JAJSFC9B September 2017 – June 2018 TPS560430
UNLESS OTHERWISE NOTED, this document contains PRODUCTION DATA.
The following operation description of the TPS560430 will refer to the Functional Block Diagram and to the waveforms in Figure 13. TPS560430 is a step-down synchronous buck regulator with integrated high-side (HS) and low-side (LS) switches (synchronous rectifier). The TPS560430 supplies a regulated output voltage by turning on the HS and LS NMOS switches with controlled duty cycle. During high-side switch ON time, the SW pin voltage swings up to approximately VIN, and the inductor current iL increase with linear slope (VIN – VOUT) / L. When the HS switch is turned off by the control logic, the LS switch is turned on after an anti-shoot-through dead time. Inductor current discharges through the low-side switch with a slope of –VOUT / L. The control parameter of a buck converter is defined as Duty Cycle D = tON / TSW, where tON is the high-side switch ON time and TSW is the switching period. The regulator control loop maintains a constant output voltage by adjusting the duty cycle D. In an idea Buck converter, where losses are ignored, D is proportional to the output voltage and inversely proportional to the input voltage: D = VOUT / VIN.
The TPS560430 employs fixed-frequency peak-current mode control. A voltage feedback loop is used to get accurate DC voltage regulation by adjusting the peak-current command based on voltage offset. The peak inductor current is sensed from the high-side switch and compared to the peak current threshold to control the ON time of the high-side switch. The voltage feedback loop is internally compensated, which allows for fewer external components, makes it easy to design, and provides stable operation with almost any combination of output capacitors. The regulator operates with fixed switching frequency at normal load condition. At light-load condition, the TPS560430 operates in PFM mode to maintain high efficiency (PFM version) or in FPWM mode for low output voltage ripple, tight output voltage regulation, and constant switching frequency (FPWM version).