TPS7A4700 low noise LDO regulator PCB

mravlca · 2015-10-29 8:05 am

Eldam said:
Hello Ales,

5 TSA boards received today.

Thank you very much for all your advices and caps adaptations .

Great help and service as usual.

See you,

Eldam

Eldam, I'm gald you like it.

shoom said:
Hi Ales

My double board arrived safely here in the UK yesterday.

I have them powering my OPUS VD section and Metronome and sounding great.

Lovely compact work.

Thanks, I would be nice to see some pictures

K i n g p i n said:
Calculation at 4,5V

Transformer: 4,5V
Load: 50 ohm
Ampere: 1A max
Rectifier Voltage: 1,1V
Usec = secundairy voltage transformer (1,41 x Utransformer)
Uc1 = Voltage across smoothing capacitor = 1,4(load) x Usec, this is your input voltage for the regulator.

Formula:
Uinput-regulator minimal = 5 + 1 = 6V
Uc1: ((1,41 x Utransformer) - 1,1) x 1,4 = 6,34V
Your max ripple voltage = 6,34 - 6 = 0,34V

That's not gonna work.

Calculation at 5,2V

Transformer: 5,2V
Load: 50 ohm
Ampere: 1A max
Rectifier Voltage: 1,1V
Usec = secundairy voltage transformer (1,41 x Utransformer)
Uc1 = Voltage across smoothing capacitor = 1,4(load) x Usec, this is your input voltage for the regulator.

Formula:
Uinput-regulator minimal = 5 + 1 = 6V
Uc1: ((1,41 x Utransformer) - 1,1) x 1,4 = 7,56V
Your max ripple voltage = 7,56 - 6 = 1,56V

If you choose a ripple voltage of 1V you need at least a smoothing capacitor of 10.000uF
Ripple current at switch on will be very high and 1V ripple is very tight if you consider that you mains power of 230V will fluctuate 10%.

Calculation at 6V

Transformer: 6V
Load: 50 ohm
Ampere: 1A max
Rectifier Voltage: 1,1V
Usec = secundairy voltage transformer (1,41 x Utransformer)
Uc1 = Voltage across smoothing capacitor = 1,4(load) x Usec, this is your input voltage for the regulator.

Formula:
Uinput-regulator minimal = 5 + 1 = 6V
Uc1: ((1,41 x Utransformer) - 1,1) x 1,4 = 8,96V
Your max ripple voltage = 8,96 - 6 = 2,96V

Ripple voltage ~ 2V will give you a smoothing capacitor of 4700uF.

Kingpin, I really appreciate all the help you are giving to others.

Best Regards,
Aleš

rickmcinnis · 2015-11-07 2:56 pm

When will these be available?

None on EBAY!

mravlca · 2015-11-09 4:30 pm

rickmcinnis said:
When will these be available?

None on EBAY!

Hello,

ebay add will be again active tomorrow (10th November 2015).

Best Regards,
Aleš

Bibio · 2015-11-23 6:25 pm

Hi Ales

i'm interested in 2 of your power supply on ebay Ultra Low Noise Power Supply TPS7A4700 for Preamplfier DAC Headphone Amp | eBay

now if my calculations are correct i will need a 6.74vac (lets say 7vac) trafo to get 5vdc? how many mA will i receive on the output?

now lets say i get a 2x7vac sec can i power 2 independent from the same trafo?

thanks.

K i n g p i n · 2015-11-23 6:57 pm

Bibio said:
now if my calculations are correct i will need a 6.74vac (lets say 7vac) trafo to get 5vdc? how many mA will i receive on the output?

now lets say i get a 2x7vac sec can i power 2 independent from the same trafo?

thanks.

Can you show us how you did your calculation and what size smoothing capacitor you need?

Bibio · 2015-11-23 9:08 pm

from the notes that mravlca provided on his ebay listing. 2x0.7v for the diodes and .340v for the regulator plus the 5v needed for output.

no smoothing capacitor, plugging straight into a RPi.

Bibio · 2015-11-23 9:19 pm

dbl post

Bibio · 2015-12-04 9:57 pm

? would it be better to run 2 pairs for longer runs so sensing is at load end. length will be about 15cm. or better to run longer shielded AC and move the regulator closer to load.

mravlca · 2015-12-05 1:37 pm

Bibio said:
? would it be better to run 2 pairs for longer runs so sensing is at load end. length will be about 15cm. or better to run longer shielded AC and move the regulator closer to load.

The best would be to make both of suggested. To use sensing and to extend AC cable, so that connection between load and regulator will be as short as possible.

Best Regards,
Aleš

rickmcinnis · 2015-12-05 3:08 pm

The boards I got are different from the ones in the manual so please excuse my question.

Do the +/- boards set come with SENSING enabled or disabled?

Can't tell!

Bibio · 2015-12-05 4:50 pm

the ones i received from Ales are bridged and as far as i can tell if you use the sensing (running 2 pairs ++/--) you remove the bridge. if you are not using sensing (2 wires +/-) then you bridge the pads on the back, like setting the voltage bridges.

rickmcinnis · 2015-12-05 5:45 pm

Thanks for the assurance. I thought it was bridged but had this nagging doubt something might have chanced from the earlier version.

Take care,

mravlca · 2015-12-05 6:24 pm

All PCBs that are sent out have sensing "disabled". In order to use it, you must remove solder jumpers on the bottom side of the PCB.

Best Regards,
Aleš

anjump123 · 2015-12-05 8:17 pm

Hi Ales,

Probably a silly question. What is the current thinking on using the 47uf 25v tantalums on the input side. In previous company we had many AVX types blow up and burn the boards.
This has put me off tantulums since then but I assume things are better now although google search still gives them a bad reputation.
Are there any alternative types?
Anjum

mravlca · 2015-12-06 3:50 pm

Hi Anjum,

I don't know much about blown AVX capacitors. For my products I use Kemet capacitors, to be exact this model KEMET T491D476K025ATs. Also I haven't received any complaints about blown capacitors.
In most of applications for which my products are meant for, all capacitors are over rated.

For alternative there are stacked MLCC capacitors, something like this KEMET C2220C476M3R2CT500 CAP, MLCC, X7R, 47UF, 25V, 2220, but the price is 3-4 times as much as tantalum cap.

Best Regards,
Aleš

anjump123 · 2015-12-07 10:06 am

Hi Ales,

Thanks for the answer. would these work or be better, i know they are not SMD.

25x SANYO OS-CON series SC 47uF 25V 105'C | eBay

Anjum

mravlca · 2015-12-07 5:42 pm

anjump123 said:
Hi Ales,

Thanks for the answer. would these work or be better, i know they are not SMD.

25x SANYO OS-CON series SC 47uF 25V 105'C | eBay

Anjum

They would work, but the question is how. ESL and ESR of electrolytic capacitors are usually greater than in the tantalum ones.
Some additional information can be found here: Decoupling Techniques - Analog Devices.

Best Regards,
Aleš

darbus · 2016-01-27 12:33 pm

Hi Ales,

Do you have on stock double rail PCB?
I need +-12 for dac analog part and single rail +12 for digital part.
I prefer to have double and single boards.

BR,
Darius

anjump123 · 2016-01-27 6:44 pm

Hi Ales,

Just ordered 2 of your PSU's form ebay. Thanks

Anjum (Saabjag!)

mravlca · 2016-01-28 8:16 am

darbus said:
Hi Ales,

Do you have on stock double rail PCB?
I need +-12 for dac analog part and single rail +12 for digital part.
I prefer to have double and single boards.

BR,
Darius

Hi Darius,

I will restock them in about 2-3weeks time. I will post here when and what will be available.

anjump123 said:
Hi Ales,

Just ordered 2 of your PSU's form ebay. Thanks

Anjum (Saabjag!)

Hi Anjum,

if lucky you should get them by the end of the week.

Best Regards,
Aleš

TPS7A4700 low noise LDO regulator PCB

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