SLYT878 April   2026 DAC8771 , DAC8775 , LMR51606 , LMR54406 , TLV9301 , XTR200

 

  1.   1
  2.   2
  3. 1 Choosing the right DC/DC
  4. 2 Controlling the DC/DC output
  5. 3 Example circuit using sourcing current
  6. 4 Example circuit using voltage feedback
  7. 5 Measurements and performance
  8. 6 Precision and noise
  9. 7 Settling time and dynamic performance
  10. 8 Conclusion
  11. 9 Additional resources
  12. 10About the author

1 Choosing the right DC/DC

Finding the proper DC/DC converter for adaptive power is challenging because of these requirements, which are contradictory:

  • High efficiency at low loads (4-20 mA). Because this is generally possible in pulse frequency modulation (PFM), the DC/DC has to support this mode. Expect an approximate 50% efficiency improvement vs. forced pulse-width modulation (PWM) mode.
  • Relatively high peak current (>0.5A) for fast settling. The peak current divided by the decoupling capacitances determines the output maximum voltage rate of change.
  • VOUT within 4V to 24V, achieved by either a buck or boost converter based on the input voltage.
  • A relatively small inductor to reduce solution size. A high switching frequency (≥300kHz) is required.
  • Available in a small package.

Some parts that fulfill these requirements are:

LMR516xx: 65V input, PFM versions at 400kHz/1.1MHz, 0.6A/1A output current

LMR544xx: 36V input, PFM at 1.1MHz, 0.6A/1A output

LMR3650x: 3V-65V input, adjustable 200kHz-2.2MHz, 0.1A/0.15A output (if fast settling is not critical)