Stefan Herzer

Capacitive-coupled current sensing and Auto-ranging slope compensation for current mode SMPS with wide supply and frequency range

Techniques for high impedance current sensing and slope compensation, common challenges for current mode switched mode power supplies (SMPS), are presented. DCR sensing, limited by conventional low impedance sensing techniques, is thus possible, enabling power efficiency gains. Auto-ranging slope compensation based on a multiplication of input voltage V<inf>IN</inf> and switching frequency f<inf>sw</inf> allows for truer current mode operation and superior line transient response for a wide range of V<inf>IN</inf> and f<inf>sw</inf>. The techniques are demonstrated in an automotive-class 60V V<inf>IN</inf> buck controller at 150–600kHz in a 0.35µm BiCMOS technology. Offset error ≪3mV over 0–10V and single-cycle stable current loop response are measured.