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.