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PTH08T230W

Roni Shoval
Prodigy 70 points
Other Parts Discussed in Thread: PTH08T230W

Hi,

 

I used the PTH08T230W to power motherboard with FPGA VIRTEX5.

I use 4 PTH08T230W modules. the modules set to 3.3v, 2.5v, 1.8v and 1.0v.

A daughter card is connected to the motherboard through board to board connectors.

The daughter card include HDMI Tx/Rx chip.

The PTH08T230W supply the power to the daughter card. 

When we make FFT to the HDMI TMDS clock (output clock from the HDMI transmitter) we got the expected frequency (148.5MHz) but we have two spikes, 280KHz from the central frequency.

When I operate the daughter card as stand alone board (not connected to the motherboard, powered from external power supplies) these spikes are disappeared.

I suspect that the PTH08T230W cause these spikes (switching frequency Fs of 300KHz?).

I connected the PTH08T230W as followed:

Pin1: Short to GND

Pin2:  Vin is 5v, connected 330uF, 22uF and 2.2uF (all in parallel) between pin 2 and GND

Pin3: connect to GND.

Pin4: connected 100uF and 4x 47uF (all in parallel) between pin 4 and GND.

Pin5: 82.5K resistor between pin 5 and pin 8.

Pin6: connect to GND. 2 pin header connect between pin 5 and pin 6.

Pin7: connected 1k resistor and 2k potentiometer (in serial) between pin 7 and pin 6.

Pin8: 82.5K resistor between pin 5 and pin 8.

Pin9: short to pin 2.

Pin10: 82.5K resistor between pin 10 and GND.

 

You can find below a list of all the capacitors i use around the PTH08T230W:

Cap  ESR  Voltage rating Tolerance  Part number Note

330u 14mOhm 16V  ±20%  APS-160ELL331MJC5S  

22u 1.6Ohm    16V  ±10%  T491C226K016AT  

2.2u       16V  ±10%  EMK212B7225KG-T X7R

100u       16V  ±20%  CKG57NX5R1C107M X5R

47u       6.3V  ±20%  JMK325BJ476MM-T X5R  

 

Please advice if you see any problem in my design or you have any recomendations

 

Best regards

 

Roni

  • 0
    TI__Mastermind 38230 points

    Roni:

    I reviewed the details on this application. it appears from your description that the switching frequency  at about 280kHZ to 320kHz i is present on the output bus. Is this the 3.3V regulator which is feeding the HDMI Tx/Rx.There are several areas of concern  regarding the application and the PTH08T230W .

    1.Pin10: 82.5K resistor between pin 10 ( Inhibit/UVLO) and GND. The UVLO detect may  not allow a voltage under 5.1V  with hystersis to func iton correctly. Please remove all 82.4kΩ resistor (Inhibit/UVLO)  to ground to insure a normal power up  operation when under 4.5V input voltage.

    2. Pin6: connect to GND. 2 pin header connect between pin 5 and pin 6.

    Do you mean 2 pin header between pin 6 (-sense) and pin 3 ( Ground)..

    The 280kHz switching noise can be reduced by possibly adding a series small ferrite bead ,PI filter  with ceramic capacitors ,directly onto  the daughter card .

    This is one possibility.

    Another possibility is air (E-field) coupling to the daughter card.

    Send me an e-mail with your contact information to discuss this question on filtering.

    Tom

    tguerin@ti.com