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Recent content by cupoftea

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    Thermocouple good at room temp is good always?

    Thanks, with the TC-08 and out proper thermocouple connectors, that go into the TC-08, it seems that if it reads room temp correctly, and then the temp starts increasing when the fet heats up, then it is highly likely that the reading will be correct to within 4 to 5 degrees C, you would agree...
  2. C

    Stability of Buck SMPS with added output capacitance

    Thanks, i understand, ..though that still does have effect on stability unfortunately...the Choi doc ref'd above being needed to re-calc the gain and phase margins.
  3. C

    SOT223 with 1.1W dissipation and gap pad to its plastic case top?

    Thanks, after extensive searching, the TLV1117 and an IRFHxxxx FET datasheet are the only smd devices that i can find Rth(j-case top) for. Which utterly amazes me since gap-pading plastic case of eg SOT223 etc to heatsink is extremely common.
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    0-10V analog isolator design

    This may have been said already, if so sorry... ..just send through PWM through a digital isolator.....then PWM a 10V rail on the isolated side. PWM of eg 60% means you get 60% of 10V on the ioslated side. Ie, do a RC filtered PWM on the other side..with PWM duty the same as the pwm you send...
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    SOT223 with 1.1W dissipation and gap pad to its plastic case top?

    Thanks, though page 4 of this https://www.ti.com/lit/ds/symlink/tlv1117.pdf ...actually supplies all the numbers for each Rth...but the figure of Rth(j-case Top) cannot be derived from the other figures given. If datasheet doesnt give Rth(j-case Top) then it cannot be calculated. On page 4...
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    Stability of Buck SMPS with added output capacitance

    Thanks, but as can be seen from page 10 onwards of the following... Hangsek choi doc ......"Practical Feedback Loop Design Considerations for Switched Mode Power Supplies" When an LC filter is added to the output of an SMPS, the control loop is further complicated, and the additional...
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    Stability of Buck SMPS with added output capacitance

    Hi, We are just about to do a Buck for 24vin, 15vout and 3Aout. We want to evaluate difference between voltage mode control and current mode control. We want as little output capacitance as possible, occupying as small area as poss on the board. But the customer may attach a product with high...
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    SOT223 with 1.1W dissipation and gap pad to its plastic case top?

    Thanks but we cant use a resistor, as sometimes we need different voltage output. Also, From the above it seems to suggest that its possible to estimate Rth(j-case Top) from the value of Rth(ja) and a knowledge of the Cu area of the a-joined Cu pad on the PCB. Though i am not certain how that...
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    Thermal resistance through plastic case top?

    As yes, thanks to Klaus and yourself FvM, i now see that the internal structure is totally different. I must confess i didnt realise that inside the plastic tab of a TO220FP, is actually a metal tab.
  10. C

    Thermocouple good at room temp is good always?

    Thanks, we are using a TC-08 (Pico) thermocouple reader into the computer. https://www.picotech.com/data-logger/tc-08/thermocouple-data-logger Its a few hundred quid and we hope it solves a lot of the thermocouple issues for us. Thanks, your info on thermocouples is really good....i will...
  11. C

    Non Sync Buck with high side Linear regulator drive?

    Hi, The attached, LTspice and jpeg is a Buck 24vin, 15vout 3Aout. The hi side drive is just done with a linear regulator. The hi side linear reg is needed as there is no low side fet to turn on and get the bootstrap cap charged. (A low side FET isnt needed.) Sync Buck is to be avoided if poss...
  12. C

    Thermocouple good at room temp is good always?

    Thanks, i guess a good quick check is to boil the kettle, dip the thermocouple wire end in and see if it measures about 100degC.
  13. C

    Thermocouple good at room temp is good always?

    Hi, If you are about to do thermal tests with thermocouples...then to see if they are ok...can you say they are ok, if when in the thermocouple reader, with the end junction bits loose on the lab table, then if they read room temp properly , then those thermocouples are OK? (at all other temps...
  14. C

    Current clamp with reference

    Interestingly, it was well stable with either 100n, 200n, 300n, 1u or 11u. I never saw any instability with it. The above are all MLCC, except the 11u which was (10u SMD Tant + 1u MLCC) I believe this reference is pretty well unconditionally stable with capacitance. The reference as such is not...
  15. C

    Can we stack gap pads?

    Hi, We want a 5mm thick piece of gap pad. so can we stack the following 2mm and 3mm pieces on top of each other? The gap pad will be 70mm x 30mm Farnell 3267478 MPGCS-020-150-3.0AA 150x150x3mm £26...
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