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_IN and switching frequency f_sw allows for truer current mode operation and superior line transient response for a wide range of V_IN and f_sw. The techniques are demonstrated in an automotive-class 60 V V_IN buck controller at 150-600 kHz in a 0.35 mum BiCMOS technology. Offset error <3 mV over 0-10 V and single-cycle stable current loop response are measured.