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
<[email protected]> 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
<[email protected]> 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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