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.

PTH08080WAD Negative Spikes on Power-up

Other Parts Discussed in Thread: PTH08080W

Hi,

I'm working on a PSU module using two PTH08080WAD switching regulators set to generate 3.3V and 5V rails, which they do admirably.

However, I'm getting positive and negative spikes on the output side of the regulators, when I power the PSU module up without a load (the 5V regulator has a 1.2V LDO on it's output).

I'm using the recommended 100uF electrolytes on the input side (ESR is not specified) and powering the PSU module with 7V from a bench supply.

Since I've had some digital circuitry fail after being connected to the PSU module, I'm wondering if the spikes could be the cause and if anyone has a suggestion how to get rid of them?

Best regards,

Baldur

  • Baldur:

    I reviewed the data in this e-mail on PTH08080WAD and 5V0 ,3V3 output  startup operation .

    The following data with PTH08080W layout power application schematic is recommended to be sent directly to tguerin@ti.com

    Baldur:

    I reviewed the data in this e-mail on PTH08080WAD and 5V0 ,3V3 output  startup operation .

    The following data with PTH08080W layout power application schematic is recommended to be sent directly to tguerin@ti.com

    ]. What are the input and output  capacitors , ceramic and polarized types, capacitance and location relative to Vin and Vout pins.

    Input capacitors

    1a1. Does each PTH08080WAD have a dedicated input polarized capacitor ? What is the physical location of each input capacitor ? Is it within 1-2cm of input (Vin) pin 1  and ground pin, pin 2.

    1b1. Output capacitors .

    What is the total amount of output capacitors, ceramic and polarized (ESR on each polarized capacitor) and its general location?   .  

    2. Inhibit pin . Is this on/off function  used to control both units  output voltage ?

    2a1. Is there any component connected to  the inhibit pin such as resistor, capacitor or FET?

    2a2. If the inhibit pin is used ,does each unit have dedicated open drain FET? Is there any direct  connection between 5V0 and 3V3 function pins?

    3. What is the input voltage range?

    4. Question on the scope data: What is its time base in ms/cm?

    Tom