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

[Scott Hall]

For linear regulators like the 78xx series you have a minimum 2-volt drop to
account for the B-E junctions of 2 transistors and the drop of a zener diode
(emitter-follower series current pass element, error amplifier and voltage
reference).  So for a 5V regulator, you need to provide a minimum 7V input; for
a 3.3V regulator you need a minimum of 5.3V, and so on.

There is a recent article in Circuit Cellar magazine, Issue 364, Nov. 2020:
"Voltage Regulators: Beat The Heat", pg. 60 (From The Bench column by Jeff
Bachiochi), that explains about this.

On 11/15/20 8:07 PM, The MacDougals via TriEmbed wrote:
>
> Can’t find ams1117-3.3  TI’s L1117-3.3 is a direct replacement.
>
>  
>
> The data sheet shows 15v (max) for Vin and nothing for min.  What am I missing?
>
> https://www.ti.com/lit/ds/symlink/lm1117.pdf
> <https://www.ti.com/lit/ds/symlink/lm1117.pdf?HQS=TI-null-null-digikeymode-df-pf-null-wwe&ts=1605410881526>
>
>  
>
> ---> Paul
>
>  
>
>  
>
> *From:* Josh Wyatt <dragojdw at gmail.com>
> *Sent:* Sunday, November 15, 2020 7:47 PM
>
>  
>
> 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 <mailto: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
>
>      
>
>

-- 
Scott G. Hall
Raleigh, NC, USA
ScottGHall1 at GMail.Com

/Although kindness is rarely a job, no matter what you do it's always an option./

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