SLUSCV2A June 2017 – April 2021 TPS54308
PRODUCTION DATA
The device is a 28-V, 3-A, synchronous step-down (buck) converter with two integrated n-channel MOSFETs. To improve performance during line and load transients, the device implements a constant-frequency, peak current mode control which reduces output capacitance. The optimized internal compensation network minimizes the external component counts and simplifies the control loop design.
The switching frequency of the TPS54308 is fixed to 350 kHz. This device operates in continuous conduction mode (FCCM) during light load conditions. During FCCM, the switching frequency is maintained at an almost constant level over the entire load range, which is suitable for applications requiring tight control of the switching frequency and output voltage ripple at the cost of lower efficiency under light load.
The TPS54308 starts switching when VIN is equal to 4.5 V. The operating current is 300 μA (typical) when the device is not switching and under no load. When the device is disabled, the supply current is 2 µA (typical).
The integrated 85-mΩ high-side MOSFET and 40-mΩ low-side MOSFET allow for high-efficiency power supply designs with continuous output currents up to 3 A.
The TPS54308 reduces the external component count by integrating the boot recharge diode. The bias voltage for the integrated high-side MOSFET is supplied by an external capacitor on the BOOT to PH pins. The boot capacitor voltage is monitored by an UVLO circuit and turns the high-side MOSFET off when the voltage falls below a preset threshold of 2.1 V (typical).
The device minimizes excessive output overvoltage transients by taking advantage of the overvoltage comparator. When the regulated output voltage is greater than 118% of the nominal voltage, the overvoltage comparator is activated, and the high-side MOSFET is turned off and masked from turning on until the output voltage is lower than 104%.
The TPS54308 device has internal 5-ms soft-start time to minimize inrush currents.