New Breed of Ultra Low Noise Regulators 2011/03/29
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
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 (~20 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.
Ignore the Noise Density numbers for now. I need to revise them. Look at the RMS values
Comment