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tps65720

harsh raju
Prodigy 40 points
Other Parts Discussed in Thread: TPS65720, TPS65721

hi,

I am working with tps65720/1 EVM modules. As a system designer i am trying to test its efficiency and compare with each other. I need help in the following topics:

1.SMPS

     a) how will PWM/PFM mode of operation accept the efficiency?

     b)does PSM(power saving mode ) and PFM same?

     c)there is no pin for setting PFM/PWM mode for TPS65720.how can i set the mode depending on load or other conditions?(TPS65721 has pins in EVM)

     

2.I intend to connect this to a microcontroller(MC), so when MC will start i want the ldo and smps to be ON! is there any register or pin i can use to do so?

3.what does CH_LDO interrupt stand for ?how can i use it?

4.what does threshold and RESET pins stand do, its really unclear from the documentaion provided.

I will be very thankful if these questiions are answered at the earliest as i am working in a deadline.

thanks

  • 0
    TI__Genius 16870 points

    Hi,

    To give you a better recommendation on device and usage can you please provide me with your application use?

    1. SMPS
      1. PFM will provide a major boost in efficiency at light loads by reducing the switching losses due to the skipped HS FET turn ons. See Figure 1 vs Figure 2 for a comparison.
      2. For this device yes the Power Save Mode, or PSM, is the same feature as PFM mode.
      3. The device will automatically switch over from PFM to PWM and vice versa. If you would like you can force PWM mode through I2C communication. That is the same control that the TPS65721 pin gives you.
    2. By default the device will have DCDC and LDO on when a valid AC supply is available. If the AC is not available, both supplyies are turned on when the push button is pressed. Use the HOLD pins to keep them on once the microcontroller is operational.
    3. CH_LDO indicates when the battery charger is in the CV phase of charging if the termination is turned off. Please see the Charger Termination ON/OFF section of the datasheet.
    4. RESET is a pin to indicate to the microcontroller of an event. For the TPS65720, the event is LDO1's power good indicator is LOW or that the LDO1 is disabled. For the TPS65721, the event is when the voltage at the THRESHOLD pin is lower than 0.57V. Please see the RESET Output and THRESHOLD INPUT sections of the datasheet.
  • 0 in reply to Michael Green
    Prodigy 40 points

    I need to have two o/ps 3.3v and 1.8 v

    what would you recommend : taking 3.3 -smps and 1.8-ldo or vice versa?

    also we were thinkng of connecting input of LDO to output of smps i.e drive LDO by smps output(our external system load will not exceed by 100mA) so for TPS65720 i think o/p max drive current of smps is 200mA ....is it fine connect in this way for good efficiency(as for LDO i/p will be 3.3v and o/p would be 1.8v so efficiency increases)? is it correct?

    ALSO i tested efficiency of LDO on diff loads and o/p voltages...i concluded that at 1.8 v it is close to 48% and at 3.1v it is 83%....is my observation correct?

    thanks