ZHCSE52B September 2015 – May 2019 TPS57140-EP
PRODUCTION DATA.
The TPS57140-EP has an integrated boot regulator and requires a small ceramic capacitor between the BOOT and PH pins to provide the gate-drive voltage for the high-side MOSFET. The value of the ceramic capacitor should be 0.1 μF. TI recommends a ceramic capacitor with an X7R or X5R grade dielectric because of the stable characteristics over temperature and voltage. To improve dropout, the TPS57140-EP operates at 100% duty cycle as long as the BOOT-to-PH pin voltage is greater than 2.1 V. When the voltage from BOOT to PH drops below 2.1 V, the high-side MOSFET turns off using a UVLO circuit, allowing for the low-side diode to conduct, which allows refreshing of the BOOT capacitor. Because the supply current sourced from the BOOT capacitor is low, the high-side MOSFET can remain on for more switching cycles than it refreshes; thus, the effective duty-cycle limitation attributed to the boot regulator system is high.