The TPS54331 is a 28-V, 3-A non-synchronous buck converter that integrates a low RDS(on) high side MOSFET. To increase efficiency at light loads, a pulse skipping Eco-mode™ feature is automatically activated. Furthermore, the 1 µA shutdown supply current allows the device to be used in battery powered applications. Current mode control with internal slope compensation simplifies the external compensation calculations and reduces component count while allowing the use of ceramic output capacitors. A resistor divider programs the hysteresis of the input under-voltage lockout. An overvoltage transient protection circuit limits voltage overshoots during startup and transient conditions. A cycle by cycle current limit scheme, frequency fold back and thermal shutdown protect the device and the load in the event of an overload condition. The TPS54331 is available in 8-pin SOIC package and 8-pin SOIC PowerPADTM package that have been internally optimized to improve thermal performance.
The TPS54332 is a 28 V, 3.5 A non-synchronous buck converter that integrates a low RDS(on) high side MOSFET. To increase efficiency at light loads, a pulse skipping Eco-mode™ feature is automatically activated. Furthermore, the 1 µA shutdown supply current allows the device to be used in battery powered applications. Current mode control with internal slope compensation simplifies the external compensation calculations and reduces component count while allowing the use of ceramic output capacitors. A resistor divider programs the hysteresis of the input under-voltage lockout. An overvoltage transient protection circuit limits voltage overshoots during startup and transient conditions. A cycle by cycle current limit scheme, frequency fold back and thermal shutdown protect the device and the load in the event of an overload condition. The TPS54332 is available in an 8-pin SOIC PowerPAD package.
The EN pin has an internal pull-up current source that provides the default condition of the TPS54331 operatingwhen the EN pin floats.The TPS54331 is disabled when the VIN pin voltage falls below internal VIN UVLO threshold. It is recommendedto use an external VIN UVLO to add Hysteresis unless VIN is greater than (VOUT + 2 V). To adjust the VIN UVLOwith Hysteresis, use the external circuitry connected to the EN pin as shown in Figure 14. Once the EN pinvoltage exceeds 1.25 V, an additional 3 μA of hysteresis is added. Use Equation 1 and Equation 2 to calculatethe resistor values needed for the desired VIN UVLO threshold voltages. The VSTART is the input start thresholdvoltage, the VSTOP is the input stop threshold voltage and the VEN is the enable threshold voltage of 1.25 V. TheVSTOP should always be greater than 3.5 V.
It is highly recommended to program the slow start time externally because no slow start time is implementedinternally. The TPS54331 effectively uses the lower voltage of the internal voltage reference or the SS pinvoltage as the power supply’s reference voltage fed into the error amplifier and will regulate the outputaccordingly. A capacitor (CSS) on the SS pin to ground implements a slow start time. The TPS54331 has aninternal pull-up current source of 2μA that charges the external slow start capacitor. The equation for the slowstart time (10% to 90%) is shown in Equation 3 . The Vref is 0.8 V and the ISS current is 2 μA.
The slow start time should be set between 1ms to 10 ms to ensure good start-up behavior. The slow startcapacitor should be no more than 27nF.If during normal operation, the input voltage drops below the VIN UVLO threshold, or the EN pin is pulled below1.25 V, or a thermal shutdown event occurs, the TPS54331 stops switching.
TPS54331EVM-232 3-A, SWIFT™ Regulator Evaluation Module
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