87%-Efficient 330-mW 0.6-<italic>μ</italic>m Single-Inductor Triple-Output Buck–Boost Power Supply

Abstract

Microsystems that sense, process, and communicate data can save money, energy, and lives. Such varied functionality, however, demands power that can easily deplete a small battery. Integrating so many analog and digital functions can also imperil performance with noise and distortion. To survive all this with an exhaustible battery, blocks require several efficient power supplies that both buck and boost the battery voltage. Luckily, switched inductors are flexible and efficient, but also bulky. So what these microsensors need are single-inductor multiple-output supplies that buck and boost. But to reconfigure the inductor for such diverse operation requires many power-consuming switches. Plus, cycling between outputs requires time and delays response time. The single-inductor supply proposed bucks and boosts and cycles between outputs frequently with two input switches, one inductor, and one switch and one capacitor per output. Other buck–boost supplies either bypass the inductor or require one to two more switches and up to one more inductor and one more capacitor. The prototype presented here bucks two outputs and boosts one output with five switches by energizing the inductor to buck outputs first. By collecting sufficient energy this way, the inductor can feed boost outputs directly. A sixth switch engages only when boost power is greater than a threshold that the input voltage and buck power levels establish. This way, the 0.6- μ m complementary metal oxide semiconductor system bucks and boosts 2.7–4.0 V to 1.2, 1.8, and 4.0 V to deliver 80%−87% of the 379–412 mW drawn. The system cycles every 1–3 μ s and responds within 5–10 μ s.