TIDT399 July   2024

 

  1.   1
  2.   Description
  3.   Features
  4.   Applications
  5. 1Test Prerequisites
    1. 1.1 Voltage and Current Requirements
    2. 1.2 Required Equipment
    3. 1.3 Considerations
    4. 1.4 Dimensions
  6. 2Testing and Results
    1. 2.1 Efficiency Graphs
    2. 2.2 Thermal Images
    3. 2.3 Bode Plots
  7. 3Waveforms
    1. 3.1 Switching
    2. 3.2 Output Voltage Ripple
    3. 3.3 Load Transients
    4. 3.4 Start-Up Sequence
  8.   Trademarks

1.3 Considerations

All voltage measurements were made relative to the 0V common GND. When taking measurements, make sure to connect the GND clips of the oscilloscope to the GND (that is, 0V) connection. Do not connect the oscilloscope GND clips to the –Vout node. Though this –VOUT is the reference for the GND pins of the regulator IC, the output is no longer considered 0V common GND, but is a negative voltage relative to GND.

In the inverting buck-boost topology, the voltage potential between the Vin and GND pins of the converter or regulator is the sum of the magnitudes of VIN and VOUT voltages. For example, with the input voltage of +18V and the output voltage set to –12V, the total voltage potential exhibited by the LM61495-Q1 is:

Equation 1. + 18 V + – 12 V = 30 V

The LM61495 has a maximum recommended supply voltage of 36V. Therefore, do not apply an input voltage greater than 24VIN to the converter, preferably lower, to provide an extra buffer to accommodate for switching voltage spikes.