SLVU641A January   2012  – November 2021 TPS54120

 

  1.   Trademarks
  2. 1Background
  3. 2Setup
    1. 2.1 Input and Output Connections and Jumper Descriptions
    2. 2.2 Modifications
      1. 2.2.1 SW Output Voltage Setpoint
      2. 2.2.2 LDO Output Voltage Setpoint
      3. 2.2.3 Switcher Slow-Start Time
      4. 2.2.4 LDO Start-Up
    3. 2.3 Equipment Interconnect
  4. 3Operation
  5. 4Test Results
    1. 4.1 Output Voltage Ripple
    2. 4.2 Output Noise
    3. 4.3 Output Turn-On
    4. 4.4 Load Transient
    5. 4.5 Efficiency
    6. 4.6 Thermal Characteristic
  6. 5Board Layout
    1. 5.1 Layout Description
  7. 6Schematic
  8. 7Bill of Materials
  9. 8Revision History

2.1 Input and Output Connections and Jumper Descriptions

  • J1-LDO OUT and J2-GND: The output of the LDO and the ground connector. The default setting is 3.3 V. This is the low noise output from the TPS54120.
  • J3-VIN and J4-GND: Input power supply voltage and the ground connector. The positive input lead and ground return lead from the input power supply should be twisted and kept as short as possible to minimize EMI transmission. Additional bulk capacitance should be added across J3 and J4 if the supply leads are greater than six inches. For example, an additional 47-µF electrolytic capacitor across J3 and J4 can improve the transient response of the TPS54120 while eliminating unwanted ringing on the input due to long wire connections.
  • J5: The SMA connector for the output voltage of the LDO. The connector for J5 is not populated on the TPS54120EVM (PWR103). This footprint allows the mounting of an SMA-style connector for more accurate PSRR measurements.
  • J7-SW OUT and J6-GND: The output of the SW and the ground connector. This is the output voltage from the switcher converter and the input voltage to the LDO. The default setting is 4.1 V.
  • J8: The SMA connector for the output voltage of the SW. The connector for J8 is not populated on the TPS54120EVM (PWR103). This footprint allows the mounting of an SMA-style connector for more accurate PSRR measurements.
  • JP1-LDOEN: LDO enable. To enable the output of the LDO, connect this jumper from the center pin to the “on” pin. This will connect the enable pin to the LDO input supply. To disable, connect this jumper from the center pin to the “off” pin. This will short the LDO enable pin to ground.
  • JP2: The jumper connection between the output of the switcher converter to the LDO input. A shorting jumper is required for normal operation. If you want to disconnect the LDO from the SW, remove the shorting jumper wire.
  • JP3-SW EN: Switcher converter enable jumper. To enable the SWITCHER output, leave this jumper unconnected (there is an internal pullup on this pin). To disable, install a shorting jumper. This will short the enable pin to ground.
  • TP1-PWRGD: The power-good connector test point. It is power-good open-collector flag for the switcher converter. Tie this pin through a 10-k resistor to a regulated supply < 5.5 V to monitor the status of the switcher converter output.
  • TP2-SENSE: The SW sense (feedback) pin test point
  • TP3-SW OUT: This is the positive switcher output test point. In addition to J7, this test point can also be used to measure the output voltage of the switcher.
  • TP4-LDO IN: The LDO input voltage test point
  • TP5-LDO OUT: The LDO output test point. In addition to J1, this test point can also be used to measure the output voltage of the LDO.