On Sat, 1 Dec 2018 at 09:58, Denny Esterline <desterline@gmail.com> wrote:

> Given that this was the unit's reference voltage, I think I'd steer away
> from any sources of noise - if practical or possible. Any kind of switchi=
ng
> regulator would certainly qualify on that front.
> Russel should be along shortly to share a circuit with a TL431  :-)
>
> Zetex version of TL431 due to usefully lower Iq than most.

But most TLV431 (half Vreg_std of TL431) have usefuilly lower Iq.
>From memory TL431 is about 80 uA max and T:V431 about 25 uS max. Memory ma=
y
be wrong.

BUT LM385 can be far lower AFAIR (a few uA)

        http://www.ti.com/lit/ds/symlink/lm185-1.2-n.pdf

Annoyingly the 10 uA Iq ones are foxed.
And the adjustables are about 50 uA Iq.

but

Some of these 3 terminal regulators look "just right"


https://www.digikey.com/products/en/integrated-circuits-ics/pmic-voltage-re=
gulators-linear/699?FV=3Dffe002bb%2C1bcc0120%2C1bcc0121%2C1bcc001d%2C1bcc01=
25%2C1bcc0126%2C1bcc0197%2C1bcc0262%2C1bcc0325%2C1bcc0326%2C1bcc0366%2C1bcc=
039d%2C1bcc039e&quantity=3D0&ColumnSort=3D477&page=3D1&k=3Dldo&pageSize=3D2=
5&pkeyword=3Dldo

Including this:

eg $0.97/1 in stock Digikey - 1.3V version

*https://www.ablic.com/en/doc/datasheet/voltage_regulator/S1313_E.pdf
<https://www.ablic.com/en/doc/datasheet/voltage_regulator/S1313_E.pdf>*

SOT23-5

Output voltage: 1.0 V to 3.5 V, selectable in 0.05 V step.
Input voltage: 1.5 V to 5.5 V
Output voltage accuracy:
1.0% (1.0 V to 1.45 V
Dropout voltage: 170 mV typ.
IOUT =3D 100 mA

*Current consumption*:
 During operation: 0.9uA typ., 1.35 uA max.
During power-off: 0.01 uA typ., 0.1 uA max.

The need to "float" the battery may be able to be overcome by feeding it
from 9V with two resistors to +9V and ground.

R < (V9Vmin-Vout-Vdropout)/Imax/2


          Russell
--=20
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