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I am modelling MAX15062 DC-DC buck converter using datasheet in PSpice, initially i worked on control loop. This buck converter has two modes PWM and PFM mode. With MODE pin unconnected works on PFM mode which changes its frequency and prevents inductor current from reaching negative at light load condition. How does it enter, sustain and exit this mode. I ran a load step analysis for MAX15062 testcase schematic designed from Maxim integrated website- downloaded the schematic and ran in EEsim (simulator).

  • Here Vin=24V and Vout=5V
  • Load current is varied from 300mA to 10mA

This is kept in PFM mode, where it dosent allowes inductor current to go negative by keeping highside FET and lowside FET off for some time.

It also skips some of the pulses and again recovers back and allows some pulses.

In light load condition max current is limited to 150mA.

I am sharing some screenshots of LX (Inductor node switching), Vout , IL(Inductor current),and schematic of the test case.Schematic of PFM with load step

Output graphs Pulse Skipping waveforms LX pin and IL Maximized LX and IL at 10mA

Datasheet of MAX15062

Reference for PFM mode

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I may be completely off the track, but are you really asking how the MAX15062 enters, sustains and exits the PFM mode?

Answer: The mode is selected by the voltage on the MODE pin. So if you want to exit PFM mode, just pull the MODE pin to GND.

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  • \$\begingroup\$ But you seem to already have a model for the MAX15062 in PSpice? \$\endgroup\$ – Stefan Wyss May 12 at 9:27
  • \$\begingroup\$ The above is encrypted model which i downloaded from Maxim and ran in eesim , i have modelled only its control loop in PSpice i.e. PWM mode feature. I want to add PFM feature to my PSpice model which can work in light load condition. \$\endgroup\$ – Adithya Pai May 12 at 9:29

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