Understanding Power Supply Rejection Ratio

What is PSRR?

Power Supply Rejection Ratio or Power Supply Ripple Rejection (PSRR) is a measure of how well a circuit rejects noise, of various frequencies, injected at its voltage input.  The ripple can be induced from a number of sources, such as a 50Hz/60Hz supply ripple, a switching ripple from a DC/DC converter, or a ripple due to the sharing of an input supply between different circuit blocks on the board.  In the timing solutions world, when discussing PSRR we are typically referring to supply ripple.

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Understanding VCXO Specifications: APR

Like most oscillators, VCXOs have many specifications. APR – Absolute Pull Range – is a single specification that combines many of them to make selection easy. The term “Pull” is unique to the oscillator industry and refers to the small frequency tuning available via the voltage control pin. Pull is measured as df/fnom in ppm.

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