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TPSM846C24: confirmation of TPSM846C24 SPEC

Yuhsuan Chang
Prodigy 50 points
Part Number: TPSM846C24

1.the maximal spec of ripple is 13mV

The actual messurement is 15.6mV (Vout: 1.2V & Vin:12V: Iout:26A) & 16mV (Vout: 0.85V & Vin:12V: Iout:18A) which does not meet the criteria 13mV

How to explain the overspec?  like the difference of Oscilloscope or the influence of probe

How to improve the measured ripple?

Test Conditions:

(1.) Set Oscilloscope BW= 20MHz and AC coupling mode.
(2.) Measure at the pins of the dc-dc output MLCC capacitor .
(3.) The outputs will be bypassed with one 0.1uF and one 10uF MLCC (type X5R) capacitors.

2.the spec of In-rush current

3.the spec of Timing and power on

4.Over current protection:

The range is 35.7A~48.3A? Because of +/-15% of 42A (Overcurrent threshold)

5. Current de-raing cannot be measured ?

Because indcutor is embedded in power module and there is no spec of current de-raing

Test Conditions:

1. Critical components must have the right rating and are used safely.
2. It is performed at the maximum DC current margin at Maximum Load condition.
3. Set Oscilloscope BW=Full bandwidth.
4. If multiple max load conditions are defined the worst case condition must be considered.
Critical components must have the right rating and are used safely.

  • 0
    TI__Mastermind 32320 points

    Hello Yuhsuang, 

    Can you please provide a plot of what you are looking into? 

    Are you using test probe with short GND as possible such as below?

    Here are some tips of best practices on how to measure the ripple.  

    https://e2e.ti.com/blogs_/b/powerhouse/posts/how-you-measure-your-ripple-can-make-you-or-break-you

    https://e2e.ti.com/blogs_/b/powerhouse/posts/understanding-and-managing-buck-regulator-output-ripple

    Thanks !

    Tahar 

  • 0 in reply to Tahar Allag
    Prodigy 50 points

    YES 

    The test probe with short GND as yours.

    Please answer the item2~5, thanks

  • 0 in reply to Yuhsuan Chang
    TI__Mastermind 32320 points

    Hello Yuhsuang, 

    2. The spec of In-rush current: 

    Answer: 12mA 

    3. The spec of Timing and power on:

    Answer: The typical internal soft start of the device is 3ms. See Figure 18. for typical Start-up Waveforms

    4. Over current protection: The range is 35.7A~48.3A? Because of +/-15% of 42A (Overcurrent threshold)

    Answer: That is correct. it is 42A typical with +/-15% Accuracy.  

    5. Current de-raing cannot be measured ?Because inductor is embedded in power module and there is no spec of current de-raing

    Answer: 270nH at 0A and -30% at 35A

    Thanks! 

    Tahar

  • 0 in reply to Tahar Allag
    Prodigy 50 points

    2. The spec of In-rush current: 

    Answer: 12mA 

    Reply: The actual messurement is 9.9A (Vout: 1.2V & Vin:12V: Iout:26A) & 0.48A (Vout: 0.85V & Vin:12V: Iout:18A) which does not meet the criteria 12mA 

    What is the spec of maximum rating current?

    3. The spec of Timing and power on:

    Answer: The typical internal soft start of the device is 3ms. See Figure 18. for typical Start-up Waveforms

    Reply: What is the spec of  rise time,falling  , setup time, and Hold up time?

    4. Over current protection: The range is 35.7A~48.3A? Because of +/-15% of 42A (Overcurrent threshold)

    Answer: That is correct. it is 42A typical with +/-15% Accuracy.  

    Reply: This resolved my issue

    5. Current de-raing cannot be measured ?Because inductor is embedded in power module and there is no spec of current de-raing

    Answer: 270nH at 0A and -30% at 35A

    Reply: What is the spec of inductor current rating? Can we desolder the inductor to measure the current? 

    Thanks! 

    Tahar

  • 0 in reply to Yuhsuan Chang
    TI__Mastermind 32320 points

    Hello Yuhsuang,

    2. The spec of In-rush current: 

    Answer: 12mA 

    Reply: The actual measurements is 9.9A (Vout: 1.2V & Vin:12V: Iout:26A) & 0.48A (Vout: 0.85V & Vin:12V: Iout:18A) which does not meet the criteria 12mA 

    What is the spec of maximum rating current?

    Answer: Are you referring to the input inrush current during start up? if you are looking at that, you need to take inconsideration the current that goes into the input caps. Also that depends on the output capacitor bank during start up. 

    3. The spec of Timing and power on:

    Answer: The typical internal soft start of the device is 3ms. See Figure 18. for typical Start-up Waveforms

    Reply: What is the spec of  rise time,falling  , setup time, and Hold up time?

    Answer: Rise time is 3ms typical from the time the device start switching to the time the device reaches regulation and Power Good goes High. The device will start switching when both VIN and EN are present and at the acceptable level. It will take about 200us to the device to start switching from the time the EN is inserted and VIN is present. fall time, my assumption is you are asking about the Internal soft-stop time that is 3ms. 

    5. Current de-raing cannot be measured ?Because inductor is embedded in power module and there is no spec of current de-raing

    Answer: 270nH at 0A and -30% at 35A

    Reply: What is the spec of inductor current rating? Can we desolder the inductor to measure the current? 

    Answer: The inductor is a 270nH typical at zero DC bias with 216nH min and 324nH max.  IRMS with 40C temp rise is 36.5A. ISAT with 30% Inductor drop of 45A. The inductor is for 35A Iop (ADC Max). the DCR max is 1.7mOhms. You you can disolder the inductor if you can, you just need to close the loop and make sure the inductor is not damaged in the process. teh additional loop will add additional losses.  

    Thanks! 

    Tahar