Supply chain

[Max01800]

Guys i need to find a buck converter whose output is going to be connected to an ADC (ads131b26-q1). Basically the ADC datasheet says that i can use just the pins APWR and DPWR with and input voltage between 4 and 16 V. the problem is that i don't know which is the maximum current that i can have in input. The datasheed is attached below.

 

[danadakk]

Just a thought but a 24 bit converter wants a low noise supply V,
so a buck followed by a LDO might make sense. Could be buck
feeds digital supply and LDO, using LDO out to supply analog side.

Datasheet shows no specs/graph of CMRR and PSRR over freq.....

What are your actual goals for accuracy, resolution, sampling rate
over T & V & noise ?


Regards, Dana.,

 

[D.A.(Tony)Stewart]

Internal core uses 1.7V LDO .
So you have 3 choices for external supply.

I recommend you use 3.3V p 238 for both Analog and Digital and dump all you heat externally.
or use 5V for both if demanded by peripherals.

e.g. if IC uses 100 mW @ 3.3V then a 4 times this voltage or 13.2V your total power is 400 mW and IC still only uses 100mW.

All you significant currents depend on your loads.

<snip from your datasheet p14>

 

[danadakk]

There are internal LDOs, no data on other than 1 KSPS typical rejection specs. OP wants
to use buck, call me crazy but I do not think buck and 24 bits A/D belong in the same
room. And lack of at least typical rejections versus frequency makes me think if I can get
a real 12 bits out of it over all possible errors life is good. Ok, 13 bits maybe....

Did I miss the INL and DNL specs .....

And this "9 GPIOs with PWM capability"

Oh ya happy to run a lot of onchip switching enhancement processes in a 24 bit environment.

Guess the qualifier its "automotive" tells us all we want to know......


Regards, Dana.

 

[D.A.(Tony)Stewart]

Put Buck regulator in Faraday cage (heatsink shield) then LDO to common analog digital with separate current paths for each from source LDO and follow Cap. guidelines with layout.

Use balanced Diff Mode (DM) low impedance sources for all analog with high impedance Common mode (CM) ( e.g. high mu CM chokes, STP wire, differential inputs and C shunts to PE earth, if you are planning on using a SMPS)

 

[danadakk]

Bypassing certainly matters :

Regards, Dana.