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Original question:

TPS62745: TPS62745DSSR

TPS62745: It is not turning on at 3.6mA

Aswin S Dharman
Prodigy 150 points
Part Number: TPS62745

Tool/software:

I had tested and confirmed it in a different board with a current source, but I had manufactured the same in a new board but it is not working properly.

My issue is like if I connected the regulator board to my base board the input voltage is reducing to 2.8V from 8.7V(At 3.6mA constant current source).

Can you please suggest any solution for this?

Please find the attached schematics of the same

  • 0
    TI__Genius 15781 points

    Hi Aswin,

    Looks like your base board don't have enough capability to supply so that input voltage would decline.

    You cab use the DC source to supply regulator board and test again.

    Thanks

    Colin

  • 0
    Prodigy 150 points

    No but I need to source using current source only, I will share you the input circuit also, can you check and confirm why it is happening. And I will share the component details too. Please check and confirm once anything from that is causing the issue. Since in all boards showing the same behavior

    Reference Manufacturer partnumber Manufacturer Description
    C92 CL21A226MAYNNNE Samsung Electro-Mechanics CAP,CER,22UF,25V,X5R,0805
    C93,C225,C226 GRM21BR61C106KE15L Murata Electronics CAP CER 10UF 16V X5R 0805
    C96 GRM32ER61C476ME15L Murata Electronics CAP,CER,47UF,16V,X5R1210
    C222 GRM155C81C225KE11D Murata Electronics CAP CER 2.2UF 16V X6S 0402
    D89,D90 KDZVTFTR5.1B Rohm Semiconductor DIO,ZENER,5.1V,1W,PMDU
    L18 LQH44PH4R7MPRL Murata Electronics IND,FIXED,4.7UH,2.5A,34.1MOHM,SMD
    L19,L20 BLM18HE152SN1D Murata Electronics FERRITE-BEAD,1.5KOHM,0603,SMD
    Q13 SI2315BDS-T1-BE3 Vishay Siliconix IC,P-CHANNEL,1.8-V,(G-S),MOSFET
    Q14 2N7002K-7 Diodes Incorporated MOSFET N-CH 60V 380MA SOT23-3
    R91 RN73H1JTTD1004F100 KOA Speer Electronics, Inc. RES 1M OHM 1% 1/10W 0603
    R92,R97,R138 CR0402-J/-000GLF Bourns Inc. RES,0402,0R,1/16W,SMD
    R135 RC0603FR-07100KL YAGEO RES,100K,OHM,1%,1/10W,0603
    R136 RC0603FR-07150KL YAGEO RES,150KOHM,1%,1/10W,0603
    R137 RC0805FR-0710RL YAGEO RES,10 OHM,1%,1/8W,0805
    U23 TPS62745DSSR Texas Instruments IC REG BUCK PROG 300MA 12WSON
    C94 GRM21BR61C106KE15L Murata Electronics CAP CER 10UF 16V X5R 0805
    R14 CR0402-J/-000GLF Bourns Inc. RES,0402,0R,1/16W,SMD
    R121 RN73H1JTTD1004F100 KOA Speer Electronics, Inc. RES 1M OHM 1% 1/10W 0603
  • 0 in reply to Aswin S Dharman
    TI__Genius 15781 points

    Hi Aswin,

    What is your load current?\

    Do you mean that using 3.6mA constant current source to supply TPS62745?

    If so, it is very easy to make VIN drop, please use a high current capacity source.

    Thanks

    Colin

  • 0 in reply to Colin Chen
    Prodigy 150 points

    The actual consumption of the device is less than 3.6mA. And I want to turn it on with 3.6mA constant current supply. But at 3.6mA it is showing 2.8V only instead of 8.7V. If I heated the cap it will work for some times. Can you please check and confirm what is the reason for this?

    I need to make it work in 3.6mA since the board is working in 4-20mA current loop

  • 0 in reply to Aswin S Dharman
    TI__Genius 15781 points

    Hi Aswin,

    Could you use a source which have higher current capability(maybe 100mA) to supply to this device again?

    Colin

  • 0 in reply to Colin Chen
    Prodigy 150 points

    It will work for voltage source. But my requirement is to make it work in 3.6mA constant current source. It is not working in 3.6mA constant current if there is no load also, that is my issue

  • 0 in reply to Aswin S Dharman
    TI__Genius 15781 points

    Hi Aswin,

    Could you test the input current and show me the SW and inductor current in normal condition?

    Usually the input current shouldn't reach to such high value as you can see the efficiency is high in light load.

    Did you try another current source to test again?

    Thanks,

    Colin

  • 0 in reply to Colin Chen
    Prodigy 150 points

    I did the testing as per the suggestion, but still issue is there, without load the regulator circuit itself consuming 14mA, what will be the reason, any of the component is misbehaving?

    But there is no short

  • 0 in reply to Aswin S Dharman
    TI__Genius 15781 points

    Hi Aswin,

    It is a little bit weird, can you test the SW and Vout waveforms to check?

    Thanks

    Colin

  • 0 in reply to Colin Chen
    TI__Genius 15781 points

    Temporarily close this thread due to inactivity.

    Thanks,

    Colin