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Original question:

TPS1663: Power good indication status

TPS1663: General questions about TPS1663

Sooraj P
Prodigy 90 points
Part Number: TPS1663

Tool/software:

Hi 

I have below questions on TPS16632.

1. If mode pin is grounded, will the device be working on auto retry mode during a output direct short to ground?

2. Should i keep the SHDN pin grounded or floating? if i am using the device on auto retry mode (Mode pin grounded).

3. why there is few NC pins (3,4,24,15) kept open, and some are connected to this ground (19,20,21,22,23) in Evaluation board schematics? (attached below)

4. why 24th NC pin is named as VIN2?

Regards

Sooraj P

  • 0
    TI__Mastermind 30681 points

    Hello Sooraj,

    Welcome to E2E. 

    1. Short circuit to GND and power into short, both are latched off fault. Device will not go into auto retry during short events.

    2. Please keep SHDN floating if you are not planning to use it.

    3. pin 24 is connected to VIN not open. pin 3,4,15 are introduced in between functional pins, so not connected. Others NC pins are connected to GND for better thermal and heat distribution.

    4. pin 24 is last pin just side to VIN. It shows there is no issue in shorting those pins. 

    You can leave NC pins floating or connected to GND. Making them GND shows improved thermal performance.

    Thanks 

    Amrit  

  • 0 in reply to Amrit Jit
    Prodigy 90 points

    Hi Amrit

    1. I have tested the device TPS16632 (mode=0) for short circuit (current limit resistor 30k in evm) and i observed no latching there. once i removed the short circuit the power good voltage went high from zero.

    (I have used the EVM and replaced the D10 led in EVM  with resistor such a way that when output is normal Pgood will give 5V)

    Regards

    Sooraj P

  • 0 in reply to Sooraj P
    TI__Mastermind 30681 points

    Hello Sooraj,

    Can you explain more about the test case?

    Is it power into short or short circuit? Do you have waveform?

  • 0 in reply to Amrit Jit
    Prodigy 90 points

    Hi Amrit

    This is output (Vout) Direct short to ground , i have video , but not able to upload, does this forrum support video upload?

    I have taken waveform for one cycle only , wont be much helpful to the context.

    Please note that I have used TPS16332 variant in EVM .

    as per datasheet The fast-trip circuit holds the internal FET off for only a few microseconds, after which the
    device turns back on slowly, allowing the current-limit loop to regulate the output current to I(OL). Then the device
    functions similar to the overload condition.

    Does it indicate ,if mode is grounded device will try auto retry during short circuit ?

    One more question , what is the recommended output capacitor for this circuit? evm i can see a 1000uF , is this large value really required?

    Regards

    Sooraj P

  • 0 in reply to Sooraj P
    TI__Mastermind 30681 points

    Hello Sooraj,

    Thanks for explaining the test case. I was under the impression that it's start-up into short condition. The behavior what you are observing is expected. Check out datasheet explanation and image below.

    During a transient output short circuit event, the current through the device increases rapidly. As the current-limit amplifier cannot respond quickly to this event due to its limited bandwidth, the device incorporates a fast-trip comparator. The fast-trip comparator architecture is designed for fast turn OFF tFASTTRIP(dly) = 1 µs (typical) with I(SCP) = 45 A of the internal FET during an output short circuit event. The fast-trip threshold is internally set to I(FASTTRIP). The fast-trip circuit holds the internal FET off for only a few microseconds, after which the device turns back on slowly, allowing the current-limit loop to regulate the output current to I(OL). Current limiting will be done based on MODE pin configuration 

    Sooraj P said:
    what is the recommended output capacitor for this circuit? evm i can see a 1000uF , is this large value really required?

    1000 uF cap on output is to depict the inrush current control and working of dVdT functionality.

    You can keep COUT based on your application requirement. There is min value for COUT.

    Thanks 

    Amrit