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TPS2113A: TPS2113A and TPS2115A configuration question

Part Number: TPS2113A
Other Parts Discussed in Thread: TPS2115A

Hi,

I've couple of configuration questions involving the  parts 2113A and 2115A. In my platform IN1 is 5V and IN2 is battery power 4.37V. IN1 is always higher.

1. If I use TPS2113A  and connect both pins EN# and SNS  to ground, it seems like the mux will always select the higher voltage between IN1 and IN2 for output  when both supplies are present, why should I use a resistor divider for the SNS pin? Is grounding SNS pin is not a valid configuration? Will the mux output not automatically switch over the secondary supply when one supply disappears?

2. If I use TPS2115A and connect pin D0 to ground and pin D1 directly to  IN1 supply then the mux will always select the higher voltage between IN1 and IN2 for output  when both supplies are present, is connecting D1 to IN1 directly is not a valid option?  Will the mux output not automatically switch over the secondary supply when one supply disappears?

3. Will there be any glitch in the mux output pin for substantial amount time to cause system to reboot when one of the power supply disappears in above two configuration (assuming the battery is fully charged when IN1 disappears?), 

Thank you for helping.

  • Hi Andy,

    Thanks for reaching out on E2E! Please find the answers to your questions below:

    1. You can ground the SNS pin in this configuration. The resistor divider on the SNS pin is a suggestion to allow for a programmable switchover threshold. By dividing the voltage on IN1, as shown in Figure 14, you can confiure the device for automatic switchover once IN1 drops below a certain voltage value.

    2. We recommend using the TPS2115A for manual switchover configurations instead of automatic switchover; it won't be able to switch back to your primary rail without an additional signal or circuitry. The TPS2113A is the best solution for automatic switchover. 

    3. A glitch on the output pin will not cause the device to reboot or restart during switchover. Since the device is powered by the inputs, there won't be any reset or restart condition during switchover. 

    Thanks,

    Arthur Huang


    To find the latest information on Power Switches, visit www.ti.com/powerswitch

    Please click "This resolved my issue" button if this post answers your question.

  • Thank you Arthur for the clarifications.  I'm still not clear on TPS2115A and like to understand the switchover. Let's look at the manual switchover, we have a board on which we can possibly use it.

    The spec says: 

    When D0 equal to logic 0 selects the manual-switching mode. In this mode, OUT connects to IN1 if D1 is equal to logic 1, otherwise OUT connects to IN2.

    In our board  D0 is grounded and D1 is connected to IN1. Also IN1  has a 1.0 meg Ohm resistors to ground, and a 100nF decoupling cap to ground. When IN1 disappears it will create a transition from logic 1 to logic 0  which the resistor will ensure, can we we not seamlessly use this configuration that will  allow OUT to switch to  IN2 when IN1 goes away? 

    I presume the spec assumes it will be done with a GPIO or a logic signal connected  D1 input for the transition to take place, can we not use  the IN1 power connected directly to D1 pin do that work as well in this board without a glitch on the output?

    Please advise. 

    Thanks,

    - Andy

  • Hey Andy,

    Yes, you can use the device in such manner. As long as IN1 operating voltage is higher than IN2 operating voltage, the device will switch between IN1 and IN2. My comment above was referring if IN2 was higher than IN1, then you wouldn't be able to switch back to IN1 using the TPS2115A automatically.

    Thanks,
    Arthur