Hier, was ein Hersteller dazu meint:

http://www.maxim-ic.com/quick_view2.cfm/qv_pk/1538
Fixed-frequency pulse-width modulation (PWM) reduces noise in sensitive communications applications. Using a high-frequency internal oscillator allows tiny surface-mount components to reduce PC board area, and eliminates audio-frequency interference. A SYNC input allows synchronization to an external clock to avoid interference with sensitive RF and data-acquisition circuits.