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    How create negative voltage -700mV - -1000mV 30mA?

    I need create negative voltage -700 - -1000mV max current 30mA (typical 5mA) from positive +5 or +3,3V and and all that best in simple and small.
    I thing switching capacitor , but small SMD IC have fixed output for example -3,3 or mirrored to the input voltage and I need -700mV ,

    Any idea?

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    Re: How create negative voltage -700mV - -1000mV 30mA?

    Hi,

    What about a SC voltage inverter plus a negative voltage regulator?
    Maybe there are even combined ICs.

    Did you use selection tools provided by the manufacturers?

    Klaus
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    Re: How create negative voltage -700mV - -1000mV 30mA?

    You can use restive divider for voltage splinting + & - voltage for small current application Click image for larger version. 

Name:	Split voltage.png 
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ID:	150708



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    Re: How create negative voltage -700mV - -1000mV 30mA?

    My application not simple and dot low power , I need only small negative for tree CMOS op amp and GND must be GND.

    > What about a SC voltage inverter plus a negative voltage regulator?
    honestly, I do not even know the integrated negative regulator for one volt or less



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    Re: How create negative voltage -700mV - -1000mV 30mA?

    Hi,

    honestly, I do not even know the integrated negative regulator for one volt or less
    Neither do I.
    Thus one of us or you should use the selection tools provided by the manufacturers.
    Did you use selection tools provided by the manufacturers?
    I recommend you do this on your own.

    Klaus
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    Re: How create negative voltage -700mV - -1000mV 30mA?

    This is a simple negative polarity charge pump circuit. You may find you can use a 555 IC for the role of both clock and half-bridge. Or perhaps it won't work from a 3.3v supply... then you'll probably need to construct an astable multivibrator.

    Click image for larger version. 

Name:	neg polarity charge pump -800mV 30mA driven from half-bridge clk 4v.png 
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    - - - Updated - - -

    The output is negative, referenced to 0v ground.



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    Re: How create negative voltage -700mV - -1000mV 30mA?

    Use the classic 7660 IC (has been around for decades) in voltage inverting mode, and clamp the output with a series combination of a small signal diode plus a schottky. A 1N4148 and a 1N5711 should work.
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    Re: How create negative voltage -700mV - -1000mV 30mA?

    Jadeit
    v_out of ICL7660 depend on capacitors
    so v_out not staple



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    Re: How create negative voltage -700mV - -1000mV 30mA?

    Hi,

    v_out of ICL7660 depend on capacitors
    This sounds as if one could control the output voltage by modifying the capacitor value.
    Where in the ICL7660 did you read this statement?

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    Re: How create negative voltage -700mV - -1000mV 30mA?

    Quote Originally Posted by wondrous View Post
    Jadeit
    v_out of ICL7660 depend on capacitors
    so v_out not staple
    That would be the purpose of the output clamping diodes.

    Also where did you read that voltage changes with capacitance on a 7660?
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    Re: How create negative voltage -700mV - -1000mV 30mA?

    Regulated SC voltage inverters are available with -1.2V Vref, e.g. lm27761. You may introduce an intentional offset to the feedback path to get lower output voltage.

    Another option, an unregulated SC inverter in combination with one of the very few negative voltage regulators exposing less than -1.2 Vref, e.g. ADP7183.



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    Re: How create negative voltage -700mV - -1000mV 30mA?




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    Re: How create negative voltage -700mV - -1000mV 30mA?

    Hi,

    So output voltage depends on a lot of parameters...

    The whole thing is a voltage inverter with series resistance.


    Klaus
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    Re: How create negative voltage -700mV - -1000mV 30mA?

    Hi
    @ KlausST : yes sir it's
    @ Jadeit : I wish you all the best and success



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