Periodic and random deviation (PARD) quantifies the total unwanted AC components riding on a DC output voltage. It encompasses both the periodic ripple generated by switching frequencies or mains rectification, and the random broadband noise from thermal or semiconductor sources. PARD is typically measured peak-to-peak over a specified bandwidth, often 20 MHz, to ensure clean power delivery to sensitive logic.
The datasheet claims a PARD of under 50 millivolts peak-to-peak, but I'm measuring closer to 100 on the scope.
Related terms
PSU
A power supply unit converts utility AC power into the regulated DC voltages required by a system.
SMPS
A switched-mode power supply uses high-frequency switching to efficiently convert electrical power.
Hash noise
A harsh, wideband electrical interference that sounds like a buzz or static on an audio output or looks like thick fuzz on a trace.