JAJSKE1 October 2021 LM61430-Q1
PRODUCTION DATA
In continuous conduction mode (CCM), the LM61430-Q1 supplies a regulated output voltage by turning on the internal high-side (HS) and low-side (LS) NMOS switches with varying duty cycle (D). During the HS switch on-time, the SW pin voltage, VSW, swings up to approximately VIN, and the inductor current, iL, increases with a linear slope. The HS switch is turned off by the control logic as shown in Section 8.2. During the HS switch off time, tOFF, the LS switch is turned on. Inductor current discharges through the LS switch, which forces the VSW to swing below ground by the voltage drop across the LS switch. Refer to the waveforms in Figure 8-17. The converter loop adjusts the duty cycle to maintain a constant output voltage. D is defined by the on time of the HS switch over the switching period:
In an ideal buck converter where losses are ignored, D is proportional to the output voltage and inversely proportional to the input voltage: