NTE1956 LDO Regulator

Discussion in 'General Electronics Chat' started by tracecom, Aug 20, 2012.

  1. tracecom

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    My NTE1956 LDO regulators came in today. The pinout is the same as the LM78xx series, but the datasheet doesn't provide any application notes. Does anyone know if the standard LM78xx circuit will work, or is there a better alternative? Thanks.
     
    Last edited: Aug 20, 2012
  2. Audioguru

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    I don't think that NTE makes anything. They probably just buy some ordinary ICs (LDO regulators here), erase the original part number then stamp them with their own part number. Then they sell them as "replacements" at an extremely high price.

    Many semiconductor manufacturers make low dropout regulators. This one is probably one of them.

    This one works when its input minus the output (its dropout voltage) is typically only 0.5V but it might need to be as high as 1.0V.
    An LM7824 works when its input minus the output is typically 2.0V but it might need to be as high as 3.0V.
     
  3. tracecom

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    I didn't find another 24V LDO, regulator, so I bought the NTE1956.

    The input that I will be using is 31.8 V with no load, but drops to 24.9 V at 1 A. I may have to limit the current to ensure that the regulator works consistently; at about 700 mA, the voltage is 26.3 V.
     
  4. Audioguru

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    I looked at all the low dropout regulators from TI-National Semi but theirs has a max input voltage of 26V.
     
  5. SgtWookie

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    The absolute maximum input voltage for the NTE1956 is 30v; I suggest that you don't exceed 29v. You say you're planning on feeding it 31.8v. You're going to go through a LOT of those regulators, as you'll be burning them up.

    It doesn't look like you'll be able to use a simple linear regulator for your application.
     
  6. tracecom

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    I interpreted Note 1 from the datasheet to mean that the device has built-in protection from a high input voltage.


    "Note 1. At the application of VIN = 30V, the overvoltage protection may be operated by the ASO protection circuit, leading to the output shut down."


    Is that not what the note means? Thanks.​
     
  7. bountyhunter

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    I know it can't work the same as the 78XX series, because the 78 series are not low dropout. They use the NPN darlington pass transistor design. They are both linear voltage regulators, but their behavior and performance is not the same. Hence, app circuits for the 78XX may not work on this one.
     
  8. bountyhunter

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    maybe..... but it does say the abs max rating is 30V so it's never smart to exceed that. You MIGHT get away with it for a one off, since the parts have a wide distribution of breakdown voltage and they set the limit at the lowest edge of the distribution. Would not be a good design to go into production with, but you might get lucky on one. The odds are good.
     
  9. tracecom

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    Thanks. The data from NTE on this device is often contradictory. For example, some places it says the drop out voltage is .5 V and other places it says 1.3 V. Some places it list the minimum input voltage as 21.5 V, which makes no sense to me for a 24 V regulator. Not very good documentation!
     
  10. tracecom

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    Thanks. Maybe I would be better off with a LM317 circuit?
     
  11. bertus

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  12. SgtWookie

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    As Bertus mentions, the LT1185 would be a far better choice.
    The LM317 would be a lot cheaper, but it will have a 1.7v dropout voltage @ 500mA - and that will increase with an increase in the output current. However, you might use one of the pass transistor schemes as shown in the application notes in the National Semiconductor version of the datasheet for the LM117/LM317: http://www.ti.com/lit/ds/symlink/lm117.pdf
     
  13. bountyhunter

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    The LT1185 is a negative voltage regulator.
     
  14. bertus

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    Hello,

    From the description on the farnell website:


    • IC, V REG, LDO ADJ, 1185, TO-220-5
    • Primary Input Voltage: 35V
    • Output Voltage Adjustable Range: 2.5V to 25V
    • Dropout Voltage Vdo: 750mV
    • No. of Pins: 5
    • Output Current: 3A
    • Voltage Regulator Case Style: TO-220
    • Operating Temperature Range: 0°C to +125°C
    • SVHC: No SVHC (18-Jun-2012)
    • Adjustable Output Voltage Max: 25V
    • Adjustable Output Voltage Min: 2.5V
    • Base Number: 1185
    • IC Generic Number: 1185
    • Input Voltage Max: 35V
    • Input Voltage Min: 3.25V
    • No. of Outputs: 1
    • Operating Temperature Max: 125°C
    • Operating Temperature Min: 0°C
    • Operating Voltage Tolerance +: 1%
    • Output Current Max: 3A
    • Output Voltage: 30V
    • Output Voltage Max: 25V
    • Output Voltage Min: 2.5V
    • Package / Case: TO-220
    • Termination Type: Through Hole
    • Voltage Regulator Type: Positive Adjustable
    Bertus
     
  15. bountyhunter

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    Here's the schematic for the 1185 on the front page of the data sheet, it's definitely a negative. The 1085 are the positive series but they only go up to 30V. http://cds.linear.com/docs/Datasheet/108345fg.pdf


    LT's claim regarding the 1185 is:

    They are just trying to pretend it's a positive regulator to sell more parts, but it's not.
     
    Last edited: Aug 21, 2012
  16. Audioguru

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    An LM317 does not have a ground terminal so its input to output voltage is 40V max. Its maximum dropout voltage is 2.25V so your input must be a minimum of 26.25V for 24V output.
     
  17. tracecom

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    So, an LM317 is out.
     
  18. tracecom

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    If I preload the input with a 330 Ω load, the voltage drops to 29.1. That would keep the input voltage below the maximum for the NTE1956. Except for continually wasting 2.56 watts, what's wrong with that?
     
  19. bountyhunter

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    Nothing, as long as the input voltage doesn't drop too low when the full load is put on the regulator output.
     
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