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TPS65261-1: V7V, Enable Pull-Up

Patrick Ruf
Genius 4965 points
Part Number: TPS65261-1
Other Parts Discussed in Thread: TPS65262, TPS65261

Tool/software:

Hi,

I have some questions about the TPS65261-1 device:


MODE is always directly connected to V7V.

1. To what voltage are the Enable pins internally pulled-up? To V7V or to VIN?

2. V7V does not switch-on if EN1 and EN2 and EN3 are tight to GND. Is that correct?

3. If I connect EN1 and EN2 to V7V and use EN3 to start/stop the sequence. Does this works? Or do I need to connect EN1 and EN2 to VIN?

If I connect EN1 and EN2 to V7V and connect EN3 to GND, I can see that V7V does not switch-on when I power-up VIN. If I then release EN3 to an open state, V7V switches on (as does VOUT1, VOUT2 and VOUT3).
When I then connect EN3 again to GND, VOUT1, VOUT2 and VOUT3 switch-off but V7V stays on.

I'm a bit confused.

Any clarification is highly appreciated. Thanks.

Best regards,

Patrick

  • 0
    TI__Intellectual 1850 points

    Hi Patrick,

    Plesae see my responses below:

    1. To what voltage are the Enable pins internally pulled-up? - EN is internally pulled up to VIN?

    2. V7V does not switch-on if EN1 and EN2 and EN3 are tight to GND. Is that correct? - V7V turns on as soon as VIN goes above UVLO threshold, it is not related to EN pin state

    3. If I connect EN1 and EN2 to V7V and use EN3 to start/stop the sequence. Does this works? Or do I need to connect EN1 and EN2 to VIN? - ENx pin can sustain max voltage of 6.3V, whereas V7V generates 6.3V output typically, which goes to 6.6V max. If you wish to use V7V to EN the device, you may need to add a resistor divider network to reduce the max voltage on EN pin.

    Regards,

    Himanshu 

  • 0 in reply to Himanshu Nigudkar
    Genius 4965 points

    Hi Himanshu,

    I do see an other behaviour of V7V. If all EN Pins are tight to GND, V7V is off, even if VIN is above UVLO. In my case VIN is 5V.

    MODE has the same voltage limits as EN1, EN2 and EN3. But in the datasheet it is written that MODE should be connected to V7V for automatic sequence.

    Best regards,
    Parick

  • 0 in reply to Patrick Ruf
    TI__Intellectual 1850 points

    Hi Patrick, 

    Let me check once again

  • 0 in reply to Himanshu Nigudkar
    TI__Intellectual 1850 points

    Hi Patrick,

    I rechecked the architecture. V7V is indeed independent of EN states and can be high even if al ENs are pulled to GND. You can refer to Fig 7.8 in DS :

    Also, connecting ENx to V7V should be sufficient as the EN rising threshold is ~1.2V. Is the issue you are seeing is repeatable? And can you help us with your schematic?

    Regards,

    Himanshu 

  • 0 in reply to Patrick Ruf
    TI__Genius 10470 points

    Hi Patrick, do you need any further help here? Please respond to Himanshu's query in that case. 

  • 0 in reply to Himanshu Nigudkar
    Genius 4965 points

    Hi Himanshu,

    I'm still convinced that V7V only turns on if at least one of the EN inputs is high.
    I found the datasheet of the TPS65262 that seems to have the same architecture. And there is this behaviour explained:


    This is exactly what I have experienced with the TPS65261. And in fact that is what the Fig 7.8 shows. Voltage limit of ENx for V7V to turn on is 0.4V.

    So maybe the datasheet of the TPS65261-1 needs to be more detailed.

    Regards,
    Patrick

  • 0 in reply to Patrick Ruf
    TI__Intellectual 1850 points

    Hi Patrick,

    Apologies for the confusion. Looks like V7V output is not completely independent of EN pins. However, V7V output turns on as soon as VEN>0.4 as you mentioned. Hence, the device need not be enabled to get the V7V output. 

    You can use EN3 to start/stop sequence, but I would recommend to use the low level for EN3 signal to be around 0.5V so the it is below EN threshold but it turns on V7V output.