[TriEmbed] Powering ESP32 from an 8v golf cart battery

[Josh Wyatt]

Yes - the minimum input to a linear regulator is usually something like
desired Vout + 1.2 volts. The sum of "drop out" voltage and desired Vout is
probably the closest analogy to minimum input voltage.

Thanks,
Josh

On Sun, Nov 15, 2020 at 10:57 PM Kevin Schilf <kschilf at yahoo.com> wrote:

> Hi Paul,
>
> To answer your question about minimum input voltage, you need to think
> about Vdropout.
>
> You apply a Vin and expect the Linear Regulator to provide Vout.
> Vdifference (Vin - Vout) is dropped across the pass element inside the
> regulator which works like a variable "resistor."  This is why the linear
> regulator while small, simple, and quiet can be very inefficient (short
> battery life).
>
> Ex.  Vin 9V, Vout 5V, Vdifference = 4V
>
> 44.4% of the power is consumed by the regulator (4 / 9)
>
> As the input drops (battery), the efficiency increases until Vdifference
> approaches Vdropout.  Vdropout is a function of load current and specific
> regulator.  In the LDO you mention, Vdropout is 100mV at a current of
> 100mA.  This is an effective dropout resistance of 1 ohm.
>
> When Vdifference <= Vdropout, the regulator is no longer regulating.  It
> becomes a fixed in-line resistor between the battery and the load about 1
> ohm in this case.
>
>
> Sincerely,
> Kevin S.
>
>
>
>
>
> On Sunday, November 15, 2020, 7:47:19 PM EST, Josh Wyatt via TriEmbed <
> triembed at triembed.org> wrote:
>
>
> Why not use something like AMS1117-3.3? Minimum voltage on your 8 volt
> battery is going to be something like 6VDC.
>
> -j
>
> On Sun, Nov 15, 2020 at 7:38 PM The MacDougals via TriEmbed <
> triembed at triembed.org> wrote:
>
> How do I find an LDO that operates on 8 – 8.8 v?
>
> I looked at a couple of datasheets and found linear regulators that take
> 9v (max) input.
>
> I did not see a (min) spec for input v.
>
>
>
> How can I tell if it works at 8?
>
>
>
> For example:
>
> https://www.njr.com/electronic_device/PDF/NJM2888_E.pdf
>
>
>
>
>
> ---> Paul
>
>
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