Update (01/29/13): Revised the noise density numbers
Update (8/27/12): Added the new TI TPS7A4700 regulator to the table. This device can source up to 1 A of current and ranks on top of the list. Also please ignore the noise density numbers, I need to revise them. Look at the RMS noise values.
The table below compares the noise level of some regulators used in current DIY modules vs a new breed of regulators that are used in portable consumer devices such as cell phones.
Just like phase noise in clocks, it is difficult to compare noise values among linear regulators because there is no common ground in specifying noise figures. Some companies report noise density, others RMS V noise, and yet others % of Vout. The frequency range for the reported noise figures also varies from company to company. Thus it is required to convert spec numbers to a common measuring unit. I chose to convert everything to “Noise Density” in nV/Sqrt(Hz) numbers. In order to understand the relationship between RMS noise and noise density, you can watch this video tutorial: http://www.youtube.com/watch?v=ywChrIRIXWQ [or here]
The noise density numbers are a good approximation and calculated in accordance to the instruction presented in the video above. They have been further normalized to a bandwidth of 100KHz. (I’ve redone the calculation and this time is correct). The number represents the “tail” of the noise spectrum which is typically a flat line.
The first two rows are application notes indicating the noise density value of the noise floor. AN51 is a discrete design using a ZETEX voltage reference. LM723 is an old part used in older designs. Newer monolithic designs have the added advantage that they are also very low dropout (LDO).
The comparison suggests that whether using a discrete design or state of the art monolithic regulators, we are very close to the measurable noise floor (~14 nV seems the best regulators so far…).
For the diyer, these devices are very small and maybe very hard to solder, especially the micro SMD bump package.
|Bandwidth for spec (Hz)||Noise Density
nV/Sqrt(Hz) Normalized to 100KHz
|AN124||Noise floor||0.16 (peak)||0-10Hz||1? (not enough data)|
|ADP151||Amanero USB, Ian’s FIFO||200||9||10-100K||28|
|LT1763, LT1761, LT1762||Buffalo II (LT 1763)||500||20||10-100K||63|
|LT1963, LT1964||Musiland power mod
|LM317, LT1117||LCDPS, many low cost devices||1500, 800||99
As previously discussed, the noise density numbers are an approximation assuming that it is “flat” throughout the bandwidth of interest. The area under the noise density trace is the RMS noise figure. So basically, if we assume a square area and a bandwidth of 100 KHz, then the RMS Noise = Noise Density X SQRT(100,000) = Noise Density X 316
Note: the second noise figure for the LM317 comes from TNT-Audio [link]. There, it is measured at 250 uV for the ~20Khz bandwidth.
Here is the project by a reader in Greece using the Arduino Nano (click for larger pictures)
From the Musiland Forum:
“Is Musiland developing an OSX driver or just intends to develop one in the future depending on the situation?”
6/1/11: From the Musiland Forum:
“I feel Musiland does not have Linux and Mac customers in their mind from the start. People looking for a Linux solution will have to look elsewhere”
“It is not that we don’t have those customers in mind. Sound cards for Linux and Mac costs thousands of kuai (implying small market). Musiland sound cards sell for hundreds (implying much larger market). How can we support so much R&D? Therefore slow development”