• State Resolved
  • Locked Locked
  • Replies 3 replies
  • Answers 1 answer
  • Subscribers 62 subscribers
  • Views 487 views
  • Users 0 members are here
Support feedback
Options
Options
Similar topics

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.

TLV757P: TVL75733 is stuck when VEN is higher than VIN

Wonjae Kim
Expert 1075 points
Part Number: TLV757P

Hello.

There is a problem when EN pin voltage is higher than IN voltage.

Briefly describing my system, VIN is lipo battery(3.0~4.2V), VEN is connected to Vbatt(3.0~4.2V) or external usb power(about 5.0V).

TLV75733 works well usually. However the problem is occurred when usb power is connected to EN pin while the battery voltage is very low. It works well when the battery voltage is normal.

TLV75733 doesn't work until disconnecting VIN when this problem is occurred.

There is not mention in the datasheet. VEN should lower than VIN?

If you need more information of my circuit, please let me know.

Thanks in advance.

  • 0
    TI__Genius 16716 points

    Hey Wonjae Kim, 

    In section 7.3.2 Enable (EN) of the datasheet (top of page 13), it talks about how having a higher enable voltage than the input voltage will increase the current going into the enable pin - see Figure 24 below. The battery in your application may not be able to source the current being drawn by the enable pin.

    Potential solutions are turning on enable after VIN has gone high or tying EN to VIN.

    Best,

    Juliette

  • 0 in reply to Juliette
    Expert 1075 points

    Hello.
    It needs more detailed explanation of my system.

    Lipo battery capacity is 2500mA, that's enough.

    There are 2 ways to enable regulator in my system.
    1) External usb power connection
    2) V_batt is connected to EN pin by internal circuit when physical switch is turned on.

    The regulator works well by both ways in normal situation.
    However the problem is occurred when the battery voltage is very low(3.0V or lower).
    1) The regulator is off state VIN(pin 6) is connected to V_batt(3.0V).
    2) I connect the usb power and EN(pin 4) pin rise 5V.
    3) Regulator does not work and it's stuck.
    4) Disconnecting usb power and turn on switch are not working
    5) It works again after I release battery from VIN(pin 6) and connect.

    This problem is occurred only when I use usb power. Enable by switch works well.
    What is the reason of this problem?

  • 0 in reply to Wonjae Kim
    TI__Genius 16716 points

    Hey Wonjae Kim, 

    Without seeing scope shots of what is happening on your enable pin, I wouldn't be able to give a definitive answer. 

    I was able to find some information on powering your device from USB in a paper referenced in the Powering electronics from the USB port App Note. The Universal Serial Bus Specification Revision 2.0 document, on page 150 figure 7-29, shows how the USB port turns on and how the connection timing events look. 

    It looks like the EN signal might actually toggle at a frequency higher than 10kHz, which the datasheet says, “If EN is driven to a higher voltage than VIN, limit the frequency on EN to below 10 kHz”.

    You could try adding an RC delay to the USB Enable connection if this does happen to be the case. 

    Best,

    Juliette