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PTV12020L: Device Will Not Reach Close to Max Amperage

Nick C70
Prodigy 190 points
Part Number: PTV12020L

Hi, I currently trying to troubleshoot this device. At the moment I am able to get 0.8 to 1.8 volts with the potentiometer which is not an issue. The current on the other hand is the issue. The current maxes out at 4amps and I need it to be in the 8-10 amp range. The current is following the voltage so 1.8v = 4a, 1.6 = 3.8a etc....

I have it set up such that:
Pin 1+2 = Vout -
Pin 3+4 = Vout +
Pin 5+6 = Vin w/ 560uF metal and 22uF metal capacitor in parallel (I'm using a 12V/3A wall wart as a Vsupply)( I measured 12.6V in)
Pin 7 = I initially had it connected to Pin 4, but removed it during troubleshooting w/ no resolve
Pin 8 = I have a 10k rotary potentiometer connected to Pin 2 GND (At my potentiometers lowest resistance I am getting 2 ohms.)
Pin 9 = I had this pin connected to Pin 5, but removed it while troubleshooting w/ no resolve
Pin 10+11: GND
Pin 12: I initially had this connected as an on/off, but removed it during troubleshooting w/ no resolve.


I noticed the emphasis on using a 22uF ceramic capacitor in the schematic, but it's all I have. I wouldn't imagine this would be the root of my issue. 

I thought it might be the potentiometer that would be the issue because it doesn't have a low enough resistance ~1.8v/8amps(target is 8-10A) = 0.225Ohms

After initial troubleshooting, I reconnected VoSense (Pin 7) to Vin (Pin 4) as well as Pin 9 to Pin 5. I tried moving the potentiometer GND to Pin 11 w/ no resolve. I removed the potentiometer and put in place a resistor 0.41ohm 5% (YellowBrownSilverGold) read 1.8v @ ~4.17 A. I tried several other resistors with the same result. I finally just put a wire instead and still got 1.8v @4.17 A.

Nothing is getting hot or even warm to the touch that I've noticed. 

I'm puzzled why it's maxing at 4 amps when the device is capable of 16 amps.

Thank you.

  • 0
    TI__Mastermind 28020 points
    What are you using as your input source? Is there any current limiting on the input supply?
  • 0 in reply to J Arrigo
    Prodigy 190 points

    J Arrigo said:
    What are you using as your input source? Is there any current limiting on the input supply?

    The input source is a 12v 3amp wall wart. I'm not aware of any current limiting by the input source. I can try another input source and see if that works.

  • 0 in reply to J Arrigo
    Prodigy 190 points

    J Arrigo said:
    What are you using as your input source? Is there any current limiting on the input supply?

    I tried a computer power supply 12 volts and more than enough amperage and the issue is not resolved. 

  • 0 in reply to Nick C70
    TI__Mastermind 38230 points

    Nick:

    I have questions  about wire type size and length used in this application.

    1. What is gauge / wire size used between Vin 12 power supply and ground return , what is its length?

    2. On the output pins 3/4 what is the gauge/ wire size between load source  and ground return?

    3. Can you measure voltage between Vin pins 5,6  to ground pins 10,11 right at the module power pins ?

    4 Track pin 9 what is the voltage or is it opened. If not used, Connect it to Vin

    5. Inhibit pin 12, Is it open or not connected. ?

    Tom

  • 0 in reply to Tom Guerin
    Prodigy 190 points

    Tom Guerin said:

    Nick:

    I have questions  about wire type size and length used in this application.

    1. What is gauge / wire size used between Vin 12 power supply and ground return , what is its length?

    2. On the output pins 3/4 what is the gauge/ wire size between load source  and ground return?

    3. Can you measure voltage between Vin pins 5,6  to ground pins 10,11 right at the module power pins ?

    4 Track pin 9 what is the voltage or is it opened. If not used, Connect it to Vin

    5. Inhibit pin 12, Is it open or not connected. ?

    Tom

    \

    1.  The wire is ~22awg about 20-22 inches long coming from the supply. 

    2. I have 20awg wire running approximately 30 inches to the load. 

    3. ~12 volts

    4. I tried Pin 9 connected to Pin 5  and Pin 9 open while troubleshooting. I recently reconnected Pin 9 to Pin 5 while testing with a wire as the VoAdjust resistor and did not observe a different result. 

    5. I have tried disconnecting Pin 12 and left it open but did not notice a change. I currently have a NOR gate wired to pull it to GND while the momentary button is not being pushed. 

  • 0 in reply to Nick C70
    TI__Mastermind 38230 points

    Nick:

    Thanks for the information .

    The wire is ~22awg about 20-22 inches long coming from the supply. 

    2. I have 20awg wire running approximately 30 inches to the load.

    a. Comment:20AWG with total length to load Vout  and back to ground  is 5 feet.

    a1. 5 Ft #20awg wire voltage drop at 6Amps = 1.8V-0.7V measured between  load, load and load ground = 1.1V or less

     5Ft #20awg ,wire  Voltage drop at 10 amps= 1.8V- 1.1Vmeasured between t load, load and load ground = 0.7Vor less.

    2Q Where  is the output voltage measured under load ? Is it directly from Pin3 or4  to ground  pin 1 or 2?  At the load , with 20 Gauge wire losses What is the load resistors or external power load?

    2xNote Insure pin 1,2 and pin 10,11 are connected externally to  common ground

    3. ~12 volts

    3Q Question is Vin 12 V measured directly on Vin  pin5 or 6 to Gnd pins 10 or 11 top power solder points  with maximum load applied to Vout

    4. I tried Pin 9 connected to Pin 5  and Pin 9 open while troubleshooting. I recently reconnected Pin 9 to Pin 5 while testing with a wire as the VoAdjust resistor and did not observe a different result. 

    I recommend to contact me directly at tguerin@ti.com on future e-mails.

    Tom

  • 0 in reply to Tom Guerin
    Prodigy 190 points

    Thanks Tom,

     I will take some measurements and try your suggestions and get back to you with the results. I will send you an email soon.