPS62140.  An apps note was written for higher current device, TPS62136 in that family. 

    https://www.ti.com/lit/ug/tiducy3/tiducy3.pdf

    Q3. TINA-TI doesn't support inverting buck simulation for this device

    Q5. As you have said, I would expect the same accuracy like the normal step-down converter.

    Q6. TPS62147 does not have discharge function, but 62148 and 62140 have.  

    Hope it helps!

    regards,

    jenson