New TI REF54EVM Evaluation Module Leaked

[laichh]

Look at what I've found.

https://www.ti.com/lit/ug/snau289/snau289.pdf

Description
The REF54EVM is a precision voltage reference evaluation module that demonstrates the performance of high precision series reference device (REF54) from Texas Instruments (TI). The REF54 is a family of high precision, low drift, low current consumption series voltage reference devices. The REF54 family offers low temperature drift coefficient (0.5 ppm/°C), low flicker noise (0.16 ppm p-p with 100uF capacitor on NR pin) and high accuracy (±0.02%), while consuming 260 μA current.

Features
• Enable and disable the output
• Capacitor at NR pin is configurable with 0 ohm resistor to optimize the noise performance

Applications
• Semiconductor test equipment
• Precision data acquisition systems
• Precision weight scales
• Ultrasound scanner
• X-ray systems
• Industrial instrumentation
• PLC analog I/O modules
• Field transmitters
• Power monitoring
• Battery management system

Introduction
The REF54EVM is a series voltage reference evaluation module that demonstrates the REF54 performance in SOIC package. The REF54 with low long-term drift (30 ppm), excellent load and line regulation helps meet strict performance requirements of high precision applications. This device also comes with a enable pin (EN) that allows the device to be set in shutdown mode to improve power efficiency. This user's guide describes the characteristics, operation, and recommended use cases of the REF54EVM. This document provides examples and instructions on how to use the REF54EVM board. Throughout this document, the terms evaluation board, evaluation module, and EVM are synonymous with the REF54EVM. This document also includes a schematic, reference printed circuit board (PCB) layouts, and a complete bill of materials (BOM).

[Andreas]

Is it anywhere available?
Not at DigiKey or Mouser.

with best regards

Andreas

[RandallMcRee]

Looks like there is a webinar announcing this product on Dec 14.

Seems like TI's answer to the ADR45xxD which has similar specs (0.8/C TC, 0.02% Vout, low noise)

[DavidKo]

If I catch it correctly, than the mentioned specs will be for 2.5V reference (one used in breadboard). I expect that at 5V the noise will be double - common in TI datasheets and specs.

[Andreas]

Yes,
Noise is given as ppm p-p in this case so uVpp/V output voltage.
with best regards
Andreas

[Andreas]

Seems like TI's answer to the ADR45xxD which has similar specs (0.8/C TC, 0.02% Vout, low noise)

Hello,
was not aware of this package.
When I worked with ADR4550B (in ADC18) the ageing drift was rather high. And also thermal hysteresis.
Do you have experience with the ADR4550D ?

with best regards
Andreas

[iMo]

While looking at the ADR4550 (and friends) output voltage vs temperature graph in the DS - not an optimal for a precision reference.. In 0-60degC a pretty downwards slope..

[RandallMcRee]

Seems like TI's answer to the ADR45xxD which has similar specs (0.8/C TC, 0.02% Vout, low noise)

Hello,
was not aware of this package.
When I worked with ADR4550B (in ADC18) the ageing drift was rather high. And also thermal hysteresis.
Do you have experience with the ADR4550D ?

with best regards
Andreas

I do have some experience, although no graphs to share. Currently, I am creating a daughter board for the AD5791 EVM using a mix of ADR4525D and ADR4550D chips. Using an LT5400/ADA4523-1 to gang up the 5v to 10v I see a daily difference <1ppm in my heated room (no enclosure currently!).

There ought to be a separate datasheet for the ADR45xxD, e.g. look at hysteresis, for example:

You can see that the D grade is quite good. Again, that has been my experience, as well. But, like much of AD's inventory, impossible to get more of, lately.

Also, the long term drift has been very low. In the datasheet, that is also broken out separately since the D grade is much better.

Thanks,
Randall

[floobydust]

REF54 seems to be a REF70 variant with added NR pin and deleted SENSE pin? The REF54EVM datasheet has cut'n'paste errors.
4.1 "The schematic for the REF70EVM is illustrated in Figure 3-3"  uh there is no fig. 3-3 and it's not the 70.

100uF for C_NR seems large, and it's a polymer tantalum Panasonic POSCAP 16TDC100MYF which has more leakage current above a tantalum-only part, not sure if that is a problem for the IC's new internal node. There's no thermal reliefs on the EVM board so working with that is not possible.

[ivo]

I did wonder why all the modern references started dropping the NR pin. A single good cap gets you to a much better starting point than having to implement a good filtering solution.

[ivo]

While looking at the ADR4550 (and friends) output voltage vs temperature graph in the DS - not an optimal for a precision reference.. In 0-60degC a pretty downwards slope..

I notice they have a typo on the vertical scale for the 4550D graph 



They all have a nice slope from 10-40, these are guestimated numbers:

grade/temp	10	40	Diff
B	5.000085	4.99985	-0.000235
C	4.99908	4.999025	-0.000055
D	4.99962	4.999538	-0.000082

The best SOIC'er wins!

Although the LCC8 is supposed to be regarded for removing humidity from the equation. Pretty sure I remember seeing some Andreas' posts on how annoying that can be to a finely tuned plastic reference over a year.

[iMo]

I did wonder why all the modern references started dropping the NR pin. A single good cap gets you to a much better starting point than having to implement a good filtering solution.

Perhaps there is not such a "good cap" available.. So they rather dropping the NR pin - otherwise the customers will complain their reference with a larger cap wired to the NR pin fluctuates much more than without the cap..

[iMo]

While looking at the ADR4550 (and friends) output voltage vs temperature graph in the DS - not an optimal for a precision reference.. In 0-60degC a pretty downwards slope..

I notice they have a typo on the vertical scale for the 4550D graph 

Keeping the 4550"D" at those aprox 45C would definitively help, it also repels the humidity off the package a little bit.

[Kleinstein]

The NR pin definitely makes sense with a reference that includes a buffer to directly drive an ADC.  Usually this is only for the higher frequency noise part, but this can still matter as some ADCs also react to higher frequency noise at there ref. input. Just a relatively large capacitor at the the low impedance reference output is not the most efficient way of filtering - though in parts also not as bad as one may think, as the output impedance is usually inductive and thus making it a 2nd order filter.
When using an external buffer / ADC driver anyway one can as well add filtering there and have the opition to choose the series resistor.

[eplpwr]

Although the LCC8 is supposed to be regarded for removing humidity from the equation. Pretty sure I remember seeing some Andreas' posts on how annoying that can be to a finely tuned plastic reference over a year.

In the ADR45xx datasheet they show the effect of humidity on the SOIC-8 references. What is missing - for comparison purposes - is how the ceramic "D" packages handle humidity. In the document "Analog Dialogue Volume 53 Number 3" there is an article called "Does My Voltage Reference Design Hold Water?" that actually gives the numbers for the LCC-8 packages as well (for ADR4525). The numbers are telling: 2.5 ppm/%RH for SOIC-8 vs 0.075 ppm/%RH for LCC-8. The article recommends hermetic packages for highest precision. The tempco is still a problem - maybe an oven can solve that?

Now, hermetic packages and an oven to handle the tempco - I think I've encountered that concept before, somewhere. 

[Andreas]

vs 0.075 ppm/%RH for LCC-8. The article recommends hermetic packages for highest precision.

I doubt this number if the package is soldered to a epoxy PCB. (even with slots).
Perhaps whole cirquit on a ceramic substrate.

With best regards

Andreas

[iMo]

Dead bug wiring should be none problem..

[Andreas]

Hello Imo,

is that picture from your ageing measurements of ADR1001 in the other thread?
(is that the reason why it is that good?)

with best regards

Andreas

[iMo]

Yes, therefore it is so good..

[laichh]

The REF54 is now in PREVIEW status on TI website:

https://www.ti.com/product/REF54

[RandallMcRee]

The REF54 is now in PREVIEW status on TI website:

https://www.ti.com/product/REF54

Yes, I noticed this, as well. And...REF54 is a big nothingburger! All of the supposedly state-of-the-art guesstimates from before are now either exactly matching ADR45xxD or are worse! For example, 0.5 ppm max TC is now 0.8ppm, same same.

It's another case of TI copying a successful ADI product, I guess.  Perhaps also a second source is profitable in a niche market like this?

[ivo]

Interesting, looking at the application note for the datasheet, they want at least a 1uF cap on the output ('must be connected') but warn against the cheapest route, X7R MLCC.

Perhaps also a second source is profitable in a niche market like this?

Having another OEM for a good part is never a bad thing

[Kleinstein]

The piezo effect of X7R and similar capacitors is well known. In a quiet environment they can still be OK and for the lower frequency part the reference and not the capacitor is relevant. So it depends on the application if an X7R at the output is acceptable. For many uses this should be OK, as high frequency noise may not be that relevant and other parts of the circuit may be sensitive to mechanical coupling too.

An iteresting point is getting low noise with a relatively low power consumpten  (like 40% of the ADR45xx).
Being pin compatible (with the optional capacitor at the NR pin) is a good thing.

[floobydust]

I think price-point of the REF54 will tell if it's a bit of competition for ADI, or just a "we're still in the game" product for TI. Website gives USD $6.95/1ku - which is a top price, and yet it's another plastic-package reference IC with marketing numbers.

All the acquisitions by TI and ADI have made a huge mess. I was reading of ADI closing the Linear Tech Hillview plant (wafer fab and packaging) where LTFLU1, LTZ1000 etc. all TO packaged parts were built- and offshoring all that, and outsourcing the packaging as well. To save not much money actually. What a heartbreaker. Hillview had a 35,862 square-foot clean room.

At a time the USA wants semi fab back in America 

[deepfryed]

The numbers are telling: 2.5 ppm/%RH for SOIC-8 vs 0.075 ppm/%RH for LCC-8. The article recommends hermetic packages for highest precision.

Can you dry the PDIP package and then coat it in a marine waterproof epoxy to get the same benefit ?