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PTH08T261W: PTH08T261W POWER SUPPLY ISSUE

Sreevaths Kasi
Prodigy 20 points
Part Number: PTH08T261W

Hi,

I have designed  a 5V 3A supply for a medical device using  the PTH08T261W it works fine when I prototype it but when I try to make another prototype the module fails to work I have observed that even adding a wire to connect the resistor to ground changes the output voltage and even the slightest change in the sense +,- Pins will cause the power supply to shutdown and not supply 5V?

Is this because of the design or due to external factors as I am prototyping on a proto board with wires?

Attached below is the schematic I am using on my PCB and proto board are they any issues that I have to correct in the design?

My output is stable on my first prototype  5V but on the second and third it varies between 4.7-4.5V and I am using the exact same parts even the slightest change in the resistor or the sense pins and the power supply fails to function as intended?

I am using a 330UF nichicon  Digi key: 493-13755-1-nd  20% 25V electrolytic polymer CAP for the input (12V 2A adapter input) and the 2 output capacitors are Digi key: 587-3152-1-ND 100UF 16V X5R 1210CERAMIC CAPS.The resistor I am using is a 169 ohm 1% 1/8W 0805 -RHM169AHCT-ND.

At load, the voltage for 5V is around 4.8V the load I am connecting the power supply to draws 5V 2.1A.

Please let me know if there are any problems in the design or the parts and why the power supply fails to work.

  • 0
    TI__Mastermind 38230 points

    Sree:

    I suggest the first test  is to remove the SMBJ5 clamp from the Output bus.  The voltage clamp may be limiting  Vout  .  Then measure output voltage directly between  pin 4 Vout to Ground pin 3.  How long are  the wire connections between pin 4 Vout to the load and ground return. When is  the wire gauge used to connect to its load?

    Tom

  • 0 in reply to Tom Guerin
    Prodigy 20 points

    Hi Tom,

    I am not using the SMBJ5 on my prototype PCB I have made a PROTO board please find attached image when the length of the wire is short it works very well even a slight change in length causes an issue I am using a 22AWG (7/30) wire.I have designed a PCB using the PTH08 the resistor is placed as close as possible and the +- sense pins are short you can see this in the attached image.Are there any other precautions I have to take during design?I have an SMBJ5 clamp to protect the circuit from transient voltage spikes this is a stepper motor driver PCB.Please take a look at the schematic and the PCB layout do you think the design will work well on a PCB are there any issues with the design?

    Thank you 

    sree