ZHCS360F July 2012 – November 2020 TPS54020
PRODUCTION DATA
The device has an integrated bootstrap voltage 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 boot capacitor is charged when the BOOT pin voltage is less than VIN and BOOT-PH voltage is below regulation. The value of this ceramic capacitor should be 0.1 μF. A ceramic capacitor with an X7R or X5R grade dielectric with a voltage rating of 10 V or higher is recommended because of the stable characteristics over temperature and voltage. To improve dropout, the device is designed to operate at 100% duty cycle as long as the BOOT-to-PH pin voltage is greater than the BOOT-PH UVLO threshold, which is typically 2.1 V. When the voltage between BOOT and PH drops below the BOOT-PH UVLO threshold, the high-side MOSFET is turned off and the low-side MOSFET is turned on, allowing the boot capacitor to be recharged. In applications with split input voltage rails, 100% duty cycle operation can be achieved as long as (VIN – PVIN) > 4 V. However, if the TPS54020 is configured for hiccup overcurrent protection, hiccup also occurs if the input voltage is insufficient to regulate the output voltage for longer than the hiccup wait time. If continuous operation at 100% duty cycle is needed, configure the TPS54020 for cycle-by-cycle current limit.