7.4.2 Pulse-Skip Eco-mode Control Scheme

The TPS57140-EP enters the pulse-skip mode when the voltage on the COMP pin is the minimum clamp value. The TPS57140-EP operates in a pulse-skip mode at light load currents to improve efficiency. The peak switch current during the pulse-skip mode is the greater value of either 50 mA or the peak inductor current that is a function of the minimum on-time, input voltage, output voltage, and inductance value. When the load current is low and the output voltage is within regulation, the device enters a sleep mode and draws only 116 μA of input quiescent current. While the device is in sleep mode, the output capacitor delivers the output power. As the load current decreases, the time the output capacitor supplies the load current increases and the switching frequency decreases, reducing gate-drive and switching losses. As the output voltage drops, the TPS57140-EP wakes up from sleep mode and the power switch turns on to recharge the output capacitor, see Figure 51. The internal PLL remains operating when in sleep mode. When operating at light load currents in pulse-skip mode, the switching transitions occur synchronously with the external clock signal.

Figure 51. Operation in Pulse-Skip Mode